Hi, my name is Ken, and I’m going into my freshmen year of college this fall for electrical engineering.
Over the course of the past year, I have been designing an electric surfboard. It uses two motors meant for e-foils directly underneath the board. When the board is outside of the water, the motors spin up very fast, however when I put it in the water, they have barely any power and the board won’t go faster than 1 mph. If I start the motors outside the water and then dip them in while they are spinning, they maintain their speed until about 90 percent of the propeller is in the water, and then they slow down again. Here are the specs of the surfboard:
Motors (2): flipsky 65111 160 kv
Props (2): 7.25 inch by 5 inch pitch (included with motors)
ESCs (2): TFL Pro High-Voltage ESC 300A with watercooling
Batteries (2 in series): Turnigy High Capacity 14000mAh 6S 12C Lipo Pack w/XT90
I have a 150A fuse which hasn’t blown, so the current on each motor must not have exceeded 75A. The motors are rated for 70 amps peak current each. Also, the speed controllers and batteries were not even remotely warm after testing it in the water even without the watercooling system running, so I don’t think that they are being overloaded either (The fuse would blow before the batteries or speed controllers were overloaded).
If anyone had any ideas as to what was wrong they would be greatly appreciated, as I have spent a ton of time and money on this project and I really want to see it work. Thanks so much!!
Here’s a picture of the surfboard: