On Jun 14, 11:02 pm, "Maxprop" wrote:
"Bart" wrote in message

ups.com...

Boat and yacht decks and hulls are commonly cored to
save weight.

What are the various types of core material?

Airex foam
End-grain balsa
Plywood
Metal honeycomb



What are the characteristics of each?

Airex: a near-perfect core material, won't absorb water, quite rigid,
fairly lightweight, far cheaper than balsa or honeycomb, provides insulation
factor.

End-grain balsa: very lightweight, expensive, labor-intensive, low-tech,
will absorb water, quite rigid, some insulative properties.

Plywood: cheap, heavy, absorbs water like a sponge, very rigid, good
backing for major hardware like winches, cleats, did I mention cheap?

Honeycomb: rigid, very expensive, won't absorb water, but if damaged during
construction water can flow into the cells, no insulative properties, high
tech and the lightest in weight of the bunch.

There are probably others, but less significant in terms of commonality.

Max

Hey Max! Good answer--worth 2 points, athough not as
funny as Joe's who get's 1/4 pt for his humor. A dozen
lashes to the Swab for being such a lame swab.

My understanding is balsa has far superior adhesion because
the end grain is rougher. Foam can suffer from extensive
delamination due to freezing--as water continues to propagate
in the layer between the laminates. Does anyone have
any experience with this?

Most builders don't properly seal the edges of the
core in areas where hardware is attached. Ensuring
water does not get into the core is not that hard to do,
but unfortunately most builders skip this step, and
few owners want to take the trouble to remove every
but of deck hardware to re-do what builders fail to do
--put solid glass or epoxy filler to seal the edges of
the laminate to prevent water intrusion into the core.
I caught one guy installing a thru-hull on my boat
skipping this step!

I've found that balsa even if rotten can still function
for a surprisingly long time in that condition. I'm just
starting to re-core the deck of my Etchells and found
quite a bit of rot, with virtually no weakness in the
deck. I attribute this to the curved shape of the
deck and coaming which the enhanced strength
of the deck.

I'm going to re-core it with balsa, although I have a
source of left over foam core that I could get my
hands on cheap--albeit I don't think it is the right
thickness for my application.

By the way, I've seen Nomex honeycomb in both
aluminum and epoxy coated paper, although I don't
know if the later is every used in boats. Does any
one know about that?

Bart