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Foam Core/Vacuum Bag Construction

Old 05-20-2007, 10:35 PM
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Originally Posted by Michael1 View Post
Is it worth the extra cost?

Worth every penny !

Here is a page you may find useful: Boat Building

Links to various companies on this subject.

Good luck.

Digital Photography & Video one BYTE at a time !
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Old 05-20-2007, 11:49 PM
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Again, I am sure that infusion is a fine way to go, and it is certainly a LOT better in reducing air pollution and toxicity to humans. We all know people that have been working with polyester for years, and their brains sure don't work like they used to.

But I disagree that its as good as pre-preg (supplier puts glue into fibers under pressure) or im-preg (put glue into fibers by a machine at the shop floor) or -- another approach -- film.

Expoxy seems to have far less vapors, and for most people, seems to have far less short and long term health effects.

Yes, pre-preg does feel dry -- to me, it feels about as sticky as a post-em, or less, perhaps more like a racing tire. The layers can be put down, and re-adjusted, easily, even on the sides of the mold they stay where you put 'em. You cook it to make it cure.

Im-preg can use any kind of glue you want, including expoxy that must be baked to go off, so it can feel exactly the same as pre-preg. One can use polyester or vinylester and have a wet im-preg, but it can be 'dry' too if that's the glue (and process) you use. The advantage of impreg over prepreg is that it allows the builder to shop around for the fiber as a commodity, and that can yield cost savings, but can lead to build time delays (sometimes the stuff you are looking for isn't available at the price you want to pay).

Yes, there is yet another mechanism, and that is where a film of resin is put between layers, and then heat and pressure gets the fiber-fiber bond. That is really amazing stuff.

A few weeks ago I was at a yard where they use prepreg or impreg exclusively. They had just popped a hull and deck for a 65 footer, 18 feet of beam, and standing headroom. The hull and deck were carbon prepreg and nomex (essentially kevlar honeycomb) core. The weight: 900 lbs for the deck, 1300 for the hull. One full bulkhead I picked up, weighed about 10 lbs. In this boat, there are no fibers but carbon, no glues but epoxy, and no core but nomex and a little bit of very high density foam where things are mounted through the deck or hull.

AFAIK, aerospace applications use pre-preg.

Last edited by carcrash; 05-20-2007 at 11:54 PM. Reason: typos
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Old 05-21-2007, 12:05 AM
Join Date: Jun 2006
Location: Sunland, CA
My Boats: 2000 Fountain 32 Sportfish Cruiser
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From those pictures on Sharkey's, looks like Outerlimits does not use infusion.

I see lots of raw cloth, so I would guess they use impreg.

There is a picture showing the outside of an oven, so I would guess they use epoxy, and cook it under vacuum.

The third from end picture on this page shows the outside of the oven, to the left side of the picture:

Not that this is conclusive, but is jives with what I know of Outerlimits and the company they bought to get the vacuum-cooked epoxy expertise, Carroll Marine.
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