French build born in [LYON]

Hello every body, I propose to share my build.
I have made different test with lot of failure, and now I can present one design well working.

First prototype with a lot of water leakage, rear bearing not protected and became rusty,

This is my actual prototype :

Now all part to waterproof motor and reducer are made in aluminium
Part 9 (red) is stick in to tube 5
Reducer is fixed on part 9

Construction :


Waterproof connection to motor :

Leakage test by replacing axes with 10mm pipe and applying 1 bar with compressor

For assembly I use thread bar to align reducer and aluminium part sticked in to pipe

I prevent rotation of coupling by inserting washer

Tuttle box is home made: 3D printed part + epoxy + fiber glass

Ready to ride.

Board has big volume and it’s really good for beginner . (has me ) . I can stand on it without speed.

Actually I can fly 30m soon continues riding

One of the first foil in LYON !! :wink:

Next step will be to reduce weight every where (board / foil / construction …)

Hope it can help someone,

Thanks to all builder,

Enjoy you ride !!


very nice built, we should meet somethings, as the “first efoil in Lyon” , i don’t know, i have been flying for a couple of weeks now :wink:

tu mets ou à l’eau sur lyon ?

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Oh nice another builder in Lyon, I was not aware, actually, I m testing it at st fons, la maison de l eau, or le grand large,

And you?

la zone ski nautique aux " petites voiles" à Trevoux 01600

one of my battery pack just burned 2 days ago, but i have another set, so if you want we can meet , and ride together :sunglasses:

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Yes could be really great I will message you in private

Awsome! Nice build!!

Nice build without a single hole drilled into the mast !

@Gobbla Nice work, It looks amazing.
You have many fantastic features in your design !
One question what is the logic behind the long propeller shaft ?

hello theone, for me the logic behind the long propeller shaft is to decrease turbulence after aluminium pipe.
i m not using princple of ducted proppler (Kort nozzle).
I m juste protecting proppler for user. It is less efficient than kort nozzle, but efficient of ready made aluminium proppler is 30% more efficient than 3D printed proppler (tested).

@SoEFoil you right i did not make any hole in the mast. i m planning to use fiber carbon mast without hole inside. ESC is cooled with air.

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Hello Gobble,
Good point turbulence / Cavitation = Reduced efficency!.
30% (TESTED) is a huge saving with a ready made prop.
As you know a Kort nozzle is not suited for high speed boats (or efoils)
What is the pitch & diameter of your propeller?
What RPM do you spin your propeller at?
Gearbox Ratio ?

Thank you Gobble

Best Regards,

I want to go the same way, but I am not sure whether a tube or a cage design will be more “effective” (sure both will create drag, the question is which one will create less, cage has less surface area but more turbulences…)
Do you know, how much power you loose by the protection/duct? (test with ampmeter with and without duct, or maybe even different ducts?)

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for the test it is here : Propellers and Ducts - #72 by Gobbla - Props & Ducts -
static trust is easy to measure

you right i dont have comparaison of drag, i have tried to reduce it with using 2mm aluminium sheet, (impossible to obtain with 3D printed part)

the best would be to test it on side of boat with scale at different speed, i will think about it for next autumn

that is not what I meant.

Okay, but my question was, is it better with intact tube or better with something like that:

Okay, but in my opinion best would be to just try it in the final setup and log everything (speed, RPM and Power). So you also see the effect of the spinning propeller inside the tube…

hum not enough specialist, sorry can not help you
i dont have data logger. (yet)

Definitely intact tube, no doubt about that. Better if you thin your trailing edge and round a little the LE… it reduces turbulences.
Long means more drag, this goes for the motor pod as well, even though good profiles of nose and back end could improve the situation. With Efoil the problem will be that the tube won’t run horizontal, almost never. You’ve to improve this by fine tuning wings AoA, this will reduce greatly the drag loss

Guys this is just a concept to stop a foot going into the propeller . Yes it still has risks albeit a little better than a foot into a propeller.

Do you think it would have lower drag? & improve safety just a bit ?
It may inspire some one to take the concept to the next step of hinging inwards when not in motion ???

@Gobbla Have you been inspired by this post ?

wood floor skirting solutions on the internet: PVC flexible skirting band, 10USD for 20 metres with 3M adhesive

I am fascinated by your metal work. My 3D printed parts look quite cheap in comparison :slight_smile:

May I ask why you built such a long tail, as the shaft to the prop is consequently very long and may accentuate vibrations ?

@SoEFoil, yes i take some ideea from this post, and adapt it to my round cable


@philgib i have made long tail to avoid turbulence before proppler.
At high speed for me it will reduce efficency of proppler.
I did not make calculation to define the best length

some of my inspiration :

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I would try to make much more room for the motor cable solder joints. Mine ended up about twice as thick as the cables because I had to make them waterproof. They are also very stiff.