Robriley - "And I am I confess a person who is far more concerned about wakes than pushing through waves, being of the school that suction being the viscous and more powerful force."
That is the conundrum. What is our real goal though, sliding through the water with minimum drag? If we want to go faster than the wavelength speed, we have to avoid a lot of rocker because that sucks (downward lift) the boat down, but that regime is the lowest possible energy state. Let's call it energy state 1.
To go faster than the lowest energy state (displacement) we have two options, to plane or to slide through the water. Planing is the highest energy state and fastest, because energy has to be used lifting the boat out of the water, let's call it energy state 2.
That brings us to the no man's land of Semi displacement where the goal is to not produce any downward or backwards lift. Or to produce any upward lift (pitch) at the bow. Fluid flow around the boat lowers the pressure everywhere, that nasty Bernoulli fellow rules.
There is an effective counter though, a U shaped bottom can increase displacement (upward force) faster than suction is created if the water line is below the top of the radius turn. That is the secret of the Slender Hull theory.
It gets more complicated, rocker helps keep the flow attached . . . less drag, but too much rocker and downward lift will overpower the hydrostatic lift. No rocker and the boat may 'plane' (lose suction) and become unstable due to the Monk effect at high speeds. Sounds like fun.
I think that is all there is to it, increase displacement volume faster than suction increases. It seems though that without changing hull shapes there is a single optimal speed point somewhere between the 1 and 2 energy states.
It is also apparent that the goal (for me) is to get the boat to the unstable 'planing' regime. And find a sweet spot somewhere where the boat likes to normally move.
I think it is going to be a U shaped hull with large radius turns. I am afraid though it is going to pound and pitch. . .
Talador
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Posted by: taladorwood@yahoo.com.au
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