John,
As a sailor, I'm sure that you've tried coming into a dock with even mild (10kt) wind. On my boat, as I'm approaching the dock at speeds of less than 2kts, I occasionally need bursts of 2500W or more to stop or steer the boat.
I would never suggest that someone attempt to dock anything larger than a dinghy with less than 1hp on tap, especially around other boats. In perfect calm, no problem, but if you're going sailing, there should be some wind...
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "John Green" <v_2jgree@...> wrote:
>
> Hi Dave, Thanks for responding.
> When you say 'pushing the motor hard' are you say by high volts, or by
> slowing it with a large load, such as too large or pitched prop?
> Looking at the speed Eric gives for a 500 watt load, (10% of what he
> uses to go only twice the speed) does this indicate that if I had his
> boat I could use, say, a 1 HP motor, and have 200 watts to spare, as far
> as heating goes? This assumes that I gear/prop it to run at a reasonable
> speed, say, only as low as maybe 80% of no load speed?
> What I am trying to say is, what would be a good guesstimate of good
> starting points as far as motor HP spec to end up with a system that
> draws about 500 to 700 watts continuous and does not waste resources by
> making heat?
> Sorry to ask questions that might have many variables!
> I do not want spare power over what is needed to dock the boat, for
> example. (I might regret this? But I want to try anyway.:-)
> Thanks,
> John
>
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