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Old Jun 11, 2014, 11:47 AM
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Shrouds and Fiberglass

Anyone have any advice for foam and fiberglass?

I want to make 30 inch diameter shrouds for a project I am working.

Could someone lead me into a good direction as to what foam I should use, the fiberglass, and possibly the differences between resin/epoxy/fiberglass/ etc.

Thanks!
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Old Jun 11, 2014, 12:34 PM
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I want to make it using this technique:
http://www.jalopyjournal.com/forum/t...shroud.380196/

but is there anyway I can do it so I save the wood frame for the other shrouds?
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Old Jun 11, 2014, 02:37 PM
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If you want to make more than one then it's well worth making a plug and from that plug make a mold.

The method shown is great for a one off. But as it shows in the procedure it's a one shot deal. And so is fiberglass over foam. So there's no saving the wood bits without taking a LOT of care and planning. And since you're asking about how to do this it's pretty likely that you're really new to it all and would not understand the ins and outs of making a direct re-useable mold.

If you go with one offs because you only need two or three then fiberglass over hand carved and shaped foam with some wood stiffeners is just fine. The trade off in making the sacrificial forms is balanced against making a proper plug then making a many times re-useable mold from the plug.

The other consideration is that with glass over foam you MUST use the more expensive epoxy resin. The cheaper polyester resin will melt the foam so you can't use it. I even found that the fumes or whatever will leak through plastic food wrap and eat the foam so painting over the foam or using food wrap isn't an option either.

So the cost of epoxy vs polyester resin will also weigh into the decision to go with one shot sacrificial forms and many time re-useable plug and mold making.

And finally the way he draped the material over the form means that you're using a lot more cloth and resin that will need to be thrown out later on. A better plywood, foam and plywood sandwich form will let you build up the cloth and resin around the edges since it would have something to lay onto.

Come to think of it with a bit of care the plywood, foam and plywood form could be coated with one layer of lighter cloth then filled, sanded and finished to make it a male plug form. You could then lay up the shrouds over this and just fill and sand the outer side. A little more work but you get a re-useable plug and parts that look decent enough and smooth enough both inside and out.
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Old Jun 11, 2014, 07:41 PM
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Hmm, So you are recommending something like this:
How To Make Fiberglass Part - Part 1 (9 min 9 sec)


Would I make two halves of the shroud? Or is there a way I can make one full shroud? Thanks,

Quote:
Originally Posted by BMatthews View Post
If you want to make more than one then it's well worth making a plug and from that plug make a mold.

The method shown is great for a one off. But as it shows in the procedure it's a one shot deal. And so is fiberglass over foam. So there's no saving the wood bits without taking a LOT of care and planning. And since you're asking about how to do this it's pretty likely that you're really new to it all and would not understand the ins and outs of making a direct re-useable mold.

If you go with one offs because you only need two or three then fiberglass over hand carved and shaped foam with some wood stiffeners is just fine. The trade off in making the sacrificial forms is balanced against making a proper plug then making a many times re-useable mold from the plug.

The other consideration is that with glass over foam you MUST use the more expensive epoxy resin. The cheaper polyester resin will melt the foam so you can't use it. I even found that the fumes or whatever will leak through plastic food wrap and eat the foam so painting over the foam or using food wrap isn't an option either.

So the cost of epoxy vs polyester resin will also weigh into the decision to go with one shot sacrificial forms and many time re-useable plug and mold making.

And finally the way he draped the material over the form means that you're using a lot more cloth and resin that will need to be thrown out later on. A better plywood, foam and plywood sandwich form will let you build up the cloth and resin around the edges since it would have something to lay onto.

Come to think of it with a bit of care the plywood, foam and plywood form could be coated with one layer of lighter cloth then filled, sanded and finished to make it a male plug form. You could then lay up the shrouds over this and just fill and sand the outer side. A little more work but you get a re-useable plug and parts that look decent enough and smooth enough both inside and out.
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Old Jun 12, 2014, 01:54 AM
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If you're going to make more than 2 to 4 of them then yes, I'd go with making a mold using a method similar to what is shown in that video. The difference being that you would have to start by making the plug since you don't have anything at this point. The "plug" in the case of that video being the initial boat hull joined to the plate.

I can't say one way or the other if you should make the shroud in two parts or one. I have no idea if what you want is a car radiator fan shroud and what car it is intended to fit onto. The choice of making it in one or two parts would depend on any number of situational factors related to what it's mounting onto and the need to fit around parts that might be in the way.
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Old Jun 12, 2014, 10:09 AM
The Junk Man
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Quote:
Originally Posted by v00d0o View Post
I want to make it using this technique:
http://www.jalopyjournal.com/forum/t...shroud.380196/

but is there anyway I can do it so I save the wood frame for the other shrouds?
That is probably the most ghetto glass work I have ever seen, but he seems like a happy camper so that is what matters I guess.

Tom

PS: The Composites forum here would probably result in a bit more help for you.
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Old Jun 12, 2014, 10:32 AM
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Quote:
Originally Posted by T_om View Post
That is probably the most ghetto glass work I have ever seen, but he seems like a happy camper so that is what matters I guess.

Tom

PS: The Composites forum here would probably result in a bit more help for you.
Didn't realize there was a different section!

Thanks.
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