Here's something else: Stiffness is often used as the primary measurement of composites. Strength is secondary. When a composite panel is stiff enough for an application it will usually be strong enough for the application and have a long fatigue life. Now, stiffer is not necessarily stronger, but a stiffer material will spread the force of impacts over a wider area and so lessen the chance of a major structural failure. There's a difference between them. (Nick's book has a nice section on this topic...)

Something to keep in mind was that test was referenced was done purely with flat panels. Finite element analysis (and experience) shows that a flat panel will behave very differently when compared to a similar panel that has compounded curves. The curves add an incredible amount of stiffness and strength. Add to that the fact that a kayak is built upon a collection of surfaces comprised of compound curves intersecting and reinforcing each other. It HAS to be looked at a a total system. Most strippers have very few flat panels, if any, for that very reason.

S&G and strip-building are both excellent ways to build a kayak and ARE comparable when looked at as a whole system. Pound for pound of overall weight a stripper CAN be just as stiff/strong as a S&G boat depending on what materials are used for the core and what the laminations are. The materials will behave differently but in the end you get a very stiff (and strong) system either way. Don't think it about it too much... it'll make your head spin.

Dan

: There have been discussion in the past, let me open this can of worms again:
: http://www.kayakforum.com/cgi-bin/Building/index.cgi/read/155107 (and
: refences therein).

: This thread quotes some results from a comparative strength test by Sam
: McFadden. My personal conclusion from the data (Sam just presented results
: without drawing conclusions) is that the data suggests that S&G is 2 to 5
: times stronger for the same weight and amount of fiberglass (as per the
: reference). I have to be a bit careful here because more data is needed
: and the results will vary depending on how much fiberglass was used. At
: any rate it seems obvious to me that plywood, which is a composite in
: itself with fibers going in different directions, ought to be stronger
: than strips glued together on the edges, fibers going in the length
: direction. Strip built boats need fiberglass reinforcement more badly than
: S&G.

: Henk

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