#### skipperdude

##### Guru

<ul>[*]Velocity = (g * Length / 2 pi) ^ ½[*]g = acceleration of gravity (32.15 ft/sec ^2)[*]Convert ft./sec. to Knots and the result is 1.34 * L^½[*]Metric V(m/s) = 1.25* LWL^1/2.[/list]

I have several friends who operate fast trawlers or other semi displacement hulls.

All are trying to slow down to save on fuel.

One *question is how to calculate the buttock angle for a semi displacement hull.

Then othe numbers come into play like the wave length vs LWL. And wetted surface.

There are boats operating on the Bering sea in the salmon fisherie. A law requires a max hull length of 32 ft. So some of these boats are 20*+ feet wide.

Anyone even fooling with this kind of stuff to determine the best speed/cost to operate the boat.

When I travel at hull speed 7.46 knts I am barley pushing 1600 rpm with a WOT of 2800 am I loading the emgine enough?

At 2000 rpm ( roughly 75% of WOT) I am running at about 8 knts. and burning more fuel to the tune of an x-tra 1.5 GPH*

SD

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*-- Edited by skipperdude on Friday 3rd of June 2011 09:49:22 AM*