: I must have started these threads about lightweight boat construction. I now see it was a mistake. Consider the following history:

: 200 or more years ago people with names like Lagrange, Navier, Stokes, Newton and many other developed the mathematics for stating all relevant engineering problems. But they could not efficiently solve those general statements. So engineers have settled for solving approximate statements of the problems. During the past 150 to 200 years every 30 years there has been a cluster of catastrophic bridge failures. These failures have been traced to solving the "wrong approximate problem". One of the most recent failures was the Tascoma Narrows bridge which failed because of a vibration instability that was dropped from the problem statement.

: What does this mean relative to lightweight boat building?

: Perhaps Nick and others including myself are looking at the wrong approximate problem statement.

: Be wary of anyone who does not talk about hull stiffness and maximun normal stress in the same sentence. Hull stiffness tells you how much a hull bends under a load. But hulls do not fail from bending they fail from the normal stress pulling the fibrglass or wood apart.

: Be wary of anyone who models impacts as static loads. The results are always wrong in the unsafe direction and there is no bound on the amount of error.

: Be wary of anyone who talks about the ease of application of epoxy. Epoxy needs to be matched to the wood and to the fabric. It takes 2 epoxies to build a boat. Note the physical properties of an epoxy change by 50% by changing from SLOW to FAST hardner without changing brands.

: Be wary of anyone who does not know the Navier-Stokes equations are 4th order non-linear partial differential equations and are hard to solve.

:
: Now that I have built a 40 pound on the water kayak, I have to leave to engineer a 30 pound one.