I am getting ready to build a model of a British police boat and I have a styrene hull that I would like to use as a plug to make a fiberglass mould. What the best way to go about doing this? At this point, the hull is just unpainted white styrene (or plasti-card) that has been vac-formed.

I'm pritty sure that the poly resin will destroy the hull you have, maybe epoxy would be better, a little pricy though.

cover the hull with a separator of some type {like a very thin coat of Vaseline} then use plaster bandage {hobby shops have rolls kind of the stuff} soak and wring out most of the water and NEATLY lay on the hull. when it has set, pop the two apart put the plaster wrap in sand so it will not change shape, Vaseline the inside again then fill with 20 minute casting plaster {hobby shops and craft stores also carry this} the mold can be worked while it is still moist. the final smoothing can be done with a wet cloth and polish really smooth. I would then let the mold dry when ready more Vaseline and lay your fiberglass. when set, unless you have some serious under cutting it should come off

Yep, thats it.

Originally Posted by TOWHOOK

I am getting ready to build a model of a British police boat and I have a styrene hull that I would like to use as a plug to make a fiberglass mould. What the best way to go about doing this? At this point, the hull is just unpainted white styrene (or plasti-card) that has been vac-formed.

I've always wondered how to do that, but never tried anything.

Guess I'll just sit back and watch what develops---.

Well Kap, what I was thinking, was give it a couple of coats of gloss paint, spray it with pva and then do a gel coat layer followed by a few layers of mat fabric or chopped mat. who knows? wait and see I guess.

Originally Posted by pamela31

I'm pritty sure that the poly resin will destroy the hull you have, maybe epoxy would be better, a little pricy though.

Yeah, I have heard that polyester resin will eat styrene for breakfast also. Epoxy was the direction I was leaning in.

I'd go using your idea, Towhook. If you seal off the plastic well enough, polyester will do it for a mold. No need to use epoxy---.

If you use too much resin, you may get the hull too hot. Make sure it is shored up so it doesn't move.


D

Originally Posted by CaptDH

If you use too much resin, you may get the hull too hot. Make sure it is shored up so it doesn't move.


D

it's not the resin that goes hot........it's the chemical reaction between the resin and the catylist.......and even using a low percentage of catylist to resin to make a slower reaction time, you will still get heat, and no amount of "barrier cream" or other barrier agent will stop a reaction between styrene and resin if it wants to get through..............DO YOU WANT TO TAKE THAT CHANCE even if only 25% when other methods can be used........I know I wouldn't.

You ruined a good one of these :-



Followed with one of these :-

And a lot of these :-

And definately loads of these :- Neil.

Regards Ian.

A lot of negatives coming in from all sides---.

Have any of you "experts" actually worked with fiberglass?

Or are you casting about theories---?

Originally Posted by der kapitan

A lot of negatives coming in from all sides---.

Have any of you "experts" actually worked with fiberglass?

Or are you casting about theories---?

You really need to see the Tee shirt, watch the Video etc. ??

I can vouch for two replies.

Regards Ian.

I would use Dostacos way FIRST. That way there in not a big outlay of cash and the original will still be around to try a differnet way if you so desire.
Heat is a major factor with the polyester way.

Epoxy does not stick to styrene very well. An example is after mixing and using epoxy in a styrene cup (not foam plastic) let the remainder set up in the cup. After dry you can just pop it out and the cup is ready for another batch. Poly resin will eat foam plastic such as used by the r/c aircraft guys. Epoxy won't. Do use a barrier such as vasiline or a wax to make removal easier.