Plaster moulds?

[ayjay]

I,ve done a bit of moulding and the advice so far is generally good.

However if you need to design a body panel from scratch then plaster is a good idea. It willneed a fair bit of sanding ,scraping ,shaping smoothing (all the s's eh!) in order to make a model .You could then use that to make your pattern mould out of GRP.
You would save a lot of time by making a rough shape out of polystyrene blocks but slightly smaller than needed then smooth on your plaster . then the hard work comes to refine the shape as S's above.
Dont use pink plaster the stuff called "onecoat" is a lot more forgiving and easier to handle( white in colour --Wickes etc)
You can easily stop it cracking by reinforcing it with thin bandage and shave it down with an angle grinder(not indoors) .Get the final mould surface with something like car body filler fine sanded to the final shape.
We used to use silicone spray as a release agent but theres probably something better specially for releasing GRP.Hope this helps---ENJOY

Imagine you have made your plug and it's shiney ready to mould...use honey wax to wax it about 5 or 6 times then decide where your shuttering needs to be to allow removal from the plug....when shuttering sorted pva release using a sponge, let it dry then gel coat, leave this to go tacky..ie you can leave a finger print in it but nowt on yer finger then startlaying up...when you have got the layers needed take the shuttering off and lay up the other side to create your joint......simples really.

Grab someone from the boat yard and barter with a few pints you might even end watching him do it for you...

[ayjay]

You obviously all know a lot more about this than I do but it all sounds like a good idea I may just have a go at front mudguards to begin with.

Don't expect top results taking a mould from body filler as even waxed and pva'd it can stick like the proverbial dogs stuff...also don't use celly paint or laquer as this too reacts these days as something has changed in the paint(yeah i found out the hard way ) Best paint to use is 2pk, don't worry about pin pricks in the surface as these will be high spots on the mould which can be flatted out with with wet n dry.

Loadsa shoulder destroying work but it can be satisfying...apart from the shoulder part of it

More often than not it's cheaper to just buy the parts if available, because to create a plug then a mould takes a lot of time and more money than you first thought.

My daft car mould took 4 months of plug work then mould took another month or so, the plug was then binned as it had served it's purpose but it hurts to throw money in a skip like that
One day it might see the light of day if such a thing is allowed by MSVA...yeah no IVA for the beast