TOPIC: GW Invader construction

Hi guys,
I have a question about the construction techniques of the GW Invader boat company. I have the 8' Ski Bird I'm restoring right now and a 10 footer I just picked up in my garage. Both boats have the balsa core that is water logged, rotted and shot. I just replaced the transom plywood today in the Ski Bird, but I'm using 1/4" (2 layers laminated to get the curve) Mahogany marine ply for the new core.
What was GW's reason for using the balsa for the core? I can not see it having any real strength as it was all end grain cuts. If it was for flotation, there was not enough in the core to make much of a difference. What was the purpose?

Thanks guys,
Jeff

Hi Jeff,

It is my understanding that balsa core in the stringers were to create the shape. The fiberglass around the core provides the complete strength.

Dean

Not quite so. The balsa makes it stiffer and allows the use of thinner fiberglass layers and reduces weight. but as you discovered, fiberglass cored with balsa is notorious for leaking and rotting. Today balsa is used primarily in decks for stiffness, and in the hull above the waterline where it won't get waterlogged. However, there are a few builders of very fast boats who still use it in the hull bottoms for it's stiffeness. It makes for a very flat, straight bottom. The kind you can put a straight edge on and not find a curve or hollow.