Sss 4092 electric hydrofoil for disbaled guy


Hey folks, planning my build and wanted to share my design with you.

Want to use the 40mm sss 4092 with 4300watts. As gearbox I planned to use a reisenauer 6:1 planetary reduction gear.
Fits perfectly on the 4092 motor with a flange. The gearbox will be screwed on the motor.
It all will fit in a 40mm innerdiameter aluminiumtube with an oil infill, means all the parts get cooled by oil and the aluminiumtube as heatsink.
Outer diameter 47,6mm of the aluminiumtube.

Wanted to use the 80mm diameter propeller as it should deliver enough power to the water.
8010 pitch

Means ESC, motor and gearbox is in the aluminiumtube.
The wings connect to the 750mm long aluminiumtube

what do you guys think about it? wanted to run the smaller motor a bit harder as due to the good cooling, around 6000watts max for short periods and 4500watts as continious.

btw, I’m disabled from the breast, so it will be the first electric hydrofoil for disabled people.
I’ll have to sit on it, any Ideas how to where to mount parts for good first try results?

The overall costs are so much smaller, that’s why I’m planning on a downscaled setup.

looking forrward for your opinions on this.

thanks alex


This is totally awesome!

My friend that has a c6/c7 injury would really like to join in on this adventure! He has asked us to build one that he can ride a couple of times, and we have been looking into it. He probably needs a bit more custom steering possibilities, but that could be arranged!

I think you could go for a slightly larger regular outboard engine prop, with a custom 3d-printed low drag propguard, this will probably be more efficient than the small 80mm, when you use a gearbox you should have enough torque to drive it.

Please let us know if you need any help with your design :slight_smile:

3000W should be more than enough to drive your setup! we use about 2000W in cruising 20km/h, with a smaller tube(less drag) the consumtion should be even lower. I would suggest using a large wing! :slight_smile:

I would consider having a separate fuselage, if you crash into something with both wings attached to your motor pod (if I understand you correctly), this will damage your entire system and could easily result in water ingress, instead of only damaging your fuselage and/or wings. This way your motor-pod tube can also be smaller.



I only have a remark concerning the oil cooling. How do you plan on handling the expansion of the oil with temperature and the resulting pressure inside your housing? I had some success with oil cooling a small outrunner, but dropped the idea because of the mess when changing parts and a lack of ideas concerning pressure buildup and sealing.


Hey Hiorth and Flo thank you!

I really appreciate your opinions.
I own a good 3D Printer, a surfboard, the aluminum 90cm mast(i mean the part which combines surfboard and motorpod.
I also own the electronic stuffs needed for such a project, I once had a downhill bike with a mid drive in the 7kw range at her very last weeks… got stolen

A wing on ebay is about 300€ I think, printed wings are much cheaper and have a really good quality when glued together, so thow it away if it breaks…

Pod electronics will be sealed with a waterproof spray, if water breaks in.
God thanks all the people are achieving such massive improvements in science these days, I mean look at all the products you can buy and the technology behind it.

@Hiorth as you mentioned I will better use a 3d printed low drag propguard, with a 40mm holder and a 94mm prop, this will make it a super clean setup I think, thank you very much.
You guys will have to help me, since I’m new to CAD, trying my first models now for ex: the backseal with a holder for the prop and stuff but it’s a bit difficult :slight_smile:
maybe you guys might help me with a slightly modified file of the 94mm prop with a 40mm diameter attachment to the tube if I can’t work it out in the next few days, It would be very polite :slightly_smiling_face:

@Flo Do you think it is possible to use a overpressure ventile like this:überdruckventil+modellbau&client=firefox-b&dcr=0&source=lnms&tbm=shop&sa=X&ved=0ahUKEwiAxsfHnbXZAhUFZFAKHanRAKUQ_AUICygC&biw=1680&bih=872#spd=4558600405950384984

in combination with sunflower oil which is biodegradeable.
If I fill the aluminum tubes center with a lot of deadspace(so that not that much oil is needed just to realise the planetary gear cooling)
and this overpressure ventil attached to a chamber inside the tubes front for the expanded oil to catch and seperate it from the mainchamber, this should work I guess?
The electric motor is open, this means oil can go through there. front and back chamber are connected.

I will try it first with my monopod with wing Hiorth^^
I think it might not be that stupid to use the 40mm tube with 47,6 outher dia. It’s a very solid piece of metal, and as you suggested I will have to use larger size wings for a better lift at low speeds.
thanks again, a lot of needed experience from your side!

have an opinion on this or suggestions to realise the oil cooling without eventually pollute the water I’m inside that much if the motor pod should really be damaged and the seals break?

Hope we can stay in contact and your friend does continue the work on his work on the custom steering, would you tell me how you planned on doing this? I don’t know how good he accomodates to his situation…
tell him please that he’s not the only disabled efoiler :slight_smile:


If you have some questions on CAD I can maybe help you as I have done some projects in this realm.
With the overpressure valves I am not sure. I don‘t have much practical experience with shaft seals. Common shaft seals are specified for 0,5 bar max differential pressure. Therefore I asked about your ideas. If you release air in a hot state you might draw in water through the shaft seal while cooling and contaminate your oil.
Concerning edible oils: I don‘t remember if I used sunflower oil or corn seed oil(„Keimöl“), but it does decompose over time. This decomposition leaves a residue that can‘t be easily removed. I removed it recently from my motor with hot alcohol, but this in turn also slightly attaked the glue fixing the magnets. An environmentaly uncritical oil that does not decompose on its own in the motor would be nice :wink:


Does anyone know If there are stl files of the 94mm prop and guard?

Thanks alex

Edit @Flo maybe a ventile from a bicycle
I will work it out somehow, because I want the planetary gearbox oilcooled. Most concerns go for the planetary gearbox now


You can also cool the gearbox the “Hiorth-way”, just add aluminium segments around the round parts that just fit into the tube. Maybe add some thermal grease to get better contact between the gearbox and the segments as well as between the segments and the tube. Easier to assemble and disassemble.


you are right lol

@Hiorth you could use gyro stabilizers for the custom steering :slight_smile:
but I think you have already a better idea?


Seems a bit easier to not use oil, the water cooling on the motor pod is pretty good, and as long as the heat is sufficiently transferred from the motor/esc/gearbox to the outer casing it should be fine. I also think the motor does not like to run in oil (friction). If you are doing it with a Long tube, you will get some air volum inside , that might pose a overpressure threat to the shaft seals (as with oil).

What type of ESC are you planning on using?

You should learn CAD, its not that hard. Use or Autodesk Fusion, both are free and easy to learn. At some point in this project you will need it anyhow! :wink: The parts you need are not that hard to construct.

Your mast is 90cm aluminium? It might be an Idea to cut it a bit down in length and re-thread the ends, the longer the mast the harder it is to ride, and the harder you will fall. We use 76cm Now, think we will go down to 65-70cm.

Was out riding today did almost the entire session sitting on the board with my feet skipping the water, its not that hard to sit on the board and control it only with your upper body! Gyro stabilizers would be nice to install, our plan would be to use a combination of software and mechanical stabilization (gyro could be one of these). But this is still down the line .

Chinese hydrofoil for efoil?

Is sitting on it easier to learn?


nice project good luck , be carefull with the gearbox , the product is very nice BUT


Hey Alex, no problem to ride disabled. Your build will work we tested similar long ago…
To ride seated don`t use a regular foil from kitesurfing. Those are not that easy to ride… We invented new sort of Foil Wing that is much more stabilizing itself and therefore very easy to ride for beginners or even disabled…
Will be available late summer;-)
If you have you build ready send us a pm, maybe we can arrange sending you a prototype wing;-)
Check this video for riding seated in a small harbour maze;-)