Complete DIY Cheap Austrian Build

Hi guys,

I am a mencanical-engineering student from Austria.
After hours of scrolling and reading through the whole efoil.builders forum, I´ve now started my 100% DIY hydrofoil project. My build will be very slow, but I would like to give you some insights into my progress.

My main intention is to build an electric foil with the lowest costs possible. To achieve this goal, I will try to do as much as possible by myself.

Because of the fact, that I am currently attending university, my budget is very tight. So I would like to ask if anybody has some “leftovers” from their previous builds, that are intact, but not used anymore. I am at the very beginning of this project, so I think that nearly everything that I can get would be an improvement for me. For sure, I would pay for these parts!

After reading hours through your posts, I think that I have now figured out my setup (Unless I find some used parts):

Foil: DIY Hydrofoil + Board
Motor: AP 80100 (https://alienpowersystem.com/shop/brushless-motors/c80100-outrunner-brushless-motor-80kv-7000w/)
ESC: Flipsky High Current ESC (https://flipsky.net/collections/electronic-products/products/high-current-fsesc-200a-60v-base-on-vesc6)
Battery: 2 serial batteries 20000mah for 12s (https://hobbyking.com/de_de/turnigy-high-capacity-battery-20000mah-6s-12c-drone-lipo-pack-xt90.html?queryID=8f7b169a85d556d7ad56ed535929b8c6&objectID=78412&indexName=hbk_live_magento_de_de_products)

So I started a week ago with building my Hydrofoil:






As you can see, I started by designing my foil in Creo Parametric. The dimensions are very similar to the Levitatz Foil.
The two wings were form glued in my fathers workshop and afterwards sanded down to the profile, that I printed at airfoiltools.com. Afterwards I added two layers of 100g/m^2 fiberglass and epoxy.
The mast has a milled wood core which is laminated with 160g/m^2 carbopn fiber and epoxy.
The fuselage is also Carbon a carbon fibred woodcore.

The next step will now be to sand the last layer of epoxy down, and then screw all the parts together.
For an extra strenght at the connections, I have 3d-printed molds with will be poured with epoxy.
The mast already has some free space for the cables.
Finally there will also be a gloss coat over the finished foil.

I would be very happy if anybody would sell me some of their spare parts or would give me some useful tips :slight_smile:

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So, after long long time, I finally finished my foil.
I´m very satisfied with it, and I look forward to test it with my kite.

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Hi levitated,

Your build looks very nice to me

I’m thinking about building efoil myself.
How did you choose foil profile on airfoils.com?
How did you come to the foil shape?
How did you make a mast? What was milled? What shape did you choose. How many layers of carbon weave and which type (g/m2)
How did you make mast foot?

I’d like to build something very similar to yours. I’m 82 kg weight.

I measured a levitaz foil and tried to take the measurements for my foil.
The mast has a wooden core that was milled. I took the profile from airfoiltools.com (sorry but I don’t remember which one I took) and made a template of it for the melling process.
Afterwards I laminated 2 layers of 100g/m^2 köper fiberglass and 2 layers of 160g/m^2 köper carbon. It is all layed by hand without vakuum.
The wings have 3 layers fiberglass.
For the connection between wing-fuselage-mast and also the mast foot, I 3d printed molds which I casted with epoxy and fiberglass.

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My complete foil weighs around 2,5 kg.
Has anybody a foil-weight to compare?
(It is my first foil and I don’t know how heavy normal foils are)
Mast length is 70cm.

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If it is with wings and fuselage it is very light. Compared to Gong full carbon which is about 3,5 kg it is significantly lighter

5,3kg for my takuma …

Weight wise, it seems pretty light but it will all come down to its ability to withstand forces created on an efoil. How thick is the profile?

Mast 15mm, front wing 12mm, fuselage 20mm and backwing 10mm maximal thickness.
Not assembled, I put the mast, the fuselage and the frotwing on two chairs and was able to stand on them. The only parts I am a little concerned about are the connection between fuselage and mast and the mast foot. But I will give it a try with my kite for a first test. I think if this foil is able to withstand a good downwind session, it will be strong enough to handle the forces of an efoil.

Update: I am using the selfmade foil for my kite. So far it works pretty good. The whole system could be a little more stiff, but it worked for me to learn foiling.

Now over one year after I started with my efoil build, I was finally able to finish it:

Setup:
Foil: RL 1150cm^2 efoil set (https://rlboards.com/product/e-foil-front-wing/)
Vesc: HGL HI 200/75 (FIRDUO HI200 75V 200A ESC Base On Vesc For E-Foil Surfboard Hydrofoil - Firduo)
Motor: APS 63100 (APS 63100 Outrunner brushless motor 140KV 4500W)
Battery: 2x 6s11p Sanyo NCR2070C 3500maH (Sanyo Panasonic NCR2070C 3500 mAh 30A 20700 | ENERprof)
Remote: Maytech esk8 remote(https://maytech.cn/de/collections/speed-controllers-and-remotes/products/pre-sale-maytech-new-remote-for-electric-skateboard-mtskr2005wf-v2-waterproof-hand-remote)

The core of my board is XPS with two plywood stingers and a baseplate with threaded inserts for mounting the foil.

On top of this, there is one layer of 200g carbon and two layers of 100g fiberglass. The lid is also plywood covered with fiberglass. After hours of sanding, a friend of mine painted the board in his car-workshop.
I decided for this beautiful metallic blue and it came out pretty impressive.
The seal is poured with Wagner Sil 32 (https://www.amazon.de/-/en/gp/product/B00U6BRVR8/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1). After three sessions with my efoil, there was not even a single drop of water inside.

The biggest challenge for me was to build the battery pack. Thanks to @wushbush for lending me the k-weld. :v: It worked perfectly and made the spot welding really easy.
The battery is split in two 6s11p packs with a total of 38500mah. It doesn`t even get warm after a full discharge. (And gives me around 1,5 hours of riding time) I use two Isdt T8 balance chargers for charging them with 15A.

In order to protect the threads and the bearings, I covered the holes with candle wax, while I covered my APS 63100 in epoxy. I also changed the bearings to stainless steel ones.

The Vesc is just passively cooled in an aluminium case with a thermal pad. So far I had no issues with overheating. (140A max motor current, 100A max battery current)
I also installed a safety-leash, which cuts the signal of my receiver and stops the motor after 50ms.

I also put the Vesc and the Battery in an extra waterproof case to be “double safe” if the first seal would somehow leak.

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Hi, 2x 6s11p batteries (i.e. 12s22p) is quite a lot, but undoubtedly the right solution. It will extend the life of the cells. I too plan on 13s and 16 to 20p, yet some here are questioning that.

However, you initially chose the APS 80100 motor and your own DIY wing, but now use the weaker APS 63100 motor and the RL commercial wing. why did you make that decision? And what type of propeller did you use? The answer will certainly be of interest to a lot of people who are just deciding on the engine type and a custom or commercial wing.

I believe he meant 2 x 6s11p in series, so 12s11p.

You’re right, I’m a little confused.

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I read a lot in this forum and came to the conclusion, that the 63100 tends to be more efficient.
Same at the foil. My DIY wing seems to be ok for kiting, but when it it comes to power consumption, I don’t think that I have a chance against commercial wings. For me it seems like the power consumption is the most important issue at the whole projekt.

This is the prop I use. Works perfectly for me.

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