Hi Jan,
hope you recover quick.
I was surprised with this post.
From the title i was expecting a new propeller design with a cut view…
You could for sure change it to “Dangers of ridding a e-foil” or “Accidents can Happen” . I am sure this is a very important post and all forum users should be aware of the dangers and that accidents are a real possibility.
Thanks for sharing.
Sorry to hear of your injury, what type of prop where you using, was it PLA or Aluminium? Could you show a picture of the duct that broke?
is this the prop/duct in question?
I would guess that a PLA prop would be less harmful than an aluminium prop, altho PLA is not safe either.
Thanks
No that was 160mm and not the duct that broke.
I used a 130mm derivied from PM now on the seabed.
The prop was aluminium.
I can inagine the spokes get deflected a little and the prop carves into the duct.
I did not use a safety leach with cut of at that particular time.
i believe the spokes can break easy.
Better with nylon.
OMG, So glad you will be ok Jan, that is terrible and makes me woozy just looking at it.
I am surprised something like this has not yet happened, maybe it has, but not shown yet. It is so easy to fall into the foil/duct its not joke and 3D printed parts break easily with impact.
Take a look at the Jet Drive with impeller inset into the aluminum tube, and nozzle behind it, it’s very protected and so much safer than riding a surfboard with a glorified outboard prop under you. In Canada we cannot even get insurance for selling a ducted prop surfboard system so that there tells you it’s not safe.
Jet is by far the safest, in my opinion, you can’t get your finger into the impeller from the nozzle end if you tried because of distance, cone, and water vanes, and the impeller is set back into the aluminum tube far so you can’t get your foot/toes into the water intake/impeller.
Hope you recover quickly Jan and have the courage to get back out efoiling once its modified to be safer.
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Wow, Glad it is not too bad. Thanks for sharing…Stay safe!
What a visual to wake up to. Glad you are ok and it wasn’t worse. Hope it heals fast. Thanks for sharing and reminding everyone here about the risks. Which version of the duct was that? There was an untested version (v2) with very thin struts for better efficiency, I wonder if you used that one.
Oh water must have looked horrible. Hope it doesnt hurt as nasty as it looks. Get well soon and thx for the pic.
U said u dont know what happened, can u remember was it the time u were climbing on the board and starting or it happened after u already started aka falling down?
The strange thing is that I do not have a clue.
There was som waves so I falling a lot of times.
Hello Merten
I am not sure I think V2.
Here is the file
Hi Jan, oh man it looks like you used this version: Parametric Propeller & Duct Design - Fusion 360 - #3 by pacificmeister - Props & Ducts - FOIL.zone. It had very thin struts of just over 3mm thickness, I never tested it because it seemed too fragile, see my old note. I just added another warning note to that old post.
Thanks for sharing.
It has been interesting to learn some CAD and 3d printing.
We all knew this could happen.
I will think of a stronger design I have a lots of Ah so I do not care so much about efficiency at the moment.
Hi Jan, I was really shocked as I have seen your injury. I hope that you doing well quite fast!
How did you came back to the beach?
hope you recover nicely and fast
I was just hanging after the board.
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Prompt recovery Jan!
I guess I will put back my duck, thanks for sharing
I’m riding ductless with 3d-print props so far. They aren’t the most effective but all edges are dull. I guess the same cut wouldn’t be possible with rounded nylon.
that prop edge looks inherently dangerous duct so 
that your cut knee wasn’t worse!
Wow! Glad to hear nothing serious happened! I ride without a fail safe leash and only rely on remote, accelormeter and my own reaction to let go the throttle! VESC takes couple of milliseconds to respond for no pwm, plus accelormeter algorithm only runs at 100 hertz, add to this bluetooth latency of max 15ms all these delays makes me very uncomfortable! at the other nad leash by itself can introduce new danger, like getting tangled to prop or other stuff!
Wow… good to hear you are fine.
Propeller safety vs efficiwncy is my main concern in developing my efoil for rental business.
My idea is to go with multiple ultrasonic sensors and capability of motor to stop fast enough (either with breaks or with “steper” feature) whenever motor does not get “positive”/“clear” ping from multiple sensors procesor.
This would open possibility to have ductless prop, maximize efficiency without compromizing safety.
Or you could simply use a magnetic switch that cuts the motor power from the ESC before the rider touches water