You can do this. Please try it. Take this heavy motor, place it into a pod adding low volume and ventilate air through the windings using part of the motors torque by an integrated fan system. Make sure the air flow is systematic. Try to build lighter than a torqu?do with more peak power. Think about the duct and the motor pod will influence each other. Your flume measurements are a best case, i do not want to critize this. Only to keep it in mind, no gear, everything well cooled and underloaded, prop without duct and motorpod, short time measures without resistance in the waterflow.
I admire your work, but i do not believe the conclusions yet. Anyhow i want to support you with ideas because i feel its a promising way.
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I agree, this flume is best for comparative data. It is a great tool (not perfect) and has helped reduce electric power requirement by a great, great deal. The Leopard motor and prop used in the video below was tested in the flume. Here are the comparative results with the best motor/prop combination so far:
160 kV Leopard motor: 20 lbs. thrust, 1,100 watts and 15 lbs. thrust 770 watts
50 (65 actual) kV Alien: 20 lbs. thrust, 360 watts and 15 lbs. thrust 255 watts
Amazing the difference a well selected motor and prop can make. I’m sure their is still room for further improvement.
The Leopard motor showed no signs of overheating in the lake testing.
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To further clarify the pod setup. The motor will be bolted to an aluminum firewall which will be welded to the aluminum pod. Distance from the motor to the aluminum tube shrouded in water is less than 3 cm. I have all the confidence that the head dissipation will be adequate. With the Leopard motor we were pulling upwards of 50 amps with no heat issues. The new setup, as you can see from the numbers, we are expecting to pull less than 10 amps.
Mike
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If the power requirements prove correct in practical testing that’s a huge improvement on existing setups in terms of battery requirements. I.e same batteries for alot longer runtime, or less battery/cost for same runtime.
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That sounds great. With 20lbs ~ 100N and 7m/s you have a power requirement of 700Watts. With prop efficiency of 75% and motor the same you will have around 1244Watts input power from the batteries. Maybe you drive slower, than your power requirement drops further.
What is the diameter of the pod?
I use windsurfboard without a wing so i calculate with 200-400N thrust, so i need around 3-5kW battery output.
So i cannot cool the motor by air in a pod. Anyhow i understand, i need some wing.
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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.
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@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.
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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
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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.