Critique this concept build: surfjet

I am getting older and want a boost when trying to get outside, or to get up to speed on less punchy waves.

It seems like I could add a small tubed propeller and a smallish battery to accomplish this since A) i’ll still be paddling but need some boost, and B) won’t be using the engine for long periods, but in bursts. I don’t want anything under the board and would like to keep weight down.

i’m looking at a 5000mah 12s battery, 200A esc, and one of the kedean jets or waterproof propeller assemblies. water cool the esc with a jet nozzle port. I’d like to be able to control the motor somehow with my body: i.e., maybe a simple small button that i can engage with my chin on the deck to put motor at 90%.

I’ll hollow out the PU, wire up the components and then glass over them.

Not sure how good the kedean jets are, but keep note that a jet does not work well when completely submerged.

the waterproof unit they sell (KED390) :

seems like it’s walking a fine line between a propeller in a tube and a jet. no stator, no details on how they sized the nozzle and the angles on the intake duct.

it seems jets are most efficient at keeping things at speed; my use case here is to give me boost, so i’m already planning to take an efficiency hit vs a prop. I can’t mount a prop in this application because it would mess up the surfing feel on a wave if anything was causing significant drag (i’m already worried about that intake hole of the jet).

however, the nozzle will be above the waterline given the board i’m going to install it on will be floaty and I’m planning to only use the jet while laying flat on the board, not standing up on it…

still trying to find a good battery pack with the right dimensions and bms included. best i can do right now because i’m impatient is a 10s4p, the 12s seem more rare and take longer to ship…

22 to 24 KG Thrust. My dad and I did test last summer with our jet board and got around range too at 15000 rpm on S12. However the amps we pull did go over the 120 amps (per motor!)

Lot of more info here: New (jet board) build discussion thread

ah that thread is great! Good work over there!

I am focused on a single nozzle/jet, single engine design, and while I am heavy (190lbs / 86kg), I will be actually surfing on waves so don’t need this engine to get me up to plane, just push me out past breaking sets or onto a wave :slight_smile:

I’m hoping this means I can use a smaller off the shelf battery pack. Even 15minutes at 80% throttle would be enough for me.