I have not seen any data on the efficiency matter yet - at least not a side to side comparison on an efoil. My main concern is safety - especially once I think about letting someone else use my board - this overrules efficiency in any case.
There are products on the market making it work - so I should be able as well.
Also I would go the minimalist-foil-assist route - just enough to get me on foil and a few 100 meters to the next wave.
Here you can see the cross-section of the impeller - 3mm at the thickest part. At the moment it is plenty strong although relatively flexible and reasonably cheap to be printed at 2,28€.
At this price I can afford many test setups to find the optimum rotor by trial and error - best case on a test bench. Same for the stator
This leads to excessive heat built up in the shaft. Is this problem ignorable since cooling is good in the water anyway or should I worry about quick wear? Please keep in mind this is not meant as 100% efoil but assist only.
Alternatives would be:
(ceramic) sliding shaft seal as with most waterproof motors
Labyrinth seal
I excpect all the other traditional boating seals to have even more friction/ thermal issues right? Even more at 800 KV 52 V
Fair point that efficiency isn’t always the primary consideration.
One of the places I’ve seen jet/prop data is from Fliteboard’s foil time calculator:
They state it’s based on rider data they have gathered. So not controlled test data, but likely averaged real world data that I suppose their owners can upload.
Can you provide more info on why you needed disassemble your ESC? I bought a FlyColor Xcross HV160A ESC and it doesn’t work, just wondering if it has the same issue as yours.
@mekanism
I accidentally ripped off a component when I disassembled the aluminium cooling plates. I did this in order to mount it in that aluminium clamp to get cooling on both sides MOSFETs.
If you did not mechanically work on your ESC and something could have been broken off in a similar way I expect it to be a different kind of problem.
Had a great time on vacation and emptied a total of 15 full batteries. I had the Indiana kid aspect wings with me, also calle “ride”. With the 1500cm2 wing I was able to do quite some pumping and training of transitions. The smaller 950cm2 wing was getting really fast and fun, but quite hard to pump, since only mod aspect ratio.
No issues with the Bopla box. Great recommendation @hangloose
Only some small corrosion on the aluminium where it is close to the carbon board and water likes to stay in between.
Now working on some further ideas - smaller/ lighter battery and waist mount.
I sketched up this design quickly. The idea is to pott only the cell terminals, strips and wires. Benefits could be better cooling of the cells an lower weight since less potting material.
@heiguga@S_Roger
Sorry for not replying.
I was and still am busy with a new propeller driven assist design. I’m trying my best to get it finished for vacation next week.
The Jet drive is giving me a hard time. So I started with quite a lot of pitch. It turned out that the motor was not producing enough thrust and current limit kickin in already way below 30% duty cycle on the motor bridge. With a high speed low torque motor that means making only little power. I had this configuration once in the lake and I could only taxi around slowly before the motor cut off.
So I lowered the pitch resulting in broken rotors - as you might remember they where Nylon SLS printed.
Latest addition is a metal rotor I just received this week. It should neither flex nor break and this will be the last chance for this motor/ jet combo from my side. If it won’t work I’d rather switch to an outrunner configuration with jet. Main reason being better weight to power ratio.
Another update on my before mentioned v2 foil assist.
I gave the body mounted approach a go.
The base of my hip bag is made from neoprene with a PE sheet as stiffener inside. I’m quite happy with the functionality but next time I would go with a kite or wing harness instead of sewing it myself.
The waterproof bag I welded from TPU coated nylon. It closes by wrapping which worked really well. Not a single drop of water inside after 3 extensive swimming/ foiling sessions.
For the receiver and BEC I printed this enclosure. After assembly I noticed the remote would not bind. After some tinkering I noticed it must have had to do with the ferrite shielded inductance. Some aluminium foil under the receiver (of course isolated with capton tape) solved the problem. No heating and no more range issues.
The mast base is custom milled to fit Indiana aluminium masts. It incorporates some space for a connection of the motor phases which is potted for waterproofing.
Sadly after a lot of work before my vacation the assist did not work as hoped. By now I narrowed the issue down to the motor which was initially a Flipsky 6374. It simply had not enough torque and stalled at 30-40 % throttle. No improvement by changing props, using bigger front wings etc. Therefore I switched back to my old BDUAV 6384. Though I can’t really test here at home.
Jet drive is still not tested in its latest configuration.
Can explain and share stl file for potting battery?
I want to do same work on mine and thinking how to solve the problem of waterproofing well both the balance plug and the power plug
@Bzhwindtalker
Sadly no foiling at all since the weak motor. I replaced it with the BDUAV just after my vacation and had no more chance to try. At home sadly it’s complicated to do testing in a legal way
I did not sketch the controller sorry, just som basic mounts and a frame for potting. It is also filled with epoxy
@Allix
There is not much to it. Just a cel spacer similar to the ones you can buy with the addition of a box shape on the welding side. After installing the cells in the spacers I glued each one with a few drops of epoxy in order to seal them for potting. Then after spot-welding, soldering cables and checking functionality I potted both sides one after the other. The plugs are not sealed. Just a regular XT90S and SubD 15 pin for temperature and balancing. Some battery grease to protect from corrosion. The idea is not a entirely waterproof battery but having a second layer of safety in case the bag collects a few drops of water.
