Using lower KV and larger prop

I’m following @pacificmeister 's build and using the SSS 56104 / 500KV motor and 5:1 gear. I remember that this means that the gear will run over its specs (assuming 12S voltage).

Now that I also got the SSS 56114/360KV motor (getting ready for belt drive :-), yes I saw the latest video, but haven’t given up hope), it made me think - maybe I can use that motor instead and compensate by increasing the prop size / pitch.

I wonder what you guys think about this idea.

I’ve the same motor an 5:1 gearbox bought from Flying Rodeo, lower rpm higher torque means wider prop and increased pitch. To get thrust out of a small prop, you need to raise rpm but efficiency drops. In my opinion, 3000rpm from this setup are a good balance, less stress on seals and allows for a 145mm prop with medium load. Flying Rodeo is riding very fast with this!



I need your help. Unfortunately, my foil does not lift out of the water, now I have already built a new board with more volume (dimensions 1,85x 60x 12 cm minus the cut-outs for the lipobox and esc)
As a motor, I have chosen the SSS 390kv with a neugart 4: 1 gearbox, so it should come at 44.4V to a speed of 4329 rpm. My weight is about 80kg.
As a propeller, I use Pacificmeister’s setup.

What else can I optimize so that the foil lifts me? Or do I have to install a new engine with more KV to get to a higher speed?
The SSS 500kv with 5: 1 ratio only comes to 4440 rpm. Does this little difference decide the success?

Please help me it is very frustrating right now.

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If I was you, I would try it without duct, before getting a new motor or anything else. Just to see if the 10-20% the duct wastes/eats will be enough to get foiling.
How does the motor/prop sound in the water? I can only imagine that the batterys can’t supply enough power to the motor. Otherwise if the load was too high either the Seaking or your motor would burn.

How is your speed? Is it really the speed which is too low, or is it more the power?!

That’s a good idea, I’ll test it without a channel … The engine sounds perfect running smooth, clean and round. As a battery, I use 2x Graphene 12000 mAh 6S 15C. The speed I can estimate bad but I think there is not much missing for the take off.

Yeah but is it close to max RPM, or more like very slow and tortured? If you can, take your phone in a waterproof case/bag and record your ride via GPS. Later you can compare these values to your setup intended speed.
You can calculate the intended speed of your setup: Pitch * (max RPM / 60) * 0,85
0,85 because props in water (should) have ~ 10-20% slip.

I dont know the Graphene batteries, but usually you say: (Rating from China) / 2
Still ~80A should be enough since you will have ~4kw (if ESC does not throttle).

Nice build! And it should work with what you have. A stupid question, have you checked if your ESC is at 100% power?
I had this set at 75% on my first trial and I couldn’t get up foiling

Very cool board. Also great for ironing. : D

You can try and tilt the front wing a little bit for more lift.

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I am smiling because I come from the drone builder world, and reading what you are describing, everyone from this drone world would ask you the same exact very stupid question, because every single drone builder went through that situation one day or another… So I apologize in advance for the naive question :

is the prop set up the right way, and is the motor really turning in the right direction in relation to the prop shape ?


Thanks for your quick help
I will test tomorrow morning (German time) the different approaches and then report.

  1. Drive without a channel
  2. To drive with a 3 blade propeller
  3. Adjust the front wing.
  4. And maybe even record the speed …
    Oh yes, and in case of emergency there will be a new ironing board :sneezing_face:.
    But your statements make me courage again. It’s not finished yet, I want to paint it and glue it with eva pad’s.

A question to Clarin: how do I know if the engine is running at 100%? I have programmed the full throttle position and idle position according to the operating instructions, but no difference to the previous original condition is noticeable.
How did you program the seaking?

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yes, the propeller is turning right, I’m driving so but it is not enough that I lift myself out of the water

An RC pusher plane with everything working totally fine except the prop with the wrong rotation would indeed fly somehow - that is why most people do not identify the issue at first when it happens - , but not powerful enough even at full engine speed. That’s why I dared to ask… Good to know that is not the case.:+1:

Another silly question. But are your batteries definitely connected in series. A parallel connection would only give you 22 - 25 volts which wouldn’t be enough.

All my research indicates that 3 blades is the optimum.

Rear Wing up? Wattmeter? Efoil fly without you?
What position did you put the mast? Should be around 20-25cm from the back, if i am right

If I remember it was one of the settings in the program to flash the ESC (I used an Aquastar)

Hey guys
today it worked out i was hovering for the first time with my efoil.
Thank you for your quick help and the good approaches.
The key to my success was a very smooth water, the change on the 3 leaf propeller and maybe I did not have breakfast.
But I will also test the other approaches to rauszuholen more efficient. I also think that I can make it even easier with the wing adjustment.
I still have to ponder because it has cut out the 150A fuse at full speed today. I do not know yet why, the cables or the ESC were not very hot and everything was dry.