15 lbs. (14.7 actually) at 15 mph is predicted by the design tool. 66.7N x 6.71m/s = 447.6 Watts.
Propeller efficiency and pod drag already included in the calculations.
Design tool predicts .74 hp or 552 watts at 15 mph with the propeller efficiency factored in.
Hello Winging-it, great work you are doing with providing this data.
I also think that it should be able to foil with less power that a lot of people assume.
There are videos of people foiling just pumping their boards. How much power do they need?
Common understanding is that Joe average can produce about 100 Watts sustainable on a bicycle. A very fit athlete maybe 300 Watts sustainable and a maybe around 1kW over a very short period of time.
So I would assume that the pump foilers also produce around 200 Watts and not a lot more. And that’s enough to keep flying. Agreed, they have slow foils, very good technique and don’t have the drag of a pod, but not a lot of power.
Main problem is take-of power…
Especially if you have a small board, you need power to take it to planning (i burnt my system once because i tried to use my very thin kite-surf foil board) , and then some more to reach flying speed (When foiling with a kite in very light wind, the challenging part is to get enough speed for take off, after that almost no power needed)
Mat, yes so many variables that effect take off power. In the video shown a few posts up; large board, large wing; take off was pretty easy with only 33 lbs. of thrust.
PB1, yes, not much data available at this time for this new sport/watercraft. I would love to have access to a real flume where I could test wings and thrusters at actual water velocities. That would greatly reduce the guess work and speed up the optimization of the efoil.
@Mat, full agreement!
That’s why I think we need larger boards.
Btw. there are many videos now of people stand-up paddling and they manage the take off. The horue guy is getting pulled by a cyclist or even a runner and manages to get up. Even on his rather small board. So the power needed can’t be that big.
@winging_it , the only scientific work I found with regards to electric hydrofoils is from a Swiss education institute from 2009.
Video:
Paper (in German):
https://www.iwk.hsr.ch/fileadmin/user_upload/iwk.hsr.ch/Publikationen/Faserverbundwerkstoffe/1001_Boot_im_Gleitflug.pdf
The focus there seemed to be on the mechanical aspect and there is almost no documentation around the electric components.
The most interesting aspect is the following chart, power consumption versus speed (Geschwindigkeit). Clearly visible how power consumption drops after take off - as expected. And it’s not that big.
Moving and I need to get rid of my flume. It has been a great tool for my project. Free to anyone who would like to pick it up in Wichita, Kansas.
Dan
Hi have you had any luck with these direct drive motors please?
thanks
Peter
Unfortunately personal circumstances have prevented any further work on this project. I think the work I did with Mikes help was in the right direction for an efficient efoil drive.
Hi Dan @ Winging_it,
Your Datas are really amazing. As mentioned on some comments, we should be able to foil using a maximum of 500W since pedal hydrofoil exist and a cyclist can produce max 300W.
From what I’ve understood, you are running the motor dry inside ann aluminium tube mounted pretty tight and the stator attached to an aluminium plate welded to the tube to dissipate a bit more heat.
How do you ensure the waterproofness of your tube ? Vring I guess ?
Too bad that you can"t keep going. I hoped you could post more videos foiling and maybe photos of your setup.
Many thanks
You probably could get a setup to work with 500w. It would however, be slow. Power requirements grow exponentially with speed. How fast do you want to go? Im looking for 40kph.
40kph is really fast ! No?
I think its about 20 Knots. It might be a little ambitious 
I haven’t finished building mine yet. Time will tell. I ride my kite foil to about 30 Knots which does feel very fast, so 20 is a good goal I think. I better make it 15-20 Knots 
I’m planning on getting up on the foil at really low speed ( 8-10kph) and max speed of 25kph which, of course, will need more power. However, I think that having a more efficient setup is achievable and will have drop the prices down (passive cooling of the ESC, direct drive, smaller batteries)
@Winging_it
Hi Dan,
I very much enjoyed your work with the flume and your detailed explanations and results, thank you!
As I’m interested in also building a flume (while I don’t know, if it will come to happen) I have questions about some points. It looks like you have used a long propeller shaft situated in a long tube that is fixed at the flume. In order to measure the thrust, the shaft must be able to move a bit in axial direction. Therefore it is not appropriate to use ordinary bearings to bear the shaft. You will have used some lubrication between shaft and tube to prevent water from outpouring, right? If so: was it water, oil, grease other stuff? Did you use seals or other means to prevent leaking? What were OD of shaft and ID of tube?
Thank you in advance for your answers.
I don’t know how Winging_it did it. This is how I did it.
I replaced the shaft that came with the motor with a shaft about 3 1/2 foot long. 12 mm shaft.
I printed a part in white plastic that held a needle bearing cage with needle bearings. I think I bought it from McMaster carr. I also installed a seal in the white printed piece to keep the water out. That white piece threaded on to 1/2 NPT pipe. On the outside of the tank you can see that the motor shaft passes through a brass colored part. That is just a brass adapter to go from NPT thread to a flair. I opened it up to 12 mm and I am using it as a bearing to keep the motor centered. It worked very well did not leak a drop for months. The tank was 6 foot x 8 foot x 4 foot deep. It also took up so much room I had to disassemble it.
Hello Heimfried,
Glad you enjoyed the flume work.
The shaft bearing was a simple nylon sleeve type. It allowed the shaft to slide and did a pretty god job sealing the water. I think I used a little bit of petroleum jelly as a lubricant and sealing media for the shaft bearing/seal.
I believe the shaft was 12mm in diameter to match the motor shaft. I don’t recall the ID of the tube, but I think it was about 1/2 and then I drilled it to accommodate the nylon shaft seal/bearing.
If I were to build another flume, I would add another motor and prop to help get the water moving faster in the flume’s test section. I had a boat speedometer in the test section of the flume but it never read more than about 5 mph. I think testing at cruising speed is really important for getting a god motor/prop combination. Just putting a propeller in a big water box will not do a good job measuring the prop performance at speed in an “unloaded” condition.
Good luck with your flume.
Dan
Dreaming on a larger scale, wouldn’t it be great to have a powered flume large enough to allow testing of complete hydrofoils/efoils in addition to the power systems. This could really help in the refining, performance and duration of an electric hydrofoil.
