Dual outrunner project



I found this web and Im thinking about to build my own efoil. I was windsurfing some time ago and Im also rc modeller and have 3D printer. I spent two days reading about hydrofoils and e-foils and I have few questions:

  1. I already sold all my windsurfing boards so I need to buy some used. Im almost 100Kg, what size do you recommend? 130L at least? Im afraid it will be very long and huge + heavy. Also what should be surface of wing? Im planning airfoil Aquila 9.3% around 700-800cm2 because of my weight.

  2. Id like to test dual outrunners propulsion system in one tube directly placed and cooled in water. My friend tested this on RC boats and it works for 2 years with no issues (not salt water only lakes). Therefore Im trying to stay under 24V (6S Lipol) for each motor to stay on “safe side” I think with these two outrunners it should work: https://hobbyking.com/cz_cz/kd-53-30-high-voltage-brushless-outrunner-190kv.html If Ill go around 80-90A each, I can get maximum 3,5 - 4kW. I hope this will be enough (I found 2kW should work)

Do you think 25V DC in not salt water is safe for human? I dont want to die during this experiment

  1. is there any free 3Dsw for boat propellers drawing and calculations? I have one but only for airplanes.

Thank you all for your opinions and help

Best regards


Check out this thread. Some info there. Welcome!



this is misunderstanding, Id like to use two outrunners (PULL/PUSH) config with one before and second after the mast. There will be no mechanical connection and probably they will rotate in opposite direction. They will also use two speed controllers. Only point I need to test is if it is better to run them in one tube or with two independent circles around

Thank you


This has been done already and Jake changed his setup to run a single motor after he tested 2 separate ones. It might be worthwhile asking him for the pro’s and con’s…


Ok, thank you. Im planning two motors because of low voltage I can get. With one motor, current must be 160 and more amps :frowning: Ill try to search thread you talk about.

Thank you


Ahh I found the thread, prefect he even use the same motors :slight_smile:


Unless you have a very good reason, I’m not sure you should stick to low voltage… I did that on my first build for space reason, and ended up very under powered…

Even if you get “low” amp per motor, very high amps will have to come out of you batteries and go through some of your setup… it’s easier to deal with higher voltage than higher amps…


You are right, but Im afraid of higher voltage from motors directly in water. I know it is not so critical, but that is the reason. Jak mentioned consumption around 2800W, that I can run with 63A which is not so critical. I also hope that I will get better efficiency using tube around propellers (tube) and also with different wing geometry. For me it is important, that I know, that these motors can be used for my project.

Running time is not so different from higher voltage systems, because I will run paralel instead of serial connection.