SlipHazard - build from Finland


After a few long years of gathering parts, learning and testing, I have reached the finishing stages of my eFoil build. So naturally I would now like to share it with you :slight_smile:

This is a 48" carbon fiber board, built with

  • 14S7P LG M50LT battery
  • MakerX HI200 75V VESC based controller
  • Flipsky 65161 120kv motor
  • FR 6" 3-blade prop
  • Gong 65cm V2 mast
  • Curve MT and Veloce MT front wings, Surf 40cm and FAST 40cm stabs
  • Metr Pro CAN for logging, with MRo u-blox NEO-M9N GPS
  • Maytech controller, with some additional waterproofing
  • 150A main fuse that also acts as a power switch (100A would probably be a better choice)

I designed my own FS65161 Gong mount: FS65161 motor mounts for Gong V1 and V2 masts

The 14A7P battery is made with LG M50LT cells that are not commonly used with eFoils. My battery simulator said that it would work, so I took the chance and used these cells. They are rated at 7.2A each when over 25 celsius, and 14.4A when under. Turns out that I never exceed 7.2A per cell even during takeoff. The battery runs cool and performs really well. I am very happy with it. More info about the battery build here: DIY 14S7P battery build in a Pelican case

Here is a video of the board in action

And a metr log


The board from the inside


Looking Good, interesting to see how warm the passively cooled VESC gets in summer. I use the same VESC with passive cooling (small heat sink that sticks out of the board). When I run fast for 10 min without water contact, the VESC remperature gets close to the limmit of 80 degrees.

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Thanks! At about 25 celsius ambient, 15-20 celsius water, the ESC seems to saturate to around max 55-60 celsius. If it starts getting much higher than that during the summer, I’ll add something to transfer heat from the ESC box to the foil mount reinforcement rails. If that doesn’t take care of the issue, I’ll start thinking about a water cooling… But I don’t think I have to go that far.

The VESC temp is visible in the Metr logs if you want to take a look

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That board looks so nice.
Is almost looks like a @noahark board!
(See: Naples, Florida Build(s) + DIY eFoil board(s) for the community - #29 by noahark )

So glad to hear you are happy with M50LT! even voltage sag is not so bad!
I decided to go with same (waiting for cells to arrive) after hours of choosing between classics (40T, P42A) and this pretty new, still unproven cell. 14s9p config, 88A max for takeoff and 30-35A cruising in my case. Ambient temperature will always be around 30 or more degrees, so that gives me 7.2A/cell discharge from start. I guess peak of 88A for take off shouldn’t warm battery too much.
anyways, great build! slim battery is something I would like to do for next build, I believe cooling is even better than classic block battery because every cell can transfer heat to case too, not just other cells.

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Is the 150A fuse oversized and limiting in some way?

I use 150A on battery for emergency, just for safety.

Well, considering that I typically use max 55-60A or something like that, I could just as well use a 100A main fuse. That would trigger earlier, so it might be a bit safer. Not much difference, though.

That’s because it is a Noahark board. Kind of. This is one of the early production test units. I had to do quite a bit of work to make it into a usable board. I converted the original lid design from 4x male thumb screws to 6x female thumb screws. I reinforced the lid as well, and changed the seal from poured silicone into a ribbed EPDM seal. I fully redid the foil mount and added battery holddown rails. The board also split open from quite a few spots along the sides of the hull, where the deck was bonded to the bottom hull, so I bonded it properly with fiberglass.


We ordered something from him, but due to problems he was having with the boards we requested our money back, and he returned it with no problem.

Here is a log of a bit longer ride. Everything worked great! My Veloce MT is also arriving today. Can’t wait to try it.

Nice setup!!

I did a build and am currently in the process of learning to fall off the board at speed😀

Many of my splashes are during the transition from kneeling to standing.

I noticed in your video that you go through that movement by first placing your back leg and then your front.

Is that the way that just felt natural to you?

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Thanks! Yeah, that simply feels like the most stable way to do it. To be honest I never really thought about it that much. I learned to get up by experimenting, not through a course or guidance from someone so my technique might be less than ideal.

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I’m finding that after I’ve watched lots of YouTube expert how-to vids I still can’t do it as “simply” as they show😉

Whatever works is my motto!! I’m going to experiment with your approach to see if it works for me as well.

I’m already craving longer run time - battery capacity, that will drive a new build so I think it’s cool that you are trying something a little out of the ordinary. Well done!


Logs with X-Over XL front wing + X-Over 46cm stab. The beginning has a section where my brother was learning, so that part is a bit messy. When exploring the lake I got about 15-17A current consumption, which is my record so far. ESC temps stabilized to about 50-52 celsius.

It’s a very nice an easy wing setup. Perfect for learning and laid back exploration.

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Sounds like this is a good foil for you.

I am a bit curious about your battery level data.
Not sure which is outbound and return track but when I tap them that level indicates 82% on both even though you have traveled quite a distance between those points??

To be honest I didn’t even know about that data channel. Never tried it before. It’s definitely incorrect… I’ll see if I can tweak the Metr settings to improve it.

The battery voltage is valid. You can use it to estimate battery level. Consumed Wh also gives you a good idea of battery use.

Longer log, warmer weather. We took turns with my brother in the beginning of the session. He is learning fast, already foiling well when kneeling, and stood up a few times as well. ESC stabilized to 60c, battery under 30c after the ride. 67 minutes ride duration. It’s possible to foil at 15A, as demonstrated during the very last minutes of the log. X-Over XL + X-Over 46cm stab.

I think up to 1.5h ride time is doable with this battery and foil set if you don’t fool around/do a bunch of takeoffs and just maintain a nice cruising speed (~18km/h maybe). From totally full to totally empty. 1h 45min is probably impossible.

Battery after the ride. Nice and cool (10c over ambient):

I recopy you answer from the other thread here to clarity:


I think I’d prefer to discuss build details in my actual build thread, but here goes… :slight_smile:

I am using Metr Pro CAN + separately bought MRo M9N GPS for logging. Unfortunately Metr is currently discontinued, and the original creators are working on a new project. Meanwhile I would look into the used market or the new Vesc Express logger. It seems to be a capable unit, but I also think that the software is not as finished as Metr.

I am using the 30A BMS, not 60A. I am not using my VESC through the BMS so discharge ratings don’t matter. Only the charge rating matters, and it is 20A for the 30A (discharge) model of LLT BMS.

You should not connect packs with different parallel cell counts in series. Unless the actual battery capacities are an exact match, you’ll end up discharging the lesser battery more, which may not trigger a low voltage cutoff early enough. This may cause the lesser battery to discharge too deeply, which damages the cells and makes charging dangerous as well.

Also, water-cooling for the VESC is probably not necessary. And it’s definitely not necessary for the battery. For me it’s enough to have the VESC in an aluminum box. It doesn’t even conduct the heat anywhere, but still stays cool enough."

HERE MY ANSWER to YOUR COMMENTS on Battery calculator for eFoil - #28 by macfly1202
1/ about Metr : I am trying to find one and have a look to Vesc Express logger

2/ super clear about BMS: you use it to charge and balance only not during riding - make senses why 30A only

3/ About my idea of 2 pack I know it must be the same in serial. I was saying I need to find which battery is more suitable from 6S10P to 6S14P but it will the same (6s10p+6s10p, 6s12p+6s12p or 6s14p+6s14p) ! safety first !

4/ about watercooling: I prefer to be more safe first and, for sure, a pump a another point of potential failure. Only data will speak > so I need to see the raw amp at high frequency to see what happen.
In my step 2 build, when I will made the board, probably I will use a passive system with CNC alu box.

Because I know very well Ardupilot, I will probably use it as a logger if a can’t find a Vespress logger or Metr. I have all spare for Ardupilot on shelve.

Kind regards, Jean