For who try/have tried direct drive with outrunner


I’ve got the same setup: 6384PG but inside a tube full of oil. 12S, VESC.
The results are the following (on a static bench test):

3prop Pacificmeister with NO duct: 22kg static thrust, 1940RPM, 3500W - Couldn’t get on the foil
3prop Pacificmeister WITH Duct: 24,8kg static thrust, 2230RPM, 3500W - Couldn"t get on the foil
Solas 7 1/4x 6" without modification, NO duct: 32kg static thrust, 1890RPM, 3500W

So more than 50% more power for the same static thrus, pretty impressive !
What Duct are you using (from what I’ve seen it’s not profiled ?).


I’ve never been convinced by the PM prop. It’s just not right for what we need. Thats why I went with a different prop.
So with the Solas prop did you manage to get on the foil?


Pacificmiesters prop works very well for people running it at its designed RPM, 3000+. Plenty of videos to prove that point.


so 6384PG with 100KV on 12S (i take 48V) on load you loose 60% of the rpm with the solas prop

with the solas prop no duct 3000rpm on load is nice (20km/h with big wing), start to foil above 2600 rpm (± i recall on my test)
for sure this propeller has a lot off thrust, i didn’t try the other, but i think if you can manage to get the 6384 to around 2500rpm you will foil, may be need to be cut to around 130mm at least or lower…

nice numbers thank you :wink:


Which motor are you using with your Solas Prop ?
3000rpm without any reduction in Diameter or with it cut down to 130mm ?


Yes, it works for people using PM setup and pulling way more amps. Unfortunately, I haven’t found any numbers regarding RPM, Amps etc from somebody using PM prop.

I haven’t tried the Solas prop yet. I wanted to try it out today but it’s really windy (25knots) here so not the perfect trial day. Probablly tomorrow, I’ll let you know.


inrunner (in water…) 40mm given for 8000W , with a 6:1 reduction, max out torque on this king of motor with 5 differents propellers

i try to cut or and reshape this propeller to get higher rpm, but no 30% was the number

solas prop: 30% rpm drop with geared 40mm inrunner
probably around 20% with 56mm geared

outrunner (dry), my best number on a small jet drive was 45% rpm drop

i think you can get the 63mm to just about 2600rpm with a cut solas propeller, others propellers i don’t know much expect the FR (less thrust but higher pitch= the same rpm drop)


Are you speculating about it pulling more amps? You say you havnt found numbers.

PM setup is 500kv motor on 12s through a 5:1 reduction. Pretty easy to work out the approximate RPM under load.

If my memory serves me well, people were posting numbers in the 60-70 on start and 30-40 on foil. Im sure the numbers are out in the forum somewhere. A few off the heavyweights were pulling bigger numbers, as you would expect.


The video’s only prove the prop works, however it doesn’t work efficiently! Hence why you can’t reach 40km/h with that prop. There are too many losses.
No one actually knows what RPM they are running the prop at. There are theoretical calculations, but no real world numbers.


Maybe its not even designed for 40kph (too low pitch). You would have to ask Pacificmiester. I think its a bit of a strech to be saying its inefficient. There are a lot design parameters in prop design and RPM is just one of them. The RPM calculations are not theoretical because we know the motor KV, and we know our voltage, and we know the gear reduction. Yes there are some variables like RPM drop under load depending on pitch, slip ect. It is reasonable to estimate an RPM based on the information we have.


Isn’t a 500Kv + 5:1 reduction the equivalent of a 100Kv motor with no gear ?
The Max “no-load” speed for both setup at 12S is identical: 4800 RPM. Or am I missing something here ?


Correct, the RPM will be the same. However the motor torque probably will not be the same. The gearbox has a multiplying effect on the torque from the motor. Im not sure how much torque the low KV motors are getting. This torque is needed to maintain RPM under load.


Can’t we use the “P= C x Omega” formula with Brushless motors ?


If I am not mistaken the SSS 56104 500kv at 44.4v and 5:1 reduction should have roughly 50% more torque that the 6384PG (in theory).


Hi guys new to the form hear Long time reader first time poster I am thankful for what you all are doing this is very exciting I come from Ebike world. And now I definitely want to build a efoil!
I would like to know if anybody has ever tried Astro flight motor? They are one of the most powerful weight two ratio motors I have ever experience. I am thinking of disassembling one of my bikes to give this motor a try.
Definitely want to go for a direct drive i would like some input .

Stock number P/N 3220
Winding 5 Turns
Speed Constant 137 rpm/volt
Torque Constant 10 inch ounces/amp
Winding Resistance 50 milliohms
No Load Current 1 amp
Max Continuous Amps 75 amps
Peak Amps 1 minute 100 Amps
Typical Voltage Range 24 to 80 volts
Typical Power Range 4,000 to 6,000 watts
Typical Efficiency Range 90 to 95%
Typical Speed Range 6,000 to 10,000 Rpm
Stator 24 slot 8 pole winding
Rotor 8 pole Sm Cobalt
Bearings Two Ball Bearings
Motor Diameter 3.2 inches
Motor Length 3.4 inches
Motor Weight 4 lb.
Motor Shaft 3/8 inch diameter

I will be running astro 3220 4T KV 169 on 12s well run 6500 RPM
Maybe a Yamaha 7 1/2 x 7 prop?


see my post on rpm drop : Rpm drop under load, Rm I

to spin the solas propeller at 3000rpm you need about 6NM


you are reffering: Any interest in a custom e-foil ESC?
Yes, its profiled, the outside is almost a straight cone, while the inside collects water and accelerates it to have the motor running at higher speed.

Well, our setups are quite different: You have it running in an oil filled tube with additional friction from oil and eddy currents, additionally you have higher induced losses because of the higher cross section area. BUT: you have a vesc delivering 3500W, thats good.

To all the plastic prop printers: What happens if you put the prop with its blades onto the end of a tube, so the blades touch the tube at 2/3 of their radius and than apply 30kg onto the hub? Does it bend or break?

At benjo:

What theory do you have in mind? A lossless gear? More amps possible for the SSS?


Well, same KV (at the prop shaft, you can do that, since the gearbox is linear) is same KM and KM unit is Nm/A, so (if you oversee the <5% difference in efficiency) it is exactly the same torque (in theory) at a given power level (I don’t think it makes sense to compare different power levels e.g. max power since max power really depends on your motor cooling and max power is no point where you want to drive your motor (permanently), because the efficiency is ~50% (in theory)).


Yes, lossless gearbox and maximum power as stated in the datasheet. So a rough estimate. I am also not a mechanical engineer or physicist :smile:


I believe that using a gearbox will actually reduce the torque, as the motor needs to use extra power to turn the gearbox as well.