Safety with eFoils

One thing that really brought this forum together was the notion that safety is super important in these DIY builds. Everything from guarding the prop, to being safe with so much electricity around the water, to making sure you don’t get a board to the face. Please share the ways you are being safe. I am currently looking for a kill-switch for my board and would love to hear what others have done. We will likely make a category just for safety as it’s a major part of our reason to collaborate.


Oh and this is the kill switch I was using which is for a boat/jet ski. The problem with it is it grounds a wire when it’s activated. So I don’t think it’ll work in my application. I have to re-think this or use a relay.

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I think a great safety is in the ESC or transmitter. As long as one of them have the fail safe feature you are covered. The feature is once the receiver or ESC lose the signal from transmitter the motor shuts down. I have this on my transmitter, and the new ESC im getting has this as well. When board is 20+ ft a way, the signal is lost and board stops. This is a standard feature in most skateboard transmitters.

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Which transmitter and ESC has these features? I don’t think the SeaKing 130 or the cheap remote control I’m using have the built-in. I also on @pacificmeister’s build that depending on how you power up the system, the motor could run when you turn the remote off! Scary!

Yes, motor will never run without a signal from transmitter with this setup. Super safe. I use This Transmitter

I am working on customizing one which floats and is waterproof so we don’t need to bag the remote anymore :slight_smile:

Seaking 130A works, but its not really professional/commercial quality to last and stay cool. I’m working with a builder of ESC’s right now to get one that will last a long time and we don’t need to worry about it overheating, melting and shorting things out and will have the auto motor shutoff feature as well.

There are three different throttle curves (Logarithmic, linear, exponential) and Throttle acceleration: Extra soft/Soft/Medium/Hard/Extra hard so users can adjust their board to the way they wanna power applied and for smoother throttle control so you fall off the back or over the handle bars when you move your finger on the throttle.

So much we can do to make efoiling a fun and affordable build! learning every day!

Some transmitters have a Throttle Trim adjuster, when I first configured my vesc for my eboard, I had to turn that down so the neutral position of the trigger wasn’t sending a signal to the receiver. My wheels would spin or sputter after powering on the board. Definitely don’t want the prop turning in the water when you are not on the board.

A big safety topic we need to talk about is the open prop. Is see in the prop thread that many are experimenting with uncovered props. Crazy dangerous! This thing cuts toes and fingers like butter. I am guilty here as well, I foiled a lot without duct in the beginning. It was super efficient and fast. And looking back it was pretty stupid too. Let’s all work together to find the perfect prop/duct combination.


WORD!. open prop is super dangerous. Should have stators covering upstream and downstream + added safety in recicer/controller unit.

Worst case with open prop is the board jumping out of the water hand hits you in the head with the prop. It happens to us. But we had a duct so it was fine.

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I meant to share this the other day… THIS IS CRITICAL FOR SAFETY.
Using this would have saved you melt down PacificMeister…

This calculator is for DC currents. You can play with it, 3% loss is the norm, and the shorter your wires the more current you can run, but with many of us running 5-7’ wires the high current is a big issue for melting, burns, fire…

If your wires are 1.5 meter or longer, you should be using 8awg to be safe.

See for yourself:

I recommend everyone to install a fuse in their systems in case of anything going wrong. A good alternative for conventional melting fuses are automatic fuses like this:
Available in different sizes, if your amps go to high, the fuse kills your circuit and if you found and eliminated the problem you can just switch it back on instead of changing expensive melting fuses everytime.


Agreed! Similar to mine. I’ll try to update my parts list soon and include all these parts.

Just got mine yesterday! (updated)

FYI that one you linked to is rated only for 24V max Tyler… you want the 48v rated one!

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Grrrr! Thank goodness Amazon has a good return policy!

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We bought only 80 and 100A, 44V, supposed to have a “ignition” safety so should handle short bursts.

My current safety feature to make sure the prop doesnt spin when i fall off the board is a reed switch cutting the 5v supply for the esc, hot glued with a small piece of magnetic metal on the inside of my waterproof electronic box… I got kind of a leash attached to my foot or hand and a magnet which i put on the reed switch so the board is turned on. When i fall of the board the magnet comes with me and the motor stops spinning after ~2 seconds. Not perfect because 2 seconds can be a long time but the motor will stop spinning even if the remote control gets wet or something… If anybody wants to know more about this setup please feel free to ask.
check if your esc really stops operating when 5v is disconnected before testing in water!

An alternative for this really cheap solution would be the reed switch connected to a heavy load relay to really cut of the current completely.

Hi Yannick,

I like your safety measures very much and I think with the following further improvements it could (eventually???) even be safe enough to get rid of the propeller duct:

  1. Reducing the stop time of currently 2 seconds once the safety circuit opens. Instead of just cutting 5v supply to the esc, which so to speak sets the desired motor state to “zero torque”, the desired motor state should somehow be set to “0 rpm” in case the safety circuit opens.
    Doing a similar thing in hardware could involve two normally closed heavy load relays on the esc-motor connection, which can short the motor phases and thereby immediately stop the motor. I am not sure if using a normally open heavy load relay on one of the battery poles at the same time can prevent the esc from being destroyed by the short. However, I think the gears might break as well and also the magnets might get demagnetized by the strong opposing field. So this could only be used as a redundancy safety measure, which engages not whenever you fall off the board, but only when at the same time there is a safety critical fault in the system, so quickly stopping the propeller can’t be ensured otherwise.

  2. Adding a handheld leash in the front of the board, like in this video:
    I think this looks like helping to have a firm stand on the board. But more importantly, another element in the safety circuit could be added at the attachment of that leash. The tension in this leash closes a normally open switch which is part of the safety circuit.

  3. Fool-proofing the reed switch leash that you already have. I am not talking about you, but about a lazy guy like myself who might get lucky enough to have a try on your magic carpet. After some unsuccessful attempts at getting onto the board, he would probably get annoyed of constantly reconnecting the magnet and would just disconnect the magnet from the leash. Considering that riding hands-free would be a thing of the past anyway with one hand at the tensioned front leash handle and the other connected to the reed-switch leash, one could just as well do the following:
    Getting rid of both the reed-switch and the wireless remote-control and instead using a wired remote control with a magnet connector like on a mac book. By disconnecting this connector also the safety circuit will be opened.

I know these measures sound quite excessive, but to all of you who know the difference of riding with and without a duct, do you think it might be worth the hassle, if it really worked and you could ride without the duct safely?

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Maybe one could alternatively use strain gauges inside the deck of the board, so the system can check that the rider is still standing on the board and stop the propeller immediately if this is not the case anymore.


Hi Efoilers

Merten and I are so happy to see you all here. I look forward to sharing my experiences. The Good Bad and Ugly

Safety is my main concern for everyone. I plan on Sharing Throttle systems, BMS and more to contribute to our efoil community.

Looking forward to everyone’s thoughts.

Please ask away and I will try and answer the best I can

Aloha don