Having a play with laminating..

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Having a play with laminating..

Postby Rich » Thu Oct 14, 2010 3:14 pm

It isn't as easy as you might think is it? Having a GRP car I thought it might be an idea to have a go, plus my youngest wants to make an airboat this year.

I picked on the tear drop panel that covers the wiper motor on the Mk3 to make a mould and used a wet lay up with polyester resin. A couple of problems with that, firstly getting the original panel out of the ruddy mould can be torturous , particularly if you only used wax as a release agent, secondly there were bubbles and folds in the fabric. Doing it all over again with some careful cutting of material yielded better results but still nothing II wanted to use.

Ok, plan B... spend some money. I bought some epoxy resin, tissue fibreglass sheet.... and a vacuum pump. I'd followed a few pumps on Ebay which had all gone for more than I was prepared to pay for an experiment. Freeads turned up an old British made laboratory pump capable of pulling a gnats gonad short of absolute vacuum for £25. With the pump comes more expense as you have to buy vacuum bagging, permeable membrane, peel ply, breathable wadding and double sided adhesive tape.

The next attempt which was my first go with vacuum consolidation which further showed up the problems with using the wax for release, the epoxy stuck like the proverbial to a blanket and some of the gelcoat ended up staying with the mould instead of on the original panel. Ok, enough of this, I'm trying to create something, not destroy what I've already got.

Luckily when the gel coat was removed form the mould the surface wasn't bad, not perfect but not bad. The next step is to use the mould to create a plug to form a final finish mould. This time I've used PVA release agent which worked far better and with only a little bit of wrestling the plug popped out of the mould. As I type this I'm taking a break from cleaning up the surface of the plug, hopefully I'll have some decent pics to put up soon.

Rich
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Re: Having a play with laminating..

Postby manifold » Thu Oct 14, 2010 4:01 pm

always use pva rich. its guaranteed to release especially with water. leave wax to the pro's....and even they cock it up sometimes.

Use 2 coats of gelcoat and let it go off and you have half a chance of not having bubbles showing too (hidden in the layup behind)
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Re: Having a play with laminating..

Postby Rich » Thu Oct 14, 2010 5:26 pm

manifold wrote:always use pva rich. its guaranteed to release especially with water. leave wax to the pro's....and even they cock it up sometimes.

Use 2 coats of gelcoat and let it go off and you have half a chance of not having bubbles showing too (hidden in the layup behind)



That's the problem, when you look it up the advice is conflicting to say the least. Anyway, PVA it is from now on.

I haven't used dedicated gelcoat as yet, just using a couple of layers of epoxy as ultimately I'll be using carbon fibre with an exposed weave. Given that it comes in at £30 per square meter I want to get this right before it gets really expensive. I've found blowing the epoxy over with a hot air gun sorts out most of the small bubbles when the resin is still flowing well. The stuff I've got now takes up to three hours to go off to touch tacky when mixed to the exact weights.

I don't suppose anyone knows what RAL colour was used for the red gelcoat by the GTM factory?
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Re: Having a play with laminating..

Postby Hans Efde » Thu Oct 14, 2010 11:23 pm

Rich wrote:I don't suppose anyone knows what RAL colour was used for the red gelcoat by the GTM factory?


It wasn't a RAL color but a DSM gelcoat. On the archive website you'll find the DSM bochure with the gelcoat spec. and colors in the dir. "brochures general".
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Re: Having a play with laminating..

Postby Rich » Thu Oct 14, 2010 11:35 pm

Thanks Hans, I'll have a dig round.

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Re: Having a play with laminating..

Postby Rich » Thu Oct 14, 2010 11:38 pm

Oooookay, a choice of brilliant, signal or pirate(?) red......
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