Hey everyone. I am working on making a bolt on efoil kit similar to the foil drive assist but with a larger motor and larger battery pack. Has anyone done this already or would be interested in one?

I've got foil drive already and like it but would also be interested in something more powerful. Not going to be building one myself though.

I'm interested in a diy foil boost for SUP and light wind wing foil days. I'm an engineer so have some applicable build skills. Challenge will be to source components that can be adapted to be salt water, sand and UV rated. Thinking that power tool tech (motor, gearbox and Li ion battery pack) might be in the ballpark in terms of cost, weight and performance.

I also have the foil drive and would be interested in this. There are a lot of learning points from the foil drive that could help to improve on the user experience. The idea of power tool batteries is neat - imagine if you could just get some Milwaukee m18 batteries and snap it in. Another option for lipo instead of li would be rc car batteries- some have bms and the chargers and maintainers are readily available.
Other things:

- programmable remote with different modes
- detachable cable from one end so you don't have to deal with the battery box hangin' free when packing it. Also adjustable/replaceable length cable so you could lower the pod for certain things and raise for others
- mast adapter for the tapering Armstrong masts (or multiple adapters for that system)
- could improve battery box to board connection - box does tend to come off more than I'd like

Things I love that should remain:
- remote control connection is solid, don't use 2.4 or Bluetooth standard, that will suck
- battery charge visible while using (could improve by communicating to remote though)
- non-invasiveness - easy to remove the system whenever needed

6S Lipo batteries will do the job for the motor power. I use them in my RC aerobatics plane. The only downside of Lipo is the fire risk during charging and transportation of the batteries while fully charged (less of a problem with quality Li ion batteries). I store my collection of Lipos outdoors in a steel ammunition box. Li ion has higher charge density I think so will give longer run time/weight ratio.

I like the "boost" concept of temporary power to get foiling in marginal conditions, so full efoil power doesn't really interest me.

I'm not an electronics engineer, but one thought I had was that for a "booster" type of drive where the high voltage/current is not constantly needed, would it be possible to use a supercapacitor that charges from the battery pack over time and discharges when the boost is used? (Possibly in combination with power from the main batteries.)

Also, I would be curious to experiment with other mounting options. One that would be interesting for me would be to use the deep tuttle box on my board to mount the batteries on top of the board, pass the cables under the board and possibly even have the prop mounted on a fin behind the foil mast. For double US box systems, it should also be possible to use a plate that goes under the foil plate and extends behind it (or in front of it?) and mounts the motor on that plate instead of the foil mast.

One video on Youtube that used theFoilDrivefor efoiling (small lake, no paddles or wings) mentioned that the "tape job" on the mast is critical to get the gear to actually foil. I think a 3D-printed shell over the original mast might be a good option and much faster to install than wrapping tape over the foil mast.

I think the battery should be on you (fanny pack, backpack), reducing the passive weight of the board and increasing your actively usable weight seems the way to go, like the guys on the lake video found out.

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colas said..
I think the battery should be on you (fanny pack, backpack), reducing the passive weight of the board and increasing your actively usable weight seems the way to go, like the guys on the lake video found out.

I agree, certainly worth considering as an option. There are some really neat, waterproof, magnetically joined, high current connectors available. Frequently used with detachable electric bicycle batteries. In the event of a crash or coming in to the beach it would just be a matter of pulling the connector apart, a little like the Apple laptop chargers.

I read the Foil Drive product page and saw a note about shipping costs due to having to ship the battery. I think it would make sense for even the commercial versions to try to make use of existing batteries that are widely available. That way the customer sources the battery locally and the rest of the kit can be shipped at a lower cost.

For example, K?rcher has battery-operated vacuum cleaners. There's a 24V battery with 7.5Ah capacity (2.1kg weight) and a 36V 7.5Ah (2.3kg weight, 270Wh). Patents on the connectors might be an issue, I suppose.

Stihl have a 36 volt 270Wh battery and also have a belt loop battery holder - makes it super easy to adapt to some sort of waterproof backpack

Just need to waterproof it!

steps the voltage down to 12 (from approx 20) and outputs 30amps.
300watts of power. (8amp hours of time). Powered a small trolling motor. (I used that for now, to take advantage of the manual speed controller) the thrust is insane on just the 3rd (of 5 settings)have exact size Waterproof box to suit.
(Yeah the post above about a fixing to the mast plate.exactly)
I'm testing a dual small prop setup (pulling the board vs pushing from behind)

fun times

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Boracay.Villas said..


steps the voltage down to 12 (from approx 20) and outputs 30amps.
300watts of power. (8amp hours of time). Powered a small trolling motor. (I used that for now, to take advantage of the manual speed controller) the thrust is insane on just the 3rd (of 5 settings)have exact size Waterproof box to suit.
(Yeah the post above about a fixing to the mast plate.exactly)
I'm testing a dual small prop setup (pulling the board vs pushing from behind)

fun times

Very Clever

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Piros said..

Boracay.Villas said..


steps the voltage down to 12 (from approx 20) and outputs 30amps.
300watts of power. (8amp hours of time). Powered a small trolling motor. (I used that for now, to take advantage of the manual speed controller) the thrust is insane on just the 3rd (of 5 settings)have exact size Waterproof box to suit.
(Yeah the post above about a fixing to the mast plate.exactly)
I'm testing a dual small prop setup (pulling the board vs pushing from behind)

fun times

Very Clever

Not me.tech guy flight junkie inspired and a couple of Chinese technicians here (on the island)
problem with the dual props is obviously drag, running them in reverse (like a dual prop plane)
but tiny weight vs the trolling motor. be careful out there, quick release connectors is key

Select to expand quote

Boracay.Villas said..


steps the voltage down to 12 (from approx 20) and outputs 30amps.
300watts of power. (8amp hours of time). Powered a small trolling motor. (I used that for now, to take advantage of the manual speed controller) the thrust is insane on just the 3rd (of 5 settings)have exact size Waterproof box to suit.
(Yeah the post above about a fixing to the mast plate.exactly)
I'm testing a dual small prop setup (pulling the board vs pushing from behind)

fun times

I'm liking this solution a lot! How does the manual speed control work?

So much written online about how to do this but as far as I know, only Foil Drive and Boost (kinda) have brought a product to the market. Would love to see more finished products available to the consumer.