Many thanks for the continued testing and reporting. This help a
LOT when trying to figure out what to do in the future -- it's easy
to speculate about motors, kilowatts, and thrust, but real data is
invaluable.
- Mike
Rick Willoughby wrote:
We finally took a day off from sailing the proa to have another go at the electric thruster;
http://www.youtube.com/watch?v=QE4YJy0JLUk&feature=youtu.be
This test was using components that are candidates for the final design. The single Mars motor looks OK but we plan to use one next to each hull to give the boat rated power of 8kW and peak of 18kW. We have found some robust nylon props and we have also found a 1:3.3 gearbox that will be suitable for the loads with some modifications.
For this test we mounted the single remodelled drive unit in the outboard hatch which is almost on the centreline of the boat. It was firmly mounted in a wooden frame that prevented it from flogging about.
We got one solid data point today holding 7kph drawing 2kW from the batteries. This was beam to a 15kt breeze with short fetch. By the time we got around to cranking it up, two of the old 12V batteries, out of 4, were down under 6V so power did not get much over 2kW total voltage was 33V instead of 48V. The highest current was 70A while the current limit on the motor was set at 200A. So the test was severely battery constrained.
Next step is to try to restore some life in the old batteries that have sat around for 7 years or so then do another test closer to the 4kW motor rating or even into overload if the batteries can hold the voltage.
Two thruster will not improve low end efficiency compared with a single unit but they will give heavy weather performance similar, or better than, the 60hp outboard. The tiny 14" prop on the outboard is cavitating quite heavily even at slow cruise around 6 knots. But worst situation is the ventilating that occurs in anything over 0.5m waves.
Rick Willoughby
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