Safety with efoil, continued

Continuing the discussion from Safety with eFoils:

I just came across this post on Instagram. Efoil accident with fingers involved. I do not know the status of person involved, but looks bad.

Just want to bring this topic back to life. As riding with a badly protected 3kw blender under your feet obviously is not for the faint of heart.

I think there is a lot that can be done so we don’t have to see more of these pictures…


  • proximity sensor
    - mag leash
    - pressure sensor
    - Thermal sensor
  • propulsion
    - soft blades
    - break off blades (3d printed props works to some extent for this).
    - jet drive
    - mesh/more struts on prooguard
    - minimize chance of unwanted throttle, by remote design and oberallsystem design (dead man’s switch, and built in safeties)
    - Proper training in board functions.
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I would add basic safety tips like never touching the prop while the system is turned on even if the remote is turned off. Never have the remote on when you are swimming next to the board. Always bring a cellphone especially if going far offshore! Always wear a lifejacket/impact vest. I know these are mainstream but they are nevertheless very important!

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Shit! Did this happen during riding or assembly.

Really sorry for the guy. Do we know if it is a DiY construction ? Looks like the 5 blade prop of the eTakuma eFoils which doesn’t seem to have a rear protection on the nozzle.
Bad news for the first brand involved if commercial or rental.

That looks really bad, I feel sorry for that guy.

I´m also thinking of an active safety system to prevent the motor to spin if the rider is not in start position. Maybe it could be possible to have one or two water level sensors along the side of the board that sense how deep the board sits in the water. For example if there is no rider on the board it will float on the top of the surface and these sensor will not get any input. Of course this is also depending on the weight and volume of the equipment. So if the rider is on the board in start position these water level sensors will sense it along with a 3-axis gyro sensor that indicates the the board is leveled in the water. And when this “start condition” is full filled the the motor is allow to spin. And then a new “riding"condition” is started. For this we could also use the gyro-sensor to limit the max angle of the board. And also in foiling condition the speed/current info combined with a accelerometer sensor could indicate if the rider falls.

If these sensor could give us more details about the riders weight that could be used to calibrate this safety mechanism and also throttle input. I assume the there is a difference on the board will react with a rider on 100 kg and another one with 50 kg. In beginner mode the lighter rider do not need so much power to be able to foil. But the heavy rider will need a lot more power to be able to ride.

Another active safety feature could be that the you need to have the remote on a certain position on the board or push a button on the board to be able to start. And this is to verify that the rider is on the board in a starting position.

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Great idea! Feel really sorry aswell.

Maybe an IMU and a current sensor is all that is needed? +clever software and a bit of machine learning. Sounds like a fun R&D project!

The flight board has somthing as you describe in thier boards.

A safety system need to be solid and guaranteed to work. This means it needs to be as simple as possible. Preferably you don’t want it to be manually set by the individual as sometimes they will forget it.
The one option is sacrificing efficiency and speed and shifting to a larger style jet drive (there are talks about it on the forum already). This means you can’t get your fingers or any other body part anywhere near the impeller.
Another option would be a system that drives the throttle output to ground if a certain weight condition is not met on the deck of the board. This could allow for weight from either lying body, knees or feet etc. Forcing the throttle output to ground would mean even if the remote is pulled nothing can happen.

Maybe we could try to gather some cases where it went wrong. I mean what type of accidents could happen when using a efoil, what is your experience? So far I have not experience any accident when riding if I don´t count flying off the board in 17 knots in a middle of a sharp turn. But I think that is a part of the sport.

Is there some kind of sensor the we could use to detect a foot a hand or something behind the prop?

I think the safety-leash is simple but I don´t know if it effects the quality of the ride. Maybe another type of switch like a big plate-button that is pressed when the rider is on the board. I was first thinking of some kind of sensor bellow the hatch that could detect the weight as it flex.

Different types of condition to protect the rider:

Carrying the equipment to the water
The motor should not be able to spin (if you don´t override the security features, inspection mode). How to detect this?

  • gyro-sensor…the board is not flat
  • no water/pressure in the cooling system (maybe the pump draws less current)
  • water level/pressure sensor.
  • safty-leash (halleffect, reedswitch) that disconnect the receiver input or something.

Board is in the water but not riding
The motor should not be able to spin before the safety feature could detect that the rider is laying in start position on the board and that the board is almost laying flat. This could be done like we mention before:

  • gyro sensor
  • water level/pressure
  • safty-leash

Started riding but not foiling
What to protect the rider from?

  • To steep angle of the board, nose to high: gyro
  • Detect if the rider is still on the board: current/rpm


  • To steep angle of the board, nose to high: gyro
  • Detect if the rider is still on the board: current/rpm, accelerometer

Waterblade (TEXAS) is selling them on their site. Need some testing for 48 to 60V though…

Connected handles detecting the rider’s will to ride the board (ala Supernova) mounted in parallel with foothooks with opto detection, easy and no gyro needed
or a footpad/mat/ containing either :

  • an electrical conductor matrix OR
  • a pressure sensor pad (no inflated pouch to avoid punctures).

Must not send OK if the board is upside down on the water surface (30kg of pressure of board and battery on the mat = false positive) so a sensor detecting the board upright position is required. This might prohibits a few tricks with the board.

The quadcopters I fly have all these safety features in the software. If one of those runs away on you you lose a finger (at best).
I’m working on implementing a off the shelf flightcontroller with standard firmware to use all the safety features that the drones offer. This includes dual stage arming (and disarming/ soft killswitch) and what they call small angle detection which uses the accelerometer to check if the drone (or board in this case) is within a certain ammount of degrees from horizontal before allowing the arming sequence to even work.

It was a pro surfer using an e-takuma

Thanks. Glad the actual source was tracked down and that we’re all talking safety. My winter project is to design some safety features as well. If I can come up with anything helpful besides a low drag shroud, I’ll definitely chime in. Curious to see what everyone else is coming up with too.

As an aside: ugh…what a douchey article…but nothing new I guess. Every sport or activity I’ve ever been drawn to always seems to have a large and obnoxiously loud scenester-y “too cool for school” faction. Get back on the water and get better at riding whatever pool-floaty you love most…that’s what makes me smile :slight_smile:

I’m frightened by the widespread of efoil rental, this one definitely calls out for some active safety on our board, besides arguable blade duct as used today. Or more sooner than later this sport will be banned or restricted as hell.
Superfast deceleration ramp, quick reacting lost signal motor cut off (you fall, 2.4Ghz remote hit water, motor off)…but definitely a “weight on board” safety like the “Driver on seat” used on lift truck would be something to implement.
There are plenty of chances to get hurt foiling, luckily the most can be avoided exercising common sense!

I will not agree about safety , as I fall many times of my board and even managed to get the mast between my legs , my back on the wing , cut my lips on the battery case in front …

The only time had trouble with the propeller was when I put the board in the water while holding the remonte , I push the remote on the board and started the motor , my arm and hand were not far from the FR prop , ( I think the takuma is made of plastic and whole have break …)

So the way I see it :

Pressure pad
Easy breakable smooth prop or prop pin on the shaft

The takuma prop is made of aluminium. Machined from aluminium like the FR props.
Regarding this accident, it is hard to find a reliable solution.
Pressure pad will need to be really wide to make sure that you will step on it 100% of the time.
Pin on the shaft could help a bit but what I think would be the best is to have a roundish leading edge on each blade.
I have had the chance to see the takuma efoil really close and touched the prop: these 5 blades are like razors. Really sharp leading edge.
I have been riding with a 80100 outrunner with a custom designed prop’ and no duct and felt on the prop few times without any injury.

If you have a big hatch on the board like Lift does I can not see how to ride it without standing on the hatch 100% of the time. Maybe if you jump you will loose pressure but then you are already pushing it.

I don´t think that the sensor needs to cover 100% of the board if it is only used as a safety feature to start the motor. This along with a gyro sensor to detect that the board is flat and when riding the gyro sensor and motor current detect crashes.

Still not clear how the Takuma rider ended up with his fingers into the prop duct. Common sense about safety calls for pressure sensor etc but a safety to be effective must keep in consideration real life accidents.
I’m afraid that also plastic prop could slice you like a salami, roundish or not! Open duct but even caged ones, if you let a finger thru will lead to the same result. With no chance to get “bounced back” by the spinning prop (remote lucky possibility).

Pictures posted by shops unboxing the product show that on 2019 deliveries, there was no rear protection on duct and no screws to fix one as on LIFT or FR. Looks like a retrofit to be announced !