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VIDEO TUTORIAL

How to Make an Accurate Composite Pattern by Hand

If you have an original design idea for a new fibreglass or carbon fibre part then before you can make the part itself, or even make the moulds you must first make a pattern.

In this comprehensive video tutorial we demonstrate a step-by-step composite pattern making process that can be used to reliably produce dimensionally accurate and professionally finished patterns entirely by hand.

TUTORIAL BREAKDOWN

1. Create the basic shape

At the start of the tutorial we explain what a pattern is and why they’re required in the composite mould making process before going on to show how 3D CAD designs can be printed out as profile templates which can be used to create a dimensionally accurate skeleton of your pattern using Closed Cell PVC Foam.

Once the profile skeleton has been created we use Low Density Polyurethane Foam to block out the basic shape of the pattern. The foam is then shaped using basic hand-tools like hacksaws, a Perma-Grit Sanding Block and Abrasive Paper.

The surface of the pattern is then smoothed and filled using a Patternmakers' Bodyfiller (coming soon) before flatting back any high-spots using a coarse abrasive paper.

2. Surface the pattern

Next, the pattern is coated in Pattern-Coat Primer which is allowed to cure before the cured Primer is then flatted back using a 120 Grit Abrasive Paper and a new layer of Pattern-Coat Primer (mixed with a guide pigment) is applied. This process is repeated until the pattern is perfectly flat with no high-spots or low-spots. If any low spots exist they can be filled using a small amount of the bodyfiller in between applications of the Pattern-Coat Primer.

At this stage, the pattern can either be flatted using finer abrasive papers and then polishing compound up to a smooth, satin finish or, for a high-gloss finish, the surface can be coated with Pattern-Coat Hi-Gloss which we choose to do in this tutorial.

3. Polish the pattern

The Hi-Gloss is then dry-flatted using 400grit Abrasive Paper and then wet-flatted using progressive 800grit, 1200grit and 1500grit Abrasive Paper. Once the pattern is perfectly flatted to 1500grit we use a NW1 White Super Cutting Compound for hand polishing progressing to TOPFINISH 2 for an ultra-high gloss by hand or machine for a ultra-high gloss finish.

The pattern is now complete and ready to be coated in release agent prior to starting the mould making process.

DISCUSSION (14)

Please share any questions or comments you may have about this video tutorial.

miller chassis

can you spray the Pattern-Coat Primer and Hi Gloss?

Easy Composites› Matt

Yes, definitely. Both the Pattern-Coat Primer and Hi-Gloss can be sprayed. Both may benefit from moderate thinning with acetone or styrene, up to about 25%. The Primer should be sprayed using a Gel Coat Cup Gun and the Hi-Gloss through a normal spray gun. Full details can be found on the Technical datasheets for each product.

Chris' RX7 FD

Do you recommend using a palm sander for a job like this?

Easy Composites› Matt

Yes, definitely - a 'DA' (dual action sander) is a 'must-have' bit of kit if you're doing much pattern making by hand. Mirka make an amazing palm sander called the Ceros - it uses a mesh sanding pad which dust can be extracted through - the sander is then connected to a vacuum or extractor. They're not the cheapest sanders but are really great for this can of work. Palm powered air sanders are also great.

0MotheGo

There is also closed cell vinyl foam, what about that? Does it sand?

Easy Composites› Matt

The thinner green foam you see us using (to make the initial structure) is closed cell PVC foam. It does sand but not anywhere near as well as the polyurethane.

Fred Feng

Hi great video. Can anyone explain what is low spot and high spot? Thanks a lot!

Easy Composites› Matt

Sure; a 'high spot' is an area of a surface which is higher than the majority of the surrounding area, a low spot is the opposite where a part of the surface is lower than the surrounding areas. The process of 'flatting' is all about getting rid of high or low spots to leave your whole surface 'flat' and smooth.

Marty Handley

Could spraying of the Pattern Coat Primer reduce the amount of sanding that will be required?

Easy Composites› Matt

Yes, definitely. Most people don't have spray equipment but if you do then you can spray the filler primer and it will give you a smoother starting point which will mean less flatting/

Jasper amirante

Can you use the Pattern Coat Primer resin be used on extruded polystyrene foam (XPS)? If not, what else can you use?

Easy Composites› Matt

No, Pattern Coat Primer is styrene based and so it will dissolve polystyrene foam instantly. If you want to use a styrene-based resin system (such as polyester or vinylester) on XPS then you would need to coat the XPS shape in a 'shell' of epoxy resin first. Epoxy won't affect the XPS and it will protect it from the solvent (styrene) in the Pattern Coat Primer.

Camden Burke

Where can I get the filler used? And what did you mix with it? Where can I find that as well. Trying to buy everything from you guys.

Easy Composites› Matt

Hi Camden, the bodyfiller is one of the only things in this video that you can't get from us, simply because it's so easy to find elsewhere we decided not to bother carrying it. We're just using a basis 'easy sand' car bodyfiller. U-POL make a good one, you can pick it up from any motor-factors, hardware store or the usual online places.

MickHornBak

This is an excellent tutorial. I wish a had a high tech machine to CNC my own complex patterns. It's really hard to do those by hand.

Easy Composites› Matt

Yes, there's time and effort goes into hand making a pattern. These days though, the price of CNC routers is coming down and machines like the Stepcraft are within reach if you feel like making an investment. Software like Autodesk's amazing Fusion360 is FREE (for non commercial use) and will output the GCODE to a router like a Stepcraft. You can then machine PU model board for instant patterns.

Avi Aero

When designing the 3d model of the pattern do you consider the tolerance from the thickness of the number of coating and primer going on to the mould?

Easy Composites› Matt

Good question! If your were going to machine the pattern and you needed a very high level of dimensional accuracy then yes you would want to take it into account. However for most less-precise projects like this, by the time you've sanded the foam and recoated it with primer, it tends to be pretty close to the original dimensions.

lpoollax7

I don't have your Pattern Coat Primer or Gloss. Is there anything else I can use in place of it to make a mold from? I have laminating epoxy and tooling gel coat available.

Easy Composites› Matt

Laminating epoxy can be harder to sand than a typical pattern coating system, but with a bit of elbow grease you can still achieve a good enough gloss to take a mould from and if you have it to hand then, yes, no reason why you couldn't use it.

Gary Leafty

Would these techniques and materials work to make a hood scoop and bond it to a metal hood to make a mold of the hood with a hood scoop to be used to make a carbon fiber hood.

Easy Composites› Matt

Yes you could do that no problem. Bond the piece into place on the hood then take care to finish off the transition between the foam pattern and the metal so the finish is smooth then take a mould off it to make the finished hood from.

George Ghaly

To be honest, this is a remarkable video and finish... Very nice job out there. But the thing is, it is very time consuming process. It can take days to do single mold. Please let us know if there is something quicker than this. Thank you.

Easy Composites› Matt

The only quicker method is to CNC the pattern into an epoxy tooling block. Although it is still a time consuming process, albeit a lot of it is hands off while the pattern is CNC cut. We have a couple of tutorials which demonstrate this process.

Ernesto garcia prieto

I'm thinking of making a mold for laminating carbon fiber by resin infusion. My mold will be modelled in a 3D software then with sliceform wood and foam as in the video. Do I need to make a pattern then a mold or could I make the mold in the first place?

Easy Composites› Matt

Whilst it is possible to make the mould in the first instant, usually it is far better to make a pattern (the 'male' shape) and then make a fibreglass mould (the 'female' shape) from the pattern. One reason being the ease of getting a good finish - it's much harder to get a good finish on the concave inside of a mould than on the outside of a convex pattern. Another being the strength and durability of the finished mould - foam, wood slices and coating resin are not anywhere near as strong as a solid laminate fibreglass mould. There's other reasons too. I would say if you only want to make one part then you can consider making the mould without making a pattern first; if you're planning on making more than one part then I would say it would always be better to make a pattern first.

Jonathan Gallenstein

Would it be possible to make a patterned gel coated piece like this and then just put a carbon fiber skin over it instead of making a mold? I want to make an original piece trunk spoiler in carbon, but don't really want to have to make a mold since i would only be making the one piece...

Easy Composites› Matt

Yes you can skin the part in carbon fibre. You may want to consider more than one layer to make sure it is strong if the pattern is not already strong enough.