Worlds claimed most efficient boat motor launched today - Who's first to take the principle to efoil

Duo-prop makes it 15% more efficient, but what I have never seen before is electric directdrive duoprop.
Who’s first to make it with Inrunner in front and hollow outrunner in the back?

“In other boat motors, be it electric or fossil fuel, the motor is typically situated in a box above the waterline, transferring thrust to the propeller through a complicated set of shafts, bearings and gears. The Candela C-POD gets rid of the gears altogether. Two ultra-compact yet very powerful electric motors are mounted under the water in a torpedo-like socket, directly driving the propellers. Each motor is coupled directly to a propeller, which minimizes friction losses. Contra rotating propellers add the benefit of very high propeller efficiency.”

2 outrunners one in front and in the back already done
Why do you say inrunner in front ? How do you see this ? Inrunner shaft running into the outrunner bolt on? Wet inrunner ?

Possible my inrunner was most of the in the water and it is still working

Please share your sauce. Making a dual drive innruner in same shell is extremely challenging.

There should be a significant vibration problem.

I tried this before, but there are 2 problems…
It makes the unit much more complicated and heavier, and latest efoils are running with 700-1000W
so efficiency gain of 15% would be some Watts…
Forgettable of you take into account the additional costs of building it
and one of the main goals on efoils is… keep it simple and cheap…
So I think we won`t see this kind of props very soon :grinning:

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Here is a nice animation of the motor.

And here some more info;


Any link ?


Sound stupid with extra complexity and not going contra prop. It’s been proven since half a decade in boating with high speed props (+2500rpm speeds) that 15% gain can be had from having straight flow exit and not rotating flow.
Would assume Flite would pursue this, since they have a complex drivetrain, but perhaps somebody has energy to check patents.
Also does anybode know of a commercial coaxial inrunner?

You could very easily do this with 2 outrunners to see how much gain can be had. You could run 2 63mm 140kv (4000W each) motors. Start the front prop at 5 inch pitch and run the rear prop at 7 or 8 inch pitch. Could be a fun little project.

Probably not going to win a lot with outrunners. The disturbed flow and added flow speed from the rotating can might very well remove the theoretic efficiency gain with contra-rotating props.

Think they need to be encapsulated in a pod Lars to streamline.
I still think this is a good idea even if complex. It completely removes the torque causing side forces on a foil. And as I mentioned earlier normally 15% more efficient since draft water flow is close to straight.
There is a reason most inboard motor boat stern drives are designed like this.

I think it needs to be done on a custom motor level. A 65mm outrunner with smaller needle bearings and a larger hollow axle/solid axle setup might be nice to start with

Still hard for me to figured out an efficient way to hold 2 outrunners ( in that case wires side hold together ) on a mast …
But may be the new 65121 with its shaft going through a 6384, bolt on it why not , just the 3 phases to take care of , the small needle bearings on a gearbox were able to take some torque and rpm
Just a lot trail and error on the 2 blades to test …fun built , efficiency worth it ?

Needle bearing ? Enough room ? 4-5mm shaft or bearing on each side ? Still need to secure the rotor of the outrunner on the hollow « shaft » …

Yes, i doubt it will work with an off the shelf motor/stator. add more slots to lower the needed stator inner width/diameter, increase the bearing diameter to be able to fit the second axle etc. I think it could be done

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