Electric Surf Board

just read the other post about the hobby king jet pump. looks good.

what about a "direct drive" jet pump kinda like a hub motor.. would be compact pretty low profile... one problem I can think of is sealing the magnet ring around the impeller from the coil housing.. And yes, 2/3 of the coils are missing to keep a low profile, electrically this shouldn't matter right? I don't really know the detail of the theory behind BLDC motors but my basic understanding is that it'll still work.

Thoughts?
Jetpump.JPG

Andy
 
Interesting idea.

So the stator is on the outside of the pipe and impeller with magnet ring on the inside?

It would have to use a plastic pipe otherwise it would have huge eddy currents induced from the magnets. And I think it wouldn't have much torque because the air gap between magnets and stator is large, assuming there is a pipe wall in between
 
So the stator is on the outside of the pipe and impeller with magnet ring on the inside?
Click to expand...
Yep
assuming there is a pipe wall in between
Click to expand...
Well actually.. I was considering sealing the stator against water and having a close fit air / water gap with the coils built into the pipe, or perhaps an oring on the magnet ring to seal against water getting between the magnet ring and the coil ring.
Thin wall plastic would also work but as you say. less torque the bigger the gap. I'll knock something up in Solid Works tonight.. to explain what I was thinking.
 
guess you'd buy an impeller, and weld a ring to it, then mount the magnets. bit hard to cast one.. Anyways I didn't get around to modelling a blade. couldn't figure it out...

Here's a quick sketch.

JetPump.jpg

Andy
 
I see what you mean now. I'm sure it could work, don't think it will be easy though!

Is this something you're thinking of building?
 
Agreed! I would be keen as to build one if only I had the time and money.

Cant seem to find any data on the Hobbyking jetpump.. My feeling is that two would be required to get decent thrust. They are nice and compact unit though
 
I haven't found much info either. The part that I don't really get is why jetski pump which isn't really much bigger than the hobby king one can produce so much more thrust capable of Powering a much bigger object heavier and with more water surface area.

I've only been looking into this for 2 days. So I guess more investigation required
 
I'm kinda looking into this for a couple of weeks. There are few jet surfboards on the market, and only one reasonably retails (soon?) at 2-3k euros. The one from AQUILA.

Hobbyking jetunit is pretty bulky and I'm hesitating if it could be fitted inside a 100L board? As an alternative there's a Graupner Jet 5 with 50mm impeller which retails in Germany at 175 eur. Maybe two of these set next to each other and powered by 1 kW motors each would do the trick? I'd be happy with 30 km/h surface speed.

P.S. you guys might also wish to check out products from this Chinese manufacturer
 
Yeah. No prices in that website but alibaba has the same ones for like $700usd for their big one, which is probably the one needed. Unless two of their smaller ones would work. Too complex.

Anyway. I emailed them. If it's under 300 I'll get it. Worth having a go for that amount.
 
Hi.

That looks good. About how long and how width is it ?

And how did you waterproof it ? Rubber seal ?
 
I emailed the chinese manufacturer told them I wanted to make a jet surf board that travels 30kmh using one of their drives. I asked for specs of their drives and got a response that they do not make what I need.
 
Email back from Kenzen RC... with their 67mm impeller at 5000W based on this motor:
http://www.hobbyking.com/hobbyking/...30KV_1280KV_Water_Cooled_Brushless_Motor.html
and 25 000RPM (which is 1280KV x 20V.. i.e 6S LiPo) they said their JPD03 unit would produce greater than 15kg. which seems unimpressive.

The question is what thrust will be required to make the surfboard get up on the plane? a big standup paddle board might not be much, but a smaller more nimble board, probably a lot more due to drag.

Andy
 
Louiss. Let's hope the new controller will work !

About the 15kg of thrust, I believe the aquilia and lampuga have about 400n thrust. That is about 40kg !

Is 25k rpm not too much for something driven in water ?
 
I left it to them to comment. But their response was very brief..
"67mm, 5000w at 25000RPM will give greater than 15kg".
That was the response . Looks like I'll have to make one. But that probably wont happen
 
Animalector said:
The question is what thrust will be required to make the surfboard get up on the plane? a big standup paddle board might not be much, but a smaller more nimble board, probably a lot more due to drag.
Click to expand...
Normally a boat need about 30 kW/1000 kg to plane. So if your boat with grew weights about 120 kg, you need about 4 kW of shaft power. The wider the board the better.
 
If your board will go about 20 knots (10 m/s) and use 4 kW electric power, efficiency min is 50%, the thrust you need is 2000 W/(10 m/s) = 200 N.
 
Bazaki I am really curious to know what jet, motor, battery(s) you are using on your board I just saw your most recent video from a few days and it looks great!
 
Great to hear that ! I will post some info about my set up later. Any idea about watt input at those 25kmh speed ?
 
Very good. Speed here is about 10- 15 kmh ? A bigger board maybe will get it in plane I hope
 
Hi Louiss, looks promising. Can't wait to see you standing up on it !

What kind of input to esc are you using ?
 
Looks good. I think you'd benefit from a wider/longer board, but I'm happy to see someone make some progress on this. I haven't had much time this year to get going and fall is around the corner for me. Still waiting to see some reviews on the Aquila/Onean board. The price is low enough to make it tempting, but the the fact that I think you can DIY for under a thousand, makes me rethink it.
 
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