--- In electricboats@
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> The conversion to a Propulsion Marine 5 KW electric drive was optimized after its initial install with great results.
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> We initially used the existing 12" diameter x 6" pitch propellor, a 1.8:1 gearbox, a Mars 20 turn motor, and a Sevcon GEN 4 controller. We achieved maximum boat speed of 4.5 knots drawing 4200 Watts , and 3 knots drawing 1580 watts. These findings are consistent with other electric boats.
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> We optimized the system by changing the propellor, the gear ratio, the number of windings on the motor, and slid the propellor back another 2 inches. (This eliminated the propellor walk to port in reverse and put the propellor out in clearer water. )
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> We now achieve 4.5 knots at 2,300 Watts, maximum boat speed of 5.5 knots drawing 5,700 Watts, and 3 knots at only 588 Watts!
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Hi James.
Very interesting. What was the original propeller rpm?, and whjat was the new?. What was the dimensions of the new propeller?.
This may show how important propeller efficiency is. Maybe it is unvise trying to use an existing propeller?.
Victor
> We had a 268 percent increase in efficiency at 3 knots boat speed!
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> This makes solar power within reach as a viable source of energy for sailboat propulsion. With 3 Sanyo 215 watt solar panels mounted on the boat, the boat could cruise indefinitely at 3 knots boat speed.
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> At 3 knots, the theoretical range, on batteries alone, of the boat has increased from about 30 miles to over 80 miles. At 4 knots we expect a range of 40 miles and at 5 knots, 20 miles. Kapowai has a 21 KWH battery bank of which 17 KWH is useable. Theoretical range does not account for rough sees or windy weather. During that time the boat will be sailing anyway.
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> Its not just about range either. Having the ability to always have thrust from the propellor gives the boat incredible seakindliness. She is always on course. The apparant wind created at 3 knots boat speed is enough to be able to harness a one or two knot breeze. Motor sailing even with the lowest power adds one or two knots to the sailing speed. The boat is quick and responsive in all conditions. You won't get stuck in irons because you can power tack. And you can hold the boat into the wind while hoisting or reefing the sails.
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> And the icing on the cake is the Clearview display. There is no need for an external shunt and all the wiring. The Clearview communicates with the GEN 4 as a node on the CANBUS. You can have the computer up and running on a second node at the same time. The Clearview monitors everything and includes a sophisticated battery monitor. Sevcon has done and amazing job with the GEN 4. It is now efficient at all points of the power curve. Unlike the Millipack which was only efficient at peak power. Definitely a leap ahead in technology.
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> At what point can you say that an electric boat is every bit as good as a diesel? For most boats, for the way they are used, we are already there.
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> James Lambden
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> Above the Waterline
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> www.propulsionmarin
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