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Old 06-11-2009, 08:06   #1
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Going 'Kinda' Solar / Renewable for Auxiliary Power

Everything I see about electric motors is "maximum" data.

Maximum Thrust
Maximum Horsepower
Maximum Wattage
Maximum Ampreage

These are, after all sailboats

The have their own propulsion units(sails)

For a twist on electric and renewable power I'm thinking more in line of using an electric motor for "assistance" to the sail.

Just a little more power . . . a little more movement . . . a little better pointing when needed.

When the sailboat is only moving 2+ knots, maybe the electric motor(running about 1/4 speed), would make about 3-4 knots achievable, which will get you to your destination "a little sooner".

When the sailboat can't quite make the high-up heading you're striving for, the electric motor(running at 1/4 power or so), will help make the heading more possible.

I'm not necessarily talking about the "electric" motor being the main source of auxillary power(although that's what I'd like).

BUT . . . rather using the electric motor at a greatly reduced power-level and coincidently using a solar panel to maintain(or better) that particular level of electrical usage.

Is it realistic to use self-sustaining electrical power to make the sailboat work just a little better?

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Old 06-11-2009, 08:18   #2
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if you want a bit more speed and the ability to point higher, you'd probably be better off investing the money on a new suit of sails.

cruising is entirely about showing up--in boat shoes.
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Old 06-11-2009, 09:32   #3
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A large 200 watt solar array, when fully producing, might be the equivalent of about 1/4 HP; which (IMO) wouldn’t make any appreciable difference to boatspeed or heading.
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Old 06-11-2009, 11:29   #4
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The real option is a second small diesel engine, even outboard style, just to provide slow motion economically.
On my Cat, originally 27HP now 43 that gives me more than hull speed, or rather doesn't.
But a 5hp diesel would be really useful for plodding through a lull, just keeping steerage way for the auto-pilot, or charging the batteries during the night.
It's such a problem I'm considering a PETROL genny just to maintain lights and auto-p on the dark and shorter days of winter cruises.
Is there no viable diesel electric low power convertion unit besides a second hand car engine? There is a diesel quad bike 20hp, maybe skid-doo's already have the ideal diesel engine, light in weight, decent consumption, reliable starting. Life expectancy isn't relevant for sailing people?
Ex Prout 31 Sailor, Now it's a 22ft Jaguar called 'Arfur' here in sunny Southampton, UK.
A few places left in Quayside Marina and Kemps Marina.
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Old 10-11-2009, 19:10   #5
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Check out for the Thoosa electric motors. Your ship is 26 foot, right? You could reasonably throw out the diesel auxiliary and replace it with electric, IF (big letters) you do more daysailing than cruising, AND your Pearson can sail at 6 knots or better (which my 10 tonne 37 footer just can't). Bill
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Old 11-11-2009, 11:23   #6
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Originally Posted by Eleven View Post
Is there no viable diesel electric low power convertion unit besides a second hand car engine?
There is, or rather was and will be again. But not yet.


The sea is always beautiful, sometimes mysterious and, on occasions, frighteningly powerful.
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Old 11-11-2009, 14:02   #7
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Max power is perhaps the most important number you need when looking at electric motors. Their power output is linear, so there is no real cruising rpm or torque curve. Once you hang a propeller off one there is. So if you are ruinnning a 72v eletric motor and want a 3 hp boost to your speed, you need 2237 watts or 31 amps at 72v. Even a 1hp boost will need 10 amps. Figure a group 31 battery has 100amp hours, so you could run a 3 hp boost for a little under 2 hours or a 1 hp boost for 5. Then do some math based on what you want to use to recharge to determine if it is worth it. You could design a really simple system with a solar panel pretty much directly connected to an electric motor. The boost, however, would likely be minimal. And electric motors don't help you point higher. In fact, motors of any kind move the relative wind closer to your bow, meaning you point lower to keep your sails filled.


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