Help with Fiberglass HowTo... Replicating from parts

[CDN224]

Team,

I'm considering using some of my car parts for moulds in fibreglassing. I was wondering if any of you have experience in this area, and particularly fender replication. Seems easy enough, and perhaps cheaper for the DYI'er.

[Rusty_OToole]

I fooled around with making fibreglass fenders years ago. Start with a good fender, or patch up the old one. The main thing is to have a smooth shiny surface.

Coat the surface with mold release. PAM cooking spray will work. Coat the fender with plaster, there is a hard plaster you can get from a good building supply place, not Home Depot but where plasterers buy supplies. One brand is Diamond Hard if you can still get it.

A coat of hard plaster 1/16 or so is all you need. Let it dry. Then you can use cheap plaster and burlap to cover the fender. Build up layers to a strong thickness, say 1/2" or so. You have to use your own judgement here, depending how big the part is.

When you are done, mold a plastic pop crate into the back of the mold to make a stand. When it is dry, carefully work the fender loose and take it out. A compressed air hose can be a help in removing a part.

Coat the mold with car wax and mold release agent and lay in your fibreglass. If you are careful and don't knock it around you can make dozens of parts from a plaster mold.

And, they are cheap. A sack of plaster and some burlap from the garden center will make at least one mold at a cost of under $20.

[CDN224]

Thanks Rusty,

Ive been youtubin this topic, and yep, seams easy and cheap.. Ill keep you posted on my progress...

I also came across this tuber... very good video... http://www.youtube.com/watch?v=GXzR17LktSg

I fooled around with making fibreglass fenders years ago. Start with a good fender, or patch up the old one. The main thing is to have a smooth shiny surface.

Coat the surface with mold release. PAM cooking spray will work. Coat the fender with plaster, there is a hard plaster you can get from a good building supply place, not Home Depot but where plasterers buy supplies. One brand is Diamond Hard if you can still get it.

A coat of hard plaster 1/16 or so is all you need. Let it dry. Then you can use cheap plaster and burlap to cover the fender. Build up layers to a strong thickness, say 1/2" or so. You have to use your own judgement here, depending how big the part is.

When you are done, mold a plastic pop crate into the back of the mold to make a stand. When it is dry, carefully work the fender loose and take it out. A compressed air hose can be a help in removing a part.

Coat the mold with car wax and mold release agent and lay in your fibreglass. If you are careful and don't knock it around you can make dozens of parts from a plaster mold.

And, they are cheap. A sack of plaster and some burlap from the garden center will make at least one mold at a cost of under $20.

Edited September 24, 2013 by CDN224 (see edit history)

[rhb1999]

The part your going to make a mold for (called a plug) should be perfect. I worked on a plug for a 28' boat out of wood then they sprayed the hull and superstructure with a primer called Duratec (I think it could be sprayed thick if needed) then we sanded everything with 150 and 220 grit and then it was able to be buffed to a high gloss. Re: the video, I don't think it would have taken much time to to put plywood butt strips underneath at the hood seams.

[Rusty_OToole]

There is a web site called "forgotten fibreglass" all about early fibreglass sports car made in the US 1950 - 1970s. It has on it several early magazine articles and books about making moulds and moulding fibreglass bodies. One article from 1954 describes making a whole car body in plaster then making a plaster mould.

It might be interesting although there must be better methods now if you do a web search.

[rhb1999]

What they did after the plug was buffed and waxed was, they sprayed a tooling gel coat over the whole thing to a specific thickness, then with a chopper gun (a device that sprays resin and catalyst and at the same time cuts fiberglass rope from a spool via a cutter wheel) the plugs were "skinned" using tooling resin made for high tempurature and strength, then alternate layers of fiberglass mat, woven roving or fab-mat (mat and roving bonded together with starch) to a thickness consistent for a mold. Fittings for compressed air had been installed in the plug, as well as "pull tabs" for attaching grappling hooks to pull the mold from the plug.

[Rusty_OToole]

I have been thinking about this since the question came up. What if there is a better more modern way to get at the same thing? How about using urethane foam, the expanding stuff you get from lumber yards that is meant for sealing cracks and holes?

Cover your part with fibreglass for a smooth hard surface then cover the fibreglass with a few inches of foam to give it body and make it rigid. You could even stick some steel or wooden braces in the foam.

Easy to do and should make a good mould without costing too much money.

[Luv2Wrench]

I make plenty of plugs with just fiberglass mats and resin. I'll add some wood bracing in the later steps if needed. If you part is relatively smooth and doesn't have a lot of detail, this technique works well and I find it easier than working with plaster (which can shrink and crack). Make sure to go and get a mold release agent. Breaking your new part and/or your mold stinks.

[rhb1999]

I have been thinking about this since the question came up. What if there is a better more modern way to get at the same thing? How about using urethane foam, the expanding stuff you get from lumber yards that is meant for sealing cracks and holes?

Cover your part with fibreglass for a smooth hard surface then cover the fibreglass with a few inches of foam to give it body and make it rigid. You could even stick some steel or wooden braces in the foam.

Easy to do and should make a good mould without costing too much money.

They sell foam in liquid form too.