25 Kw Electric Jetsurf


#1

Hey guys I have been doing a lot of reading on the forum but haven’t found anyone who has built a really successful electric jetsurf. I was doing some research and it looks like a lot of the company’s selling the commercial ones use a 24kw gas engine. I was thinking about using one of the massive 25kw 120mm alien outrunner motors along with a massive ESC to power the jet. This is the motor I was thinking about.

Anyone have any ideas? Or think it would work?

Sorry this is not an efoil but I think it’s related.

Thanks for help,

Matt


#2

i wanted to build a jetsurf before my efoil , i might do that next year, i have done a lot of research over the past 2 years about it, the way i would built is:

1 drive :
https://www.mhz-watercraft.com/shop/en/jets/497/jet-64-for-electro-surfboards-max.-12-kw?c=110
with this motor or tp, inrunners (for coolling issues)
https://alienpowersystem.com/product-category/brushless-motors/100mm/
chosse kv depending on nb cell, aiming for 16000rpm

esc ???

i would prefere 2 drives:

2 jets drives 52mm or 58mm

with 2 motor sss 56104 en 480kv working on 12S

esc:
2 heifi X pro 300A

8 lipo multistars 6S 20000mah


#3

I thought these things needed more power but I guess I remembered wrong. The Race Titanium board which is the company’s most powerful board, shown below only has a 9.5 kw engine. And the most powerful gas jet drive I could find was 15kw one. I would like to find a motor that is close to these numbers but It’s hard to tell for most of the electric motors what the continuous wattage is I feel like most of them put the max possible wattage which can be pretty missconseaving. Does anyone have any tips on this?


I was initially thinking about using 2 drives as well with maybe 2 sss 360kv motors because I know veFoil has had some luck with them or something similar. I changed my mind because I feel like most of the time 1 big drive system is more efficient then 2 smaller ones. I know you were looking at the pre built ducts and I see that the 16000 RPM produces the most thrust so hitting that rpm would be good. Those ducts look sweet but a little to expensive for me and I think I’m going to try to make my own duct and impeller. Which is also why I only want one jet drive because that means less work. I was also looking at specs for jet skies and other jet powered boats and most of the time the rpm is around 5000 which I’m guessing is a good one. The jet drive boards above that I posted the picture of say there engines run between 6700 and 7700 rpm. So I’m going to aim for something around 5000 TO 7700 rpm I think. Not sure what kV I should get though because its definitely going to change when the motor is under load. Also with only having one motor I only need to get 1 really powerful ESC which might possibly save money… not sure. What makes you prefer 2 drives instead of one?

I would like to stay with outrunners if I can because they have high torque and low KV’s which means I can run everything at high voltages with out a ridiculous RPM. I like the higher voltages because that means less heat and greater efficincy I’m not sure how high I want to go though the motor has a max of 100 volts which would give me a good rpm but that high of a voltage kind of scares me. The biggest issue with outrunners for this application is the cooling because you can’t use a water jacket. The alian motor linked in the last post is water cooled which is cool even though it’s a little OP. Maybe I can find another outrunner that is still water cooled but less powerful or just make a really overkill jetdrive with the 25kw motor. Also what made you choose that battery capacity?

Also does anyone know how much thrust the commercial ones put out ? I know the one that you posted above with the dule set up could put out close to 50kg of thrust which seams like a pretty good amount but I’m not sure?


#4

between what i have read and what i have done myself:

  • outrunner have more torque yes, but you will have a cooling issue for sure, efficency not that good (65% mesured) , you will have a rpm drop (about 20-30%), this on the small jetdrive i have built for testing using a kmb28 and a outrunner

  • jetdrive are more efficent thrust wise/power when smaller, but at some point you will be missing top speed

  • you need a least 30km/h to fun and with a decent size board may be 50-60kg of thrust

  • two jetdrives:
    because you split power by two (esc wires motors…) more thrust/power on 52jet or 58jet rather than one 64jet
    it has be done and this step work, but you will not go at 50km/h ( is it very important?)

-one drive:

we find motor, but esc??? really expensive, keeping blowing, espacially cap because on high voltage high amp on start

10000W 50v : 200a… a motor rated for 300A can pull maybe 450A on start (depending on brand)

if i built a jetdrive, it will cost me some money so i will do what i know that will work aiming for 30-35km/h

2 X JET58 , 56104 480KV, 12S, heifi 300a

  • battery:

i know the 56104 480KV will pull this 128a at half rpm, half max voltage
JET 58: 330N with 6000W : 125A on 12S (simplified)

this is at max, start, planning speed might be less, closer to 5000W for 30km/h, i guess

so 2 packs , 125A on 2 or 3c : at least 42A 12S

you will use 70% on the pack, so to safe and have a decent play time : one pack will be 12S 40A

i think the most important: is not to under estimate KV:
you will have a rpm drop on load, rpm drop with voltage battery
if you spin to fast : 25000 rpm on 52jet you will have caviation, to low: no top speed
esc more happy with 100%, rather than 75% tps apparently


#5

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#6

See also http://www.efoil.builders/t/from-rc-toys-to-esurf-jet-on-a-tiny-pond/2156/4?u=soefoil

Mark is using two 53mm jet propellers that he sells 203 GBP each. FAr bellow the 25KW of this post.
Other candidate, the Graupner 49mm jet unit:


The Graupner jet propulsion unit model 5 ref 2347 slightly less powerfull than the MHZ (but much cheaper too) with a 49mm impeller sold 150£ (GBP) =167€ from UK