a dutch merchant vessel of 1664. the keel, part 13/15

The keel.

The slipway.

The keel is set in its position on the stocks. But what is this position exactly? In this regard it is good to say something about the slipway because the slope of the slipway has a thorough impact on certain procedures during construction. Cornelis van Yk mentions the slipway in chapter 6:

DEn Scheeps-bouw-meester, met geseide Deugden, en Hoedanigheden begaavd, sal, en om aan sijn Volk, tot het verrigten van haar ruimte, van noden hebbende werk, behoorlijk plaats te verschaffen, en om sijn van noden hebbende Hout, wijt genoeg van den anderen te plaatsen, om met de minste moeite, en tyd-verlies, het bequaamste, en tot het werk alderbest voegende uit te konnen kiesen, sig van een genoegsaam groote, en om de Scheepen gemaklijk te doen van Stapel loopen, van een agter hoog, en voor laag leggende, Werv voorsien. En op dat sijn op Stapel staande Schip, sig niet ergens, buiten sijn oogmerk, mogte ontsakken, soo sal hy, op dito Werv, een Beddinge van Planken, ter langte van 130, of 140, en ter breedte van 10 of 12 Voeten, om de onder de Kiel leggende Stapel-bloks daar op, te plaatsen, bereiden. (p. 23, l. 36) (The master shipwright, endowed with mentioned virtues and qualities will, to be able to give the necessary space to his people needed for the work and to be able to place the wooden parts wide enough from each other, and to be able to choose the best and most appropriate parts with as less effort and loss of time possible, will provide himself a yard, large enough to launch the ships quite easily, behind lying high, ahead lying low.And that his ship on the stocks, will not sag somewhere, as is not his intention, so he will make at this yard a slipway made of planks, long 130 or 140 and wide 10 or 12 feet, to place the stocks, lying under the keel, upon.)

So Cornelis describes the yard as a piece of ground with a slope and gives the length and width of a reinforced part of this slope: the slipway. This slipway measures 36,80 to 39,63 meters long and 2,83 to 3,40 meters wide, 104 to 134,6 m2. About the actual slope of the slipway nothing is said. Nicolaes doesn’t say much about the slipway but he mentions:

“Een kiel stapelt men achter hooger als voor, op dat het Schip te bequamer af loope; waar toe de werf ook wel vast dient te zyn". (p. 110, c. 2, l. 48, 1690) (A keel is lying higher on its stocks aft than fore so the ship will launch properly for which the yard has to provide a stable ground)

This stable ground would have been provided by a slipway as described by Cornelis. The construction of the slipway is for this analysis not very important but the gradient of the slope is. It influences the direction of the keel i.e. the whole ship and has major consequences for several procedures and building stages. In his article ‘Archeologie op Oostenburg’, Jerzy Gawronski describes the remains of a VOC yard in Amsterdam and mentions the slope:

“Tot de belangrijkste structuren die aan het daglicht kwamen behoren twee scheepshellingen. Deze installaties lagen in de zeventiende en achttiende eeuw bij de oever van het werfeiland aan het toenmalige IJ. Ze bestonden ieder uit een vijftig meter lang en twaalf meter breed kleitalud dat ineen hoek van ongeveer 2-3˚ schuin afliep naar het water”. (p. 24, l. 23) (To the most important structures who came to light belonged two slipways. These installations were situated in the 17th and 18th century at the shore of the yard island at the former (river ed.) IJ. They consisted each of a slope of clay, 50 meters long and 12 meters wide which ran with an inclination of 2-3˚ to the water.)

Blaise Ollivier gives measurements in his ‘Remarks on the Navies of the English and the Dutch’ taken during his visit in 1737 at the naval shipyards in the Dutch Republic. In Amsterdam he mentions a length of 160 feet and a difference in height of 6 feet. If we determine the angle of this slope we see that sinα equals 6/160 which yields an angle of 2,15˚. In Rotterdam he describes a slope of 150 feet long with a difference in height of 8 feet .Here sinα equals 8/150 which yields an angle of 3,1˚. (p. 197 and 199 of the translation by David H. Roberts). These measurements confirm the findings of the remains of the Amsterdam shipyard.

Jaap Luiting © 2016

The keel.

Lets assume our ship of 155 feet is built on a slipway with a 3˚ slope and that the reinforced part of this slipway has the same inclination. To be able to establish the way the keel and later on the ship is lying on the stocks we have to know what the procedure of the launch exactly is. To establish the direction of the keel in this respect we have to use a line of reference because every plane and line of the keel is curved. This line is already mentioned and we will use this line to measure what the direction of the keel is:

“Dese, op de Bloks leggende Kiel, word aan de boven sijde met een Schrap, van vooren tot agteren, in haar Midden, doortrocken, gemeenlijk Middelschrap gezeid; over welke een Lijn gespannen sijnde, men siet of sy niet Krom, of met Bogten, op dese Stapelingen geklampt en gekneeveld werd”. (p. 55, l. 48)(This keel, laying on the stocks, is provided with a scratch from fore to aft, named ‘middle scratch’, above which a line is strung so one can see the keel is not crooked or curved when cleated and forced with ropes on the stocks)

We give the reinforced part of the yard, the slipway, a length of 39,5 m and a width of 3,4 m. The stocks are made out of different wooden blocks of approximately 1 foot square with a length of 3 feet, 880 mm.. In those days they would have used old wooden blocks of different shapes and sizes to combine these to the desired height. The wedges have a slighty lesser width as the stocks, say 8 inches, 21 cm and a lesser length, 0,7 m, at the high end 5 inches, 13 cm, at the lower end 2 inches, 5 cm. The stocks are placed heart to heart:

“ontrent 6 Voeten, een weinig meer of min, naar believen, van den anderen mogen leggen”. (p. 55, l. 23) (who are about 6 feet apart, sometimes a bit more or a bit less, measured from heart to heart.)

6 feet measures 1,70 m. The ‘dompblok’ or heave block is situated at 1/5th of the ships length measured from the ‘hieling’:

“Het grootte Block, daar op dat men voornemens is het Schip, ontrent het afloopen, te laten Evenaren, en gemeenlijk Dompblok genaamd werd, komt meesten tyd, een vijvde Deel van Schips geheele Langte, agter uit de Hieling te leggen. De hier agter-leggende Stapelblocken behoeven met geen Stootkeggen voorsien, om dat in Schips nedersetten van sig selvs los vallen: maar alle die de Kiel voorwaarts onderschragen, mogen deselve geensints ontbreeken”. (p. 55, l. 30) (The ‘big block’, on which the ship tilts forward when launched and usually called ‘Dompblok’ (‘heave block’), is normally situated at one fifth part of the total length of the ship measured from the ‘hieling’, the keel aft. The stocks behind this heave block don’t have to be provided with thrust wedges because when the ship tilts forward when launched they are automatically released but in front of this tilting block these thrust wedges are essential.)

1/5th part of the total length of the ship makes 8,78 m. In this case the heave block would stand exactly underneath the second joint so this block is placed a bit more in forward direction. The measurement for placing this heave block is measured from the ‘hieling’ of the keel about which more later on.What is the procedure of the launch and how does this effect the placing and height of the stocks? Cornelis describes in detail how this was done. In chapter 18 he mentions the fact the ship has stood long enough on dry land and preparations to launch ought to begin. After mentioning some things that can go wrong with this launch he concludes by saying:

“Hier uit meen ik den Bouwmeester nu genoegsaam te sullen blyken, dat ontrent sijn Schip in ‘t water te brengen geensints los, of het Werk klein agtende moet wesen, maar met alle Omsigtigheid hier in te werk gaan”. (p. 94, l. 35) (This, I think, will prove clear to the Master Shipwright that concerning launching his ship he will not be careless, or consider this a small work, but instead act with very great care.)


The keel.

After this Cornelis starts to describe the procedure of launching a ship. For the moment we will have a look at the understandings who are important for us to know for placing the stocks. The complete procedure is explained in chapter 8 about the hull.

Thans zal den Bouwmeester ‘t gemelde Dompblok los maaken, twee, ter wederzyden, met Kaarsroet wel vet gesmeerde Wiggen, sodanig daar opschuiven, dat gevoeglijk voor by den anderen konnen heen schieten, en die door de Ram wel dra laten aanstooten. Twee Klinken, op dathet Schip in ‘t nederzetten niet voorwaards mogt schieten, daar op voegen”. (p. 95, l. 2) (Now the Master Shipwright will loosen the mentioned heave block and apply two wedges, at both sides, well smeared with soot and tallow, in such a way they can move against each other and be rammed by the beetle. Two ‘klinken’ are applied to prevent the ships movement forward during its movement downward.)

This movement downward is defined by Cornelis as ‘Evenaren’ and ‘Nederzetten’. What seems to happen is the ship is making a movement downward by hinging at this heave block. During this procedure the danger exists the ship makes a sudden move forward which is prevented by applying these ‘klinken’. What did they look like? In the paragraph about the joints we saw that Nicolaes defined the ‘klink’: “Klink. Het krom omgeslagen eindt van een spyker, of bout”. (p. 599, c. 1, l. 45, 1690) (‘Klink’. The hammered bent end of a nail or bolt). In this case this ‘klink’ could look like some kind of clamp or cramp. Basil Greenhill and Sam Manning give a picture of what this could have looked like:

The keel on stocks with timber dogs. The Evolution of the Wooden Ship, Basil Greenhill and Sam Manning, p.99.

They call these ‘timber dogs’ and are used for temporary fastening. That is exactly what a ‘klink’ in this circumstance has to do. They can be used to fasten the wooden blocks out of which the stocks are composed and to fasten the keel at these stocks. The question is how the keel is lying on the stocks. We know the stocks are placed 1,7 m from each other so lets first make this distribution on the slipway. Second we have to decide what the direction of the keel should be on the slipway. Before the master shipwright is able to do that he takes into account the following:

“Nu zal hy even agter ‘t voorste Stapelblok, een Smeerhout leggen, ter Dikte na dat hy ‘t Schip wil nederzetten, en wel toesien dat de voorste t’ elkens nog lager


The keel.

komen, geplaatst werden. Van ‘t Dompblok, tot op dit Smeerhout, een Touwtje spannende, mag hy al d’ andere regtlynig daar onder schikcen”. (p. 95, l. 16) (Now he will place just behind the first stock a grease timber, as thick as he wants to put down the ship, and look to the fact the one lying fore another is also lying lower. He strings a rope from the tilting block till this foremost grease timber and places all the other in between alongside in a straight line.)

This is an important circumstance. The grease timbers are the wooden blocks on which the ship actually glides forwards into the water, the stocks on which the ship during its construction rested do not serve this purpose. So the direction of the keel lying on the stocks is not the direction just before launch. According to the described procedure, setting up the keel on the stocks can be regarded as the first stage of the ships launch. The next stage starts with loosening the heave block and replacing it by two wedges, hammered against each other and the upper wedge at its upper side heavily greased. After this is done, grease timbers are put between the stocks beginning between the first and second stock. Cornelis says the foremost grease timber is the lowest of all compared to all the grease timbers behind it. If this wasn’t the case the ship would get a lift off instead of a proper launch. This foremost grease timber is installed lower in height compared to the first two stocks: “ter Dikte na dat hy ‘t Schip wil nederzetten”, (as thick as he (the master shipwright) wants to put down the ship) The mentioned ‘thickness’ is the difference in height between the stocks and the grease timber and is at the same time the maximum height the ship tilts downward. This height is subject to the discretion of the master shipwright. The heave block serves as a ‘hinge’ and this moving downward is only possible when, eventually, all the thrust wedges on the stocks in front of this heave block are removed while their function as support for the ship is taken over by the grease timbers. To analyse this it is best to have a look at the profile of the keel seen in sideview. The following picture gives several situations.

Situation 1 is the plain keel with given rocker and shoe in side view. The stocks, wedges and slabs of soft wood are omitted.Situation 2 is the keel with rocker while the strung line above the keel is drawn in red which is the line of reference. The blue line represents the horizontal plane and both lines run parallel to each other. The deepest point relative to the blue line is exactly in the middle. Since the keel is not lying on a horizontal plane but on a slope with an angle of 3˚ with the horizontal, situation 3 arises. The Jaap Luiting © 2016

The keel.

figures behind the keel are the angles the red line makes with the horizontal plane. In situation 3 the blue line represents the slipway and the red line is running parallel to it. The deepest point is still in the middle because the mutual position of the red and blue line, i.e. the keel and the blue line, did not change. The difference in height between the underside of the shoe fore and the blue line is of course exactly the amount of rocker the keel is given: 200 mm. because this keel doesn’t taper in forward direction. Aft the difference in height is 405 mm. a bit more than the sum of rocker and taper 200 + 180) because of the fact the measurement is done at the end of the hieling which protrudes about 375 mm. towards aft relative to the end of the upper side of the keel. Because the direction of the underside is at its steepest fore and aft, a difference in length means a significant difference in height. The measurements are in all cases made perpendicular to the red line.Now the master shipwright has to decide what he wants to do. Does he lay the keel on stocks in this direction as pictured in situation 3 or a bit lower fore? This decision depends on the desirable height the ship moves downward during the launch procedure and the height fore and aft the master shipwright wants to have his keel on the stocks. Cornelis doesn’t mention the height the ship moves downward so lets first have a look at the height of the stocks in the different situations. To make this a bit more presentable these measurements are given in a table. In all variations of situation 3 the direction of the keel stays the same just like in situation 4. Measurements in mm.

In situation 3-1 the height fore between the underside of the shoe and the slipway is 200 mm. fore and aft 405 mm.. If we want the first stock and wedges to have a height of lets say 350 mm. the height at the three locations will be as in 3-2. This leaves little space to work under the keel for which Cornelis advises to have a distance of about 1 m..So, if we give the keel a height of 1 m. above the slipway midships, the height fore will be 1000 + 200 = 1200 mm. and aft 1000 + 405 = 1405 mm.. Also not very desirable because the stock fore is much too high to be able to launch the ship properly because the first grease timber should be positioned as low as possible to enable the ship to touch the water as soon as possible and it seems improbable they let the ship fall downward about 800 mm. prior to launch. The only way to change this is to position the keel in such a way that he lies deeper fore than aft, something Cornelis mentions:

“voor minder, agter wat meerder, na reden dat de Werv meer of minder nedergaande is”. (p. 55, l. 29) ((…..) fore less, aft a bit more according to the slope of the slipway, (…..)),

as well as Nicolaes:

Situation Measured to Height fore Height middle Height aft

3-1 underside shoe 200 0 405


3-3 underside shoe 1200 1000 1405




5 underside shoe 510 435 900

5 underside rabbet 1030 905 1245


The keel.

“Een kiel stapelt men achter hooger als voor, op dat het Schip te bequamer af loope; waar toe de werf ook wel vast dient te zyn". (p. 110, c. 2, l. 48, 1690) (A keel is lying higher on its stocks aft than fore so the ship will launch properly for which the yard has to provide a stable ground)

In situation 4-1 the keel has its deepest point fore so the height fore towards the blue line is 0.This position adds a 1,3˚ extra to the slope of the red line. If we want to have 1 m. beneath the keel the heights will be as in 4-3. This is also not desirable because fore is much too high. Situation 4-2 is much more desirable although the height aft is considerable. All in all the master shipwright will have to find a way to balance the following requirements:

* The keel will eventually have to lay on the grease timbers with a slope to give it its deepest point well before the heave block at the moment of launch because this will be the place where the keel will be supported during launch,* The first grease timber has to be the lowest with regard to the ones behind it and together their upside surfaces form a straight surface for the keel to slide upon,* The first grease timber is as low as possible.

The height under the keel is another circumstance. We have already seen when we give the keel a height midships of 1 m. the height fore and aft reaches undesirable measurements. But if we give the keel this height, measured from the underside of the rabbet towards the slipway the situation will be like in 4-2.In this situation the underside of the rabbet midships is 985 mm. above the slipway while the height under the keel still measures 505 mm. which seems enough for the work to be done there. Also the height fore and aft is much more favourable. The most difficult job next to do on the keel is the cutting of the second stage of the rabbet and the mounting of the garboard strakes. Presumably Cornelis intended to refer to the underside of the rabbet instead of the underside of the keel. This is the only conclusion possible when you want to meet the mentioned 4 requirements. So if we put the keel on stocks in such a way that all the above requirements are met, taking into account the average height of the underside of the rabbet towards the slipway is about 1 m., we finally arrive at position 5. The measurements are given in the table for the underside shoe as well as the underside rabbet.This is the definitive position of the keel as it is placed on the stocks during construction. The angle the red line makes in this position with the horizontal is 3,4˚. The master shipwright can choose how much he wants to make the ship move downward, lowering it on the grease timbers just before launch. This will result in a slight displacement of the deepest point towards fore and an increase of the angle of the red line with the horizontal which gives the ship an extra impuls for launch. The following pictures depict the keel in this position.


The keel.

The keel in its final position on the stocks seen from the front/port side.

The reinforced slipway is the plane in grey, the horizontal plane is blue, the line of reference red. The first stock is placed just before the reinforced slipway. It is dug in into the slope which consists of compressed clay and sand. This block will be completely removed just before launch by digging it in further and/or cleaving it and remove it. The stocks before the heave block are supplied with thrust wedges.

The keel in its final position on the stocks seen from behind/starboard side.


The keel.

The stocks behind the heave block are without thrust wedges as Cornelis describes. Also clearly visible is the ‘hieling’, the end of the keel aft. Cornelis does mention the word but doesn’t give a description. But he gives a picture of a ships hull just before launch where the ‘hieling’ can be seen very clearly.

A ship ready for launch. Cornelis van Yk, p. 100.

As we have seen Nicolaes describes the ‘hieling’ and the purpose of it:

“De lip, die achter aen de kiel uitsteeckt, stut het roer, en verhindert dat ietwes tusschen steven en roer in kome te schieten, en zoo onklaer werde”. (p. 331, c. 1, l. 49, 1690) (The ‘lip’ which protrudes at the underside of the keel protects the rudder and prevents something invading between stern and rudder and thus jamming the rudder.)He gives a picture:

The keel aft with hieling (‘b’ to ‘d’). Nicolaes Witsen, plate 48, 1671

So the oblique side is running from the upper to the underside of the keel, b to d in the drawing, and in both cases in an angle of about 45˚ with the dashed line.The complete launch sequence is discussed in chapter 8 about the hull.


a dutch merchant vessel of 1664. the keel, part 13/15

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