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Making a Fiberglass Hull... Custom made

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Making a Fiberglass Hull... Custom made

Old 02-29-2004, 11:47 PM
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XLR8_01
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Default Making a Fiberglass Hull... Custom made

Ok, So my dad has had these 1/4 scale crackerbox plans. I had a bright idea to make a Fiberglass mold, instead of building the whole damn thing and buying the kit. So, i took the plans, and alot of that DENSE pink foam they put outside houses up here in Cold RI ... anyway... i carved the whole boat out... my plan is to make a female mold (two seperate ones) or the hull and the deck. cut them in half, and use them as the molds (cut in half so when the male mold dries, just unscrew the female mold and u dont' deal with suction) Has anyone done this prosses before? will the foam melt if i put epoxy fiberglass on it? or what should i coat the prototype crackerbox in before i fiberglass over it? ANY BODY taht has experience please help.
Old 03-01-2004, 12:47 PM
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Tachikaze
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Default RE: Making a Fiberglass Hull... Custom made

You can place epoxy resisn over teh pink foam without a problem. This is a common techique.
You will not be able to remove the epoxy resin and glass from the pick foam mold without ruining the pink foam, at least I have not been able to do that. There is a rumor that you can coat it with a petroleum jelly and slip it out that way, but I have not tried that. When the epoxy sets up I use acetone to remove the pink foam, shrivels right up.
Old 03-01-2004, 01:13 PM
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Default RE: Making a Fiberglass Hull... Custom made

After you shape the foam you can glass it then use Econocoat to cover it. Wax it several times and do your mold, the Econocoat will help it free up.
Old 03-01-2004, 04:20 PM
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Default RE: Making a Fiberglass Hull... Custom made

Ok, sounds good. but my only concern was that i know some chemicals will melt foam... and epoxy gets hot whets hot when it cures with fibreglass. I know for a fact of experience that styrofoam melts if you spray it with spray paint (the aerosal melts it) I just want to be sure before i go and ruin the prototype. I can imagine looking like the three stooges trying to get the fibreglass and epoxy to stay over the foam covered in petroleum jelly... slide ~catch it quick~ thanks, if you have anymore comments, please tell... i'll try and get a picture of the foam up here today
Old 03-02-2004, 10:05 AM
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creola
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Default RE: Making a Fiberglass Hull... Custom made

I would like a copy of your 1/4 scale crackerbox plans. Can you tell me where you father got them?
Old 03-02-2004, 03:26 PM
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Aaronie
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Default RE: Making a Fiberglass Hull... Custom made

[link=http://www.2brothersrc.com/powerpete/cboxplans_sheet1.jpg]http://www.2brothersrc.com/powerpete/cboxplans_sheet1.jpg[/link]

[link=http://www.2brothersrc.com/powerpete/cboxplans_sheet2.jpg]http://www.2brothersrc.com/powerpete/cboxplans_sheet2.jpg[/link]
Old 03-03-2004, 03:08 PM
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Default RE: Making a Fiberglass Hull... Custom made

Ok, sounds good. but my only concern was that i know some chemicals will melt foam... and epoxy gets hot whets hot when it cures with fibreglass...
Actually, your concern is well placed. Epoxies have been used for glassing over styrofoam for years because the resin doesn't attack the polystyrene -- But the other side of the story is that chemicals used in most of the hardners don't hurt your foam, but chemicals used in some do hurt it.

Be sure to test a little of the epoxy you're planning to use on a scrap of foam and let it go through the curing process before you trust it on a carved foam plug.
Old 03-04-2004, 08:45 AM
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virginia6634
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Default RE: Making a Fiberglass Hull... Custom made

Polyester resin, which is what you will find in hardware stores, and is less expensive, will melt the "pink foam". It will not melt polyurethane based foams. Polyurethane foams are more expensive, however. Epoxy resin, which is more expensive, will not melt the "pink foam" or polystyrene foams. Unfortunately, you can't use the cheap stuff, with the cheap stuff.
Old 03-05-2004, 09:39 AM
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Default RE: Making a Fiberglass Hull... Custom made

Epoxy resin, which is more expensive, will not melt the "pink foam" or polystyrene foams. Unfortunately, you can't use the cheap stuff, with the cheap stuff.
I'll try and explain my previous post -- the part about your concern being well placed...

It may be true that epoxy resins per se do not eat polystyrene. However, to use those resins, you mix them with a "hardner" that can be any of a whole class of chemicals, and it may be thinned with any of a at least a few another classes of chemicals... bipolar inorganics, alcohols, alkanes(some of which dissolve or soften styrofoam), ketones (which absolutely and dramatically dissolve syrofoam), or others whose identities and chemical properties we could only guess at. It may also have additives to clarify it and/or to color it, to make the resulting epoxy more flexible, or to make it more impervious to special environmental conditions. Your so-called resin is actually a chemical cocktail that includes things that they do not list on the front label, they do not talk about in the product description, nad some of which WILL eat styrene plastics.

Bottom line -- your actual resin may be perfectly safe but it may still be unusable because of an unsafe "hardner." I can tell you first hand that it is not cool when you've carved a boat hull and put the time and effort into dressing and prepararing it, only to see the fiberglass go limp on the surface as the epoxy hardner eats your carefully created original.

Whether or not you test your chemicals is completely your choice, but don't be misled into thinking that there's no reason to test. There is a reason. it only takes a couple of drops of resin and a few hours of cure time to test it and be safe. By not testing, you could save that time and resin. But to me, spending that little bit on testing is way better than spending the time would have taken me to replace my boat hull form -- which I never did: I was disgusted enough to scap the project altogether, so it really cost me a whole boat.
Old 03-11-2004, 03:59 PM
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XLR8_01
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Default RE: Making a Fiberglass Hull... Custom made

hey, thanks everyone

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