Hi, today I tested my first build. Flipsky 7070 engine, Flipsky 75200 esc, GONG 105l inflatable, foil GONG 1400cm2, mast 85cm, battery 12S6P 21700, boat prop 6". My weight is about 75kg. Tried to increase max phase current to 100A.
The maximum speed was 10km\h only. Battery current 40-45A max, ESC power - about 2000W max.
Looks like you need one of those:
-propeller with less pitch
-more phase current
-motor with more torque per amp
Also, the motor mount would probably benefit from a more stream-lined cover in the front
I have tried to increase max phase current to 100A. It’s the max allowed by specs value for 7070. It has AWG 12 wires.
You can safely increase average current if your outrunner is water-cooled. The motor’s amp rating is usually based on heat dissipation. With proper water cooling, continuous current limits can often be increased by 50–100%, depending on the setup.
For example, a 7070 outrunner on a 12s6p 21700 pack (50 V) rated at 100 A max can likely handle 110–130 A continuous with effective water cooling — assuming good thermal contact, constant water flow, and internal protection against moisture. That’s ~6–7 kW continuous vs ~3.5 kW air-cooled.
Just make sure your ESC and wiring can handle it, and monitor temps during early runs to avoid overheating.
Trying a different prop and the cover should make some difference for you. Also, and if you have wing experience I’m sure you know this, but trying to take off with the wind at your back will make things easier.
I’ve had good results with this prop made by @kevintran:
(though I use it with a 65161, could still work on a 7070 motor)
Success!
I have increased max motor current to 130A. Downgraded ESC firmware to 5.03. In a fixed swimming pool tests I reached 3600W with 80A battery current.
Today I tested my setup with 2100cm2 GONG foil and 55cm mast.
I have tested 3 props and took off without any problems with all of them on flat water. Battery current required for takeoff is about 45A and 20-25A - to flight.
Max speed is 21km\h.
P.S. This is a prototype, next I’m going to build a board myself.
You may have issues with cavitation based on the câble management around your mast, it takes a lot of power to drag this câble outside of mast, and can help air bubbles to come all the way down to the prop.
You will be surprised how much of a difference it can make to have the wires inside the mast or fully faired.
Good Luck!
