A friend and I have decided to jump on the Electric surfboard bandwagon and the foil idea seems to be the best in terms of efficiency and probably simpler to build (famous last words).
I have a 3D printer so have made a start on both a Jet Pump similar to those from Mhz Watercraft and also a 3D printed Hydrofoil (that would then be laminated in carbon).
The Jet pump is quite nice with a 65mm propeller, you can see the plans here and can download them for $12.
I am waiting on the drive shaft and some bearings to arrive before I can test.
The Hydrofoil is shaping up nicely. I downloaded some plans that were available on Grabcad, sliced them so I could then print on my i3 Prusa Mk2. I started documenting the build here,
I'm happy to share the foil .stl files or gcodes if you have a similar printer. The Jet pump files you will have to purchase yourself from Cult3D. So far I have printed the rear and front wings and the printer is in the middle of printing the fuselage.
I am going to have to modify the mast design as I would like to have a tube running down the centre to take the power cables for the motor. I have no idea how to design or edit anything in OpenSCAD so please jump in if you think you can help. The foil has been built by the designer and he shares his photos on GrabCad.
https://grabcad.com/library/kitefoil-hy ... id=2902073
The motor is proving more of a challenge. Pacificmeister seems to have got a bargain with his Gerarbox for $60 as they seem to be over $300. A gearbox is also less than ideal. However there may be a bit of good news from Bruno at Alien Power System. I got in touch to ask about low Kv in runners and he mentioned that they are developing a 58mm 80Kv inrunner motor. No detail yet on specs or pricing. He just responded this morning to say wait a few weeks for more info. Sounds very promising though. Most other motors that will run at around 3,000 RPM and have sufficient power are either out runners or just too big.
Enclosing an out runner is plan B although there do seem too be a lot of ROV builders who just run out-runners in sea water without short term issues. I can't see it lasting all that long before corrosion eats away something important but it might be good enough to test other parts of the construction.
The board is likely to be a recycled surfboard. My friend Nick is begging a board or two from a contact of his. Hope to share more soon, especially on the 3D printed foil.