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post #4 of Old 04-16-2007
Telstar 28
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Cored Hull Pros

Stronger and stiffer deck or hull for the same weight
Better insulated, reduced condensation problems inside boat

Cored Hull Cons

If deck hardware or thru-hulls not installed properly, water can migrate into the laminate and cause the core to delaminate.

More difficult to lay up laminate properly IMHO... so more prone to lamination failures.

There are three materials normally used as core materials: foam, plywood and end-grain balsa. Some other things can be used, but they aren't proper core materials IMHO.

End-grain balsa is in many ways the best of the three, since it reduces water migration through the laminate core, which can cause larger areas of the deck to delaminate fairly quickly. Balsa also generally has better adhesion and bonding characteristics than the foams do, and greater compressive strength and sheer strength than most foams. Finally, end-grain balsa has the highest temperature resistance to softening.

Some of the foams, when exposed to higher temperatures can soften, causing the hull or deck to deform. However, foam tends not to rot, and as such.

Plywood's only major advantage is that it is far more resistant to crushing damage than foam or balsa.

Hardware installation on a cored deck needs to be done properly, which means removing the core and potting the area with thickened epoxy to protect the laminate core from any water leaks.

Properly designed, a cored hull can be much stronger and lighter than a non-cored hull. However, all the through hulls should be through areas of solid glass. Potting is only a second-best measure below the waterline IMHO.

Solid glass is far easier to repair and less subject to problems of delamination. It's major problem is weight.

Vacuum infusion, properly done, is going to yield a very high-strength, low-resin, laminate. However, it is also pretty easy to screw up vacuum infusion—which can lead to voids that were never properly wet out and have very little strength.

That's it in a nutshell. The strength of a cored laminate is very dependent on the quality of the lamination as well as the choice of material for the core. Early laminates used foams that had lower sheer strengths, and in certain situations, the laminates would fail as the foam material itself sheered, allowing the laminate to separate.

Personally, I believe that the hulls should be solid laminate, and that the only place for cored laminates is the deck and cabin top of the boat.


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Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Last edited by sailingdog; 04-16-2007 at 06:13 PM.
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