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, buy the right busbar materials and layout is important to guarantee a nice current path.
About the risk of shock. 14s will give max 58.8v @4.2v per cell. How dangerous is ~60v, worst case if one of the phase wires insulation was compromised and I touch it laying in salt water.
Voltage as low at 12V can kill you in the right conditions.
The major issue is whether the current crosses your heart and disrupts it.
I don’t think a single phase wire should cause you much issue unless you become the main path and bridge the circuit.
The risk of touching a phase wire is mitigated by having them internal to the build. Ie waterproof hatch, wires routed through mast etc. If you have wires exposed to touching then even more care should be taken inspecting to ensure the insulation is intact.
As far as shock risk is concerned you will likely get a varied response here about what’s “safe”.
The internet is full of articles describing what can happen. Such as this one.
I use 12s because then I can plug together 2 6s and for 6s it was much easier to find a balanced loading device (I dont have a BMS). Maybe that is also relevant for you.
Regarding the topspeed, I dont think it is the voltage what will limit you. 1500cm is a hell lot of lift. But I am not an expert.
The 12s ist also enoght punch for me with the flipsky 65161.
I would not give my information to much value because i am more a beginner, but maybe it is a helpfull impuls.