I have 100 21700 50s cells. Should I build 12s8p or 14s7p
Motor is flipsky 65161 using a flite propeller.
Foil is a Naish Thrust XL (~1500cm²)
14s has 2 more cells, so slightly more wh.
12s maybe safer and higher amp capacity/torque
14s ~8v more so possible higer speed
Id go for the 14S7P setup, the 50S cells can do 20A continious, giving you 140A continous for battery power, i can tell you already, you will never reach that. There is a big difference in terms of battery vs motor current (on the phase wire). Also prefering 14S as a higher voltage will give you more speed, you will need less amps to reach the same power, so it is also more efficient (less heat losses), and will put less strain on your system.
Just make sure to very well design the battery and you will be fine, but the rightbusbarmaterials and layout is important to guarantee a nice current path.