GRP tips please

[steve-V8s]

Posting this question here because I guess some of you kit car lot may have more experience of GRP than others. I have a removable roof panel which has tapered ends front and back that fit into mating recesses on the car. I want to make a copy roof panel but as it is cloth covered taking a mould of the tapered bits will not be easy. What I would prefer to do is form some GRP bits directly into the mating parts on the car. Question is what can I use as a barrier between the car and the GRP ? It needs something a bit thicker than wax release agent, how about aluminium foil, or plastic damp corse sheet any tips anybody ?

[tribbles]

I've used tin foil as an experiment - it worked fairly well, although it was a bit creased so this would be an option if you wanted a rough mould that you intend to smooth over.

Doing it "properly", I've also used PVC as a barrier (I think), which I got from a GRP place in Havant. It needs several coats to be sure that you've got a barrier. However, it'll probably be thinner than wax, but much more even (and you can brush it on, which saves a lot of elbow grease).

[Joe T]

I have used cling film successfully when taking moulds of glass windscreens that were delicate.

[tribbles]

I did consider cling-film, but I was worried about the heating process of GRP causing it to melt. I take it that didn't happen to you then

[Joe T]

Nope it was fine, the first coat was a thin one and then we let that go off fully before applying the next layers.

http://silicon.fastnet.co.uk/specialist-car/php/ob...

You will get the odd line or wrinkle but it does allow the mould to come out easy. The glass is still in the car and fine.
I would experiment on something else first to see how it goes for your own peace of mind etc.

Edited by Joe T on Friday 1st January 18:03

[Steve_D]

I have used cling film and it melted/disolved so it may depend on what type of resin you use.

A test piece would give peace of mind.

Steve

[steve-V8s]

Thanks for the replies. Will try some foil to start with.

[GTRCLIVE]

Am I missing something here ? whats wrong with 4 coats of wax then 1 coat PVA ?? will it not work on glass ???

[gtmdriver]

I've certainly used PVA release agent on glass. I would have thought that would be the way to go?

[Funky Diver]

I've used vaseline for all manner of "masking" parts, including solid epoxy resin based modelling. The beauty of it is that once formed it just washes off with soap and water.

[GTRCLIVE]

PVA is water soluble. Just a damp rag cleans it off...

[tribbles]

I did mean PVA, rather than PVC

[qdos]

PVA is the stuff. If you use wax use Mirrorglaze about 3 applications ideally before applying the gel but you're best off using PVA