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Posted

Thanks for the link. Though i don't particularly care for the styling, the guy is very skilled and has a good technique.

I've used the expanding foam myself for making quick armatures to sculpt aftermarket body parts over. It's a great way to build lightweight volume quickly.

Posted

I myself have never used the product. I didn't know it hardened like that. I thought it stayed to a sponge type consistency.

Posted

I'm guessing that's a resin he's mixing that gives the foam a hard shell. It's a fascinating idea, overall, and he obviously knows how to make it work!

Now, where's that Big Deuce kit of mine . . .

Posted

Yow. It's not for me, but I appreciate the work that went into it. It looks like one of those Jada diecasts with those awful wheels. I wouldn't call it a "sports car", however. It probably weighs a LOT more than stock and handles like a pig.

Posted (edited)

I myself have never used the product. I didn't know it hardened like that. I thought it stayed to a sponge type consistency.

There are many different foaming 2-part urethane products available...some soft, some hard.

You can use the "Great Stuff" canned household foam in a similar manner.

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Edited by Ace-Garageguy
Posted

Yow. It's not for me, but I appreciate the work that went into it. It looks like one of those Jada diecasts with those awful wheels. I wouldn't call it a "sports car", however. It probably weighs a LOT more than stock and handles like a pig.

The "right" way to use the foam is to do exactly as he's doing, but go another couple of steps and pull molds from your finished bodywork, and then make lightweight fiberglass parts in the molds. You then remove the "plug" made of foam and bondo and replace it all with the fiberglass parts...getting rid of all the extra weight in the process.

Of course, that requires having to engineer brackets and other attachments for your finished parts.

Posted

Ed "Big Daddy" Roth made his plugs from plaster, over wood and chicken wire armatures. It's the old-school, and still effective way to make plugs for custom bodywork. Roth would make molds of his finished work, and make fiberglass parts in the molds...throwing away all the heavy plaster work.

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A "plug" is simply a full-scale model of the final shape you want. What material you use is relatively unimportant, so long as it will take a slick finish (for molding) and support its own weight without cracking.

Posted
Ed "Big Daddy" Roth made his plugs from plaster, over wood and chicken wire armatures. It's the old-school, and still effective way to make plugs for custom bodywork. Roth would make molds of his finished work, and make fiberglass parts in the molds...throwing away all the heavy plaster work.

Ed Roth also mixed Vermiculite into his plaster of Paris plugs.

I have seen plastic tooling shops use the expanded foam for plugs, never included in the finished product though. I doubt that the stuff being used is all that hard even after the magic ingredient is mixed in.

Posted (edited)

I have seen plastic tooling shops use the expanded foam for plugs, never included in the finished product though. I doubt that the stuff being used is all that hard even after the magic ingredient is mixed in.

You're right...it's not all that hard, and it needs to be covered in fiberglass to make a suitably stable surface against which to build a good mold. The foam work is typically done somewhat undersize to allow for the thickness of a layer of glass, and finishing fillers like bondo or Polyfair.

This is my avatar, the full scale mockup (on the left) in my old shop. It's being made from foam planks over foam bulkheads. The planks are cut from foam boards, which are made from a foam very similar to the free-expanding stuff shown above in this thread, but under controlled industrial conditions. The product is then factory-sliced into standard sizes, which I've cut into flexible planks on a table saw. More complex shapes are easier to make with the free-expanding stuff.

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Edited by Ace-Garageguy
Posted

I had a 76 Cutlass that I filled the holes in the lower rear fenders with spray foam in a can. Kept the trunk dry for two years while I owned it. It was soft but was a good backer for the rusty metal. You do what you can afford to do.

Posted (edited)

I don't know how it would hold up with that much used. Would it hold up in a crash???

Not the way it's used in the Mercedes modifications shown above. That usage of the foam is really only sufficient for show-cars and mockups. That particular foam itself has about as much 'strength' as beer cooler foam, though when employed in composite structures correctly, it can add significantly to a vehicle's overall rigidity.

Expanding foam is commonly injected into door pillars by manufacturers these days to stiffen them. Expanding foam has also been used by manufacturers inside bumper covers to provide a measure of crush-resistance and initial crash-energy absorption.

Several current small aircraft have skins made of carefully laminated fiberglass, carbon fiber or Kevlar, with a relatively thin (1/2 inch or so) urethane foam core of tightly controlled density. This provides a very light, rigid structure, similar in overall strength to an aluminum aircraft.

This shot shows foam core correctly employed in an aircraft part, with thin carbon-fiber facings on either side. Parts manufactured this way are incredibly light for their rigidity and 'strength', but are not really suited to a civilian surface-vehicle environment where people routinely drive into each other's vehicles with little thought for the consequences of minor damage.

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Edited by Ace-Garageguy

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