Boats are designed to be supported at many point by water. While
three points may define a plane, it is a poor way to support a boat
and exposes it to stresses never anticipated by the designer.


Disagree. I recall discussion in both structures and hull design classes
about accounting for loads associated with construction, launching,
dry-docking, grounding, and other special conditions.

I would not swear that recreational boats are subject to the kind of
analysis performed as part of a ship design, but I would expect that
ABYC structural requirements are intended to account for such loads.
Think of ABYC as analagous to your county building codes. The architect
won't calculate snow loads on the roof because the mandated timber sizes
and spacing allow for those loads.

dave
BS Naval Architecture & Marine Engineering, Webb Institute, 1982