I'd like to see someone look at semi-monocoque aluminum construction as a design exercise. Floatation bags would be important, eh.

> Gentlemen: I have read with some interest the discussions of
> strength and stiffness. There are several points which should be noted.
> Strip built and plywood hulls are quite dissimilar in construction
> and the way hull forces are distributed will be different. Strip built
> hulls are very curved and hull forces (those that act as point loads)
> are distributed to the rest of the structure as compression loads
> only, these do not behave as flat panels as most tests appear to be
> done on but rather like stone arches which have resisted compression
> loads for centuries. Compression loads just need sufficient cross-sectional
> area to resist them. Distance between inner and outer layers has very
> little bearing on this type of stiffness unless the hull is so thin
> that it fails in local buckling. The amount of stress imparted to
> the wood or glass is proportional to their relative moduli of elasticity
> thus the glass will take on 56% of the load and the wood takes 44%
> of the load. Thus there is a slight benefit in increasing glass thickness
> over wood thickness, unless one considers weight to be of prime importance
> then wood (red cedar strips) which weighs 1/3 that of a glass and
> resin mix would be the preferred item to be thickened. All other discussions
> considered it would still seem that the best proportions have been
> arrived at through many years of trial and error. It would then appear
> that if one wanted a hull with slightly different properties then
> both wood and glass thicknesses should be adjusted in tandem. Bram
>