Assist / Light build from France [maytech kit]

New builder from Lyon, France.
I really enjoyed wake and wind foil this summer, but the conditions are not often good.
I have quite a lot of experiance with this king of systems (controllers, batteries and such) but using that in the water not so much!

F one rocket 70L board
Slingshot fpump quantum 100 (1750cm2)
8S4P 21700 (50E cells, 50A max on the pack) no bms yet as I could not configure one properly in 8s
Maytech kit with 6374, folding prop in printed nylon, vesc 100A
Ammo Can box for all electronics

I used a Waterproof yf-24 connector on the back of the box to have Quick connection and ease the handling. The connector is probably the first and early failure point, as it is only rated 20A RMS, 30A on some docs.

I modified the tool less/QR mast mount from the fusion files (thanks to the original designer) to have slingshot mast profile, also found here on the site.

Missing some bolts and proper mount to the board until I Can test it, probably this weekend with great weather.

I weight 67 kg so hopefully it survive!

Processing: VID-20230929-WA0008.mp4…

I think you are the first one to use such a box for the electronics in a project, especially for an Assist. Members prefer plastic cases and use the amo box as a protection against fire for battery storage.
A few questions:

  • You want to build “light”. What is the box empty weight ?
  • Material: is it rustproof ?
  • Is it watertight ? Since you cannot use a Schrader valve that needs wall thickness, did you submerge it for an hour or two under a water metre ?
    'Search results for 'schrader' -


I tested two minutes under water, splashing the box in all direction, seems ok and waterproof so far. It will likely be a temporary solution as I test and debug the system.

“Light” was mainly regarding the power, the box IS not the best lightweight solution, but I had it available and it fits the 8s4p 21700

Test this afternoon After I figure how to mount the box secure and safe to the board. I have heavy duty velcro and will use the leash mount as safety.

First test went without drama, but without succes either. The VESC was set first with 60A phase, and the system could not make more than 15A battery then. After setting phase amps to 75 then 100, I could reach 25 then 40A battery current.

Unfortunately, the VESC goes into some throttling after 5 seconds or so. I could not get on foil yet, combinaison of the techchnique and lack of power so far. I think I have to mount the vesc directly to the box to cool it. I dont think I was hitting LVC, at least I could not really see it on the remote.

I had a litte bit of water coming in from the bottom connector screws, I re-did that with better sealant compound tonight. The connector itself survived and was not hot.

I tried different mast positions, and different foil settings, but each time it felt like it pitched up way too much (some pictures show it, I was leaning forward as much as I could)

For the next ride I will be a little more agressive with LVC :


I would offer a suggestion. Before you try standing try to get up on foil while you are on your knees. Keep the board flat on the water and get it going at least 15kmh before flying The idea is to get sufficient speed through the water BEFORE you try lifting off.
The photos look like you are getting stuck with a very steep angle of attack on the foil and the board trying to push through the water. Very hard to get the board levelled off once you get in the position. Just stop and save the battery capacity and simply start again.

Thanks for the tip, I briefly tested that but with similar pitching UP.

I will try some things tomorow like having the stabiliser upside down as shown in some slingshot photos…

This is the Slingshot FSUP foil I used before I went to Gong. Stabilizer is flipped on mine compared to yours but it only goes on in one orientation so not sure if you can flip yours. Worth trying I guess.

When I started efoiling I was having the same pitch up issue. The only thing that fixed it was more board speed and then a slow rise out of the water onto foil.

Have you tried moving the motor either up or down the mast??

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Connect the mast into the wing. That will change the game completely. That way it’s currently set up means you need to get your weight right up front.

Thanks, I tried that but only on the begining when I had only 15A.
Will try again today !

Regarding stabilisers, the 48 seems to mount to the under side of the mast, while the 42 mounts to the top side. The text writing is on the top of the stab each time.

With a mast placed in the middle of the fuselage, it seems you have a windfoil version of this hydrofoil.
If your F-One wingboard allows it, your feet should be positioned 15+ cm further forward than with a “classic” wing foil which could be uncomfortable. Try to borrow a wingfoil gear and test again.


Changed some settings for today tests
Little higher temp of the mosfets
Safer / reasonable power limits.

I tried on the most forward position on the mast/board and the front wing position, not middle.

I managed to get on foil when kneeled on the board, by pumping it. The vesc thermal throttling comes top early, I need to make a new and and better heatsink. Still a half succes :wink:

Did not manage to get on foil when standing, even when all the way forward.

The waterproof connector also bit the bullet as expected, actually the ground connection was smaller than L and N, did not see that. Motor was starting in either direction due to the phase disconnected :sweat_smile:

I will try to redo this connexion with MR60 connector in epoxy.

With the overheated connector, water was coming thru the connector body, apparently no damage to electronics.

realistic current and wattage limits

Use a 3 pin ec5 connector. It can handle mor amps. The mr60 wil get seriously hot and probably desolder.

I use MR60 at work on bikes pusing 2500w and 90+ phase amps for minutes, never had issues. I will check if I find another waterproof connector.

Prepared the next tests:

Thermal pad for the controller to dissipate to the case
Mt60 connector pass-trough, cast in epoxy.

It is an extra failure point, but at least I would be able to remove the controller from the box! The controller is mounted by 4 strong magnets to the box.

What do you think about the wires mast mount, last test I taped the wires but it is not efficient and takes a long Time.

There are builds where they are in a printed Channel, or thru the mast. I will look at a spare mast in the future to run the wires inside and reduce drag.

Third session went well.
Some hiccups with the remote connection, printed mast mount failing, and my Friend fingers into the michhobby prop that exploded.

Other than that, we managed to run the battery down and get some good runs foiling feet on the board.
I got the start technique dialled and I feel like I Can start on foil with much lower power now.

Zero water in the box! Happy about that

I need a New prop and improved mast mount now :wink:


Hello from south of France :wink: !
I am just getting started on my own project, thx for sharing yours !
Why not putting the box in the middle of the board rather than at the back ?

I do not have enouth wire length, plus the board does not have a hole to run wire throuth. Because the board has no straps holes, I need a flat surface without grip foam to mount the velcro.

But it would solve most of the connection problems and improve COG.

When you look at the pictures, it still feels like the foil has the wrong attack angle.

I also use it for pump foiling and it is not gliding like I want, I feel stalled unless all weight is on the front, but it is like an airplane with too much UP trim. It will fly if enouth weight is UP front, but it will not glide well or require lots of motor power.

In dock start one Guy had good sucess with the 48cm rear wing, so I ordered one for tests. In the meantime I will design a New mast clamp, slip on in hard tpu.

Here is what I will try next, in hard TPU for the mount, and PLA for the cable guide

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