Are you sure? As I understand - I don’t more current but more torque to push me up lift of speed. Like tractor and car motor. If you wish to go let’s say 40km/h and you have 100hp motor. Both motors are able to get you to this speed but tractor motor has torque to pull big ass load uphill and car simply can’t. I see kV like something comparable to “gears”
Here is similar motor. In version with 315kV max torque is 8.3 and in 100kV version it is 10Nm. Also, 100kV motor for his bigger torque uses less current.
Correct me if I am wrong, I’m here to learn. 
Yes, i’m sure. Kv isn’t anything like gears, it’s a winding constant that should be selected to be balanced with the esc and battery choice.
Basically, you can’t trust chinese motor specs or datasheets. An example from your pic, current capability is proportional to kV so a motor with 100kV that has max current of 100A will have a max current of 120A at 120kV. This is not the case in the chart and it tells us that they did not feed the motor equally in their tests for the max - the data is not coherent and can not be used for anything but guesswork and rough estimations.
Physically the magnetic field of the coils is given by ampere x winding turns. This means a field (and resulting torque) of 1A and two turns of winding is equal in strength to 2A and 1 turn of winding (both 2 ampereturns in field strength)
Torque is proportional to ampereturns up to the point when the motor steel starts to saturate, then the torque created with more ampereturns is falling off gradually. At max torque, the stator steel is completely saturated by the fields and adding more current or turns will not create more torque, only heating. This max torque is a constant for each motor design, not dependent on the winding. Max is max, so to say 
The case when lower kV does result in more torque: if you don’t feed enough current to create the max magnetic field then the motor will produce more torque with same current and lower kV, but it’s not due to the kV making a ”higher torque motor” or whatever people say, it’s due to enough current through the winding to come closer to max torque.
What is enough current then?
350A will in theory create 28Nm of torque with a 120kV motor - if the motor is not saturated at that current. Obviously 350A is more than needed for saturation to occur in your case as the real max torque for a 65161 motor is probably more like 15Nm (for a split second, then 
)
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Thanks for explaining this.
I’ve ordered most stuff except foil, cells and aluminium parts.
Can you estimate power needed for achieving “medium speed” (lets say 35km/h) for my 130kg?
I am trying to go to and back from island which is 12km away.
I am guessing around 2500W? So 2.5kWh battery should do the trick and have some remaining capacity to spare
Well if I remember correctly from other threads it’s about 3kw to get up on foil and then 1-1.5 to stay up.
Still, I built a 20S battery pack for my rubber boat and I am breaking that apart going ahead, because of safety concerns. Larsb gave me a good lesson on that in the thread I started on my combined 85165 outboard/ rifle case eFoil build.
I decided to build the outboard first separately with the 86165 and then build the eFoil with a lighter 65161 motor I’ll order later. The latter being underpowered for a outboard (if you want any decent speed at least) and the 86165 being a bit too big to put on the rifle case eFoil.
I’ll also split my 20S pack in two (it was already a HEAVY! 2x 10s21p stacked pack so easy to split), because salt water and anything over 50v is really taking too high risks. At the end of the day, my 20s is lethal. And that’s just not an OK risk to take with our hobbyist approach to this.
With 2.5kwh you’ll have enough and a margin to winds and harsh conditions. Normally you can calculate about 60wh/km so that’s roughly 1.5kwh for the return trip.
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What about battery configuration? 16S or lower? Fully charged 12S is around that magical 50V DC limit. Seems kinda slow for me.
60Wh/km is for normal people Then for me it is at leas 75Wh/km.
I have my eye on Samsung INR21700-50S 5000mAh - 35A.
For 2.5kWh pack I need around 135 pcs (each is 18.5Wh).
16S8P, 14S9P/14S10P, or 12S11P ?
So the config is going to be 14S10P of those 21700 5Ah 35A cells.
I haven’t noticed that you guys are putting BMS’s?
For me - it is risk that I’m not willing to take. Imagine lending your e-foil to someone who is laymen/careless about charging.
I’m considering this JBD BMS. It has 8-21S input, BT, 200A continuous and 600A peak.
https://www.aliexpress.com/item/1005006216353065.html?spm=a2g0o.productlist.main.23.116c59c35ymmZZ&algo_pvid=9192fc80-9e29-4ddc-a153-f5514196dfc3&algo_exp_id=9192fc80-9e29-4ddc-a153-f5514196dfc3-11&pdp_npi=4%40dis!EUR!83.00!58.1!!!83.00!!%402103080b17016876711162290e7de2!12000036319757356!sea!HR!804175018!&curPageLogUid=MzDQ1xpaiMnF
I ordered that one too. But actually it feels a bit over the top and I’m buying it because I would like to pull a bit extra when using it with my 85165 outboard. I have a hard time seeing myself pushing 50v*200A, that’s 10kw. Its probably easier to 3D print a bow to make the case more hydrodynamic (that’s my plan). I have a hard time seeing that even you would need 10kw to get on foil when everyone else mostly needs 3kw. Are you buying it to be able to dual use it for the outboard too?
With your weight it might be more about making sure it’s actually big enough to keep you afloat. If your weight pushes the case to become submerged it’s gonna be damn hard to make it go at any speed.
Yes, I’ve selected 350A VESC and 200A BMS to have option to use it on my future rubber boat. I can reuse this parts and only buy 85165 motor.
I’ll learn by experience how much power will I actually use for e-foil.
I’ve also planed to 3D print a bow. We have many things in common. How good are you in 3D design? If you make it - please share thingiverse link or even better - complete step file (or Fusion360 file).
It will not get submerged because I will put only part of my weight on the stern. Anyhow, bow needs to stay a float because the signal doesn’t propagate in water.
Antenna will be close to the tip of the rifle case.
Well not great at CAD, just completed my first OnShape course but it gave me the skills I needed. I don’t think it’s particularly hard to design the bow in itself. The design challenges are to create something that is easily detached while staying rigid/stiff and won’t break where it attached to the case while remaining reasonably light in weight. Got lots of ideas 
Currently I’m designing the outboard, where the main challenges I took on was to make the mast and pitch/attachment to the boat as 3D printable as possible. I’ll share all files as STL when I’ve tested them!
Try AutodeskFusion360… It is free for personal use - hobbyist (3 year licence).
Yep, securing it with screw is simplest to design, but some kind of strong clip would be easiest to operate. I’ll try to design something once my rifle case arrives in few weeks.
Hello. I liked your idea! But the foil case has better hydrodynamics of shape:
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Did you try that on the water yet? Any noticeable improvement to how its behaving? If no, wanna share the design so I can give it a try on mine?
Btw, did not see if you already decided your battery voltage, but my rifle case is also running on 20S, with the 75200 and 65161 motor. But with the prop everyone else also uses, so motor current still goes up to 200A while starting, but battery currents are way less of course. The hardest I challenged the system was with 5kW / 180A constant load for 10 minutes straight (foiling while towing a big SUP with a person on board - quite challenging to ride like that but very fun 
)
I am waiting for cells to arrive. It’s going to be INR21700-50S 5000mAh - 35A in 14S10P configuration. I’ve f*cked up during ordering process and I ordered 65121 instead of 65161. Now I don’t know what to do. Since I am 130kg guy I really doubt that this puny motor will suffice. And I also need to buy wings for my Naish mast and fuselage. You aren’t afraid of 72V in salty water?
I can’t upload 3mf(they are like stl 2.0) files here so here is link to wetransfer
(it is valid only 7 days). Check them for dimensions before printing… or you can design them yourself. Sides of coffer are 5% inclined outwards so take it into account.
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