dog wrote:
Yes, there are many foams to choose from, but few have the same
characteristics that make end-grain balsa such a good core material.
Few of the foams bond and wick epoxy resin as well as end-grain balsa.

Are you looking for bond strength / peel resistance? Some
foams are better in this regard.


Few of the foams have the compressive and sheer strength and resistance
that end-grain balsa has.

Now that's just plain wrong, it is very easy to find foam
that is better in these characteristics. The question is,
can you find better foam that is still lighter, and also
doesn't cost a lot more?

Look into the specs on foam in the 20# and up range.


... Few of the foams have the high temperature
resistance to softening and deforming that balsa has.

Considering the temp characteristics of epoxy, I don't think
this makes much difference. OTOH it is possible to use
fire-retardant foams... balsa is wood after all, and will burn.


... To date, nothing
that I have seen is better than a good end-grain balsa for most
applications.

That statement leads me to wonder how far you've looked.

... There are a few high-tech honeycomb materials that are
almost as good, but they're generally far more expensive and difficult
to work with than end-grain balsa.

It's true that balsa is relatively inexpensive and easy to
work with. I like it... but for my ownpersonal super boat
project, I picked a type of foam that a friend used in
airplane kits. Has some drawbacks, but I have no doubt that
it will be lighter and stronger than balsa... and it won't
ever ever ever rot.

Fresh Breezes- Doug King