improvement of surfboards design and production process

Improvement of surfboards design and production process | Maciej Wozniak

Page | 1

Universidade de

Aveiro

2019

Departamento de Mecanica

Maciej Kazimierz

Wozniak

Improvement of surfboards’ design and production

process.


Page | 2

Dissertação/Relatório apresentada(o) à Universidade de Aveiro para

cumprimento dos requisitos necessários à obtenção do grau de

Mestre em Engenharia Mecânica, realizada sob a orientação

científica do Doutor Ricardo de Sousa, Professor do Departamento

de Mecanica da Universidade de Aveiro


Page | 3


Page | 4

o júri

presidente Prof. Doutor Alfredo Manuel Balaco de Morais

Professor Associado da Universidade de Aveiro

Prof. Doutor Ricardo Jose Alves de Sousa

ProfessorAuxiliar C/ Agregacao de Universidade de Aveiro

Prof. Doutor Daniel Gil Afonso

Professor Adjunto da Universidade de Aveiro


Page | 5

agradecimentos

I would like to dedicate this work to a number of people.

All my family

For supporting me on every step of my journey, accepting and

understanding my crazy ideas of life and my passions.

My father

Who showed me, how education can shape your life.

My mum

For unconditional love

My sister

For editing and correcting this work

My brother

Who can understand my passion to the sports

All my Professors

For educating me and making it possible for me to get so far.

Especially:

Professor Ricardo de Sousa

Who accepted the idea and gave me necessary support during

my project.

Professor Francisco de Melo

Who helped me with theoretical part and shared many amazing

stories

with me.

Professor Mariusz Ptak

Who introduced me to cork material during my bachelor

thesis back in Poland.

New coast boyz

My surf crew who shares my passion to the water with me.

Bruno and Hugo

For sharing their knowledge of shaping with me.


Page | 6


Page | 7

palavras-chave

Design, LCA, Surfboard, FEM, Abaqus, SolidWorks, CAD,

Python, Optimization


Page | 8

resumo

The subject of this thesis is analyzing different ways of producing

surf boards, visiting several shaping companies to

understand what problems they may have and try to find out

possible solutions for them. After that, different types of

surfboards and materials used to make them will be described.

Next, two surfboards will be made, according to the preferences

of majority of the surfers. The first one will be the prototype and

the second one, the improved version, also in the ecological

aspect. In this work I will focus mainly on the smaller local

workshops which made custom boards.


Page | 9

Table of Contents

1. Introduction ........................................................................................................................................ 18

2. History of surfing ................................................................................................................................ 19

2.1 History of the sport ...................................................................................................................... 19

2.2 Raw Materials ............................................................................................................................... 20

2.3 Surfboards history ........................................................................................................................ 21

2.3.1 The hollow board................................................................................................................... 21

2.3.2 The Hot Curl board ................................................................................................................ 21

2.3.4 Fiber glass boards .................................................................................................................. 22

2.3.5 Commercial surfboards ......................................................................................................... 23

2.3.6 The short board, twin fins and the surf leash ....................................................................... 23

2.3.7 Three Fin Thruster ................................................................................................................. 24

2.3.8 Pop out and Foam boards ................................................................................................. 24

3. Design and production of surfboards of surfboards .......................................................................... 25

3.2 Shape ............................................................................................................................................ 25

3.3 Start of the manufacturing process – shaping a blank ................................................................. 25

3.4 Stringer ......................................................................................................................................... 26

3.5 Tools ............................................................................................................................................. 26

3.6 Laminating the outer shell ........................................................................................................... 27

3.7 Fin boxes ....................................................................................................................................... 29

3.8 Sanding the board ........................................................................................................................ 29

3.9 Quality Control ............................................................................................................................. 29

3.10 Toxic materials and safety considerations ................................................................................. 30

4. Different types of surfboards ............................................................................................................. 30

4.1 Short board ................................................................................................................................... 30

4.2 Longboard..................................................................................................................................... 31

4.3 Fish ............................................................................................................................................... 32

4.4 Hybrid surfboard .......................................................................................................................... 32

4.5 Gun ............................................................................................................................................... 33

5. Different parts and dimensions of surfboards ................................................................................... 33


Page | 10

5.1 Length ........................................................................................................................................... 33

5.2 Width ............................................................................................................................................ 34

5.3 Nose .............................................................................................................................................. 34

5.3.1 Pointed Nose ......................................................................................................................... 34

5.3.2 Rounded Point Nose .............................................................................................................. 35

5.3.3 Round Nose ........................................................................................................................... 35

5.4 Tail ................................................................................................................................................ 36

5.4.1 Pin Tail ................................................................................................................................... 36

5.4.2 Round Tail Surfboard ............................................................................................................. 36

5.4.3 Squash Tail Surfboard ............................................................................................................ 37

5.4.4 Swallow Tail Surfboard .......................................................................................................... 37

5.4.5 Square Tail Surfboard ............................................................................................................ 38

5.4.6 Asymmetrical Tail .................................................................................................................. 38

5.5 Rocker ........................................................................................................................................... 39

5.5.1 Nose Rocker ........................................................................................................................... 40

5.5.2 Tail Rocker ............................................................................................................................. 40

5.6 Rails .............................................................................................................................................. 40

5.6.1 Curvier rail line ...................................................................................................................... 40

5.6.2 Straighter rail line .................................................................................................................. 41

5.7 Deck types .................................................................................................................................... 41

5.7.1 Dome deck ............................................................................................................................. 41

5.7.2 Flat deck ................................................................................................................................ 41

5.7.3 Step deck ............................................................................................................................... 41

5.8 Foil ................................................................................................................................................ 42

5.8.1 Nose Thickness ...................................................................................................................... 42

5.8.2 Middle Thickness ................................................................................................................... 42

5.8.3 Tail Thickness ......................................................................................................................... 42

5.9 Bottom contour ............................................................................................................................ 42

5.9.1 Flat bottom ............................................................................................................................ 43

5.9.2 Belly Bottom .......................................................................................................................... 43

5.9.3 Concave Bottom .................................................................................................................... 43

5.9.3.1 Single Concave ................................................................................................................ 43


Page | 11

5.9.3.2 Single to Double Concave ............................................................................................... 44

5.9.4. Channel Bottom .................................................................................................................... 44

5.9.5 Vee Bottom............................................................................................................................ 44

6. Fins ..................................................................................................................................................... 45

6.1 Fins configuration ......................................................................................................................... 45

6.1.1 Single fin ................................................................................................................................ 45

6.1.2 Twin fin .................................................................................................................................. 45

6.1.3 Thruster/Tri - fin .................................................................................................................... 46

6.1.4 Quad fin ................................................................................................................................. 47

6.1.5 Five-fin ................................................................................................................................... 47

6.1.6 2+1 fins .................................................................................................................................. 48

6.2 Fins’ properties and dimensions .................................................................................................. 48

6.2.1 Sweep (Rake) ......................................................................................................................... 48

6.2.2 Flexibility ................................................................................................................................ 49

6.2.3 Height (depth) ....................................................................................................................... 49

6.2.4 Cant ....................................................................................................................................... 50

6.2.5 Base ....................................................................................................................................... 50

6.2.6 Foil – section shape. .......................................................................................................... 50

6.2.6.1 Inside Foil ........................................................................................................................ 51

6.2.6.2 Flat Foil ........................................................................................................................... 51

6.2.6.3 50/50 Foil (symmetrical) ................................................................................................ 51

6.2.6.4 80/20 + 70/30 Foil (Asymmetrical) ................................................................................. 52

7. Composite materials in surfboards .................................................................................................... 53

7.1 Introduction .................................................................................................................................. 53

7.2 Production process ....................................................................................................................... 54

7.2.1 Contact molding .................................................................................................................... 54

7.2.2 Vacuum molding .................................................................................................................... 55

7.3 Fiber .............................................................................................................................................. 56

7.4 Ply ................................................................................................................................................. 57

7.4.1 Differences between isotropic and anisotropic material ...................................................... 57

7.4.2 Strength of the ply. ................................................................................................................ 61

7.4.3 Fractions in a ply. ................................................................................................................... 63


Page | 12

8. Sandwich structure ............................................................................................................................. 66

8.1 Properties and tests on the sandwich structure .......................................................................... 66

8.1.1 Stress – bending .................................................................................................................... 66

8.1.2 Buckling ................................................................................................................................. 68

8.2 Honeycomb .................................................................................................................................. 69

8.2.1 Honeycomb structure strength – ply .................................................................................... 70

8.2.2 Honeycomb structure strength – core. ................................................................................. 71

9. Cork material. ..................................................................................................................................... 73

9.1 Making cork. ................................................................................................................................. 73

9.2 Enhancing cork properties by addition of reinforcement materials ............................................ 75

9.3 Properties of cork ......................................................................................................................... 75

9.4 Differences in cellular materials ................................................................................................... 76

10. Tests of the boards. .......................................................................................................................... 78

10.1 Yellow egg shaped short board. ................................................................................................. 79

10.2 Short board ................................................................................................................................. 81

10.3 MSD hybrid fish tail board. ............................................................................................................. 82

10.4 Summary ........................................................................................................................................ 82

11. Designing process ............................................................................................................................. 83

11.1 CAD model. ................................................................................................................................. 83

11.2 Design improvement ...................................................................................................................... 84

11.2.1 Thickness optimization. ........................................................................................................... 85

12. Production analysis. ......................................................................................................................... 90

12.1 Cost of materials......................................................................................................................... 90

12.2 Cost of machining ....................................................................................................................... 92

12.3.Sanding cost ............................................................................................................................... 93

12.4. Price of the tools. ...................................................................................................................... 93

13. Prototype and redesign .................................................................................................................... 94

13.1 Testers ........................................................................................................................................ 94

13.1.1 Juan...................................................................................................................................... 94

13.1.2 Micheale .............................................................................................................................. 95

13.1.3 Joao ..................................................................................................................................... 95

13.1.4 Wiktor .................................................................................................................................. 95


Page | 13

13.1.5 Maciek ................................................................................................................................. 96

13.2 Redesign ..................................................................................................................................... 96

13.2.1 Design .................................................................................................................................. 96

13.2.2 Machining ............................................................................................................................ 97

13.2.3 Finishing ............................................................................................................................... 97

13.2.4 Taking out weight ................................................................................................................ 97

13.2.5 Glassing................................................................................................................................ 99

13.2.6. Finishing ............................................................................................................................ 100

13.2.7 Testing ............................................................................................................................... 100

14. Comparison of two models. ........................................................................................................... 101

14.1 Ecological impact. ..................................................................................................................... 101

14.2 CFD analysis .............................................................................................................................. 104

16.2.1. Results of the first board .................................................................................................. 104

16.2.2 Results of the second board .............................................................................................. 105

14.3 Stress analysis ........................................................................................................................... 106

14.3.1 Results of the first board ................................................................................................... 110

14.3.1 Results of the fish board .................................................................................................... 111

14.3.1.1 Large grain ...................................................................................................................... 112

14.3.1.2 Cork small grain .............................................................................................................. 113

14.4 Performance difference summary ........................................................................................... 114

14.5 Summary .................................................................................................................................. 114

References ............................................................................................................................................ 115

Equations

Equation 1 Stress/strain matrix for isotropic materials. [31] ................................................................. 59

Equation 2 Shear module. [31] ............................................................................................................... 59

Equation 3 Poisson ratio for anisotropic materials. [31] ........................................................................ 60

Equation 4 Elongation module depending on angle of the force. [31] .................................................. 60

Equation 5 Ultimate strength of a ply. [31] ............................................................................................ 62

Equation 6 UTS regarding on the direction of the force. [31] ................................................................ 63

Equation 7 Mass fraction equations. [31] .............................................................................................. 64

Equation 8 Volume fraction equations. [31] .......................................................................................... 64

Equation 9 Volume and mass fraction of fiber depending on the density. [31] .................................... 64


Page | 14

Equation 10 Shear and bending stresses. [31[ ....................................................................................... 67

Equation 11 Contribution of bending and shear. [31] ........................................................................... 68

Equation 12 Deflection. [21] .................................................................................................................. 68

Equation 13 Critical force for buckling. [31] ........................................................................................... 69

Equation 14 Sandwich composite beam strength. [30] ......................................................................... 70

Equation 15 Critical stress for intercell buckling. [31]............................................................................ 71

Equation 16 Shear stress for honeycomb beam. [31] ............................................................................ 71

Equation 17 Bending of honeycomb beam. [31] .................................................................................... 72

Equation 18 Stress appearing while crashing the honeycomb cells. [31] .............................................. 72

Tables

Table 1 Elongation and shear modulus and Possion ratio of different fibers. [21] ............................... 61

Table 2 Different fiber volume fraction, referring to the production process. [21] .............................. 63

Table 3 Ply's thickness, depending on the fiber and Mass fraction. [21] ............................................... 63

Table 4 Comparison of glass and carbon fiber properties. [21] ............................................................. 65

Table 5 Comparison of epoxy and polyester resin properties. [21] ....................................................... 66

Table 6 Cork Properties. [16] .................................................................................................................. 76

Table 7 Cost of the materials used in creating the surfboard. ............................................................... 90

Table 8 Price of the electric energy used in the shaping process. [33] .................................................. 92

Table 9 Costs of finishing the board. [33] .............................................................................................. 93

Table 10 Comparison of the influence of different holes types and shapes on deformation of the blank.

................................................................................................................................................................ 98

Table 11 Ecological impact of the first board. [35] .............................................................................. 102

Table 12 Ecological impact of the second (cork) board. [35] ............................................................... 103

Figures

Figure 1 Old Hawaiian shape boards (Olo on the left). [35] .................................................................. 20

Figure 2 Different parts of a surfboard. [36] .......................................................................................... 21

Figure 3 Hot curl board. [35] .................................................................................................................. 22

Figure 4 Bob Simmons riding a wave. [3] ............................................................................................... 23

Figure 5 Big swell in Teahupo’o. [27] ..................................................................................................... 23

Figure 6 Foam boards. [27] .................................................................................................................... 24

Figure 7 Cutback Surfboard shaping room. ............................................................................................ 25

Figure 8 Bruno from Cutback taking out first layers of the board with electric planer. ........................ 26

Figure 9 Tools used while shaping a blank from the left: Electric plane, Surform, Mini Planer (for the

stringer) , Sandpaper Block, Screen Sander. .......................................................................................... 27

Figure 10 Glassing in Freshline Surfboards workshop. .......................................................................... 28

Figure 11 Scheme of the fin boxes location for different surfboards and a fin plug. ............................ 29

Figure 12 Short board. [7] ...................................................................................................................... 31

Figure 13 Longboard. [7] ........................................................................................................................ 31


Page | 15

Figure 14 Fish. [27] ................................................................................................................................. 32

Figure 15 Hybrid board. [7] .................................................................................................................... 32

Figure 16 Collection of Gun boards. ....................................................................................................... 33

Figure 17 Pointed nose. [7] .................................................................................................................... 34

Figure 18 Rounded point nose. [7] ......................................................................................................... 35

Figure 19 Rounded nose. [7] .................................................................................................................. 35

Figure 20 Pin tail. [7] .............................................................................................................................. 36

Figure 21 Round tail. [7] ......................................................................................................................... 37

Figure 22 Squash tail. [7] ........................................................................................................................ 37

Figure 23 Swallow tail. [7] ...................................................................................................................... 38

Figure 24 Square tail. [7] ........................................................................................................................ 38

Figure 25 Asymmetrical tail. [7] ............................................................................................................. 39

Figure 26 Rocker. [38] ............................................................................................................................ 39

Figure 27 Board position on the face of the wave. [39] ......................................................................... 40

Figure 28 Different types of the rails. [40] ............................................................................................. 40

Figure 29 Dome deck. [40] ..................................................................................................................... 41

Figure 30 Flat deck. [40] ......................................................................................................................... 41

Figure 31 Step deck. [40] ........................................................................................................................ 41

Figure 32 Flat bottom. [40] .................................................................................................................... 43

Figure 33 Belly bottom. [40] ................................................................................................................... 43

Figure 34 Single concave. [40] ................................................................................................................ 44

Figure 35 Double concave.[40] ............................................................................................................... 44

Figure 36 Channel concave.[40] ............................................................................................................. 44

Figure 37 Vee concave.[40] .................................................................................................................... 45

Figure 38 Single fin.[41] .......................................................................................................................... 45

Figure 39 Double fin. .............................................................................................................................. 46

Figure 40 Thruster. ................................................................................................................................. 47

Figure 41 Quad fin system. ..................................................................................................................... 47

Figure 42 Surfboards with 5 fin boxes. ................................................................................................... 48

Figure 43 2+1 fin solution. ...................................................................................................................... 48

Figure 44 Sweep of a fin. [19] ................................................................................................................. 49

Figure 45 Depth of a fin. [19] ................................................................................................................. 49

Figure 46 Cant of a fin. [19] .................................................................................................................... 50

Figure 47 Base of a fin. [19] .................................................................................................................... 50

Figure 48 Inside fin foil. [19] ................................................................................................................... 51

Figure 49 Flat fin foil. [19] ...................................................................................................................... 51

Figure 50 50/50 fin foil. [19] ................................................................................................................... 51

Figure 51 Asymmetrical fin foil. [19] ...................................................................................................... 52

Figure 52 Contact molding - glassing. [7] ............................................................................................... 55

Figure 53 Vacuum molding surfboard.[43] ............................................................................................ 56

Figure 54 Ply. [21] ................................................................................................................................... 57


Page | 16

Figure 55 Comparison of deformation between isotropic and anisotropic materials - compression. [21]

................................................................................................................................................................ 57

Figure 56 Comparison of deformation between isotropic and anisotropic materials - tensile. [21] .... 58

Figure 57 Different stresses appearing in isotropic material. [21] ......................................................... 58

Figure 58 Different stresses appearing in anisotropic material. [21] ..................................................... 59

Figure 59 Direction of the force inside affecting fiber. [21] ................................................................... 60

Figure 60 Dependence of elongation module on angle of the force. [21] ............................................. 61

Figure 61 Tensile strength of different plies (the most important for this care are epoxy plies). [21] . 62

Figure 62 Sandwich structure.[21] ......................................................................................................... 66

Figure 63 Bending of sandwich beam (e.g. surfboard). [21] .................................................................. 67

Figure 64 Buckling. ................................................................................................................................. 69

Figure 65 Bending of honeycomb beam. [21] ........................................................................................ 70

Figure 66 Buckling in honeycomb cells. [21] .......................................................................................... 71

Figure 67 Bending honeycomb. .............................................................................................................. 72

Figure 68 Local crushing of the honeycomb cells. [21] .......................................................................... 73

Figure 69 Cork growing process. [15] ..................................................................................................... 74

Figure 70 Influence of cork density on its mechanical properties [45] .................................................. 75

Figure 71 Behavior of cork cells while applying a force. [practical exercise] ......................................... 77

Figure 72 Majority of the testing team. ................................................................................................. 79

Figure 73 Till testing the egg. ................................................................................................................. 79

Figure 74 Egg board. ............................................................................................................................... 80

Figure 75 Short board. ............................................................................................................................ 81

Figure 76 MSD fish tail............................................................................................................................ 82

Figure 77 Preferences of surfboard properties. ..................................................................................... 83

Figure 78 2D drawing of the first surfboard. .......................................................................................... 84

Figure 79 Surfboard mass depending on the thickness of core (ec) and ply (ep). ................................. 86

Figure 80 Buckling strength, depending on the thickness of core (ec) and ply (ep). ............................ 86

Figure 81 Algorithm for optimizing the minimum thickness.................................................................. 88

Figure 82 FEM analysis of beam model used in the optimization algorithm. ........................................ 89

Figure 83 Board used in the simulation. ................................................................................................ 90

Figure 84 CNC machine used to shape surfboard blanks. [34] .............................................................. 92

Figure 85 Cost of shaper work. ............................................................................................................... 93

Figure 86 First surfboard (PU). ............................................................................................................... 94

Figure 87 Ecological impact of each part of the first board. ................................................................ 102

Figure 88 Ecological impact of each part of the cork board. ............................................................... 103

Figure 89 Definition of the fluid for CFD analysis. ................................................................................ 104

Figure 90 Section of the model for CFD simulation. ............................................................................ 104

Figure 91 Fluid pressure over the first board. ...................................................................................... 105

Figure 92 Fluid speed over the first board. .......................................................................................... 105

Figure 93 Fluid speed over the cork board. .......................................................................................... 105

Figure 94 Fluid pressure over the cork board. ..................................................................................... 106

Figure 95 Definition of the composite layup. ....................................................................................... 107


Page | 17

Figure 96 Definition of epoxy/E glass ply. ............................................................................................ 107

Figure 97 Properties of EPS. [37] .......................................................................................................... 108

Figure 98 Tie constraint. ....................................................................................................................... 109

Figure 99 Force applied on the board. ................................................................................................. 110

Figure 100 Stress in the ply in the board ply. ....................................................................................... 111

Figure 101 Definition of cork properties (large grain). [37] ................................................................. 112

Figure 102 Stresses in the large grains cork board. ............................................................................. 112

Figure 103 Stresses in the fine grains cork board. ............................................................................... 113

Figure 104 Properties of small grain cork. [37] .................................................................................... 113


Page | 18

Section I

Surfing 101

1. Introduction

Surfing is not just a sport. It is a way of life which gives the freedom in action and in mind. By starting

it and treating it like a real passion, every person can achieve something which, in my opinion, cannot

be achieve by any other sport – complete fulfilment, relaxation and the deepest enjoyment. One can

forget any problems, by having a wholesome surfing session. This sport improves both physical and

mental condition, but also allows one to recognize any lacks in general wellbeing or fitness. It requires

to move and stretch not just while surfing but also after it.

I was always in love with water sports and I practice several of them. However, I have never found

anything as great as surfing. This is why I decided to connect my passion with my studies. In this thesis,

I am analyzing different ways of producing surf boards as well as visiting three local shaping companies

to understand what problems they may have and to find out possible solutions for them. After that, I

will present different types of surfboards and materials used to make them. I will also try to discover a

way to manage huge amounts of waste produced during surfboards production. In order to do this,

two surfboards will be made and many more will be tested.


Page | 19

2. History of surfing

2.1 History of the sport

Surfing is claimed to be one of the oldest sports on the planet [1] which may seem surprising for a lay

person. The art of wave riding is a mixture of different athletic skills associated with ability to appreciate

the beauty and power of nature. Surfing has created its own lifestyle and subculture, not only of people

who practice this sport every day, but also for many individuals who never tried it, yet enjoy spending

time at surf spots, listening to surf music and wearing surf clothes. [1]

Surfing was born in West Polynesia, more than three thousand years ago [1]. One of the first surfers

were fishermen, who were surfing as a way to return to the shore after fishing.

In some sources [14], it can be found that in 15th century kings and queens of the Sandwich Islands

(Hawaii) were training "he'enalu" which means wave sliding. “He’e” means melting the solid body and

“nalu” is the name of the movement on the wave [1].

In late 18th century, after first contact of Europeans with native Polynesians, Captain James Cook,

described Tahitian people catching waves with their canoe just for fun. "On walking one day about

Matavai Point, where our tents were erected, I saw a man paddling in a small canoe so quickly and

looking about him with such eagerness of each side. He then sat motionless and was carried along at

the same swift rate as the wave, till it landed him upon the beach. Then he started out, emptied his

canoe, and went in search of another swell. I could not help concluding that this man felt the most

supreme pleasure while he was driven on so fast and so smoothly by the sea”. The Three Voyages of

Captain James Cook Round the World (…)” [2].


Page | 20

The native Polynesians who arrived to

Hawaii islands hundreds year ago were

already familiar with surfing. They were the

ones who popularized the sport in that

region. At the beginning, it was practiced

only by the high class Hawaiians. Special

prayers, boards’ shapes were developed by

them and the hollowest waves were

reserved for them. Only they knew which

wood is the best to use for a surfboard.

Moreover, board shapers performed special

rituals while shaping them. After a chosen

tree was cut down, a fish was put in the

same place as a tribute for the ancient gods.

After that shaping process could begin. A

number of different shapes and sizes were

already known by the Hawaiian community:

- The paipo or kioe, a body board, 2-4 feet

long, usually used by children.

- The alaia (ah-LAI-ah), a mid-sized board, about 8 feet or longer.

- The kiko`o, larger than the alaia, between 12 and 18 feet; good for a bigger waves, but requiring

higher level of skill to handle.

- The olo (O-lo), a very long surfboard reserved for royalty, could be as long as 18-24 feet [1].

2.2 Raw Materials

The most common material for the core of the board is polyurethane foam. Polystyrene foam is also

regularly used material but it is not the one that most shapers prefer as it is harder to shape by hands.

Moreover, it reacts with polystyrene resin during glassing, so can be only used with epoxy. Stringer

(Figure 6) is usually basswood or redwood. It can be also made from PVC (Polyvinyl chloride) which is

cheaper. Stringer is not essential, and instead of it, an extra line of fiber e.g. carbon fiber can be used.

The paint can be put in different phases of the production process. It is possible to color the foam

Figure 1 Old Hawaiian shape boards (Olo on the left). [35]


Page | 21

before covering it with ply (outside layer of the board). Similarly, a colored fiber or resin can be used

(to color resin usually an acrylic paint is added to the mixture of resin and catalyzer). Fins are made by

plastic or resin covered by fiber glass. The fin boxes, ranging from one to five are placed on the tail of

the board [6].

Figure 2 Different parts of a surfboard. [36]

2.3 Surfboards history

2.3.1 The hollow board

In 1926, a major change was made when Tom Blake [3], one of the first notable surfers, constructed a

hollow board. It was made from redwood and had hundreds of holes drilled through it. The board was

15 feet long and weighed 45kg. At first, none of the Hawaiians appreciated his work until they saw how

fast it was in the water. Blake’s boards appeared to be a great success and started to be mass produced.

He was also the first person to use fins in the board which allowed for better stability and faster

maneuvers.

2.3.2 The Hot Curl board

In 1934, a group of local people inspired by Blake’s design [3], began to experiment with different

shapes of tail. They shaped the tail more rounded, which improved both the turning speed as well as

created a wider capability for more dynamic actions. The boards were called “hot curled” and the main

figures involved in the production process were Wally Froiseth, John Kelly and Fran Heath [1]. The board

allowed for riding on really steep waves and even for catching barrels (tubular waves). In 1940s, Balsa


Page | 22

wood from South America was claimed to be the best material for production of surfboards. Balsa

boards were made with several layers of varnish used for water protection. The weight of the board

decreased by over 60% in comparison with redwood ones. The significant decrease in weight was the

biggest step in surfboards design. The only problem was the accessibility of the Balsa wood in large

amounts. In order to satisfy clients, most of the mass production boards were made from a mix of Balsa

as a main material, which allowed lower weight and size, and redwood which was increasing durability

and was used on the rails, nose and tail. [5]

Figure 3 Hot curl board. [35]

2.3.4 Fiber glass boards

The end of the second World War opened new possibilities in design and production. While a lot of

new materials were developed during this time, fiber glass appeared to be the best one and was used

together with polyester resin or the first time by Pete Peterson in 1946. The board was molded with a

redwood stringer and sealed with fiber glass. In 1949 Bob Simmons [3], who was a well-known wooden

boards shaper at that time, made his first full “sandwich” construction board with polystyrene core,

encased in a thin layer of plywood with wooden rails and coated in fiber glass.


Page | 23

2.3.5 Commercial surfboards

In 1950s, the surf revolution started in California. Wooden boards were still popular and commonly

used, however, most of the people were moving towards the foam ones. Dale Vezy, one of the greatest

shapers [5] in mankind history, took his knowledge from old shapers and decided to improve their

creation. He made a “pig board” and a “sausage board”. His boards were renowned and in high demand

among the local surf society. Towards the end of the decade, polyurethane foam was discovered and

started to be widely used. Thanks to that and growing popularity of Hawaiian Islands, big waves surfing

got more popular and accessible. Guns, special boards to ride on big waves, were created. Casual

boards still were 9-11 feet long, however, that was going to change soon.

Figure 5 Big swell in Teahupo’o. [27]

2.3.6 The short board, twin fins and the surf leash

In the early 1970s, the first short boards were constructed. Due to the reduction in length to 6 feet,

these boards could be used to ride the pockets of the waves (the points where the wave is breaking),

and were therefore usually called the pocket rockets. Brewer, one of the shapers at that time, is claimed

to be the father of this invention. As it was discovered before, shorter boards were facilitating faster

turns and more aggressive surfing style. With the board, new fins combination [3] was invented. New

short boards were equipped with two fins which increased their speed and stability, but still allowed

surfers to slide easily. Shapers also started to pay more attention to the rails, bottom contour, height

Figure 4 Bob Simmons riding a wave. [3]


Page | 24

of the rocker and another parts of board. As a result, many experimental shapes were designed and

tested.

In 1966, Nat Young won the World Championships while riding a short board, which promoted the

shape and persuade most of the surfers to start to use one. The 1960-1970s were the times of many

more inventions. Fins became much more flexible and shapers moved from glassing fins directly to the

surfboards to removable fins in order to allow easier replacement in case of damage. In 1971, one of

the most important invention was made. The sons of Jack O’Neill, a wetsuit inventor, introduced the

very first surf leash. It made the life of surfers all around the world much easier. Moreover, it allowed

for the surfing sessions to be much longer due to the fact that surfers did not have to waste their energy

on swimming to catch the board after every wipe-out [4].

2.3.7 Three Fin Thruster

Three fins system was already used in some boards as an experiment for years, however, in 1981 an

Australian Simon Anderson designed the first three fin “thruster” board [3]. Using the best

characteristics of twin and single fin systems and combing them together, he designed a system which

allowed to control board even better. This system is still widely used nowadays. More information

about different fins combinations can be found in the further chapters of this paper.

2.3.8 Pop out and Foam boards

Pop out and foam boards, big volume boards used by the surf

schools for teaching, were design in the 1970s [3]. Learning on

these boards prove to be much easier, and because of that

surfing became more popular among younger and less sportive

people. Riding on these boards does not require maintenance

of a perfect balance. These boards make it possible to not only

ride the green waves (the waves before they break), but also

smaller ones as well as the white water – white foam, appearing

after a wave break.

Figure 6 Foam boards. [27]


Page | 25

3. Design and production of surfboards of surfboards

3.2 Shape

The shape of the board depends on the client preferences. All different shapes will be described in the

chapter 4. Diverse shapes are developed for varying weather conditions. Usually, professional surfers

have over 30 different types of boards. For each session, 5-10 boards will be taken in order to be

prepared to surf various weather conditions. There is also a significant contrast between the shapes

used by longboard riders, big waves riders and casual surfers, which will be described later in this paper.

Figure 7 Cutback Surfboard shaping room.

3.3 Start of the manufacturing process – shaping a blank

The manufacturing process does not vary much between a small, local surfboard company and a big

worldwide factory. In both type of companies, blanks are made from a mixture of liquid foam which is

evenly distributed into a mold. Obtained blank is a foam which is then shaped into a surfboard,

however, initially it is twice as thick, 1.5 times wider and usually 0.5m longer the final product in order

to be formed as desired by the client. The blank is ready within 20 min. Another possibility is to cut out

the blank from a big foam block (200x200x200 [cm]) [8]. The block is being cut with hot wire technology.

After that, the blank is formed by CNC machine or by hands.


Page | 26

Often, shapers order pre-shaped blanks from factories as they have a stringer already glued in them.

Even the most famous shapers in the world, use CNC machines to cut the outline of the blank and only

then make small corrections by hands. They design the surfboard using programs like Shape3D,

Akushaper or BoardCad.

Something to take into consideration regarding the process of blanks shaping, is that they are very hard

to recycle. However, recently companies like Reef began the campaign where they collect used foam

from surfboards, packages etc. and, in collaboration with Marko Foam, are transforming it into new

surfboards, using new, not widely popularized technologies[9].

Figure 8 Bruno from Cutback taking out first layers of the board with electric planer.

3.4 Stringer

Stringer (Figure 6) is a stripe of wood, glued to the blank of the surfboard, after it is cut in half (in case

of EPS – polystyrene blanks) from nose to tail. In PU, polyurethane, blanks, stringer is put by the blank

factory. Stingers provide additional stiffness and increase bending strength of the board, making it

more durable and maintaining its original shape.

3.5 Tools

Various tools are used during the different phases of boards shaping. After the blank has been cut out

by a CNC machine, a person specialized in board sanding corrects and adds the final touch by an electric


Page | 27

planner and other tools (Figures 8 and 9). Before this, the shapers draw a shape on the board with the

use of special measuring tools in order to measure how much material needs to be taken off the blank.

Those tools are mostly made of wood, however, nowadays younger shapers also use pre-cut shape

templates printed on paper. Following that, a planer is used for shaping the foam and a mini planer for

cutting out additional material of a stringer. Next, a small wooden block covered with sand paper and

screen sander are used for perfecting the details such as rails or the concave. All tools are showed on

the Figure 9.

Figure 9 Tools used while shaping a blank from the left: Electric plane, Surform, Mini Planer (for the stringer) , Sandpaper Block,

Screen Sander.

3.6 Laminating the outer shell

After obtaining a desired shape, glassing and laminating process begins. First, a layer of fiber glass is

put on the top of the surfboard. Usually, it is 2 layers of 4 oz/m2 fiber on the deck and 1 on the bottom.

The most common glass’ sizes are 4 or 6 ounce (452 g-678 g) per 1 m2. These are often used for

longboards or more durable ones, e.g. big wave boards [7]. This mixture of resin and catalyzer

(substance which helps in the solidification process) in proportion about 1:2 (100:48 [ml]) [10] is evenly

distributed over the board. Sometimes a hardener can be added which decreases the time of the whole

glassing process but also forces shapers to work faster. To clarify that, Bruno from Cutback boards has


Page | 28

just 8-10 minutes to glass the board and if he makes any major mistake, he may not have time to correct

it. Effective catalyzers are e.g. carboxylic acid, alcohols (phenols) and tertiary amines. Resin soaks into

the fiber and creates a shell during the polymerization process. Resin mixture of around 1.5 kg is used

for first layer at both the top and the bottom, and then 0.5 kg for the finishing on both sides?. Those

proportions are the recipe of Hugo from Freshline. On the other hand, according to Bruno, it is better

to use 1.2 kg for every short board and around 2 kg for longboards, trying to use as few resin as possible

in order not to create too much waste.

After the drying process, which usually takes about 24 to 30 hours, depending on the technique and

the amount of resin used, the board is turned onto the opposite side. A wet surfboard cannot be

touched, otherwise greasy stains and fingerprints will be visible on the board after the whole process

is finished [8]. For this reason, shapers flip the board in Latex gloves and put it on a rack which is secured

with plastic foil. Following that, the mixture of fiber and resin can be put on the bottom of the board.

After the mixture has dried, another layer of only resin combined with hardener is placed on the board.

This mixture is first added and left to dry on the top, and only then it can be placed on the bottom of

the board. This creates an additional layer which strengthens the ply. Normally the mixture which

remains after the glassing process is used in this step. This part takes about 3-5h [8]. Another possibility

is to perform this whole process inside a vacuum, in order to reduce the processing and drying time

and to distribute the resin and fiber evenly (more about vacuum molding 7.2.2).

Figure 10 Glassing in Freshline Surfboards workshop.


Page | 29

3.7 Fin boxes

The fin boxes are placed during the shaping process before glassing. After determination of their

location, the spaces around fin boxes are sanded. At the same time, a small hole is drilled into a deck

on the tail and a leash box is put there.

Figure 11 Scheme of the fin boxes location for different surfboards and a fin plug.

3.8 Sanding the board

After placing the last layer of resin, each board has to be sanded to make it smoother and take out

overlapping fiber layer. This step does not require a lot of work and is usually performed with very thin

sand paper.

3.9 Quality Control

The quality is not usually checked in small surf companies. However, in the bigger ones dimensions of

the board can be check by e.g. a coordinate dimension measuring machine. Shapers, who shape by

hands or with the help of CNC machine, check the dimensions before glassing. Some of them do it

throughout the whole production process, while others check it after the shaping process is completed,

and only then they apply any necessary corrections. Bruno and Hugo check the thickness with a very

simply device (Fig. 9). The width and the length are measured with wooden or paper shape, prepared

or printed. The shape is being put patrilinear to the stringer and this shows how much material is still

needed to be taken out [7] [8].


Page | 30

3.10 Toxic materials and safety considerations

Some of the materials used in the process are hazardous for human’s health. Necessary safety

equipment, such as protection googles and mask, should be used at every step of the process.

Unfortunately, it is often not utilized. Polyurethane foam contains chemicals which can seriously

damage the respiratory system [41]. Especially while shaping and sanding, a lot of dust and powder is

constantly breathed in by the shaper. The blank by itself should be made in the explosion proof

environment due to fumes of polyurethane liquid which are easily explosive. Moreover, appropriate

humidity and temperature should be provided to ensure optimal setting for production. Additionally,

the room for glassing is needed to be ventilated since resin is vaporizing and its fumes are poisonous.

The materials such as foam or resin are hard to recycle and, unfortunately, usually are not. The main

effort made by the shapers I met is to keep everything closed, meaning not letting resin spread all over

the place, have a special vacuum over the CNC machine, which collects the foam powder ect, in order

to be able to collect and throw away all the trash, not leaving anything behind.

4. Different types of surfboards

4.1 Short board

Short boards – known as performance boards. They are one of the most commonly used all over the

world. Most of the pro surfers are only riding short boards while they are competing. Their shape allows

for very vertical riders, going up to the lip of the wave and even flying in the air [12]. They are usually

characterized by big rocker which causes a loss of speed unless surfer is constantly turning or going up

and down (pumping). In which case a very high speed can be achieved. While riding short boards, surfer

should stay at the top of the wave for a longer time waiting for an appropriate moment to perform a

suitable maneuver. Short boards are usually thin and not as wide as fish boards. Since less material is

used for them, they are also more fragile e.g. than longboards.


Page | 31

Figure 12 Short board. [7]

4.2 Longboard

Longboard is, as the name suggest, a long board

normally used for rather not too steep waves. It is

much more stable than a short board, however, is not

simple to ride on. To maneuver on a board like this,

surfers are forced to walk to the front when they

want to speed up or to the back when they want to

either turn or slow down. In opposite to short boards,

longboards are not ridded from rail to rail but most of

the time it is sliding on the whole bottom surface [14].

The design is usually called “egg shape”, however, the

tail can also be square or even pin (information about

different parts of surfboards can be find in the next

chapter). The number of fins depends on the model

and costumer’s preference. The most common

systems are a single fin or 2+1, which means one big

fin in the middle and two 2-3 times smaller ones on

the sides. The length of a longboard varies between 8- Figure 13 Longboard. [7]


Page | 32

12ft but the most popular ones are between 9 and 10 [11]. Much more material is being used for these

boards – more resin mixture and fiber glass. Moreover, fiber glass cloths, which are used in building

longboards, are normally 6oz not 4oz like in short boards [12]. This variation makes them more durable

but also much heavier.

4.3 Fish

The fish board is quite similar to the short board but it is

wider and thicker. What makes the biggest difference is

that the fish tail is actually two separate pin tails. Rocker

is flat or sometimes almost non-existent. Most common

fin combinations are double fin or 3 to 4 twin systems

[13]. Fish boards are amazing for small, mushy waves.

Flat rocker and fish tail allows to keep the speed and get

the wave much earlier than on a short board. The

swallow tail provides both stability and good

maneuverability. It is not as easy to accelerate as on the

Fish board due to a lack of rocker which makes it harder to perform vertical and more aggressive moves.

Nevertheless, the fish board is very good for tight turns [14].

4.4 Hybrid surfboard

Hybrid board is a board whose design combines both short board and fish. It provides high performance

abilities as short board, but it is wider and has thicker rails and tail as a fish [16]. The nose can be pointy

or round, however, it is still much smoother than in short boards. Bigger volume of the hybrid boards,

compared to that of short boards, helps

with catching waves much earlier and

surfing well through flat sections of the

water. Greater width provides stability.

Another hybrid is an egg-shaped short

board. It looks very similar to longboards

but it is shorter e.g. 5’6 long. People are

often afraid to buy or surf such boards, Figure 15 Hybrid board. [7]

Figure 14 Fish. [27]


Page | 33

but it is very stable, perfect for small waves and much convenient for traveling and transportation

purposes. Due to higher volume hybrid boards are achieving a desired speed much quicker and do not

lose it as rapidly as short boards [16]. They can ride vertically, however, due to a very small rocker it is

quite hard to perform air tricks on this boards.

4.5 Gun

Guns are the boards which are designed for big waves (over 4-5 m) [16] and most of surfers do not

need one. They are usually between 6.5 – 10 ft long. They are thicker in order not to start to vibrate

during high speed. They are very narrow in the

nose and usually pin tail is used on the back.

This kind of construction gives the possibility

for the rails to have better contact with the

wave. It is happening that the Gun is designed

for a specific big wave type which appear on

the spots as Maveric or Jaws or Nazare.

The drop is completely vertical (sometimes up

to 10-20 m) and after that surfer has to stand

up on the board as fast as possible, sometimes

while flying. The board has to provide the high

speed and prevents of losing it.

5. Different parts and dimensions of surfboards

5.1 Length

Stability, paddling power and speed loss depend on length of the board. The longer the board is, the

more stable it gets and surfers can lie down and paddle comfortably on it. Also the greater length

prevents from putting legs into the water and dragging them behind while surfing, which decreases the

speed due to increased resistance area. On the other hand, it increases volume and usually the total

mass of the board, making it harder to manipulate. The shorter the board is, the easier it turns. For

more professional surfers it is not a problem to lie down as they feel stable and paddle on a short board.

Figure 16 Collection of Gun boards.


Page | 34

Their legs are usually close together and placed just above the water surface, while the hips or knees

are placed on the tail of the board [14].

5.2 Width

The width of a board is measured at its widest point. Increment of it, raises bottom surface and provides

stability while sliding. At the same time, it makes it harder to ride from rail to rail. That is why the most

of professional surfers’ boards are thinner. The width affects the size of the channels in the concave

and the size of the bottom curve which is one of the most important in the design. The placing of the

widest point has also very important effect on the board’s performance. If the board is designed to

accelerate quicker and is destined for bigger waves, the widest point should be placed around the

center, more towards the nose. If a board is made for smaller waves, the widest point should be placed

more in the back.

5.3 Nose

The nose is the front part of a surfboard. It has the biggest impact during the drop and duck dive (diving

under the waves). The most common nose shapes are as follows.

5.3.1 Pointed Nose

The most common shape of nose is the pointy nose. In this type, the rails are more curved off the plan

shape if compared to a round nose. This helps dropping into steeper waves and makes a notable

difference when it comes to duck diving since pointy nose requires smaller force to put it under the

water [15].

Figure 17 Pointed nose. [7]


Page | 35

5.3.2 Rounded Point Nose

This shape is a transition state between pointed and rounded nose. Commonly seen in fish boards. It

adds extra volume in the front and helps catching flatter waves. Moreover, it gives more stability and

makes it easier to balance [16]. These boards are harder to maneuver but duck dive is still relatively

easy.

5.3.3 Round Nose

The round nose provides bigger volume at the front of the board and allows catching waves much

earlier than with pointy nose. It is commonly used in longboards due to necessity of walking to the front

and back while surfing [14]. Round noses makes it easier to paddle because they do not go underwater,

which is causing slowing down and losing balance, very easy.

Figure 18 Rounded point nose. [7]

Figure 19 Rounded nose. [7]


Page | 36

5.4 Tail

Tail is the back part of the board. Different shapes of tails have an influence on the stability and speed

of the turns. Some of them are better for steep waves while other ones perform much better while

tube riding. The most common shapes are as follows.

5.4.1 Pin Tail

Pin tail is usually a part of big wave boards – guns. It provides better stability on the waves. Pin tails are

very narrow. Thanks to that, it allows a board to sink into the water, causing it to ride stably into desired

direction. The shape of the tail is a straight line converging into a point. This design gives maximum

water flow although is not ideal to perform fast and aggressive maneuvers [16]. Moreover, it is usually

designed for bigger waves and is not going to work well on smaller waves. This is because riding smaller

waves requires a lot of pumping and turning in order to maintain the speed, while in big wave riding it

is essential to have a maximum control in a high speed [16].

Figure 20 Pin tail. [7]

5.4.2 Round Tail Surfboard

That shape allows water to go around its contour which gives better traction and speed in the steep,

big waves [15]. It is universal and has a wide range of condition in which it can be used. It increases the

surface area in the tail which gives better floating and results in good maneuverability. It is commonly

used on the tubular waves since it allows quick acceleration [16]. Turning with this tail is smoother then

with squashy or square tail.


Page | 37

Figure 21 Round tail. [7]

5.4.3 Squash Tail Surfboard

This is a square tail with smoother corners. This shape allows quick change of a rail and makes a board

very responsive to surfer’s moves. The shape adds more width to the board in the tail which eases the

speeding and makes it prefect for smaller, not very fast waves. Rounded edges at the corners provide

more control while turning. The squash tail is the most universal one, and that is why it is being chosen

most frequently by different shapers [16].

Figure 22 Squash tail. [7]

5.4.4 Swallow Tail Surfboard

The swallow tail (commonly called “fish”) is an assembly of two pin tails. They give the board more hold

and traction. The “V” which is cut out in the tail allows better flow of the water under the board as well

as smooth turns [15]. Due to that shape, volume and surface area of the tail are increased which makes

the maintenance of the speed through flat sections of a wave easier [15]. This tail can be use in hybrid

or fish boards. In fish boards the cut is much deeper which makes it harder to change between the rails,

however, it makes the board more stable.


Page | 38

5.4.5 Square Tail Surfboard

This tail is the oldest one used in surfboards’ design. It is wide and provides extra stability [15].

However, extra width causes less curvature of the rails. Due to its sharp corners, the board digs into

waves very easily and can make pivotal turns quicker than with smoother corners. Normally used on

the longboards, but it is possible to see them in short boards as well [15].

Figure 24 Square tail. [7]

5.4.6 Asymmetrical Tail

Asymmetrical tail is used just in the custom shape boards and can be a combination of several different

tails. It can be made for specific point breaks (surf spots, where the wave breaks due to ‘meeting’ an

obstacle on its way e.g. reef, big underwater rock formation) occurring in a particular surfing spot where

it is only possible to ride a wave in one direction (e.g. right). In that case, more stability is going to be

added on the chosen side as the drop is going to happen only there. Asymmetrical tail shapes are

usually experimental and not commonly used.

Figure 23 Swallow tail. [7]


Page | 39

Figure 25 Asymmetrical tail. [7]

5.5 Rocker

Figure 26 Rocker. [38]

Rocker is the bottom curve seen from a profile of the board. It stars at the tail and goes up to the nose.

The most important reason of this curve is fitting a board to the wave profile so that it can adhere well

to the surface of the water. The size of the rocker and its length will affect the turning ability of the

board. Boards with bigger rocker are allowed to turn with smaller radius and are better for hollow

(tubular) waves. It is most commonly used in short boards. Small and flat (low) rocker is common in fish

and longboards and provides good speed without an easy of losing it. More surface is fitted by the nose

and tail as it is smooth and wide rather than pointy and thin [15].

In the Figure 27 it can be seen how different angles of the rocker are going to influence the contact of

the board with a face of the wave. After analyzing the picture, it can be concluded that steeper waves

are easier to surf with board which has a bigger rocker, while the smaller rocker boards are better for

flatter waves [28].


Page | 40

Figure 27 Board position on the face of the wave. [39]

5.5.1 Nose Rocker

Nose rocker is designed to prevent surfers from digging the water with their board’s nose and to help

them with a bottom turning on steep waves. Only a very small part of the board’s surface adheres to

the waves [22].

5.5.2 Tail Rocker

The tail rocker is designed to help make deep turns and change directions very quickly. Thanks to that,

the rocker is easier to drop later and do not dive into the water allowing the pointing of the nose up in

the air [22].

5.6 Rails

The line of the rails gives ability to “cut into the wave” as well

as have influence on the radius and speed of turns and

maneuverability. As seen in Figure 28, there are many

combinations between these two main types.

5.6.1 Curvier rail line

Round rail line allows going deeper into face of the waves and

provides more acceleration out of the turns. Due to this shape,

the board has higher volume and allows surfers for better

floatation. Because of smoother shape, the resistance force of

the water is smaller and changing of the direction is easier [16].

The more round the rail is, the easier it is to change directions,

however, it becomes harder to keep it going straight ahead.

Figure 28 Different types of the rails. [40]


Page | 41

5.6.2 Straighter rail line

Often used with long boards or guns [28]. Provides higher speed and control while going fast [16]. A

board loses ability to turn quickly and deeper turns are required in order to change direction. This type

of design provides greater surface area for contact between surfboard’s bottom and face of the waves.

Better stability is gained, however, a lot of speed is lost while turning.

5.7 Deck types

Different shapes of the deck have influence on the shape of its rails and volume of the board. Most

popular ones are as follows.

5.7.1 Dome deck

The most common deck type which is used to add more volume to the board. Reduced size of the rails

make the board easier to cut into the wave which helps in quick maneuvers.

Figure 29 Dome deck. [40]

5.7.2 Flat deck

Flat deck is more round. Volume is added to the top and rails. With an increase of these dimensions,

the board will get thicker and will be hindered from cutting into the wave’s face. This can be a

disadvantage, however, it definitely adds to a greater stability of the board.

Figure 30 Flat deck. [40]

5.7.3 Step deck

When thinner rails are needed, usually step deck is chosen. This type of deck is made to gain more

paddling power and amortize the surfer after landing from the tricks [27].

Figure 31 Step deck. [40]


Page | 42

5.8 Foil

The foil is the name for the thickness distribution of the board. It describes where and how much foam

is placed in each section of the board. The three main parts should be consider: nose, middle and tail.

Greater thickness eases paddling and catching waves. It also keeps the speed of the surfboard while

riding through flat areas of the wave. However, too much thickness can hinder riding and makes it

harder to maneuver quickly.

5.8.1 Nose Thickness

Foil in the nose part has an essential influence on turns. If the nose is thinner, it is easier to turn quickly,

however, if it is too thin, it will sink into the water, causing a surfer to fall off the board. On the other

hand, too much foil in the nose can cause the board to slide and drift out of control.

5.8.2 Middle Thickness

The biggest thickness is usually located in the midsection and it is between 2 ¼” to 3 ¼” for all board

types [16]. The thickness should be adjusted to each surfer separately. Those with higher bodyweight

should search for something thicker while those with lower bodyweight should choose thinner boards.

Thinner boards will turn with smaller effort. Too much thickness can cause too much resistance

required to lean on boards edges, therefore surfers with lower bodyweight and less strength may find

such boards impossible to manipulate.

5.8.3 Tail Thickness

Increment of the board thickness will provide better paddling and will decrease the force needed to

accelerate as a result of an increase in flotation. It will not lose the speed on the flat areas, but it will

be harder to perform quick turns and bottom turns.

5.9 Bottom contour

The shape of the bottom have a big influence on the stability and flow of the water under the board.

While directing water flow under the surfboard, it will affect its turning and acceleration abilities. It is

important to understand that in most of the surfboards, bottom shape is not constant. It changes while

moving from the nose to the tail. The most popular shape is a single to double concave, which means

that a board has a single channel from nose to the middle and then it smoothly goes into double one.


Page | 43

5.9.1 Flat bottom

Flat bottom is designed mostly for beginners’ boards or big wave surfing due to difficulty of making

turns on the rails. It provides best contact between the wave and the board which makes it quick and

very responsive to surfer’s manipulation.

Figure 32 Flat bottom. [40]

5.9.2 Belly Bottom

This kind of bottom is usually placed in the nose’s part of the board, up to 1

3 of its length. This shape

“cuts” the water and allows better and smoother turns, making it easy to go from rail to rail in fast

surfing. It is used for bigger waves (2-3 m) where getting the speed is not so hard and control is a more

important property. However, this is not the fastest type of the bottom shape. The acceleration is not

as quick and it is rather easy to loose speed, which can be challenging especially for beginner surfers.

Figure 33 Belly bottom. [40]

5.9.3 Concave Bottom

Concave bottoms increase pressure of the flow of the water under the board, causing it to lift and

decrease dragging. Water is being squeezed out towards tail which makes acceleration through turning

very simple. This shape should be used on smooth, glassy waves. With choppy face of the wave, it is

not going to perform so well.

5.9.3.1 Single Concave

Usually used in big, clean waves. Most of the single concave bottoms are flat 1-2” from the nose or

have a slight “V” shape. Towards the middle a single concave starts to appear, first very shallow, going

slowly deeper and deeper until the first two fins and then gradually going flat again towards the tail.

Single concave bottom allows very tight turns. However, sometimes it may stick to the wave too much

causing loss of traction and maneuverability. That is why single to double concave is more popular

nowadays.


Page | 44

Figure 34 Single concave. [40]

5.9.3.2 Single to Double Concave

Usually single to double concave means single concave structure up to approximately middle of the

board and double concave, gradually going deeper, from that place until the tail. Single concave at the

front gives nice drive and good stability when going on the rail. Double concave will divide the stream

of the water into two streams which goes through the fins out in the tail. In short boards this type of

concave provides loose feel of the board and a good speed associated with control of traction.

Figure 35 Double concave.[40]

5.9.4. Channel Bottom

This type of bottom shape is different for each board. It provides even number of channels around the

main middle one (between 2 and 8). They propel bigger amounts of water throughout the board,

speeding it up without losing control.

Figure 36 Channel concave.[40]

5.9.5 Vee Bottom

Vee shape is usually placed towards the back 1

3 of the board. Like in belly bottom shape, the middle

works as a balance point while changing rails. As a result of the shape being moved towards tail’s

direction, tail is extremely responsive. Energy is lost very easily when water is parted and goes out from

the rails. It makes the shape not effective on smaller and mushy waves. However, with big and clean

waves this shape will work perfectly.


Page | 45

Figure 37 Vee concave.[40]

6. Fins

6.1 Fins configuration

Fin configuration have a very big influence on the board’s performance, speed and drive. Most common

fin configuration is thruster system – three fins with approximately the same size but different cant. In

longboards it is more common to use 2+1 or single fin system. While double fin system is commonly

used in fish boards, especially old-school ones where fins were glassed directly to the board.

6.1.1 Single fin

Single fin is the most common configuration in longboard. Turning is limited but it is perfect with fast

and forward movement. It makes maneuvers of the board more predictable, longer and smoother. Fin

box as well as the base of the fin are longer. It is the best to use it in small waves (up to 3-4ft). With

bigger waves, a single fin should be accompanied by 2 smaller fins on the sides if possible (see 2+1 fins).

Figure 38 Single fin.[41]

6.1.2 Twin fin

The twin fin system is good for improved maneuverability. Turning one of the fins will act as a pivot

point and because of the lack of the middle fin, the board will go exactly where the surfer directs it.

This configuration is claimed to be a very fast one, mostly due to the lack of a middle fin which usually


Page | 46

causes drag, however, this makes the board slightly slower. While using only 2 fins, board is more

unstable and can spin while performing deep bottom turns with great speed. It can slide easily which,

depending on the type of performance, can be advantage or disadvantage. It works best with clean,

non-tubular, waves up between 1-6 ft. Riding the barrel requires better traction and control and

without it the board can slide unexpectedly, causing fall and heavy wipeout. If surfers have possibility

to use just twin fin in their boards, they should use this configuration to see how performance of the

board changes. Twin fins are bigger than 2 front fins from 3 fins set. They have a greater depth, bigger

surface and base.

Figure 39 Double fin.

6.1.3 Thruster/Tri - fin

The most common fin configuration nowadays which can be found with various surfboard shapes and

sizes is the thruster. The straight fin on the back with 90° cant is supported by two fins on the opposite

sides, closer to the front, with slightly bigger angle but with the same size. They are both stable and

quite fast. Fins on the sides help to accelerate while pumping (turning left and right, up and down

rhythmically). It also gives opportunity to ride in twin fin configuration.


Page | 47

Figure 40 Thruster.

6.1.4 Quad fin

Quad fins offer higher speed by directing stream of water to the tail of the board. This is the best

configuration for surfers who prefer higher stability while surfing bigger waves and generate good drive

through turns.

Figure 41 Quad fin system.

6.1.5 Five-fin

Five fin configurations are not meant for surfing with all five fins in place at the same time. Five fin

boxes allow you to mix and match fins depending on your preference and the surfing conditions. It

allows for the freedom of a twin fin, to the traction of a thruster, to the speed of a quad without

changing boards.


Page | 48

Figure 42 Surfboards with 5 fin boxes.

6.1.6 2+1 fins

2+1 is used for egg shape board, stand-up paddle boards or sometimes longboards. The big middle fin

is supported by 2 smaller fins on the opposite sides. It helps to turn and provides better control during

fast turns.

Figure 43 2+1 fin solution.

6.2 Fins’ properties and dimensions

6.2.1 Sweep (Rake)

The sweep is the angle between fin and Z axis. The curve of the fin in relation to its base is measured.

The smaller the rake is, the better acceleration it provides. Smaller sweep is also more stable but do

not work very well with sharp turns. Fins with lager rake allow for tighter turns with smaller radius [19].


Page | 49

Figure 44 Sweep of a fin. [19]

6.2.2 Flexibility

Stiffness or flexibility is one of the most important properties of the fin. It makes a huge difference

during turns with a high speed [17]. The biggest influence of that property is the material of which the

fin is made. It is usually resin reinforced with fiber or carbon glass (the second one is only used in the

production of more expensive fins) [19]. More flexible fins provide nicer feeling of the board and makes

riding very fluent. More rigid fins are great for higher speed and faster moves [19]. The best fins are

made with a fine balance between flexibility and stiffness because if they are too stiff, they can break

or break the fin base. Moreover, different flexibility can be applied in different parts of a fin. Usually

they are more rigid near the base and softer at the tip due to the grater thickness in this part of the fin.

6.2.3 Height (depth)

Depth of a fin is measured from the bottom of the board (base) to the highest point of the fin. This

property changes the stability of the board and its grip during curves. Fins has depth from 10 (small

ones) to 12 cm [19]. The deeper the fin, the easier it is to control and handle a board during the turns.

Shorter fins do not provide a very good grip, however, this is sometimes desired in order to successfully

perform sliding and snaps (tricks) as the fins need to go out from the water as part of the maneuver.

Short fins can also cause spinning while turning without pressing on a tail with too much force.

Figure 45 Depth of a fin. [19]


Page | 50

6.2.4 Cant

Cant is a deflection of the fin in relation to the surfboard’s base. If it has no cant, it means it is at 90°

which makes a board ride faster, however, it is not as responsive for turns as with greater angle [19].

Increase of the angle shortens the time of the reaction between surfers’ actions and boards’ reactions.

To sum up, bigger cant provides bigger maneuverability and smaller one – higher speed.

Figure 46 Cant of a fin. [19]

6.2.5 Base

It is length of the edge which sticks to the surfboard bottom. Base is directly linked with a drive and

stability. Longer base provides better drive and acceleration [19].

Figure 47 Base of a fin. [19]

6.2.6 Foil – section shape.

The foil, which is the shape of the fin’s section area (as shown in figures 48 - 51) has a major influence

on the fins’ performance. It determines the water flow on the surface of the fin and affects the

properties such as hold, release or speed. In the picture, it can be seen, how the different foil shape,

influences turn radius, making it bigger or smaller.


Page | 51

6.2.6.1 Inside Foil

Figure 48 Inside fin foil. [19]

− the main difference is the concave shape of the inside of the face

− allows surfers for better hold and lift while significantly reducing drag

− reduces speed lost during the turns [19]

6.2.6.2 Flat Foil

Figure 49 Flat fin foil. [19]

− created for quick and aggressive turns, usually used by advanced surfers

− combination of drive, pivot and hold [19]

6.2.6.3 50/50 Foil (symmetrical)

Figure 50 50/50 fin foil. [19]

− symmetrical fin is usually used in a single fin system and sometimes in quad ones

− they provide even water flow, make turn a slower and longer but with very good stability [19]


Page | 52

6.2.6.4 80/20 + 70/30 Foil (Asymmetrical)

Figure 51 Asymmetrical fin foil. [19]

− asymmetrical one is usually used in a quad fins system,

− provides both stability and ability for control fast, deep turns [19]


Page | 53

Section II

Materials

7. Composite materials in surfboards

7.1 Introduction

At the beginning of this part one question should be answered: Why are the composite materials the

most commonly used in production of surfboards?

Composites have very high corrosion resistance connected with very light weight. Low production and

maintenance costs are another big advantage. Composite replacement of any metal is much cheaper

and lighter than its pure form. Naturally, their ultimate strength is different, however, the fatigue is

similar [21]. These characteristics made the composite materials more popular than e.g. wood.

Boards are usually made from composites materials when polystyrene or polyurethane foam is a base.

A foamy blank is usually covered with:

− Different fiber type as a reinforcement,

− Different resin type as a matrix.

Depending on the type of foam is being used, appropriate resin is chosen. With polyurethane foam

both polyester and epoxy resin can be used. However, it is necessary to remember that polyester resin,

even though it is the most favorite one within the surfing community, bonds very poorly with any fiber

different than fiber glass [20]. Moreover, it is impossible to use one with polyester foam due to


Page | 54

chemical reaction which occurs between them and cause the polystyrene foam to melt. That is why a

lot of shapers and surf board companies, stopped to produce polyester boards and focused just on the

epoxy ones. Epoxy bonds much better with carbon, Kevlar or woven fabrics. Working with epoxy is also

easier and much more pleasant due to lack of irritating smell produced by polyester resin. There is also

a difference in price. Epoxy resin is the most expensive one while the polyester is the cheapest [10].

The biggest difference in the product itself is that polyurethane surfboard is heavier, due to the density

of the foam and more common for these types of boards, wooden stringer. Surfers are saying that

“they don’t feel so well the board” when it is epoxy. What they mean is that the board is harder as well

as reacts slower while performing some turns and evolutions. On the other hand, epoxy is much more

durable so for beginners and schools these boards are usually the choice.

7.2 Production process

There are many different ways to produce and process composites. However, when making surf boards,

it is a sandwich structure which is a desired end-product. There are two main ways of composites

production used in surfboarding industry:

− Contact molding – used usually by higher quality brands or smaller surf shapers,

− Vacuum molding – used usually at a high volume manufacture level (mostly lower quality

boards, such as Torque).

7.2.1 Contact molding

Contact molding is the process most commonly used by the best shapers all over the world. In each

surf factory, there is one person or a team specialized in contact molding, which in surf industry is called

glassing. Layer of fiber is being put on the board, and after that a specified amount of resin is placed on

top of it. Materials are bounding during polymerization process.


Page | 55

Figure 52 Contact molding - glassing. [7]

7.2.2 Vacuum molding

Vacuum molding is very similar to contact molding performed under pressure. Due to this more resin

can be applied and bound with fiber glass. It is much simpler than in other industries. After putting the

layer of fiber glass on the foam core, both parts are covered with special plastic layer and resin with

hardener are injected. Following that, the air is being sucked out and resin mixture is being distributed

evenly all over the board. This method is not used by most of the shapers since it does not require

much knowledge about the amount of material which is inserted there. The materials polarize under

pressure and sometime UV light or increase temperature. This method has an advantage over contact

molding in time and air bubbles elimination, however, it is claimed to be less professional and precise

as parts of board, such as concave or rails, end up in poorer shape. However, this method is widely used

in production of windsurf boards or high volume surfboard production. Why this method is not

commonly used in the higher quality brands? When each board is different is harder to specify an exact

amount of resin needed for glassing and due to this, a lot of shaper used contact molding to be able to

control it (add or subtract a resin from the board), what is impossible in the vacuum molding.


Page | 56

Figure 53 Vacuum molding surfboard.[43]

7.3 Fiber

It is a material which is made of several thousand filaments, each one 5-15 µm in diameter [24], which

allows them to be processed on a textile machine. Because of that, the filaments and final product

fibers should be as thin as possible. Moreover, decreasing diameter increases rupture strength of fiber.

The small diameter allows to bend fibers until they reach small ratio of curvature. The most popular

fiber for surfboards is invariably glass fiber. In more expensive models we can also find elements of

Kevlar or carbon fiber as a reinforcement on the rails or tail. Stringer can be just a line of carbon fiber

at the middle of the board. There are also some experimental models which uses woven fiber as carbon

and glass fiber, are used in the board (e.g. Lost surfboards) [25]. Generally full carbon boards are rarely

seen in the water as most of the surfers prefer less stiff boards, which are cheaper in production and

maintenance.

Lately, due to marihuana legalization and ecological trend natural hemp fiber started to be used in the

production. It is said to be stronger and more flexible than fiber glass. During production of these kind

of boards, usually eco resin and foam is applied, which makes the board almost 100% recyclable, and

hence the product does not cause any major harm for the environment [26].

Filaments in a fiber can be oriented in various ways:

− unidimensional,

− bidimensional,


Page | 57

− tridimensional.

7.4 Ply

Ply is the name for a mixture of resin and fiber. In this chapter properties of it will be presented.

Figure 54 Ply. [21]

7.4.1 Differences between isotropic and anisotropic material

Since ply can be anisotropic or isotropic material it should be explained how both of these materials

behave under applied stress. The most common material used in board construction is still fiber glass

which is isotropic. New, more durable material which is unidimensional is carbon fiber [21]. First

difference can be observed while compression test (Figure 55) While isotropic material is going to

deform coincidently with axes (left), noticeable differences can be seen in anisotropic material (right).

Figure 55 Comparison of deformation between isotropic and anisotropic materials - compression. [21]

The same thing happens during tensile tests on these two types of materials (Figure 56)


Page | 58

Figure 56 Comparison of deformation between isotropic and anisotropic materials - tensile. [21]

To understand it better strain stress matrix for both cases should be analyzed. First, in isotropic material

strain in both directions of axis is symmetrical and if applied forces are equal, deformation also will be

equal. This is presented on the model and then described in the stress – strain matrix equation (Figure

57 and Equation 1) [21].

Figure 57 Different stresses appearing in isotropic material. [21]

While considering anisotropic material difference can be observed quickly. First of all, it is asymmetrical

which creates 4 different constants in the equation (Figure 58) [21].


Page | 59

Figure 58 Different stresses appearing in anisotropic material. [21]

Equation 1 Stress/strain matrix for isotropic materials. [31]

Since the constants are not symmetrical they have to be calculated, depending on the material and

direction of an applied stress.

Shear modulus G is hard to calculate and it is usually determined experimentally. However,

approximated value can be achieved from the Equation 2 [21]:

Equation 2 Shear module. [31]

The Poisson coefficient shows difference between elongation in different axis and for anisotropic plies

can be approximated by [21]:


Page | 60

Equation 3 Poisson ratio for anisotropic materials. [31]

Elongation module can be calculated for any values, knowing angle between filaments and force as well

as properties of the material. Angle θ (figure 59) and force direction are defined by c and s where c=cosθ

and s=sinθ [31].

Equation 4 Elongation module depending on angle of the force. [31]

Figure 59 Direction of the force inside affecting fiber. [21]

Fiber is usually applied in variably oriented layers, mainly -45o,0o, +45o [24] which results in better

properties in different directions, not only along the filaments. In the Table 1, the comparison of

different plies is presented. It is easily seen that the main advantage of glass fiber is being an isotropic

material. In spite of being extremely strong in along filaments, other fibers’ strengths in transverse

direction is much smaller.


Page | 61

Table 1 Elongation and shear modulus and Possion ratio of different fibers. [21]

The difference between a longitudinal modulus, and by that the strength of the ply with stress applied

in the direction of axis and one when stress is applied under an angle, can be seen in the graph (figure

60) where angle θ is the angle presented in the figure 59 It is clear that the angle and E are inversely

proportional.

Figure 60 Dependence of elongation module on angle of the force. [21]

7.4.2 Strength of the ply.

Ultimate strength should be taken under consideration. There is a main difference between isotropic

and anisotropic plies during tensile test. Even though carbon fiber has very high UTS (Ultimate tensile

strength), it does not show plastic deformation before failure. In glass fiber UTS is much smaller,

although elongation before a rupture is significant (Table 1). Elongation in isotropic composites can be

a disadvantage or advantage. For example in bows or poles it is an advantage. However, in surfboards


Page | 62

it is consider as disadvantage since the forces can be high in different directions. On the other hand,

with fiber glass surfers can perform more complicated evolutions due to better feeling of the board

and its reaction with the water e.g. after landing after jump from the wave.

Figure 61 Tensile strength of different plies (the most important for this care are epoxy plies). [21]

Ultimate strength of a ply along the fiber direction, can be easily calculated when the fraction (next

chapter) and elongation modules are known [21].

− 𝜎𝑙 𝑟𝑢𝑝𝑡𝑢𝑟𝑒 is the fracture strength in the direction of the fibers

− 𝜎𝑧 𝑟𝑢𝑝𝑡𝑢𝑟𝑒 is the fracture strength transverse to the direction of the fibers

− 𝜏𝑙 𝑟𝑢𝑝𝑡𝑢𝑟𝑒 is the shear strength in the plane (ℓ, t) of the ply

Equation 5 Ultimate strength of a ply. [31]

𝜎𝑙 𝑟𝑢𝑝𝑡𝑢𝑟𝑒 = 𝜎𝑓 𝑟𝑢𝑝𝑡𝑢𝑟𝑒[𝑉𝑓 + (1 − 𝑉𝑓)𝐸𝑚

𝐸𝑓 ]

- E is Young Module (of matrix and fiber),

- Vf is a volume fractur,

It is slightly more complicated to do when a stress is applied in a transverse direction of the fibers.


Page | 63

Equation 6 UTS regarding on the direction of the force. [31]

7.4.3 Fractions in a ply.

In ply we have different mass fraction and volume fraction. After this values are established, density

and thickness can be calculated. It is worth noting that these dependencies are not constant. They can

be and are changed during the production process depending on the constructor’s project. Below we

can see how thickness of ply depends on fiber mass fraction and what is the usual fiber volume

depending on which production method is chosen.

Table 2 Different fiber volume fraction, referring to the production process. [21]

Table 3 Ply's thickness, depending on the fiber and Mass fraction. [21]

Fiber mass fraction (Mf) and resin mass fraction (Mm) can be defined as [21]:


Page | 64

Equation 7 Mass fraction equations. [31]

Volume fraction is defined as:

Equation 8 Volume fraction equations. [31]

From this we can easily calculate density of both of them by solving these easy equations [21]:

Equation 9 Volume and mass fraction of fiber depending on the density. [31]

Finally, it is worth familiarizing with the comparison of the two plies mainly used in surfboards. First

main difference observed is density. Density of glass fiber is around 30% more than carbon [24]. Tensile

strength is twice higher while using carbon fiber ply. The transverse strength in glass ply is better. Since

the material is isotropic there is almost no difference between longitudinal and transverse strengths.

Compressive strength is similar for epoxy and carbon in transverse strength, but much smaller along

the fibers in carbon ply (as seen in Table 4) [21]. Elastic modules for both were presented previously.


Page | 65

For building surfboard carbon fiber seems much better but in fact can be too rigid and make riding the

board not very enjoyable.

Table 4 Comparison of glass and carbon fiber properties. [21]

After evaluating different kinds of fibers it is essential to consider two main resins. Mostly polyester

and epoxy is used in the boards’ construction. They are not very different especially within mechanical

properties. Shear and elastic modulus in epoxy resin are just 10-15% higher than polyester. However,

it has quite a big influence on tensile strength which is more than 50% higher for epoxy. The big

advantage of polyester resin is its price which is much lower than epoxy one. Usage of polyester is time-

saving. Polyester dries faster, which can be a big plus for high volume manufacturers or big

disadvantage for less skilled shapers. Density is variable for different kinds of epoxy and polyester resins

but the differences are rather small.

Health and ecological concerns are another thing. Polyester has much harder, chemical smell, which

makes is much harder to work with and makes the work more exhausting. Both of the resins are very

harmful for the environment, however epoxy release around 75% less VOC (volatile organic

compounds) to the atmosphere while curing. It also can be cleaned with less toxic materials, e.g. citrus

based cleaner, when polyester has to be removed using e.g. acetone.


Page | 66

Table 5 Comparison of epoxy and polyester resin properties. [21]

8. Sandwich structure

The sandwich contains two thin layers (e.g. fiber/resin ply or metal sheet) assembled by bonding on a

light core which provides the shape and adds stiffness as well as strength to the construction. The core

is usually made of polyurethane or EPS foam, while the layers are ply of fiber and resin. Usually ep/ec is

between 10 to 100 [30].

Figure 62 Sandwich structure.[21]

A significant advantage of that structure is its extremely low weight in comparison to e.g. a metal part

with the same properties. Good flexibility is a cause of the distance between the skins which increases

the moment of inertia. However, is it very poor damping material [24] which is problematic when trying

to achieve a high speed on big waves with not necessary flat surface. Vibrations of the board can cause

riding much more difficult and make turning extremely hard or even impossible.

8.1 Properties and tests on the sandwich structure

8.1.1 Stress – bending

To properly understand stresses in the structure it is necessary to separate a an elementary slice of

thickness equal to dx . After that it is possible to observe how shearing stress T and momentum M is


Page | 67

deforming an examined material. Due to bending momentum, normal stress (σ) appears and shear

force cause shear stress distribution (τ). Normal stress occurs only in the skin and in the transverse

direction where shear stress can be found only across core thickness. It is quite easy to approximate

these stresses. Stress direction and equations are showed below. As it can be easily observed, the stress

increases when decreasing the thickness of a particular part of the layer in a sandwich beam (Figure

63) [30].

Figure 63 Bending of sandwich beam (e.g. surfboard). [21]

Calculations of deformation while bending is not complex. The only variable which is needed to be

obtained is the elastic energy (W). The values of EI and GS in the equation [21] can be obtain from the

following calculations.

Equation 10 Shear and bending stresses. [31[


Page | 68

Equation 11 Contribution of bending and shear. [31]

M is the bending moment

T is the shear force

Ep is the modulus of elasticity of the skins material

Go is the shear modulus of the core material

Equation 12 Deflection. [21]

8.1.2 Buckling

Another property which is essential in the production of surfboards is buckling. Local buckling can

happen while compression. Usually is caused by impact or constant concentrated force. When

observing a used surfboard, one can spot multiple marks indicating previous usage. This is because e.g.

a surfer fell down on a surfboard with his/her elbow or the surfboard hit the reef. Despite the dramatic

sound of it, such strains have very little influence on surfboard’s performance and in fact 99% of

surfboards, especially polyester ones, have marks like this.


Page | 69

Figure 64 Buckling.

Buckling, as showed in Figure 64, can be caused by forces F2 or F1, however, in surfing it is usually force

F1. The force bends and stretches the ply at the same time as well as compresses the foam. Critical

forces are easily calculated (Equation 13) [24] when the mechanical properties of both materials are

known.

Equation 13 Critical force for buckling. [31]

Where ep and ec are thicknesses of ply and foam core, while Ec and Ep are Young modules of those

materials. With greater force ply is going to crack, and this will be followed by the damage of foam

core. With deformation caused by buckling material will be weaker and can be initiation point for cracks

caused by e.g. bending.

8.2 Honeycomb

Honeycomb structure is a shape inspired by nature. It can be seen in the nature in bee hives, many

plants and even butterfly wings. In early XX century, people adopted this solution in order to create

composites with high strength and reduced weight. Honeycomb structure is usually used as a core and

is reinforced by a ply, made by fiber and resin. It is widely used in e.g. aeronautic and airplane industry

[29]. In this project, honeycomb will be used for the same purpose, however, instead of metal or EPS,

cork will be used to make the board more ecological. The main differences between the artificial foam

Mark of buckling

Foam

Fiber glass and resin ply

F1

F2 F2


Page | 70

and this natural material is its ecological impact on the environment. Another difference, which

unfortunately makes cork less popular, is its weight and cost. Cork is much heavier and, unless it is

being cut into a honeycomb or combined together with EPS or PU, it would not be possible to use for

surfboards production.

8.2.1 Honeycomb structure strength – ply

First, we will focus on bending stress. In order to estimate it, the facing sheet is considered isotropic

and of equal thickness throughout its whole length. In order to simplify the calculation, beam with the

constant thickness can be analyzed.

Equation 14 Sandwich composite beam strength. [30]

𝜎 =𝑀𝑚𝑎𝑥

ℎ𝑏𝑡𝑓

σf is bending stress in the facing sheet

Mmax is the maximum bending moment in the structure

tf is the facing sheet thickness

h is the distance between centroids of the facing sheets

b is the beam width.

Figure 65 Bending of honeycomb beam. [21]


Page | 71

Figure 66 Buckling in honeycomb cells. [21]

As it was mentioned before (8.1.2), buckling is a big problem in the sandwich structure composites, and

in honeycomb it has more probability to happen. Due to the empty spaces in the surfboard’s core,

intercell buckling may also appear if the walls between the cells are really thin. The critical stress to

prevent this from happening is calculated in Equation 15.

Equation 15 Critical stress for intercell buckling. [31]

bcrib is critical stress for intercell buckling

Ef is elasticity modulus of the ply

λ is 1-f2, where f is a Possion ration of the ply, tf is facing ply thickness and S is the size of the shell.

8.2.2 Honeycomb structure strength – core.

To define the strength of the core, several factors have to be taken into consideration. First of all, the

shear stress which can be calculated as shown in Equation 16.

Equation 16 Shear stress for honeycomb beam. [31]

Vmax is max shearing force


Page | 72

h is the thickness of the board

b is the beam’s width.

Next, it is important to establish the bending in the core. In order to calculate it the Equation 17 is used.

Equation 17 Bending of honeycomb beam. [31]

σf is bending stress in the ply calculated before

Ef is Young modulus of the ply

d is the thickness of the beam

tf is the thickness of the ply.

Figure 67 Bending honeycomb.

Moreover, the local crushing in the honeycomb has to be calculated. It is a function of a pressure and

the area of a cell.

Equation 18 Stress appearing while crashing the honeycomb cells. [31]


Page | 73

Crushing comes together with all the other failures but can also be caused by the impact force.

Figure 68 Local crushing of the honeycomb cells. [21]

9. Cork material.

The surfboard is an extremely unecological product. It is hard to recycle and all its components have a

strong negative impact on the environment. Surfers are the people who are usually taking much more

care of the environment than the others. In order to make the product more environmental-friendly,

many different cartoon or wood construction were designed and constructed. However, there is one

material which is not as popular as the others which may have already been used as a substitute for

expanded foam – it is cork.

9.1 Making cork. Cork is a skin of the cork tree. The biggest producers of this material are placed in Spain and Portugal.

The trees are being planted in millions and are a huge investment since the first harvests can be made

just after 25 years. Following that, the harvests can be made every 8 years. It is possible to obtain 20-

25kg of cork from a single tree. A significant advantage of the cork trees over other species is that they

are much more resistant to wild fires. This is very important since, these trees are grown in a part of

Europe which is often affected by extreme droughts and fires are an inevitable part of majority of

Spanish and Portuguese summers. The harvests are made by qualified workers and leave no harm for

the trees. After collecting enough material, it is being cut for smaller pieces and usually boiled in the

water in order to make them more flexible and easier to process. Next, they are being left outside for

up to several months, in order to absorb humidity.


Page | 74

After this, the cork is being crushed into small pieces, creating a mixture of small grains. Following that,

they are formed into blocks or cylinders under high pressure and temperature which is curing the glue

used for connecting the grains.

Figure 69 Cork growing process. [15]

The cork is not an isotropic materials and its properties highly depend on factors such as age, type and

treatment. In case of cork, which is being glued together, the material used to connect the pieces of

cork as well as its final density have an extensive influence on the final properties of the product. The

natural cork contains more waxes and fats than secondary cork. Another determinant factor is the time

of the year when the cork is being collected. The winter cork has thinner cell walls while spring cells are

not as dense as in autumn. [45]


Page | 75

The influence cork density on the Young modulus can be observed in Figure 70.

9.2 Enhancing cork properties by addition of reinforcement materials It is a common practice to use some reinforcement, in order to improve the properties of a cork, In cork

agglomerates different materials can be added to make structure more compact or e.g. bounds more

solid and resistant. One of the most ecological solution, is adding coconut fibers into the mixture in

order to improve mechanical properties. Addition of 10% of this material to cork, can improve Young

modulus up to 47% in comparison to unreinforced cork composites. [44] This way of thinking help the

cork industry to make the products more ecological and encourage them to use less resin and more

ecological products.

9.3 Properties of cork Its properties depend mainly on the type of product and what will be added to the mixture of cork.

When speaking about the cork as an engineering material, in a lot of cases it is used for the artistic

purposes. It can also be used for acoustic and thermal isolation and due to its poor conductivity

properties. However, cork is also used in less common products such as bicycle helmets, kitesurf boards

or surfboards.

Figure 70 Influence of cork density on its mechanical properties [45]


Page | 76

Table 6 Cork Properties. [16]

Main properties

Density 100 - 140 kg/m3

Conduction T=23 C 0.039-0.045 W/m.C

Specific heat capcity (20st C) 1.7-1.8 kJ/kg.C

Yield stress 50kPa

Module of elastic compression 19-28 daN/cm2

Thermal diffusion 0.18-0.20x10^-6 m2/s

Possion coefficient 0-0.02

Strain causing fracture (along the length) 1.4-2.0 daN/cm2

Strain causing fracture (tangent to the

length) 0.6-0.9 daN/cm2

Strain causing fracture (axial) 0.5-0.8 daN/cm2

Stress causing 10% strain 1.5-1.8 daN/cm2

9.4 Differences in cellular materials

There are two types of cellular materials, natural or synthetic. EPS is a less ecological but widely used

option in every type of industry from construction to aerospace. However, it has a big disadvantage as,

after the first impact, it does not come back to the previous form. This is different in cork which

characterizes by a big capacity of energy absorption. It is also easier to recycle than EPS.

These kinds of the materials have different states of deformation. At the beginning, the cell walls bend

and the material deforms elastically (still able to come back to its original previous shape). Then,

without significant increment of the force, the walls are buckling and deforming. This is the biggest

phase of the deformation process which, when reached, will last and cause greater deformation with

almost constant force. The last phase is densification – collapsing of the walls of the cells, causing

unrecoverable changes to the shape.


Page | 77

Figure 71 Behavior of cork cells while applying a force. [practical exercise]


Page | 78

Section III

Shaping and testing

10. Tests of the boards.

In order to understand the influence of the shapes on surfing, two boards of Freshline Surfbords and

one board of MSD (Manila Surf Design), who are two of the three local shapers in Aveiro, were tested.

Boards had different shapes and were made for different conditions. Testers were ask to judge the

boards on their stability, speed, ability to make fast turns and ability of duck diving. The boards were

tested by 10 intermediate surfers (not advanced surfers, just casual riders – mostly Erasmus students).

Level and experience of testers were different. Most of the group (7 of them) have been surfing

regularly for about 2-4 years. One tester was a member of Dutch National Surf team and two of them

were beginners with just a few months of experience. Each surfer had 1-2 hours session on each board

under similar conditions. Most of the tests took place at Praia da Barra, Praia Costa Nova or Vagueira

in central Portugal around October/November of 2018. Most of the times waves did not exceeded 1 -

1.5 m. However, during 2 test days in Costa Nova, swell reached 2 – 2.5 m, however, the waves were

not hollow and steep. Unfortunately, for a number of reasons only 4 test surfers were able to test all 3

boards.


Page | 79

Figure 72 Majority of the testing team.

10.1 Yellow egg shaped short board.

This board is an egg shaped short board which resembles a miniature longboard with squash tail, 5’8”

in length with 34l of volume. It was tested with thruster system with FSC fiber glassed fins of greater

stiffness than usual fins. Most of the testers really liked this board. They described it as a “wave

catcher”. The surfers could catch waves very early and were able to get high speed without much effort.

Another advantage of this board was ability to keep the speed on the flat areas of the wave. While

testing it in Costa Nova its biggest advantage was an ability to drop very early which allows appropriate

positioning and gives time to gain stability on the wave. Unfortunately, several disadvantages were

discovered during testing days. It was almost impossible to duck dive because of the nose’s shape and

volume. Duck dives are essential to go inside and position yourself on a lineup. Duck diving is diving

under the wave to pass it and avoid

the force of white water which pushes

back towards the beach. Moreover,

due to the board’s shape, much more

force and time was required to turn.

It did not allow for pivot turns but

Figure 73 Till testing the egg.


Page | 80

only long and deep ones. On the other hand, thanks to the large volume it

was very easy to achieve high speed on the wave as well as when paddling.

Especially on the waves in Vagueira, which are very quick, majority of

testers found it quite easy to get a long wave and control the speed. The

beginner surfers really liked the board due to stability and ease when

paddling, which is thanks to the flat deck, thick rails and single to double

concave. The board did not have a wooden stringer but just a layer of

carbon glass (about 7 cm wide) on the bottom of the board. Ply was made

from epoxy resin and 4 oz fiber glass while the core from polystyrene foam.

Because of lack of the stringer, the surfers really appreciated amortization

of the board while standing up and dropping in the waves.

Figure 74 Egg board.


Page | 81

10.2 Short board.

This board was made much thinner than the yellow board. The nose was

pointy, concave was shaped as single to double and the amount of rocker

was bigger than in the egg or MSD ones. Volume of the board was the

smallest of all tested ones. Rails were thinner and were allowing on cutting

into the face of the wave. Lack of the rocker on the tail and majority

concentrated on the nose was causing diving into the wave while

dropping. Small size of the board did not allow on early drops, forcing

surfers to stay very close to the breaking point of the wave. At this point,

a very good balance is required as well as ability to place oneself on the

board in appropriate position straight away. Putting a leg too far away

from the center could cause loosing balance as well as speed. Therefore,

this board was impossible to ride for the beginner surfers. However, more

advanced testers really enjoyed the maneuverability of the board. To

speed up, a surfer needed to ride up and down the wave, keeping an

appropriate riddim or move the nose from left to right (pumping) while

going down the wave. Without this skill some testers were losing speed

very quickly. Nevertheless, all testers agreed on one aspect – the board

was the easiest, out of all three, to duck dive. It was an effect of small

thickness and volume of the board, as well as a pointy nose. It was very

easy to perform nice, quick and steep turns on the small waves after

getting appropriate speed. On the other hand, when waves were choppy

(destroyed by the wind) the board was losing speed very quickly. One of the intermediate surfers, who

is 190 cm tall claimed it to be difficult to surf due to its length – he had problems with positioning his

feet in the right place. This board was made from epoxy resin with 4 oz glass fiber and polystyrene

foam. Although the board was the most difficult and unstable one, some of the testers liked it the most.

Figure 75 Short board.


Page | 82

10.3 MSD hybrid fish tail board.

This board can be described as suitable to ride for both intermediate and

beginner surfers. It encompasses some properties of both the first and the

second boards. It had round – pointy nose and medium thick rails. It had less

volume than the yellow egg board, about 29 l. Wide deck and quite flat nose

rocker provided stability on the wave. Fish tail gave stability on the steeper

waves and allowed higher speed. Thick rails and single to double concave

allowed for fast turns, however, slower and longer than while using the short

board. When discussing this board, it is necessary to highlight that, in

comparison to the first two boards, it was made by Manilla – one of the most

experienced Portuguese shapers. That is why the shape of the board was

developed with the highest precision resulting in a perfect form. There was

also a big difference in materials. Manila used polyester resin with 4oz glass

fiber and polyurethane foam with wooden stringer. Due to this, the board

was more flexible and softer on the waves. The problem of this board was its

fragility. It was damaged twice during the tests. The first time it was damaged

due to a crash with another surfer. It was necessary to take the board to a

shaper who took about 5 days to dry it and repair it. The second time it was

hit very hard by a surfer and a part of the rail was broken. However, it was

possible to repair the rail with special fix (Solares) in just 1 day. Nevertheless,

testers enjoyed this board the most because of the fusion of properties of

both fish and short board which allowed surfers the most satisfying rides.

10.4 Summary

It is clear that even though some of the shapes and properties really matters, some of them can only

be appreciated by more experienced surfers. Less advanced surfers tend to enjoy boards with higher

volume and more round shapes, while more experienced ones can take advantage of different shapes.

The beginners were only able to really voice their opinion about the yellow egg shaped board as they

were not able to position correctly and surf on other ones. In conclusion, it was confirmed that the

different shapes of surfboards’ parts have big influence on their performance.

Figure 76 MSD fish tail.


Page | 83

11. Designing process

The process of designing was quite complicated. After finishing the practical tests with different

surfboards, it was necessary to analyze what is needed in order to have a shape, which will be attractive

for both, advanced and intermediate surfers. I asked a group of 40 surfers of variable levels of abilities,

what surfboard would they like before starting to design one. The obtained results are presented in

Figure 77.

Figure 77 Preferences of surfboard properties.

As seen the dominating preferences are rather clear. The rocker and the nose aspects have the least

variable values as the surfers, even though they surf, they often do not fully understand the actual

functions of these properties. Nevertheless, the surfboard with squash tail, pointy nose, single to

double concave, medium rocker and 30-35 l volume was chosen. After conducting pre-design research,

the plan was made. The length was harder to discuss due to different heights of the surfers but at the

end it was set as 5’11.

11.1 CAD model.

Following the results of the survey, the volume of 31 l was chosen. Maximum thickness of the board

was 2 7

16 ft and the max width was 19

7

8 ft. The nose was pointy but without very sharp shape. The

squash tail was made a bit wider in order to facilitate the take off and allow the surfer to stay more

0

10

20

30

40

50

60

70

80

Ro

un

d

Fish

Squ

ash

Ro

un

d

Po

inty

Hyb

rid

25

-30

30

-35

35

-40

sin

gle

sin

ge t

o d

ob

ub

le

man

y ch

ann

els

smal

l

med

ium

aggr

essi

ve

tail nose volume concave rocker

Per

cen

tage

[%

]

Surfboard preferences


Page | 84

stable on the back of the board. Rocker size on the back is 2 1

16 ft and on the front was 4

1

2 ft, which is a

medium size. If the rocker was more aggressive, it would be around 2 1

2 ft on the back and 5

1

16 ft in the

front. The board had a single concave on the front, changing smoothly into double concave. The

functions of all the parameters were described in the previous chapters. The board was made in a CAD

program called Shape3D, however in order to analyze the strength of the board, it had to be created

once more using SolidWorks (Shape3D has separate packages, which have to be purchase in order to

have an access to some options, such as converting models to .step or .igs).

Figure 78 2D drawing of the first surfboard.

11.2 Design improvement

After over half a year of testing it appeared that the board needed some improvements. The nose of

the board was perfect for the clean and non-windy conditions, however the shape of the nose was

failing with stronger wind or chop water due to being too long and having small surface area with big


Page | 85

volume. This shape allowed better surfers to make more aggressive turns, however was almost

impossible to ride for less advanced surfers. Another aspect needed to be changed was the size of the

tail. It should be thinner, which would make the board faster and more stable on bigger waves. The

first product was made of polyurethane foam and polyester resin. Corrected model will not only

provide better performance, but also will be more ecological than the previous one. The core made

from cork in the honeycomb structure will provide the proper weight of the board as well as the needed

strength. The redesigning started from minimizing bending stresses by moderating the thickness of the

designed board and trying to develop the algorithm which can do that for different composite

materials.

11.2.1 Thickness optimization.

The idea was to minimize the bending energy equation [21].

First constrain which needed to be considered was the mass of the board [31], which should have not

been higher than 4.5 kg.

Main function [21]:

W(ep,ec) = ∫𝑀2

2𝐸𝐼 dx

𝑙

0 + ∫

𝑘𝑇2

2𝐸𝐼 dx

𝑙

0 = ∫

𝑀2

𝐸𝑝𝑒𝑝(𝑒𝑐 + 𝑒𝑝)2

𝑙

0dx + ∫

𝑘𝑇2

2(𝑒𝑐+2𝑒𝑝)𝑙𝐺𝑐dx

𝑙

0

Constrains [21]:

M(ep,ec) = ρcV ec/e + ρpV ep/e < 4.5 kg

F(ep,ec) = 1.64eplEp(𝐸𝑐𝑒𝑝

𝐸𝑝𝑒𝑐)1/2< 1080 N

Bounds:

1 < ep < 3

30 < ec < 70

After formulating the problems it was necessary to see graphical dependency of the constraints on

different properties. Using python library matplotlib formulas and 3D graphs was generated. It can be


Page | 86

seen that the mass increases with an increment of both ep and ec . However, it is quite interesting that

the maximum buckling force, decreases with decrement of core thickness.

Figure 79 Surfboard mass depending on the thickness of core (ec) and ply (ep).

Figure 80 Buckling strength, depending on the thickness of core (ec) and ply (ep).


Page | 87

To solve the problem, Sequential Quadratic Programing [4] method with multistart was chosen. The

multistart was added to the method in order to make sure that the program was not ending at local

minimums. The initial values of ec were varied between 30 and 50 mm and ep between 1 to 3 mm. The

properties of material were either calculated or found in the literature on composite materials. As it

was mentioned before Sequential Quadratic Programming algorithm with multistart was used to

calculate this problem (figure 81). After calculating the constraints, Jacobian matrix was calculated in

order to discover monotonicity of the functions. Next, df /dx was calculated and added to the initial

value or value from previous iteration xt =xt−1 +dx. If xt is within the constraints and bounds and KKT

conditions are satisfying, the solution is saved into the array and program runs again with new initial

values. If not, next iteration is made. After minimum was found for all different initial conditions, the

minimum was chosen from the array as the minimal solution [3].


Page | 88

Figure 81 Algorithm for optimizing the minimum thickness.

After obtaining the results it was clear, that this method allowed the appropriate values to be obtained

which are global, not local, minimum. This is because even though the multistart with different initial

values was used, the variations of results were not bigger than 5%. The minimum value of the function

was about 70 MPa, when using ec=33 mm and ep=2.75 mm. The constrain values for this thicknesses

are equal to:

Mass = 4.5 kg

Buckling strength = 2485 N


Page | 89

These values are in the limits of the constrains. Mass is maximal and the buckling strength 50% higher

than the minimal

Figure 82 FEM analysis of beam model used in the optimization algorithm.

After obtaining these results, the CAD model of the board was created and the stress and strain were

calculated using FEM simulation. First, the simple beam was calculated and the results were close to

the ones calculated by the formula, they were equal to 82 MPa (Figure 82). It is interesting that there

were almost no stress in the core part of the beam and the biggest stresses appeared on the supports.

After that the simulation on the real board with the surfer on it was run and results were much smaller

than in the beam, about 35.4 MPa in the board.


Page | 90

Figure 83 Board used in the simulation.

After closer analysis it was decided that unfortunately the perfect model was just a theoretical one.

Such an accurate ply thickness is not possible to achieved in the workshop conditions and such a thin

core, according to Bruno from Cutback, would not be functional in the water, so the thickness had to

be increased.

12. Production analysis.

12.1 Cost of materials Table 7 Cost of the materials used in creating the surfboard.

Cost of the materials

Blank Shapers Foamez Viralsurf

Average

56.95 55.36 72 61.44

Glass fiber Area Hexcel 4shapers Aerialite Cost

3 x (1x2m2) 5.9 4.9 8.5 26.46

Vector net Cost


Page | 91

Carbon

fiber

Uni

Greenlight

20

Strand

Web

area for

carbon fiber

5.77 8.52 9.1 0.5 14.8

Resin

(polyester)

Shaper

supply Shapers South coast Average Cost

15 22 14 17 34

Fin boxes FCS

Made in

china1

Made in

China2 Average

Cost for

5

24 9.18 11.28 14.82 18.525

Fins FCS

Future

fins Capitan Fin

Average

70 79 48.4 64.45

Leash Decathlon Dakine FCS Leash plug Average

20 25 45 1.5 29.73

Total cost of

materials

(without tax

15%)

211.99

As can be seen in Table 7, prices were estimated based on the internet stores. Actual prices can vary,

depending on the available supplies. However, some of the values need additional explanation. Total

area of surfboard is around 1.5 m2 but a shaper puts double layer of the fiber on the bottom and one

layer on the top, using around 2 m2 sheets and then cutting additional fiber. The fin box’s cost can vary,

dependent on the amount of fins which are put in the surfboard. The price of the fins can vary from 15

euro up to 100-200, so a medium price model was chosen.


Page | 92

The cost is calculated for this specific board. For example, by using epoxy resin and EPS blank, price

would change. Estimated price of epoxy resin, necessary for the board would be around 100 euro

without tax. It is around 3 times more expensive than polyester. However, price of the blank is around

25 euro, assuming it will be ordered as a big block of EPS and cut at the shaper’s factory.

12.2 Cost of machining

Machining costs of the surfboard were based on the specific machine used by Bruno at Cutback. The

energy price includes: computer, suction pump, motor of the cutting tool and 3 motors for XYZ axis.

Figure 84 CNC machine used to shape surfboard blanks. [34]

Table 8 Price of the electric energy used in the shaping process. [33]

Total power of

the machine [kW]

Time of the

machining

[hours]

Price [euro/1kwh] Cost [euro]

5.5 0.5 0.2246 0.62


Page | 93

12.3.Sanding cost

Cost of sanding can vary, depending on whether a sanding machine is being used, or if hand tools are

used instead. First, the time spend on affination and modeling details made after CNC was calculated.

Next, the time an operator spent on sanding using the sanding tool was calculated.

Table 9 Costs of finishing the board. [33]

Time[h] Power of the

machine [kW]

Price of work

[euro/h]

Electricity price

[euro/KWh] Cost [euro]

1.5 0.3 20 0.2246 30,2

Full price of shaper’s work, using his hands, spent on creating the prototype is around 70 euro.

Taking this into consideration, the total price of the prototype is around 282 euro.

12.4. Price of the tools.

The most dominant price in this case it’s the price of the CNC machine which is around 28900 euro. The

price of the other tools like sanding machine and other hand tools can vary depending on the producer,

however they are all usually one time investment and the only thing Bruno has to change often is a

sand paper. The price of these type of the materials were not consider, due to a small impact on the

price.

Figure 85 Cost of shaper work.

Time [h] Price of work [euro/h] Cost [euro]

2 20 40


Page | 94

13. Prototype and redesign

The prototype was made in cooperation with Bruno from Cutback surfboard design. The shape was

chosen based on other surfers’ opinions, my own preferences and Bruno’s suggestions and corrections.

The testing of this surfboard took several months and allowed some advanced surfers to voice their

opinions. The board was ridden by around 10 semi-pro surfers who provided their thoughts and

suggestions. After that, I have also consulted the shape with less experienced surfers (less than 1 year

of experience) in order to improve the shape and volume of the board, so that it is suitable for a greater

part of the surf society. I chose some of them below.

13.1 Testers

13.1.1 Juan

Juan is a lifeguard and Spanish surfer who spent his last years chasing waves in Morocco and Iberic

peninsula. He is experience in riding wide range of surfboards types in various conditions, from wind

swells of Mediterranean sea, to heavy winter Galician swells. This is what he said about the board:

It is short but wide. You can easily dive and make steep drops. It is easy to catch the waves because of

the volume. The nose shape is maybe helping to turn faster, but the nose rocker is a bit too long for

smaller waves. You can catch small and bigger sets because of the volume and wide tail.

Figure 86 First surfboard (PU).


Page | 95

13.1.2 Micheale

Michaele is a surfer and an enthusiastic fisherman from Finland, especially enjoying extraordinary

sports which allow him to connect with wildlife. He is used to heavy Irish swells and cold water of Arctic

ocean or Baltic sea. Except of surfing, he is an amazing snowboarder and extremely talented

skateboarder which you can easily see it by his surfing style. His opinion of the board was extremely

valuable.

The surfboard gave the opportunity to challenge steep waves and practice fast departures. The board's

agility rewarded me? when I got well on the wave. The board does not forgive surfer’s mistakes in the

same way as the longboards or hybrids, but on steeper and faster waves, the board felt like it was at

home. I paid attention to the position of the legs when boarding the board, like a skateboard at the

ramp drop. I was trying to be a bit further up the board when paddling " to get the magical glide" and

I was able to move quickly when I got to the wave. I liked the board especially in fast-paced waves. The

board is sensitive to the shift in focus, while maintaining stability and speed in transition.

13.1.3 Joao

Joao is a beginner surfer from Aveiro. He is much more in love with windsurfing than surfing and he

prefers when it is windy so he can glide in the speed of light around the Costa Nova lagoon. His opinion

gave some contrast to the semi – pro surfers’ opinions.

The board was a bit shifty and less stable than the other boards I used (usually around 7-8 ft). This board

was definitely too small for my level of experience. The long nose area and rocker made paddling harder

than I expected. I also could not get enough speed to get the proper waves.

13.1.4 Wiktor

Wiktor is a professional kitesurfer, who started his surfing adventure last winter. As any person

passionate about water sports, he dedicated himself fully to it. This is what he thinks about the board:

The board designed by Maciek gave a wonderful surfing experience. I was surprised how easy it was to

catch the waves and paddle in comparison to other boards I tried before. In my case finding the balance

in take-off was a bit challenging as I am used to riding wider boards with more volume. Another thing

was that I was able to generate a really high speed while riding. The board is perfect for intermediate

surfers and it will help them to improve their turns and other vertical maneuvers.


Page | 96

13.1.5 Maciek

I am a surfing and windsurfing instructor who is in love with water and all the water sports. I can

confidently say that you can ‘give me a board and I will ride it‘. Thanks to having an ocean in my

backyard, I am surfing as often as possible. I had a chance to try this board in different conditions when

waves were between 0.5 up to 3 m high. This is my opinion about it:

The board is an amazing performance board. It gives the speed and turns extremely fast. It is a perfect

board for an experienced surfer. It requires good balance and paddling skills in order to get good waves.

The problem with it is that it requires very clean conditions. With too much wind the nose area it taking

too much resistance. Similar thing happens when waves are too ‘choppy’ as it is really hard to get the

speed required to catch the wave. I definitely made this board too much for myself and my level of

experience. The volume was chosen correctly. The nose should be modified and made smoother and not

as long. Squash tail is really good for turns, however it provides less stability and is not appropriate for

mushy waves. The best way to connect its performance and stability is to change the tail for either

hybrid or fish tail. This would give possibility for surfers with less skills to also enjoy the waves. Rail is

perfect and cuts into the wave as a knife. The board was theoretically designed to ride with 3 fins,

however for the waves above 1 m, I found 4 fins combination much more stable and easy to turn. Two

or a single fin systems are definitely not appropriate for that type of board.

13.2 Redesign

In order to improve the design of my board, I took into consideration all the valuable criticism I received

from other surfers as well as my own opinion. After talking with both shapers: Bruno and Hugo, I

decided that the best option for all the surfers to enjoy my board is to modify it into the modern fish

shape. The volume will be kept the same, around 30 l. However, the nose of the board will be much

wider and smoother in order to stabilize the board and make the take-off easier. The fish tail will allow

the beginners to take longer, more satisfying waves, while the more advanced surfers, will appreciate

smooth transitions and long turns without losing the speed.

13.2.1 Design

I based my design on the Go Fish model made by Rob Machado – a legendary, hippie surfer. He is a fan

of ecology and preserving the planet so his idea fitted perfectly with my project. I changed the width

of the board and its rails to make it suitable for beginners. After consulting my plan with Bruno, I

achieved a perfect shape of the board.


Page | 97

After the four blocks of cork were glued together to achieve a raw material, it was cut on CNC machine.

By that time, it was clear that the board will be extremely heavy. The block by itself weighted around

15kg before the machining!

13.2.2 Machining

After glue dried, we started to shape the block. At the beginning everything seems easy and we were

sure it will not take more than half an hour to finish. However, the cork is much more resistant than

EPS and the whole machine started to vibrate due to extremely high linear speed. We were forced to

decrease the advance speed to 3-5 % of maximum speed, which resulted in an enormous increment of

machining time. Instead of around 15-25 minutes as for EPS boards, it took around 4-5 hours. During

the process, some pieces of cork, located close to the edges, were chipped off, due to small amount of

glue in these areas. Fortunately, we managed to fix it later in the process.

13.2.3 Finishing

Next, the surface was evened out and the fish tail was cut by hands using saw, planner and sand paper.

13.2.4 Taking out weight

The board in this state weighted approximately 9 kg, which made it around 6 times heavier than a

normal surfboard blank. In order to remove some weight, holes were made in the board. After running

some simulations and considering pros and cons of different hole sizes and shapes, the circular holes

with diameter of 25 mm were chosen. They had the biggest resistance and the smallest displacement

in proportions to weight that was taken out.


Page | 98

Table 10 Comparison of the influence of different holes types and shapes on deformation of the blank.

Hole size/

type

Project Displacement

D=10,5 mm

Hexagon

D=40 mm

Hexagon

D=30 mm

Hexagon

D=10

Circular


Page | 99

D=25 mm

Circular

D=30 mm

Circular

D= 35 mm

Circular

At the end of the process, the final weight of approximately 7 kg was achieved. It was still a lot, however

due to the cork which was available, it was not possible to achieve smaller weight while keeping the

same properties. If I had an access to more blanks to test drilling, I could

13.2.5 Glassing

Glassing, in comparison to machining, was not as challenging. Before starting the process, the missing

parts of cork at the edges, were glued back together. In order to do this, a mixture of resin and cork

powder was made. Following that, the bottom of the board was glassed using around 800 g of epoxy

resin mixed with catalysator in proportions 1:2 and 2 sheets of 4 oz fiberglass. After drying the bottom,

excess ply was cut off and the same amount of resin and fiber was applied to the deck. Due to the holes,

it was a bit complicated to evenly distribute the resin, however, in contrary of what was expected, the

resin stayed on the fiber and did not dripped through the holes. Some minor air bubbles appeared and

were caused by the porosity of the cork. They should always be removed as they make the ply structure

less consistent and more fragile. In EPS before coating a special white paste is applied in order to cover

a surface of the core and block the air circulation throughout the blank. In this case, it was not done, to

keep the original color of the cork. However, the remaining bubbles were removed during final coating.


Page | 100

After both sides dried out, a new layer of resin was put and the places with air bubbles were pierced to

allow resin to fill them.

13.2.6. Finishing

To achieve the perfect shape, the board has to be sanded after coating. Small improvements are made

during this process to keep the original shape of the board as per project. The biggest focus was on the

tail area and concave (channel). It was necessary to take out some parts of ply in order to keep the

board’s designed shape intact.

13.2.7 Testing

The board was tested at many spots in Portugal. I started testing it in beaches of Aveiro(Barra and Costa

Nova). Later, I moved to southern part such as Ericeira and Lisbon area. The board was tested by surfers

with different skills. There are some of their opinions:

Thiago – Brazilian surfer from Florianopolis, tested many boards and surfed different kind of waves. He

represents a high level of surfing and is able to make many advanced maneuvers.

The board was really funky. It was not as hard to turn as I had expected. It kept good, high speed on the

wave and allowed me to have a lot of fun. It required more force to turn and I was not able to have a

vertical maneuvers but I enjoyed the session a lot!

Marta – Italian surfer from Genova. She learnt a lot about surfing in Portugal during her Erasmus

internship and UK where she lives and studies every day.

The board is amazingly beautiful. For me it was really heavy. When I was duck diving, I was going really

deep into the water what was kind of annoying and made it hard for me to reach the lineup. I got couple

of nice ones but I would prefer the board to be a bit lighter and has more volume .

Pawel – Polish traveler, surfer and surf trips organizer. He surfed waves all around the world and likes

fish – type boards.

The board was really fast and I could enjoy big waves with it. I was able to make long carves ride the

waves till the end. I was surprise that, I did not feel its weight while riding, however it was pretty heavy

and not so easy to walk with this board.

I think that the board ended up much heavier than was expected. It was a result of me not making

enough holes and being afraid to make more. It was a result of being afraid to make the hole to close

to one another and rill through its walls which would create bigger hole and could make glassing


Page | 101

impossible or harder. However, I really enjoyed surfing with this board on big waves with wide, open

face, where you have a lot of room to make turns.

14. Comparison of two models.

The cork board was developed for a couple of reasons. First off all, to prove that the same product can

be made using materials which have smaller impact for the environment. The reason for change in

shape was to improve the performance and allow less experienced surfers to enjoy using this board.

The last reason, was to show that the cork board is as durable as the traditional surfboard.

14.1 Ecological impact.

Seeing surfboard made of cork or wood gives an immediate impression that this material is more

ecological. Unfortunately, it is not as obvious. The ecological impact is measured per kilogram of

material. In traditional surfboard, the blank of polyurethane weights around 1 kg, while the cork block,

which was used for producing the fish board, weighted between 15-20 kg. The cork which was used for

the production was not 100% natural as well. It was being made by crashed pieces of cork and glued

together under pressure and high temperature. Because of that, this material is almost as unecological

as PU or EPS. However, the transportation of cork had definitely a smaller impact. The blank used while

making the prototype was ordered from Brazil, while the cork was transported by car from Cork Ribas

factory located only 40 km from Aveiro.


Page | 102

Table 11 Ecological impact of the first board. [35]

Figure 87 Ecological impact of each part of the first board.

PU board

Transport Material Recycling Packing


Page | 103

Table 12 Ecological impact of the second (cork) board. [35]

Figure 88 Ecological impact of each part of the cork board.

Cork board

Material Transport Recycling


Page | 104

14.2 CFD analysis

CFD (Computational fluid dynamics) tests were made in order to show how the air or water flow over

the board’s shape. The model for analysis was constructed in Solidworks, by making cube extrusion, as

individual body, intersecting the board. After that the board shape was cut out from the inside of the

cube, which was simulating the gas/fluid over the board. After that the fluid around the board was

defined as perfect gas. Inlet and outlet were also defined.

Figure 89 Definition of the fluid for CFD analysis.

The walls around the board were given a speed only in the direction of the flow, so that the water could

not ‘escape’ the testing space.

Figure 90 Section of the model for CFD simulation.

The difference in the pressure and velocity over and below the board, were easily observed. The

difference between two boards is not significant, however it is really interesting to see how the fluid

behave around them both.

16.2.1. Results of the first board

Due to a bigger rocker, a higher pressure in the bottom area of the nose was observed. Thanks to this

the board has higher speed, but is also more vulnerable to the blows of the wind.


Page | 105

Figure 91 Fluid pressure over the first board.

The speed, as suspected is a bit higher in this board due to the shape.

Figure 92 Fluid speed over the first board.

16.2.2 Results of the second board

The difference in the velocity and pressure are caused mainly by the rocker of the board. Higher

pressure in the front of the board, more or less equally distributed allover the length of the board will

make it more stable, but harder to turn.

Figure 93 Fluid speed over the cork board.


Page | 106

Figure 94 Fluid pressure over the cork board.

14.3 Stress analysis

The models of the board were imported as a STEP from Solidworks to Abaqus. After that, ply of the

board was created using the option ‘Create>>Shell>>From solid’. Then, in both projects, the materials

were defined.

The ply was defined using the ‘Composite layup’ tool. As in the actual process, the number of layers

was set as two. The total material thickness was set as obtained in the optimization calculations and

was equal to 2.75 mm.


Page | 107

Figure 95 Definition of the composite layup.

The material, which is assigned to the ply, is epoxy and was defined using engineering constants [37].

Figure 96 Definition of epoxy/E glass ply.


Page | 108

Next, the core material had to be defined. The EPS was defined as crushable foam and cork as

hyperfoam.

Figure 97 Properties of EPS. [37]


Page | 109

Two parts were meshed using tetra type of the elements and assembled together using tie constraint.

Figure 98 Tie constraint.

The boundary condition was fixed at the back bottom of the board where surfer is usually standing.

Then the pressure was equally distributed over the deck of the board, simulating the pressure of surfer

walking over the board.


Page | 110

Figure 99 Force applied on the board.

14.3.1 Results of the first board

After meshing the board for the ply, the following results were obtained:

Total number of nodes: 3744

Total number of elements: 3802

3682 linear quadrilateral elements of type S4R

120 linear triangular elements of type S3

For the core:


Total number of elements: 17190 C3D10 type

As seen on the cross section in Figure 99, the whole stress was absorbed by the ply with no significant

stress being absorbed by the core. The parts did not crash and could withstand the force of the crashing

wave, which was already proved in the physical tests. The board proved to be extremely durable, and


Page | 111

despite experiencing intense crashes, no major damage appeared. As seen the maximum stresses are

63.43 MPa.

Figure 100 Stress in the ply in the board ply.

14.3.1 Results of the fish board

After meshing the board, following elements were created for the ply:


Total number of elements: 561

547 linear quadrilateral elements of type S4R

14 linear triangular elements of type S3

And for the core:


Total number of elements: 146278, type C3D10

As it can be observed, the differences between two different grain sizes are not significant and they

differ by approximately 0.1 MPa. Maximum stresses in large grain are 19.05 MPa and in the smaller

one 19.87 MPa. The stresses higher than in case of EPS may be due to extremely high weight of the

core.


Page | 112

14.3.1.1 Large grain

Figure 101 Definition of cork properties (large grain). [37]

Figure 102 Stresses in the large grains cork board.


Page | 113

14.3.1.2 Cork small grain

Figure 103 Stresses in the fine grains cork board.

Figure 104 Properties of small grain cork. [37]


Page | 114

14.4 Performance difference summary Unfortunately, not everyone, who tested the first board, managed to test the second one. However,

the main difference, especially for the beginners, was the shape. The fish provided easier shape which

was much more appreciated by them. It was steady in the water and to balance on as well as easy to

take-off. However, the intermediate surfers did not share their opinions. They claimed that due to a

high weight of the board, it was much harder to ride. According to these testers, the board did not turn

as easily and they could not enjoy fast maneuvers as on the first one. All in all, this board performed

well on big, thick waves where the surfer could take more time to make long, wide turns.

14.5 Summary

Working on this project was an amazing experience which taught me a lot about surfing and boards as

well as production methods. I was able to further explore my passion, while learning at the same time.

First, it is necessary to focus on the goals and whether or not they were achieved. The final board was

much easier to ride on for beginners, but intermediate surfers could also use it as a fun board, therefore

this aim was achieved. The second goal was to make the board more ecological. This unfortunately did

not work out. The overall ecological impact calculated was smaller for the cork board only because the

cork was taken from Portugal, while the blank for the other board was transported from Brazil. If only

the material types are taken into consideration, the cork board is actually less ecological than polyester

board. The overall process of creating cork board also appeared to be less ecological. This is mainly due

to the fact that more time has to be spent on machining (4 -5h) which further worsens the ecological

impact of the production process.

The type of the cork which was available to me was extremely hard to process. By the end of the

production process, the board appeared to be less attractive in the matters of performance, price and

ease of making than the polystyrene one. Moreover, the market for the cork boards is not as big as for

the traditional ones, therefore the problem of demand appears. another problem appears.

Nevertheless, the good outcomes in both cases were that they were extremely resistant and able to

endure the weight of the surfer without suffering any major failures during testing. As we can see on

the example of the cork board, not all the stuff are as they seem. Awareness should come from science

and research because some of the products can seem eco – friendly, when in the reality they are not


Page | 115

References

1. (http://www.surfingforlife.com/history2.html,https://hawaiianpaddlesports.com/news/histor

y-of-surfing/ (accessed on 10/10/2018)

2. James Cook: The Journals (Penguin Classics) Paperback – Abridged, 2 Sep 1999 by Captain

James Cook (Author),Philip Edwards (Editor)

3. http://files.legendarysurfers.com/surf/legends/ls15.shtml (accessed on 15/10/2018)

4. Jack O'Neill: It's Always Summer On the Inside November 16, 2011 , by Drew Kampion

5. The Surfboard Book: How Design Affects Performance Paperback – May 27, 2014by Sean

McCagh (Author), Tom McAuliffe (Illustrator), Simon Anderson (Contributor)

6. . Surfboard Design and Construction by Kinstle, James. Natural High Express Publishing

Company, 1975.

7. cutbacksurfboards.com (accessed on 01/11/2018)

8. freshlinesboards.com (accessed on0 1/11/2018)

9. https://markofoamblanks.com/ (accessed on 2/11/2018)

10. entropyresins.eu (accessed on 02/11/2018)

11. Surfing: The Ultimate Pleasure Lueras, Leonard. Workman Publishing, 1984.

12. Surfboard Shaw, Stephen M.. Transmedia, 1983.

13. The Complete Book of Surfing. Wardlaw, Lee. Cowabunga!: Avon Books, 1991.

14. The History of Surfing Young, Nat. Palm Beach Press, 1983.

15. Orbelian, George. "Essential Surfing." Orbelian Arts, 1987

16. surfscience.com. (accessed on 10/11/2018)

17. https://www.evo.com/guides/how-to-choose-surf-fins (accessed on 30/01/2019)

18. http://www.tactics.com/info/guide-to-surfboard-fins (accessed on 30/01/2019)

19. fcs.com (accessed on 01/02/2019)

20. A review on the development and properties of continuous fiber/epoxy/aluminum hybrid

composites for aircraft structures Edson Cocchieri BotelhoI, II, *; Rogério Almeida SilvaIII, IV;

Luiz Cláudio PardiniI; Mirabel Cerqueira RezendeI).

21. Composite materials - Design and application (3rd edition) - Gay Daniel, CRC Press,2015

22. Instrumentation of a surfboard to evaluate surfing performance Aitor Hernandez Mitxelena,

John Summerscales

http://www.surfingforlife.com/history2.html,https:/hawaiianpaddlesports.com/news/history-of-surfing/

http://www.surfingforlife.com/history2.html,https:/hawaiianpaddlesports.com/news/history-of-surfing/

http://files.legendarysurfers.com/surf/legends/ls15.shtml

https://markofoamblanks.com/

http://www.tactics.com/info/guide-to-surfboard-fins


Page | 116

23. Resin Types and Production - Brian Windsor (Purolite International Ltd)

24. PRINCIPLES OF COMPOSITE MATERIAL MECHANICS – Ronald Gibson

25. Lostsurfboard.net (accessed on 02/11/2018)

26. magicseaweed.com (accessed on 10/16/2019)

27. worldsurfingleague.com (accessed on 10/16/2019

28. Theoretical design and analysis of a honeycomb panel sandwich structure loaded in pure

bending, Gaetano G. Galletti, Christine Vinquist, Omar S. Es-Said

29. ., Structures Sandwiches, Gamski C, Techniques de l’Ingénieur, Paris, France, February 1981.

30. Transverse Shear Deformation in Bending of Composite Beams of Any Cross Section Shapes, Gay

D., Mechanics of Structured Media, Part B, pp. 155–171, Elsevier Scientific Publishing Company,

Amsterdam, the Netherlands, 1981.

31. http://files.legendarysurfers.com/surf/legends/ls15.shtml (accessed on 02/02/2019)

32. https://www.pordata.pt/en/Europe/Electricity+prices+for+households+and+industrial+users

+(Euro+ECU)-1477 (accessed on 16/06/2019)

33. Unoshapercnc.com (accessed on 15/06/2019)

34. https://www.tomwegenersurfboards.com/history/alaia-story (accessed on 15/06/2019)

35. https://thronperleenee.ga/difference-entre-les-planches-de-surf-soft-top-longboards

36. Helmet Design Based on the Optimization of Biocomposite Energy-Absorbing Liners under

Multi-Impact Loading Fábio A. O. Fernandes 1,* , Ricardo J. Alves de Sousa 1 , Mariusz Ptak 2

and Gonçalo Migueis

37. https://gravityking.ch/2016/12/14/surfboard-buying-guide/(accessed on 20/06/2019)

38. https://greenlightsurfsupply.com/ (accessed on 20/06/2019)

39. https://www.boardcave.com/the-surfers-corner/surfboard-shapes-tails-rails-and-noses/

40. http://plaza.ufl.edu/pskeddy/ (accessed on 15/10/2019)

41. https://www.surfingaustralia.com (accessed on 15/10/2019)

42. http://vacuumbagmisohodo.blogspot.com/2017/03/vacuum-bag-surfboard.html (accessed

on 15/10/2019)

43. Novel cork–polymer composites reinforced with short natural coconut fibres: Effect of fibre

loading and coupling agent addition Emanuel M. Fernandes ⇑ , Vitor M. Correlo, João F. Mano,

Rui L. Reis

44. Futuros produtos de cortica para a construcao civil (Cap 13) Luis Gil

http://files.legendarysurfers.com/surf/legends/ls15.shtml

https://www.pordata.pt/en/Europe/Electricity+prices+for+households+and+industrial+users+(Euro+ECU)-1477

https://www.pordata.pt/en/Europe/Electricity+prices+for+households+and+industrial+users+(Euro+ECU)-1477

https://www.tomwegenersurfboards.com/history/alaia-story

https://thronperleenee.ga/difference-entre-les-planches-de-surf-soft-top-longboards

https://gravityking.ch/2016/12/14/surfboard-buying-guide/

https://greenlightsurfsupply.com/

https://www.boardcave.com/the-surfers-corner/surfboard-shapes-tails-rails-and-noses/

http://plaza.ufl.edu/pskeddy/

https://www.surfingaustralia.com/

http://vacuumbagmisohodo.blogspot.com/2017/03/vacuum-bag-surfboard.html


Page | 117

45. http://www.beachapedia.org/Environmentally_Friendly_Surfboards (accessed on 04.11.2019)

http://www.beachapedia.org/Environmentally_Friendly_Surfboards

improvement of surfboards design and production process

Documents