Lets compare the foams with balsa at equivalent densities. Boat builders may
use balsa at 8-12lb per cubic foot density while they use foams at aound 5-6 lb
density. If the builders used the same density foam as balsa, it would be no
contest, such foams as PVC would win hands down as they would be more than
twice as strong as what is normally used by boat builders, as it has a leg up
in being much tougher.

My sevs use 4.5 lb urethane foam, fragile, for the homebuilders, but certainly
very workable. While a planing boat is trying to break itself in half at the
spray root when it pitty pats along or hits a bump, the surface skimmer
actually sees a mellow down load on the center of the hull as the bump forces
are delivered through the air cushion to the entire underside of the craft.

I also use 5.5 lb PVC, much stronger. The fiberglass skinned foam is ideal for
surface skimmers, especially when considering they don't have to live in the
water, but need to haul themselves out, a necessity to avoid marine growth on
the hull and skirt.

Why the boat builders do not seem to use higher density foams, in the area of
balsa, I do not know. A web site this thread directed me to was very
interesting, but the surveyor who wrote it failed to realize that "composite"
structures are not loaded so that "peel" forces are exerted if they are
properly designed.



Subject: cored hulls
From: "Lew Hodgett"
Date: Mon, Feb 2, 2004 4:29 PM
Message-id: . net


"gltlwlelilslslsl" writes:

Any opinions out there on the use of coring on a power boat hull?
snip

Airex yes, anything else, especially balsa. forget it.

--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures

BRBR

Barry Palmer, for A
HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A