was gonna say about the same, my little mini-henley slipper launch is only 12' long with a 41" beam at waterline, 12v to a 36lb MK with a kipawa prop, does 4.5 mph on 400w, is about 85% of its hull length speed.
some folks dont consider anything under 24' to be a boat (I understand why now, with waterline length square root x 1.56 x 0.8 for speed estimating).
waterline length, beam, displacement, hull shape, are all pretty big factors calculating. same kind of next to nuthin power to a 21' canoe shape might give 6 mph. this is just me at the novice-hobby level scratch building, tinkering to wring some efficiency from TM's.
--- On Wed, 7/11/12, Tom <boat_works@yahoo.com> wrote:
From: Tom <boat_works@yahoo.com>
Subject: [Electric Boats] Re: Knots to Watts
To: electricboats@yahoogroups.com
Date: Wednesday, July 11, 2012, 12:06 AM
Would this data be useful without knowing something about the boat? I'd think you'd want to know at least the W/L length, displacement, and general hull configuration (monohull, multi-hull).
-Tom
--- In electricboats@yahoogroups.com, "James" <james@...> wrote:
>
> We are working on building a range calculator and could use some help from the members of this group.
>
> Please send your numbers for knots to watts.
>
> We are asking for how many watts it takes to power your boat at 3,4,5, and 6 knots in calm conditions, no wind, no waves, with an average of two runs in opposite directions to average out the effects of any tides or local currents.
>
> Please let us know voltage and current, the meter you measure with,
the system you are using, and the propeller and reduction gear ratio.
>
> Thanks to all who participate in this gathering of data.
>
> Happy Sailing and Thanks!
>
> James
>
> Propulsion Marine
>
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