Vefoil supposedly succeeded in this path. I say “supposedly” coz no one has heard from him for a while nor seen a Vefoil commercial product.
Boards advertised as 50kmh + are using 94-100mm stator. Mako is using 93mm high pitch 3 blades impeller, same diameter as Lampuga if memory serves. There are not that much electrical motors able to run these impellers. LMT is still one of the best choice because you can customize the Kv.
I think it also depends on impeller pitch, because if memory serves, Mako was in the range of 6000 RPM.
A design out of my own conception iv’e been playing with. Mine is a 65mm jet. Iv’e ran it to about 60% of its design speed (7000rpm) and it makes about 45lbs drawing about 2Kw.
Compared to youngsters it would be much more efficient but my guess is; it would lack in top end speed due to my rpm. A single SSS 56114 at 320kv is not enough. I hit about 100 amps in this 60% test. I need a 80mm or 100mm motor like a TP100. When my wallet gets heavier ill get one and test higher rpm. I considered coupling 2 SSS motors together but bahh with all that. A single good motor will be best here.
For questions around single jet design boards… look to Radinn as they are doing it pretty good. That would be my design profile if i were making one.
My dad and I finished building a seaflea Minimost some time ago.
It has a 5HP Mariner outboard on it. WOT is 32 km/h.
At some stage we were thinking of putting 2 jets in it, but decided not to do so cause we love the sound of the outboard motor
That’s awesome! I actually did something REALLY similar. Initially i started out working on an 85mm jet project for a kayak. Obviously i ran into power issues, and since it was a kayak i considered open prop. I made a 4 blade 6" prop. It was a wet design with the prop fitting over a 5065 outrunner. Motor would not have lasted. It pulled around 150 amps.
Pitch is more a product of RPM here i’m guessing. How much pitch your impeller can run is dictated by the compression profile you design. Water can only be compressed so much before it cavitates. That’s partially why i say this is a science.
Lets look at how thrust is calculated.
Go to this link and play with this calculator - Rocket Thrust Calculator
Play with the different variable and see how it effects the thrust output.
What tends to matter is FLOW RATE (mass loss) and PRESSURE (at nozzle).
FLOW RATE
What determines flow rate on a jet? Well diameter (of impeller) and RPM as i suggested above.
This is why youngsters makes 50lbs of thrust with a smaller 54mm jet at 24,000rpm and i make 50lbs of thrust with a 65mm and 7,000 rpm. I move more water but slower and thus less pressure.
PRESSURE
Purely compression nozzle. Flow rate changes how much pressure is created in a logarithmic way based on compression ratio. The pressure is dictated by part design and the flow rate is dictated by impeller size and rpm and we said above.
Part design. I mention this because no matter what; how you design this part it has a limit of pressure. With machined parts… hell even jet ski’s… you don’t see more than 4-6 bar (60-90psi). It goes without saying you wont have those high pressures with plastic.
Don’t forget this is a mix water + air bubbles. I think he means you can compress the air bubbles inside the mixture. At least I thought that’s why jets are placed on the surface, to suck both air + water
Over 50 simulations of trying different blade counts, pitches, hub diameters, hub angles, compression ratios… to get to this haha. Lets not hi-jack this thread though. PM me for some more info.
I definitely would love some more people testing my drive. But the motor profile is pretty specific. 80mm-100mm diameter motors are the only thing suitable in my opinion. I think i can get 20mph and 30 minute run-times with the right drive and motor setup.
