The wood in a strip built boat does add significantly to the stength. It serves to keep the inner and outer layers of cloth seperated. By keeping the layers apart the load on the cloth is distributed over a larger area and the stress on the cloth is reduced. The core increases the mechanical advantage of the cloth for absorbing the load.

In order to do this, the core does not need much strength parallel to the plane of the layers, it just needs good compression strength perpendicular to layers. This is why end-grain balsa makes a good core material even though it is very weak by itself.

> I have been thinking about this post for a couple of days because,
> although it seems okay in theory, it doesn't match up with practical
> evidence.

> What I think is this. If you double the thickness of the core you will add
> very little to the strength of the composite. You will probably double the
> strength of the "core" but cedar strips add little or no
> strength to the composite because they have very little structural
> strength to begin with.

> In stripper construction the strips serve two purposes; one is a form over
> which we can lay our structural material (glass/epoxy), and two as a form
> of artistic expression for the builder.

> If we laid all of our epoxy/glass on the outside of the form the boat
> would be just as strong! But it wouldn't be waterproof. If we laid up all
> of the epoxy/glass on the inside and then removed the strips the boat
> would be just as strong! But it wouldn't be pretty. So we put half inside
> and half outside we get everything we need from this method. However,
> George using 1/8 strips and claiming is boat is just as strong is
> "TRUE". The fact that George claims his boats are actually
> stronger means that he has figured out another property of composites that
> the rest of us overlooked or felt wasn't important.

> The cedar strips are not a component of this composite. The composite is
> the glass/epoxy only, just as in a commercial fiberglass boat. Fiberglass
> boats are heavier for many reasons; gel coat, hardware (most homebuilders
> talk weight before rudders, foot pegs, rigging , etc., are installed.)and
> liability considerations.

> So now the mystery is how to get more strength for the same weight in our
> layups.I think that George has found that multiple lightweight layups are
> stronger than single heavyweight layups.

> Ian Johnston