After a lot of reading on this forum, it’s time to build an eFoil. Actually two eFoils, because me and my friend want our own boards. We are engineering students trying to keep the costs down as much as possible, while still maintaining performance. Anyway, here is the parts list that I’m ordering soon.
Electronics:
Motor: Flipsky 65161 120KV 6kW
ESC: Flipsky 75200 V2.0 Pro water-cooled VESC with a builtin anti-spark switch
I know that using a LiFePO4 pack is kind of unusual, but I have seen a few positive reviews of this exact battery configuration here. The main reson for going LiFePO4 is that we have no experience building packs, so we don’t want to burn our houses down. There is no welding required as the pack simply bolts together. Total weight is 12.0kg. It’s just 4kg heavier than the Li-Ion equivalent. +4kg for a completely safe, powerful, high cycle-life battery is an easy tradeoff in my opinion.
Board:
XPS Foam sheets glued together with expanding foam and cut to shape
Glass fiber lamination
Wooden plank to bolt the mast on
Waterproof inspection hatch commonly used on boats (35x60 cm)
Smaller waterproof inspection hatch
—> Cost: Around 150 SEK
The board’s look isn’t a priority. I’m thinking one large waterproof hatch where an enclosed battery pack goes, and another hatch for ESC, waterpump, and receiver.
Foil & prop:
GONG v3 Ascent 19mm (XL front and rear wing)
Fliteboard propeller
—> Cost: Around 650 EUR
I weigh 90kg, so I believe that this setup will work? We have tried to find cheaper foil alternatives without success. It seems stupid to buy an AliExpress no-name foil for a little cheaper than GONG.
Interesting build, if you want to keep the cost down i can suggest a 65220 motor and an aliexpress flipsky foldable propeller for around 50 EUR. Furthermore, check out LIPO batteries from a place like hobbyking.com, it is going to be even cheaper and much much lighter.
Maybe also convert this thread to EUR currency so that we will know what you are talking about
Spot welding honestly is not that bad, I was nervous about it but it’s honestly a breeze. Your batteries are going to take up a lot of space, you’ll have to position them inside your cavity carefully. You should spend the time to make a cad model so you can lay everything out before building.
The 65220 is tempting, but I am considering the 65161 with a separate ESC for more power. I have read that the fliteprop is the ideal match for the 65161. I don’t want to deal with lipos. My experience is that cells puff, and die easier. I cannot easily replace a cell in a lipo. I will change to EUR currency
Yeah, I’ll make a complete CAD-model of the foil at first. Alright, I didn’t know about the square/rectangular hatches leaking. Everything behind them will be closed on boxes anyways. You’ve got a point about the price, I just listed up the most expensive parts. A lot will be 3d-printed, and I have the tools.
I will strongly advice against Daly BMS even for balancing. If it’s the standard one, the balancing current is too small for large batteries. JK smart BMS is much better on all accounts even price. Active balancing with 0.4A and BT app for $35 is a bargain.
Edit: Just checked last Daly offerings and they may have improved since I moved over to JK, but in any case make sure it has active balancing as passive balancing is typical 30mA.
Don‘t bother using a square hatch they leak and are not stiff enough to step on them. Either go split pack 2x6-8S that fits through a round hatch or build a lid with seal. You find many working builds od either type on this forum. If you build a lid, put the cam latches outside of the dry zone so yoo don‘t have to waterproof them.
Thats the one I use for my efoil and ebike batteries, about 5-6 pc for 3 years without problems. It’s so important to be able to monitor cell voltage to catch drift or bad cells in time. Also good idea to put the temp sensor(s) inside the battery shrinkwrap.
water pomp also is unnecessary. mount waterhose in tip of motor mount and by movement of the foil the water ciculates in to your your esc (i have it like that and works fine)
I have crimped the knockoff amphenol surlock connectors now. In order to use these with 8 AWG (8mm^2) wire, I had to stuff the barrel with 4x original cable size. I cut off three extra lengths of wire and used cable ties to group them together with the wire. It is very packed. Then I used a crimping tool in the 25mm^2 setting.
I have also made some progress with the board. I glued the XPS foam sheets together with polyurethane foam. It foams up when you spray it with water. I did that to the second board but it was more of a disadvantage.
The sides were cutout with a diy hot wire cutter using nichrome wire and a lab PSU. I discovered that support on both sides is crucial. I used aluminium profiles on both sides in order to cut straight. Then I made two plywood templates with a spline profile on one side, and a radius on the other side.
Next step is to make a radius to round of every edge except the trailing bottom edge.
I have designed a spacer from the motor to the propeller, and a tailcone for the propeller. They are precisely streamlined with tangent splines from every edge. There is only 0.5mm of tolerance between the propeller and the spacer. I hope that they will not contact under load. The spacer is mounted with three M4 screws. The tailcone is designed with a thread for the flipsky shaft and has a hole for easy screwing.
I had to buy a propeller puller tool because my propeller was drilled out with a 11.9mm drill instead of 12mm.
Everything is printed out of ABS except the propeller pin spacers, which are out of TPU.
The new Daly series (blue housing with built-in Bluetooth), balance with 1A current and I am very happy with them. I have two 150 A in the batteries for the efoil and one smaller one for the skateboard. And the application they made is very decent… I have not used the wifi module, I consider it unnecessary.
