Doesn't something like this change everything?

[PonoBill]

3500 watts, hmm, that's 4.7 hp. Yeah, that would do it.

[SUPdad]

I’m with Ponobill. While it’s possible, I doubt an inexpensive product like that is doing anything other than turning the motor on/off at full speed.

This isn't how simple electric motors work.  Hook up a brushed motor to 12V with no load and it'll spin up to its max speed.  Load it up with a torque load and it'll run slower.   This behavior would work just fine as you paddle and accelerate the rpm of the motor can increase (with a decrease in its torque output, but still positive torque = positive thrust).  If they put a propeller on with too low of a pitch such that at the no-load speed of the motor the pitch velocity is slower than we want to ride, well then we're out of luck.  Hopefully this kind of thing would be figured out in the development phase.

If they use a brushless motor (doubt it) with a controller that is controlling RPM that'd be a problem.  One would want to use a brushless motor controller that could control torque.

In summary, if they aren't stupid, this could work just fine as an augmentation of human powered paddling.  Once you're on the wave, that's another story - seems super draggy.  luckily not a problem for us foilers wanting to try this.

I experimented with brushless motors many years ago so not up to speed on the latest tech. However, the physics probably haven’t changed. If you’re trying to regulate rpm via torque value, you’re still gonna to run out of rpm at some point, dependent on the Kv and voltage used. Not sure if there’s enough range to have high torque at low board speed and enough rpm left to maintain that torque at higher board speeds. Anyway, I’m a simple minded person so most of this is over my head. But my supposition is that this thing is low tech and unable to defeat the laws of physics. For a surfboard, I’m sure it’s a product destined to fail. For a foil board, I actually do have some hope. Key being able to get the prop out of the water once in a wave.

[PonoBill]

That's a typical speed range problem with model boats and a reason most high-speed ones use surface-piercing props--and can barely maneuver at low speed--rudder authority and prop drag. Reduce drag at high speed and you reduce thrust at low speed. Prop drag isn't an intuitive effect, but it's one of those nasty exponential issues that limit top speed. the easiest way for me to think of it is as a screw, rotating through the water. And one of the prime characteristics of screws is that you can't push them, as screw jacks and garage door openers demonstrate every day.

I doubt that really applies too much here, the range of speed we're looking for is very small. If the drive can push a board with a foil to 5 mph we're gold, and anyone who can't downwind will suddenly be able to. That's why they got my money. I don't think it will happen, but I'm happy to try.

[jondrums]

...For a surfboard, I’m sure it’s a product destined to fail. For a foil board, I actually do have some hope. Key being able to get the prop out of the water once in a wave.

Amen, totally agree.  If it works at all for this, I think we might see someone do a more tailor-made product in the right form-factor for foil boards

[SUPeter]

WOW!  After seeing the video that SanoSlatchsup posted, I'm a believer.  That motor has some incredible thrust.  Just a little of that right before the mellow swell reaches you and your up and flying in no time.  All this in a relatively small and lightweight package.  Just build an addition to the rear bevel, behind the mast to hold a fin box.  adjust your foot placement to counteract the weight shift, a little practice, and that just may be the ticket to effortless wave catching.  Just think how early one could hop on a perfect face.  Mind-blowing!  Might be just what I need as I get older.

[jondrums]

The barrier to rigging up one of these is pretty high right now (at least how everyone is attempting it) - Motor and ESC are pretty available, but you gotta make a battery pack, wireless controller, pick a suitable propeller, and integrate it all in a fully waterproof way.  Super difficult to hit all those points well.    I might have to give it a try

If I did, I think I would probably try to get everything into a Pelican case with a shaft seal for the prop shaft angled out the bottom.  And I'd use off-the-shelf Milwaukee power tools batteries - those things are incredible for power to weight and ruggedness, probably can't beat that with a homebuilt unless you use hobby grade stuff that will catch fire eventually.  Speaking of, I bet the brushless motor and electronics out of one of these high power hammer drills would do the trick pretty nice. 

I wonder if I could glass a dual track system into the bottom of a pelican case.  Build the rest of the board around that - hmmm....

[Phils]

Do it.  Someone who understands foiling needs to make this work.  I have been communicating with the Boost guy and when I mention foiling, he thinks efoil.

[surfcowboy]

I’m gonna say that 15 minutes over on efoil.builders site would sort all of this. Just take their rigs and use smaller batteries and such. But they have all the mounts he everything sorted.

I’ve been thinking of trading some guys there boards for the running gear prints and info to help me build the motor gear. A trade that would help me and the electro boffin who’s never made a board get efoils running. Especially now that I have a dang board factory in my garage. (Wrapping up shaping board #3 of my Covid Cuiver)

They have sorted all this motor stuff out. You just need to scale it all back to a short fast push and slide the mount up under your board.

[jondrums]

efoil.builders site is quite a hoot.  Thanks for that recommendation, not sure how I didn't find that before.  I went over to spend 15 minutes looking around and went to be 4 hours later with my head full of ideas.  A lot of them are buying hollow boards from either Lift or Flying rodeo, very few guys are building boards, so I think you might get some traction making a trade like that.

[surfcowboy]

Anything to avoid another computer based project lol. I really need to quit my job so I feel like using a computer after hours. But I’d probably end up doing something stupid like making foils lol As it is I hate to even open zoom to see friends after a long day.

Glad you enjoy it. I think Pacificmeister from YouTube started it but I’m not sure. I love that a group could solve problems together like that.

I think they have it down to where a decently skilled and patient person could make one work.