Re: [Electric Boats] RE: 5KW or 10 KW [1 Attachment]

On Mar 22, 2014, at 17:32, Electroprop <james@electroprop.com> wrote:

I We are, after all, on the leading edge of this technology.  

Indeed, in some aspects "we are on the leading edge of this technology," or rather guinea-pigs collecting empirical information.

The "rule of thumb" 1kw/ton to reach hull-speed is probably an adequate estimate for the typical small to mid-sized boat.

But you are only taking three parameters:  motor torque, hull displacement, and waterline length. The advantage is that everyone knows these parameters or can guess them fairly accurately. The "hull-speed" is itself a rule-of-thumb sort of calculation.

Naval Architects use the froude number and a few other complicated parameters.  Dimensions such as the block coefficient (the shape of the boat), the beam, the draft, the sea state, the center of gravity and buoyancy, condition of the bottom, hull appendages, etc will all effect a vessels speed.  The 1kw/ton rule will probably not be straight line scalable.

Empirical vs Theoretical - we'll both get the same result in the end given enough time.

Bill