New battery Pack
Buit a new pair of batteries from Samsung 21700 40T. They were available for a good price from nkon. I built them like the first ones, apart from the main wire connection to the nickel strip. This time I soldered them to the nickel before spotwelding. This way the cells do not absorb heat from soldering which could damage them. Tested them once, they work great. Capacity is slightly lower than the molicel p42A pack but that’s justified by the lower price of the cells.
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Hi
Your pack looks great, thanks for the heads up on Nkon samsung 40T cells, I was looking for some Molicel p42 but these will work out cheaper at 4.10 euro per cell. Hopefully they won’t sting me for import tax to the UK.
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Got them from ru.nkon.nl, the shop for non EU customers:
https://ru.nkon.nl/samsung-inr21700-40t-4000mah-30a.html
3€ without tax
Thanks for the info, I’ll email them and check which site I should use. I’ll have to pay import tax when they come into the UK still.
Thanks, I thought Fogstar were the cheapest but Nkon wins at the moment.
Fogstar wholesale is £535 for 120 x molicel P42
Nkon is £300 + £70 tax and duty for 120 x Samsung T40
FlightAssist
Added a new gadget to help control of height when the water surface is really flat. Sometimes when there is no wind I find it hard to judge the height above the water surface and the motor breaches the surface.
I built a little helper to show the height. It is based on Arduino and an ultrasonic sensor.
Hight is measured every 5ms, one of the 8 LEDs shows the position in green, lowest and highest in red, 2nd in orange.
I only tested it once but it seemed to work quite ok. Added a filter for better stability of the LED display.
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Do you plan to interface this with a servo at foil level, front wing or stab ?
No, I don‘t want too much automatic controol, prefer to keep that manual. Could be useful for a boat on foil though. The question is if the measurement is fast enough.
What is your sensor reference ?
Do you mean which Sensor I use?
This one, PWM: US $9.57 21％ Off | NEW PWM DC5V Ultrasonic ranging sensor ultrasonic waterproof distance sensor waterproof probe RS485 ultrasonic sensor module
https://a.aliexpress.com/_mP8oixy
There is a link to a Github repository where you can find the Arduino code, a BOM, STL files of 3D printed parts and a schematic drawing.
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@sat_be it’s fun because before I start my eFoil project, I bought few month ago a waterproof ultrason unit with the same idea in mind but for my wingfoil board. A winter project 
I don’t know what is the max Hz of your sensor versus the one I choose. Will try to find this info soon. Congrats for idea, perfect achievement and the most important, you share it on github #opensource 
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Surface sensing wand: it’s pretty curious that nobody has attempted to develop a mechanical wand to sense water level and adjust the foil height… as moth boats do.
Great idea… i have similar problem…
Im riding on a lake that can get like a glass when thare is no wind so it is realy hard to know hight.
Can you share your design?
Further up in the post you can find a link to a github repository with code, schematic, parts list, stl files of the enclosure, all you jeed to build it.
ohh thank you i missed the link… My bad.
New setup
Got a new HA wing: North Sonar HA950
The hole pattern of the North Sonar wing matches the RL Fuselage (3xM8). This allows to use the wing with just an adapter to match the round connecting surface of the wing with the flat fuselage (blue part).
The printed adapters were made to find the right angle, I plan to build a stronger one from cfk.
This wing is efficient at higher speed but needs a bit more speed to takeoff.
Best speed is around 30km/h where consumption is 60-70Wh/km.
See metr log: Apr 8, 2024 - metr.at | ADiqD
I also built a smaller rear wing with a symmetrical naca 008 profile to match the HA wing. It hase a surface area of 220cm2, AR 7.2, thickness 6mm, 40cm span, -2.5° AoA
Link to 3D printable mold: Hydrofoil rear wing 220cm2 mould by dfi - Thingiverse
PM me if you are interested in the fusion file.
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How is yaw stability with such a rear wing?
The setup is agile but not instable. You need to stay above the stall speed of the main wing which is a bit higher than with a low aspect wing.
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Hi @sat_be Daniel, great build. Are you using a fuse for the battery pack? Also, you are connecting 2x 8s3p packs in series, I believe. Would it be possible to have a pick of this connection? Or a schematic? That would be most appreciated. Thanks