On Wed, 24 Nov 2004 11:26:29 GMT, Short Wave Sportfishing
wrote:

Which brings us back to the original question in a circular sort of
way: When is a boat "on plane" ? I'd be inclined to vote for 2.5X
the theoretical hull speed. Easy enough to calculate, and sort of
intuitive. It may not be dead right for every boat but it should be
in the ball park.

I just thought of something - would this be true of displacement
hulls?
==========================================

A lot of so called displacement hulls could probably plane to some
extent if you could get enough power to the water. There are many
heavy sailboats that will briefly plane if you can get them surfing
down a wave with a lot of wind in the spinnaker. I suspect there are
some hulls, tugboats come to mind, that would be hard pressed to plane
regardless of power. The hull shapes just don't have enough flatness
to them. Lack of planar areas? It's difficult to skip a round rock.