Bolt-on build in Perth

Our first build has been in progress for around 18 months. Went through a few iterations of boards, motors, props, etc. Ended up coming in at around AU$2,500 all told.

  • Board - second hand ~$500
  • Battery - 13s9p (48V 20Ah) ~$500
  • Foil - Aliexpress - $700
  • Prop & motor mount - 3D printed
  • Waterproof case $80
  • Motor - 8384 120kV direct drive outrunner - $80
  • ESC - 120A - $120
  • Controller - $50

Went through quite a few iterations on the propulsion system. Ended up going with a 150mm diameter 3.5" pitch 3-blade prop printed in PLA. Design is custom and pitch of blades is defined parametrically. Use some filler to prime and sand to get a good smooth finish.

The battery we got from Ali Express was a bit dodgy (LiitoKalo brand). All the current is sinking out of the nickel strips which are only rated for around 10A. Ended up having to take it apart and rewire it after we noticed some heat damage. Also the battery was sold as 30Ah (ie 3.3Ah per cell) but actual capacity was 20Ah (ie each cell said 2.2Ah).

This is the controller and ESC - seems to be alright for the price. The controller in particular does not seem waterproof at first glance, however I took it apart and was impressed with the build: no mechanical switches or connectors (uses magnets and reed switches/hall effect sensors), wireless charging, and circuit covered in resin.
image image

This shows arrangement of direct drive outrunner mounted to mast. The battery and ESC fit inside this waterproof yellow box which is strapped to the back of the board. It’s worked out quite well that the whole propulsion system is pretty much a bolt-on to any foil-board setup.


Still learning how to ride it, but seems to be pulling about 60A to get up to speed and 30A to keep going once foiling. Seems to get foiling at very slow speed around 15km/h; we do have quite a large foil on it.

Here it is in action :slight_smile:


Nice project.
Oh, you’re using the Seashark from this Chinese ESC brand called Favourite (fvt for short) , 12s compatible. They have 120A cont/240A burst ESC for 80usd and a 200Acont/ 350burst ESC for 116usd.

Their boat ESC model from their commercial site :
Where did you get your current data from ? A separate data logger ?

[Edit:] @Mab did find a way to make his Seashark 200A work, setting the timing to “high”.

Thanks :slight_smile:

Yes correct on the ESC.

Yes separate data logger which is custom Arduino build. MicroSD card module, hall effect current sensor, ublox GPS, MPU6050 IMU + kalman filter running on Arduino.


Another nice project into the main project.
Many people here might be interested :+1: If you don’t mind me asking, to what amount did all those elements sum up ?

Around AU$65

  • ACS758 current module - $10
  • Arduino nano - $15
  • UBlox neo-6m module - $15
  • MicoSD module - $10
  • MPU-6050 IMU - $5
  • Prototype board + headers + connectors etc - $10

Do me a favour and yous a hall current sensor. I used the same module once and I had a nice fire near my battery pack. Wouldn’t recommend the sensor at all. Also hall current sensor are fairly accurate. I can get readings 0,2A± exact.

ACS758 is hall-effect current sensor as far as I knew. Interesting you had a fire with this sensor, has been pretty reliable for me for a number of applications.

yep it is a hall sensor, problem is that the current needs to flow through the part. When you have a split core hall sensor you dont need any soldering and it is much safer, as you dont have a direct connection. This is just my personal expreience.


Very cool project, great results, I like the simplicity of using outrunners.
You said you’re using a 8384 motor? Did you mean 6384?
One more thing about the prop, which nozzle size you printed with?
How many hours of print?

Thanks! :slight_smile:
Yes outrunner has been going well so far. Every time after we use it we take it apart, wash in fresh water and spray with WD-40. So far we haven’t seen any major corrosion issues.
Yes that is a typo - 6384 motor is correct.
Prop was printed with a very standard printer (Solidoodle 2) which I believe default nozzle size is 0.4mm. It was around 4.5 hour print.

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Thanks, that’s awesome!
Good luck on your future plans!

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Given your voltage, KV, and prop-pitch, I calculate that you should get a theoretical speed of 19.1 mph; and guessing a real-world speed of 15 mph under load. Does that sound right?


Hey yep that’s what I get for theoretical speed.
We’ve got a very large foil (1900cm2), so it gets foiling at 16km/h (10mph), so haven’t tried taking it faster than that yet.

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Which amps support your ACS758 module?

What are the experiences of the last months? Does the engine run smoothly or has it been worked on?

Motor has been washed in freshwater and sprayed with WD-40 and has lasted well over a year

The bearings did finally go, and the wires corroded between where the regular wires are soldered to the copper windings of the motor

I got a new motor and installed ceramic bearings, and treated the stator with epoxy as per @e-Jetter good instructions.

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Thanks man, very glad things are going well for you, keep on rocking :ok_hand: