I did my first water trial last weekend, so wanted to write it up and share it with the group. My goal was to start with an eSUP and hopefully get up on a plane. I am interested in foiling one day, so decided to get a mast and an old beat up board with a deep tuttle port.
- Flipsky 50A VESC based on V4.12
- Flipsky 5085 650W motor
- 6S battery (some generic 4 Ah thing)
- Custom mast clamp (onshape)
- Custom prop, approximately D=170mm P=140mm (onshape)
Here’s a view of the drive:
First problem I ran into was weeds! But apparently trying to go weedless is a bad idea since it greatly reduces efficiency. Surprised that the commercial eSUP I tried didn’t have this problem at all, but it had a duct and I don’t. The solution was just to go to a place without weeds
I first set a current limit to 30 A which is what the motor is rated for, but found I was going way too slow (about 1.5 m/s) so decided to try luck and set current limit to 50 A, and got to about 2 m/s. I pushed it to open throttle, which got me to 7.3 kERPM. From my testing with slow motion land video, I think I have 7 sets of coils in the motor (no spec sheet, sadly), so that’s about 1050 RPM in the water. The motor is rated at 140KV so 3500 RPM without load. I got above hull speed which I calculated to be 1.9 m/s, but feels like very far from a plane. No real heat issues, though the VESC did get quite hot, and I ran the whole battery down in about 15 minutes (about as expected). Here’s some data I captured from the VESC:
And a more complete video if anyone’s interested.
At this point, I’m trying to decide what’s next. Using the board as a SUP wasn’t very fun since turning was very sluggish. The motor is positioned at the very back of the board because that’s where the tuttle port is, and putting the paddle into the water to turn as on a whitewater kayak did basically nothing. So I had to come to a stop, turn, and then speed up again. Video of me going at speed isn’t that exciting, but here it is for completeness.
Currently considering various options:
Try again with a higher pitched prop that I printed impulsively, but suspect it will actually be worse since I’m not getting to a full duty cycle as is.
I do have another 5085 motor coming soon since a contact came off on my motor and I thought it wouldn’t be recoverable (it was!), so I’m considering a dual drive with something like this build.
The obvious option is to scrap this and go up a half order of magnitude in power and use the gear that most new builds seem to be using:
- Get a really long board (maybe 4m, current one is 2.5) and embrace displacement (not planing) and mount the motor in the centre so that it’s easy to turn. I could probably get to twice the speed, especially if I double up the motors (at 1300 W).
This has been an incredible project so far, my first foray into electric vehicles and power electronics. I want to thank all of you crazy people for being so damn inspiring.