Nice cut from propeller

Yesterday my knee somehow hit the PLA duct that broke and the wetsuit got tangeld in the prop.
After a night in the hospital I am ok no vital parts of the knee was affected.
When thinking about it, the PLA is so weak and do not give much protection at all.
I was lucky it was my self that got hurt and not a friend trying the board.
I have no idea what happend I just know it did. I will not try it again until I have metal protection around the prop (or maybe a jet). Just to let you know it can happen.

Ive been waiting for this post, unfortunatly. Im glad to hear that you are OK.
I really thought it would be from someone running without a duct!

I have spent money on SLS Nylon Parts so they have some durability.

I hope you recover quickly.

p.s. Maybe a graphic warning on the post for the weak stomached. Graphic, but effective.

Glad that this is only a tissue wound. I had a scissor stuck there once and it looked similar, but was gone after two weeks. All the best.

You could wrap the duct with kevlar or glassfibre in future. How come the prop was still spinning?

Appreciate this post Jan. Thanks for showing that serious injuries can happen!
I am sure that this will help contribute to the safer design amongst both the DIY and even the commercial eFoil community.

I wish you a quick recovery and hope that you can be fit enough to get out on the water riding again soon!!

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.


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.


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 - 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?

:relieved: 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