T-Pain Is On A Boat: Re: [electricboats] Quest for 2X Hull Speed

Sunday, October 25, 2020

Re: [electricboats] Quest for 2X Hull Speed

Really nice looking boat, did you buy plans or design her yourself?

Thanks

Kevin

On Sun, Oct 25, 2020, 3:16 PM Keith M <kmerranko@gmail.com> wrote:

Baseline - The boat runs at about 5 mph with the NV86, which is just slightly faster than my Minn Kota 30. The NV86 runs a little over 700 watts typically, and it is rated for 1,142 watts (24 volts x 48 amps).

Air Plane Pusher Propeller (15x7) - In speed 1, it runs about 0.75 mph faster. In speeds 2 through 5, it does not go any faster and the whole lower unit has a resonant wobble and probably cavitation. I gave up on that idea.

Epropulsion Propeller (10.2x6.73) - Of course the big issue for trolling motor is the lack of higher pitch LH propellers. I tore apart the NV86 to determine if the commutator is advanced, and if I could change the setting to optimize the motor for reverse. I found the brushes, brush holder, magnets, and coils were all aligned. The exception is the commutator is advanced 11 degrees from the coils. So I built a steel ring to rotate the magnet assembly by 22 degrees counterclockwise (return to 0 degrees and advance 11 degrees in the reverse direction. The boat reached 7 mph right at 1,000 watts, all the while the propeller was cavitating, there was a rooster tail, and water was spraying in all directions (trolling motors are not hydrodynamically shaped). At zero load in the OEM configuration, the motor turns at 1,930 RPM at 1.4 amps in both directions. With the 22 degree rotation of the magnets, the motor performs about the same in reverse, but in forward it runs over 250 RPM faster. That makes me question if the OEM commutator configuration is aligned to the neutral axis. I do not have a good way to test. I restored the magnets to the OEM configuration and added a cavitation plate and a fairing for the propeller hub and motor shaft. I am waiting for good weather to test.