Hello Guys,
here I’d like to show you what my Version currently looks like and what I’m planning to develop till next summer.
Sadly I can just add only one pic in the thread, so I have to split a little.
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So where I started… last year I tried to bring my sailboat up foiling, so I developed foils (front and rear types CFD calculated and optimzed with special winglets). First test this year showed that they can cope with 100kg in 8 knots of driving speed as you can see here:
But where I come from is one of the lasiest lakes in bavaria regarding the wind… going out for foiling is possible only a few times during the year.
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Earlier this year I saw the efoil concept coming up on youtube, and I fell in love immediately, so I decided to build up my own (and hopefully better and cheaper one than what was available).
I started from the beginning on with the concept that the drive is in line with foils:
This has, in my opinion, several advantages, first is that the prop will not breath air too early, second the forces are acting in line with the drag causing foils and third is that is hydrodynamically better than a clamp on version e.g…
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I used the already developed foils and attached them to an aluminium pipe with the diameter close to the one of the motor. First motors were Outrunners and direct drive, but forget it, the fun is always just for 5 min until the winding will overheat, but the succes started with this:
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After some further development I landed at the current concept:
What I use is:
Board: Naish Hover 160 with 20l
RC: AlienPowersystems (for electric skateboards) and a waterproof document bag
Prop: Yamaha 7 1/2 x7 (biggers are more efficient than smaller props)
ESC: Multiplex Roxxy Blcontrol 9100-12 Opto modified with Peltier element attached to a aluminium plate on top of the Box (better heat shift and circulation within box)
Accu: Turnighy high capacity ( but I want to shift to 18650 Li Ion types by LG)
Profile shaft and tube: custom shaft and welded on tube(Da45mm) with aluminium front cap
Bearings and sealings seat: aluminium milled
Motor and Gearbox: Inrunner motor special gearbox, output 100KV
50 min of flight time is no problem with 36Volts and 16Ah. Max Speed ~35km/h. I started with 8S, this is also possible but speed was only 25 km/h.
Next step is -of course- 12S 
Starting power consumption is ~1,8kW, flying speed at 25-30km/h is 400-500W(!) I was very surprised with that! A friend of mine with 85 kg needs 30% more power.
The concept is quite cheap, parts cost ~650€ excluding board (350€ in summer sale)
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For next year I will improve security with a duct, as this is necessary, of course. My idea is to have the duct also acting as rear foil, like this(raw design):
Probably I can even avoid the side wings… but this has to be tested.
I also want to build an “easy to start” version with a bigger board or an inflatable SUP, a very safe version with special wings and a high power edition (speed >50km/h).
If you’re interested in parts, I can try to arrange and build some for you.
Sadly I cannot upload any video… I would love to show you in action. 
So now tell me what do you think about this concept?
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Servus @Peter! That is a fantastic built and success story here! Love it! Thank you for sharing. Innovation aus Bayern! What lake? Chiemsee, Tegernsee? Those are some good skills getting up on that little board. Congratulations and please keep sharing your progress.
Hello peter
Very happy yo see your project. Like you I have a big propeller, a solas one 7.25 x 6.
I’m afraid because everybody who try to use direct drive with outrunner has burn the motor! But have you try to cool it by different way? I will use the motor in oil box to cool it. Only 80watt more compared to air!
You, how have you done to cool it? What do you thing about my propeller?
Very nice concept and thank you for sharing!
Hello Vincent,
thank you!
I went over to an Inrunner motor with gearbox, because I found no way to cool the windings sufficiently. You would have to implement a water cooling in the sheet metal package. Further the overall efficiency of outrunners is in the range of 60-80%, even worse in partial load. Thats very poor if you compare it to an inrunner and gearbox (1 stage) combination, 0,9*0.95=0.85. Further the installation space is much smaller for inrunners.
If you want to get on with direct drive, you can probably use an inrunner in 56mm size and a propeller smaller than 100mm dia. The rpm has to be increased to over 10.000rpm → I call it the mixer Version 
I already thought about an impeller version with water accelerating shape, like this: http://www.modellbau-peters.de/ds-30-dia-hdt-high-dynamic-thrust.html
But this goes into a jet setup direction.
Here the overall efficiency will suffer, an efficiency is all if you don’t want to spend too much for your batteries.
What are currently working on?
Regards Peter
@Peter I am currently building a setup using the same approach. A 90 KV 50mm outrunner with oil cooling. Fingers crossed that this could be the solution to the direct drive!
Hi Peter,
I really like the clean design of having the propulsion inside the fuselage! And the efficiency seems to be pretty good as well.
The prospect of being able to replace the back wing with a propeller duct would make this even so much better! And I also think this should be possible, although I’m afraid riding it will be more challenging compared to a real back wing. But hopefully not as difficult as riding a Monofoil:
Br, Lukas
I am quite surprised anyone was able to balance on a monofoil! @Peter, One thing I understand about the rear wing is that it needs a little decalage (negative angle of attack relative to the main wing) for added pitch stability. This brings up an important question to everyone: Has anyone experienced poor pitch stability due to the angle of the thrust?
Hey Peter, i really Like your concept anderen would Like to build a prussian Style sister model. What Motor did you pick and did you make the Aluminium stuff yourself?
Really nice build! Also thought about building with the duct as the rear wing, less parts=better and less drag. Our new setup os modular so think we will try that and see how it work out.
@Jsonnett Let us know if managed the cooling!
@Lukas Respect to the monofoil rider 
Instabilty is what I totally want to avoid, so the overal construction has to be very stiff and adjustable in angle of attack. l’ll post some pics when I finished building it.
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Hi,
I am from bavaria too (currently living/studying in munich). I really like your concept! How did you build/made the wings? Are they 3D-Printed? Are you willing to share the files? I am studying mechanical engineering, so maybe we could share our experices/ideas 
Where are you from and where are you riding it?
Can you log how many amps you draw peak? I would like to rebuild it with the ESC (a VESC) in the tube and with an inrunner direct drive ~200KV and a bought ducted prop from aliexpress (80mm, @peak 3000W ~27kg thrust) the 8010 one.
Did you see the multistar batteries? I guess the 4s 16Ah are the cheapest (per Ah).
Best,
Chris
@windchaser Sure we can meet --> see Email
@Giga We can talk about the concepts, of course, and munich is not to far, so if you’d like to come here on weekends, just tell me.
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Servus Peter!
Bin extrem begeistert von deinen Konstruktionen.
Ich stehe ganz am Anfang und möchte über den Winter ein E-Foil bauen.
Habe viel Erfahrung im Modellbau und bin viel am Wasser unterwegs (Katamaran Segeln) und suche neue Herausforderung.
Komme aus Salzburg und würde mir sehr gerne deine Teile in Natura anschauen.
Von welcher Ecke in Bayern kommst du und wäre ein Treffen in naher Zukunft möglich?
GLG aus Salzburg!