: on this sandwich construction: wood as the core and fiberglass as the outer
: layers. does the distance of the fiberglass layers play a part in
: strength? I would think that if the glass is farther apart(the wood layer
: is thicker)it would be stronger. is this assumption correct? For instance:
: if a stronger wood is used then a thinner strip of this wood can be used.
: But the glass layers will be closer together. will this have to be
: considered in over all strength of the construction? thanks

Your assumption is pretty much bang on, although to be pedantic it's the stiffness that increases as the fibreglass layers get further apart which is not exactly the same as stronger. Nick's book gives a pretty good explanation of how this all works.

The problem of substituting a stronger wood is that the density of a wood species tends to go up as it gets stronger, so sure you may be able to get away with a thinner strip but your boat may be just as heavy and may well be less stiff than a boat that uses thicker, weaker wood.

A further complication in all this strength vrs spacing stuff is that when a kayak is finished you essentially get a closed section beam which is inherently very stiff for its weight already. So I’d imagine that as you increased the distance between layers of fibreglass that you would eventually get to a point of diminishing returns as the most stiffness comes from overall shape of the boat.

I guess that’s why most boat builders seem to follow the light weight wood, 6mm thick standard for kayak building. It also works well with cove and bead router shapes I’ve seen.

On a side note one of the theories at to why Viking Long Boats were so sea-worthy is that their flexibility enabled them to flex with the waves enabling them to ride out rough weather more easily. I'm not sure if I believe that theory but I guess "youse pays your money and takes your choices"