I am slowly working on jet drive since efoil would potentially be used also by my son and grandson. First I wanted to go with JetWave motor and impeller like Kian, but like he wrote, JetWave would only sell to those parts to those who already own the whole board. Fortunately Aerofoils sells impeller replacement kit without such constraints. I tried to obtain 65161 motor with 220 or higher kV, and couldn’t get one. So I bought LMT30100 motor and proceeded designing waterproof housing for it. Now I have to decide between two versions, one with original Gong fuselage and another shaped like Aerofoils, JetWave and others that have wing in front of the motor. I really heve no idea which one is better from practical point of wiev, so i am looking for some advice.
My opinion for what it’s worth😀
There may be some benefit from mounting motor inline with front foil (like Fliteboard) but that drives a complexity in the build as you then have to create a fuse that “bends” below the motor.
To me a lot simpler and less expensive to buy stock Gong mast-fuse setup. Lots of efoils built this way and they perform well.
This is how we have our jet in combination with Gong.
We wanted it as simple as possible.
Another option would be to mount just the stabilizer (needs to be a V1/2 one) on the jet it self
Thank you for all answers. I will try to explain my dilemma further. My motor mount is essentially replacement for original Gong connector
https://www.gong-galaxy.com/en/products/gong-foil-alu-mast-v3-mfc?variant=54816761872759
It will be 3D printed from aluminium, but will need additional machining of motor seat and back edge surface for gasket. For machining version with Gong fuselage I would need to have clamping device machined, while I imagine that version with integrated fuselage could be clamped in a 4 jaw chuck. I am not a mechanical engineer, so I have no idea what is feasible.
Another unknown is how good will 3D printed conical part at the bottom seat into original Gong fuselage. It would be quite hard to have additional machining of this section.
I will post some pictures in additional posts since I am allowed to to attach only one picture at a time.
Here is picture of proposed clamping device
Here is look at motor holder with integrated fuselage. Curved part for stab is transitiom from NACA 0021 profile to stab cross section. NACA profile width is 16mm so i hope it would be able to withstand the forces.
How do you want the phase wires to run?
Like drawn in the picture?
The channel at the front and the one at the back are not big enough to run all three wires through.
Also, why not remove the stab completely and make one yourself?
If so, you could mount it at the back of the jet. You have two possible positions.
Win-win: less drag and easier to make.
Yes, phase wires will go exactly like sketched. Front channel will be for ESC cooling. There is a wall between front and middle compartment in motor mount, so water will go up only in front channel. As this is 19mm mast, there is no 3rd channel.
Regarding stab wing mounted on impeller duct that is doable. I already have this stab
https://www.gong-galaxy.com/en/products/gong-tail-wing-carbon-v3
and tail wing
https://www.gong-galaxy.com/en/products/gong-tail-wing-fluid-h-v3
Tail wing is top mounted on stab, so I would have to mount it in top position. I have never seen a configuration like that. What I am a little worried about is that then the motor and jet assembly will have to withstand forces in vertical radial direction while otherwise there would only be forces in axial direction. Impeller shaft assembly is mounted to the motor with 4 M4 screws and depth of thread in motor is only 4mm. and there are only 2 M5 screws that hold motor sleeve to motor mount.
Thanks for the suggestion. Do you know how much vertical force does tail wing exert on stab? Stabs are quite thick usually.
Have a look at JetWave.
They have the stab on the jet (it’s on the bottom).
Making a small adapter to mount the stab on top doesn’t really look like it would be difficult.
No, mounting on top is no problem. I have a question, would tail wing mounted on top produce instant nose dive when breaching surface? Like this learning aid from Sifly that produces controlled descent upon surface breaching but still has submerged tail wing to rely on. I intend to learn efoiling on this thing, when it is complete.
@jozagulikoza You might be making this more complicated than it’s worth. 
@kian approach was much easier to implement and takes advantage of using Gong foil system that has lots of choice of foil, fuse and stab so as riding evolves it easy to change things up.
Why not design a motor mount that attaches to the mast in the more traditional way? That seems to be driving a bunch of questions that aren’t easily answered as not many builds here are as “unique” as your end of mast approach. You certainly seem to have the cad stuff wired so might be worth a think.
I was working on classical approach in June, but I didn’t get very far. Problem is, that my motor is not waterproof like 65161 and i need to design waterproof housing for it.
This is how my motor looks:
I thought to seal phase wires with O rings and machined acrylic pressure plate. Here are some pictures of the abandoned design.
I guess it is time to try to continue with this version, since it was advised by both you and Kian. It gets rid of 3D printed metal part with loose tolerances. And I already have Gong V3 fuselage and 19mm mast fuselage connector. If someone needs 3D model of this connector i can share it as soon I finish drawing it.
Thank you again for all answers.
I can understand your dilemma about this
,
My perspective comes from the easy to implement 65161 motor, an attitude of keeping things as simple as possible and following an already established build so not sure you should listen to what I have to say
What reason did Flipsky give about not being able to meet your KV requirement?
There are a few motor clamps here (albeit for the Flipsky motor) for the new V3 19mm profile that might provide inspiration.
I was not talking with Flipsky but with Reacher, that supposedly sell 270 kV motor.
https://reacherbrushless.com/product/products-8-60.html
At that time they didn’t have any stock. Also at that time Kian was reporting (IIRC) that JetWave needs around 17000 RPM for full speed although he only tested it at 12000 RPM.
So I went safe way (hopefully) and ordered LMT 30100 motor.
https://www.lehner-shop.com/en/inrunner/series-30/30100
This one is supposedly capable of 50000 RPM and 40kW peak power, although torque is not very large as this is an ironless motor.
My dad talked with the people at Lehner for quite some time about developing a motor.
They definitely could make one, but he would need to order a minimum of 10, I believe, to make it reasonably affordable.
Also, they couldn’t make the motor waterproof, so he would need to design a sleeve around it, like you did, to make it waterproof.
Making this for 10 motors would be a big job, and there would still be a lot of unknown issues.
In the end, he decided not to go ahead with the idea.
Did you have a look at the motor from JetWave?
We are using it now, and it works well.
However, our VESC (75200) cannot handle the RPM the motor needs, so we are not able to use it to its full potential.
Sorry about assumption.
Perhaps take a giant step back and reassess why you are going jetdrive vs prop. I “assume” that safety was the biggest driver especially with children involved. Lots of builders here start out with the assumption that prop is dangerous (myself included) and design accordingly (prop with duct, enclosed jet etc).
I’m not saying that getting hurt by the prop isn’t possible but from the collective experience here and elsewhere that is extremely rare. Much more common source of injury is fall on or kick foil etc and they are rare also - EFoil injury is no more common than any other sports activity.
@Kian Yes, like I wrote I wanted to start with JetWave motor and jet propulsion set. I have put both into basket, but upon checkout, postage was 400EUR to Slovenia. That was reasonable for the whole board, but not for ordered items. So I contacted them, and they first agreed to send separate invoice with lower transport charges, but then changed their mind and told me they would sell only to those who already own the board. They asked why I need those items and I told them that it was for DIY project, and that I don’t want their electronics, as all updates go through their serves. If they go belly up, I am left with bunch of electronic waste. They contacted me a few months later and offered special price for the whole board, but I didn’t answer.
@Foilguy I know about dangers, and I agree that jet is not panacea for all dangers, especially like falling on foil. My motivation is a little different. I am semi retired and I have a lot of spare time so simple and fast project is not for me. But thank you for steering my project back to basics. I managed to finish motor mount to mast, It only needs some polishing like tolerances and maybe replacing gaskets with O rings.
Yes for many here the build journey is as much or perhaps more enjoyable than the riding part.
Given that you are now going with a more traditional mount have you decided on what version of Gong foil to purchase? I have used XOver and find the foil shape and longer fuse/stab section provides a good learning/progression system. The Gong system has almost limitless combinations so easy to try different things out.
I also had a thought that given your design capability have you considered making an attachment for your motor that would mount a prop? Might be fun to try both propulsion methods. The reason I suggest that is if you were to go prop at some point you would need clearance above the fuse where the jet might require less and you find your motor isn’t in the right place on the mast.