80100 direct cooling

It’s not 80Kv looks more like 95-100ish…

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My Test for spinning under water was 825W, but battery was only 44,4V (not fully charged).

I guess with full battery, i would be in exact the same range


Had my first run yesterday. I did not waterproof the wires. Normally it is not a problem but now they are so close to eachother it is a problem. It felt like sync problems. But anyway I still had enough power to foil. But I was laying on the board and really hard to stay in balance. I used my Fone hydrofoil for kitesurfing and that is working fine. But this seems to be much harder to learn. 14s at 130kv with pitch 5 is probably way to much rpm also and therefore to hard to control the throttle

Not a foil question
I really want to build a small electric boat for my kids, thinking about building it from the Glen-L MiniMaxed drawings (https://www.glen-l.com/designs/outboard/minimaxed.html)
This boat is to plane with a motor of 5hp. Will the C80100 engine and propeller you use be enough to make this boat plan with a kid on board?matt-fitzgibbon-001

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Should be fine.
Here is the boat I have built for my daughter.

It is powered by 56114 with gearbox.


it’s actually easier to balance standing up than lying down :slight_smile:
What remote are you using?
It makes it much easier if you have a “cruise control”. on my remote, I have a trigger that arms it and then a thumb wheel to accelerate/decelerate. When I let go of the wheel, it keeps the speed constant. and if it let go of the trigger, it stops everything.

It should be ok. My board is a bit smaller and and lighter… but i’m heavier than a kid :slight_smile:
and i get it on plane with no problem.
The only difference is that you’ll have higher currents continuously as it won’t flying, but with a cooling pump it should be a problem, will only impact the autonomy if think…

@foiledagain Did you ever try your 2 blade propeller? I ran a print off and run over the weekend and it works very well. I’ve got some temperature issues in my esc (its under size, nothing to do with the prop) but could fly along with the 2 blade version.
Also I think its more efficient as I ran longer before the thermal cut off kicked in. There’s a video of me face planting the river using the 2 blade in my build thread.

Where do I find this 2 blade propeller?
My board is almost finished and I tested it before without board 10kw input that was no problem. Now all is in the board and I get something that looks like timing error again. But maybe the motor, or wire connections are not waterproof anymore. If I now put the motor under water i measure per phase wire 1 m ohm or 1 M ohm is that too much maybe ? I can ride 6kmh and it will stall because it loose sync

Its designed by foiledagain. It was originally a 3 blade but has since changed to a 2 blade when you open the fusion file. Not sure if this was on purpose but it works well. I’ve had a few runs on it, but threw both the blade at once! I did a static test in the water and I guess the extra force of not moving the board forward was enough to break the both clean off!

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Thanks I will try that. I did a no load test. Only the motor in the water full throttle is 4700watt with the cap on top 3700 watt
No prop. That was with open phase wires. So I made phasewires waterproof and still same results. 58v at 130kv is about 7500 rpm way to much. I do measure about 1 to 10 mega ohm when having a probe in the water and at a phasewire. This can not be the problem right?

The smaller 3d printed c80100 experimental modified prop is giving me out of sync and the aluminium 7 1/4 pitch 5 is running good. Maybe the 3d printed prop is too much pitch? Im a bit stuck now.

I’ve never tested resistance with a probe in the water so not sure.
I do have to shift the motor timing to around 20 deg to get around sync issues though. This is with the 3D print prop.

3700W seems like a lot without prop… you filled the gaps between the magnets?

Gaps are filled. I think it is because of 14s at 130kv. I just ran the old aluminium 5 pitch prop and I get a lot of thurst with low rpm with just 500watt. I also can run 5kw and much more without sync problems now. So it looks like the few Mega Ohms is not the problem. But the 3d printed prop with too much pitch for 130kv at 14s. I also have to move the throttle just a millimeter and I get a few kw. Very hard to controll. Hopefully the 2 blade work better or making a aluminium prop smaller in diameter or run maybe 10s battery

The esc makes the conversion for watts needed between the battery and the motor
The best to me here is the lower the kv of the motor if you want less rpm ( not the battery because you will raise the amp for the same power )
Or decrease the thrust of the propeller , the right combo between diameter pitch and blade area

It is pretty hard because in my case I need almost x2 the power between 20km/h and 30km/h

Can you measure the RPM at full throttle in air? Could it be that the magnets have been overheated once before? Most usual neodym magnets are rated for 80°C only, so they loose most of their strength when overheated. The effect is a much higher Kv. Into such a damaged motor you can pump lots of current and power with little effect. Of course the winding is heated, but with direct water cooling you wont burn the winding. All your descriptions point in this direction.

Hi that is 130kv so about 7500 rpm at 58v.

I ordered it from a guy from this forum as a 80kv motor.

You have a good point

It makes a big difference for the efficiency if the higher Kv is reached by demagnetization or by a different winding, so maybe you can compare the winding with other 80Kv and 130Kv motors.

Well, today I could ride for the first time without problems. I made a 100% waterproof hatch. Also made a waterproof dashboard with big screen gps speedo 2x temp watt amp meter and battery level indicator.

I made a magnet switch to the side of the board with a bunch of relais, also a timer delay relais so when I click in the magnet from my leash everything will start and after 2 seconds a big relais will switch on the esc after first the capcitors will charge. I run about 5kw to foil and than i crash. It goes so very fast, too fast. I have a hydrofoil with a 850 cm2 front wing and with kitesurfing it is so stable. But now im only crashing. I need now 20kmh to lift off at 40% throttle. I have seen around 8kw at 70%throttle. I guess all is good but the 130kv at 14s is too much rpm. What cm2 wing is ok for an efoil?

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you’re getting there…

Depending on the wing you use, the acceleration when you take off is normal… all the energy that was used to make the board plane is now accelerating you.
It’s easier (not easy) if you keep your throttle steady and focus on stabilizing instead of trying to decrease the throttle as son as you take off.
“Cruise controle” on the remote makes it easier to get into a stable flight before trying to adjust the speed.

Also, to take off with less power, you can try to get your weight forward on the board so that it plane easier…and then just shift your weight back once you’re ready to take off.

Only solution to reduce speed to to get down to 12s and/or reduce pitch.
for a quick test you can try printing the same prop but scaling it down in along its axis… the blades will have less angle… probably not perfect, but it’s simpler than modifying it and will give you an idea…

Regarding the surface of the wing, it’s not the only parameter… the profile influence a lot how much lift the wing creates and how stable it is.
I’m using an liquid force impulse (1126 sq cm and very thick).
I tried with my old foilfish (i think 860 sq cm very thin) and i could barely get on the foil, it was less stable and i suspect the extra current needed to take off was somehow messing with my remote signal.

note, for reference on the wing size, the chart below is very handy.