Design
John---
Perhaps the difference stems in how we each define a boat. If you have a boat that planes--- achieves a full plane, not plowing along partway up--- then to me, it's a planing hull regardless of what the hull shape happens to be. I have always categorized boats by what they can do--- plane, partial plane, not plane at all, and so on.
So by my definition--- and I'm not saying it's the one everyone should follow--- if I have a rock and I can strap a great big engine to it and get that rock up onto a plane, it is a planing rock as far as I'm concerned. By my definiton, a planing hull must have the right combination of weight, power, and hull shape to get onto the plane. They all contribute to the boat's ability to plane. To me, a semi-planing boat is one that doesn't have the right combination of weight, power, and hull shape to get onto a plane.
However....*if you are using the term semi-displacement to define a particular hull configuration, then I have no argument with your statement.* *If your boat has a sharper entry, deeper and more rounded forebody to cut through waves rather than slam into them, and then a flatter cross section aft to allow it to achieve faster-than-displacement speeds (and better stability in some situations), and that is how we define a semi-planing hull, then yes, I would say your boat has a semi-planing (or semi-displacement if you prefer) hull even though you can get it up onto a full plane.
So if we accept that I define a boat type strictly by what it can achieve in terms of performance*and you define a boat type by its physical configuration and how it behaves, then we're both right.
-- Edited by Marin at 17:21, 2007-12-06
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