: Hi there, can anyone tell me if there are practical alternatives to wooden
: strips ie foam? I have designed and built an 8 chine S&G which was very
: successful and would like to build a surfski (long narrow racing sit on
: top). . .

Why not stick to building Stitch & Glue style with plywood?

Here are some links to a motorized paddleboard which is made of plywood. While the size is not the same as what you are considering--and I'm sure you don;t want the motor in it-- take a good look at the exploded views of the construction and yo may get some tips for building a reinforced, hollw surfski from thin plywood. You are already familiar with the design and construction techniques, so this may be a faster project than if you go into some new (foam) material.

The main plan is at:

http://www.buildakayak.com/boatpix/paddle1.tif
other pages from the article are at
http://www.buildakayak.com/boatpix/paddle2.tif
http://www.buildakayak.com/boatpix/paddle3.tif
http://www.buildakayak.com/boatpix/paddleboard4.tif
http://www.buildakayak.com/boatpix/paddleboard5.tif

Hope this helps

PGJ