casting instructions jan22

Automotive Design Model Shop

Instruction Manual

Congratulations! You have created your very own custom car

design using the Design Studio Pro automotive design car builder kit.

Copyright March 2012

Automotive Clay Model Casting and Fabrication

Copyright 2012 - Claymodelers.com

Table of Contents

Step 1 - Flanges ............................................................................................................................................. 4

Step 2- Mold Surface Preparation ................................................................................................................. 5

Step 3 Applying Gel Coat ............................................................................................................................... 5

Step 5 - Body Side Flange .............................................................................................................................. 7

Step 6 - Body Side Gel Coat ........................................................................................................................... 8

Step 7 - Body Side Lay-Up ............................................................................................................................. 8

Step 8 - Top Of Mold Lay-Up ......................................................................................................................... 9

Step 9 - De-Molding ...................................................................................................................................... 9

Step 10 - Prepping The Mold ...................................................................................................................... 10

Step 11 - Body Gel Coat .............................................................................................................................. 10

Step 12 - Body Lay-Up ................................................................................................................................. 11

Step 13 - De-Mold The Body ....................................................................................................................... 12

Step 14 Clean Up And Paint: ....................................................................................................................... 13



Model Builder Automotive Clay Model Casting and Fabrication - Instruction Manual

This manual explains, step-by-step, how to cast your model. If your clay model is in great shape,

continue to the casting directions. However, if you would like to improve the clay surfaces before

casting you may follow these steps.

1. Use sprayable Shellac™ to seal the clay. Spray the entire model evenly. Try to avoid making runs

in the surface. Allow 24 hours for the model to dry completely.

2. Use a Scotch Bright™ or sand paper to lightly scuff the model surface in order to take the shine

off of the Shellac™. Use sanding filler primer to prime the model evenly. (You can buy sanding

filler primer at your local auto parts store). Depending on the clay surface, you may want build

up layers of primer to fill the low areas on the clay model. Use a sanding block and 150 grit sand

paper to surface the model. (Use spot putty or body filler to make surface repairs if needed). Be

very careful not to burn through (sand until there is no primer) to the clay.

3. Once you have the surfaces at a satisfactory level, prime the model once more and sand with

300 grit paper.

Congratulations! You are now ready to cast your model! Continue to the casting instructions.

All materials needed for this model building exercise are available at any local boat supply store or a

home center such as Home Depot.

Items needed to complete the car body 5 piece mold are:

Polyester gel coat- 1 quart

Polyester resin- 1 quart

Two yards- 10 oz. Fiberglass cloth

12 oz. Bottle of PVA mold release

1 roll of ½” masking tape

8-16 oz. Paper cups(for mixing resin and gel coat)

8 cheap 2” paint brushes

1 can of mold release wax

1 can Spray on vinyl strippable (optional)

8 pairs of latex gloves



Casting Directions

Step 1 - Flanges

Mark all graphic lines in the clay. The first step in casting your clay model is to create flanges.

You can cut shim stock or use clay. Look at the 5 piece mold we took off our clay model, we

placed our flanges along the corner edges of the model. You should do the same to decrease the

chances of die lock. (Die lock is where the angle of the tool (mold) is negative and restricts your

ability to pull the mold off of the plug (the part you are casting). The plug in this case is the clay

model.

Start by casting the front and rear ends. Build the flanges for both ends before applying the

mold release agents.

Use a black marker, indicate on the clay where you want to place the flanges. You may use the

DSP clay or other suitable clay from your local craft and hobby store. Protect the clay surface

where you will later place the flanges with masking tape.

Put the edge of the tape on your marked line. The flange edge should be at least 1-1/2” from the

clay surface.



Now that the clay flanges are complete, measure the entire area of the casting surface. (You will

cast the entire area of the car as well as the clay flange). Use these measurements as a guide to

cut the fiber glass.

Pre cut at least two pieces for each section. Use a strong pair of scissors. Set the fiber glass aside

for now. Cut 2” strips of glass cloth. You will use these to strengthen the flanges.

Step 2- Mold Surface Preparation

Once you have created your front and rear flanges, cover the clay model with masking paper.

Lightly tape the masking paper to the back side of the clay flange.

Note: Be sure to wear gloves throughout the casting process.

(Optional) Get your can of Strippable release. Shake the can very well. Spray very thin and light

coats at first. This material has a thin consistency and runs easily if you spray too much. After

establishing a thin layer you may use the spray more liberally (allow Strippable to dry

completely).

Lightly brush PVA release agent over the casting area. Brush at least two coats (allow PVA to dry

completely). Use the mold release wax and lightly wipe the casting surface.

Step 3 Applying Gel Coat

Protect your working area by placing masking paper underneath the casting areas.

Measure out 4 oz. by weight of Gel Coat (surface coat) and place the proper amount of hardener

in a resin bucket.



Mix the gel coat well, lightly brush the surface of the casting area. Build up a 1/16” thick layer.

Brush the Gel Coat on both front and rear ends. You can use the Gel Coat as filler for the hard to

get to negative details in your design.

The Polyester Gel Coat we are using may kick (Become solid) quickly depending on how much hardener

you add to your gel coat mix. Try to keep to the manufacturer recommended mixing ratio. If the Gel

Coat kicks in the bucket, simply mix a little more. You will need to apply the resin coat while the Gel Coat

is still partially sticky. However, if you apply the fiberglass coat too soon, the glass mesh may be

imprinted onto the mold surface. (If at any time one of your gel coat or resin coats dry completely

between steps, scuff up the surface with sand paper and repeat the process). Drying time may vary. If

proper hardener ratio was achieved, the surface coat should be ready for the lay-up within 1/2 hour.

Check the flange stickiness often.

Step 4 - Front and Rear Lay-Ups

While the Gel Coat is still sticky, start the fiberglass layup process by gathering the pre-cut fiberglass

pieces. Measure out 2 oz of resin and place the correct amount of hardener in the resin bucket. Start

with the front or rear end. Be sure to mix the resin well. Lay-up one end at a time.

Use a clean brush to wet out (paint) the casting surface with a thin layer of resin. You can verify

the readiness of the gel coat by touching the flange area. It should feel sticky; but at the same

time not transfer to your fingers.

Mix two ounces of resin. Make sure to use the appropriate amount of hardener (mix well). Using

clean brush paint a thin coat of resin onto the sticky gel coat surface. (Warning) If the gel coat

has dried to long and is not sticky, you must sand the surface to create a physical bond between

the gel coat and the resin.

Take one piece of the fiber glass and place it over the casting surface. Use your brush to press

and push the fiber glass onto the gel coat surface. If the fiberglass layer looks wet enough, take

your second piece of fiber glass and place it on the same area. Use your brush to push, dab and

press the fiber glass cloth onto the casting area. Apply the fiber glass strips around the flanges.

Trim the outer edges with scissors (use Acetone to clean the resin or gel coat off the scissors).

You may use your fingers to help the glass stay in place while it is kicking (getting hard).We do

not need the casting area to be dripping with resin. Only wet your brush as needed. You may



need to apply pressure using your fingers and a brush as the resin kicks in order to make the

stubborn areas stay in place (in-takes, chin, and the flange negative intersections).

(Warning) The resin may get hot and kick in the bucket if it sits in there too long. Be sure to work

quickly. However don’t panic. You can always get a new bucket and brush. To clean up after laying up

the fiberglass, use Acetone and a rag. Be sure to clean your scissors with acetone before the resin

hardens. Follow the safety steps listed on your resin container.

Step 5 - Body Side Flange

Let the front and rear lay-ups completely dry. (It may take several hours. To check if the lay-ups

are dry, carefully touch the part, if it is still sticky, it is not dry).

When dry, carefully remove the clay flange off the model. Be sure not to pop the part off of the

clay. We need the fiberglass part and flange to remain on the model.

Next, we create flanges along the cars rail. Use the same method as before.

Try to make the flange be one continues flange from the front to the rear. If you need, use clay

to seal up the flange intersections and corners.



Step 6 - Body Side Gel Coat

Repeat the strippable, PVA and wax process for both body sides of the car. (Warning) Be sure

to have adequate mold release agent on the fiberglass flange. The Polyester resin may want to

create a chemical bond if the flange is not properly prepared with the mold release agents. From

this point on it is recommended to apply 3 coats of PVA mold release agent.

Repeat the process of brushing the gel coat onto the casting surface. Mix as much gel coat as

needed to cover both body side and flanges.

Measure the body side fiberglass pieces and pre-cut. Cut 2" strips for the flange strength.

Step 7 - Body Side Lay-Up

Repeat the process of laying up the fiber glass.

Cut strips of fiber glass cloth to strengthen the flanges. You may need to cut the fiber glass to

get it to wrap under the wheel openings. You may need to apply pressure as the resin kicks in

order to make the stubborn areas stay in place (wheel openings, rocker, and the flange negative

intersections).

Repeat all the body side lay-up steps on the opposite side of the clay model.



Step 8 - Top Of Mold Lay-Up

Allow the body side lay-ups to dry completely, then remove the clay from the body side flange.

Repeat the Strippable, PVA and wax steps for the top surface of the model. Be sure to use plenty

of mold release on the flanges.

Pre-cut your fiberglass pieces. Cut strips of fiber glass cloth to strengthen the flanges. Mix

enough gel coat to complete the mold. Build up a 1/16” surface and layup the top surface the

same way as the front, back and sides.

After your mold is completely laid up and fully cured,(allow 24 hours) drill several small holes

through the center of the flanges every few inches. Drill more holes as needed. Bolt the mold

completely. Use ¼” x ¾” bolts.

Step 9 - De-Molding

Once the mold is bolted together, use a grinder, saw or sand paper to clean up the mold edges.

Cut the front, rear, rocker, and wheel opening edges so that their return is about a 1/8”.

De-mold the clay model by removing the bolts and using a scraper or thin spatula to remove the

parts off of the clay model. If your parting flanges are placed in the right place and you have

enough mold release, your part should pop out of the mold with ease. If you find that the mold

is sticking or being held up, lightly tap the mold with a rubber mallet. You may need to use

multiple wedges to spread the flanges. Apply the pressure evenly. If the mold is still hanging up,

drill a small hole through the mold layer of fiber glass, use air pressure to help release the part.



After you have completely removed the mold off of the clay model, use water to clean the PVA

off the mold surfaces.

Step 10 - Prepping The Mold

Clean and wax each piece of the mold thoroughly at least 3 times per part (wax on, wax off).

Bolt the mold pieces together snugly. Use your finger to press mold release wax into the mold

parting lines. Brush the PVA over the whole surface of the mold at least two times. Wax the

outer shell of the mold as well, this well help keeping it clean.

Step 11 - Body Gel Coat

First, cut the fiberglass that goes from the front edge to the rear edge including the roof section.

Cut that piece about two inches longer than the overall measurement and about two inches

wider than the width measurement. Cut your body side pieces using the same technique. Cut

some thin strips of fiber glass to beef up the flanges and mold part lines. Make sure that your

layers of fiberglass overlap. Mix enough gel coat to cover the entire mold.

Build up the 1/16" surface coat. Protect the outer surfaces by putting tape on the mold.



Step 12 - Body Lay-Up

Once the gel coat layer is at a firm yet still sticky point, wet out the front, roof, and rear sections

of the mold with resin.

Lay in the large piece of fiber glass from front to back. Use a brush and continue the layup

process. Once you have at least two layers of this section complete, layup one body side at a

time. Try to overlap each layer. Remember that you only need enough resin to wet the fiber

glass. If you make a part that is to wet, the part may kick quicker than expected.

As the part is kicking, use your fingers and brush technique to keep all the edges down. If any

areas are stubborn and don’t want to stick, Use your scissors and make relief cuts in the fiber

glass. If any areas need relief cuts leave areas with no fiber glass, Cut patch pieces. Make sure

you have at least two layers of glass over the entire mold.

Allow the fiberglass to cure in the mold for at least 24 hours.



Step 13 - De-Mold The Body

Once the part is completely cured in the mold, (It should not be sticky at all) remove the bolts

from the mold one section at a time. Use a scraper or spatula and carefully separate the mold

from the part.

If your parting flanges are placed in the right place and you have enough mold release, your part

should pop out of the mold with ease. If you find that the mold is sticking or being held up by

something, lightly tap on the mold with a rubber mallet. You may need to use multiple wedges

to spread the flanges. Try to apply the pressure evenly. If the mold is still hanging up, drill a

small hole only through the mold layer of fiber glass and use air pressure to pop the part.

Clean up the mold pieces with water and acetone then bolt it back together. You should store

your mold as one piece. Clean the PVA off the car body with water and a sponge.



Step 14 Clean Up And Paint:

Clean the PVA off the car body with water and a sponge. The PVA is water soluble.

Use a grinder, saw and or sand paper to clean up the edges. Use a medium hardness sanding

block and 150 grit sand papers to knock down (sand) the mold parting lines on your car body.

Sand the entire body lightly. This will help to clean up the Gel Coat surfaces.

Using a can of sanding primer, prime the car body once, then sand it with the 150 grit.

Depending on the model surfaces, you may want build up layers of primer to fill the low areas

on the clay model. If the car body surface needs spot putty or body filler, be sure the surfaces

are clean from dust and oils.

Prime again and sand with 320 grit paper. If you still need to spray more primer, sand with 600

grit for final paint prep.

You may use any model paints.

Congratulations! You have created your very own custom car design using the

Design Studio Pro automotive design car builder kit. And now you have your custom RC car or

Display model complete. That was a lot of work. Well done!

casting instructions jan22

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