To use #14 wire for a 12ft machine at 24v you will have to use 2 strands in hand.
Probably you will find that with care you can get in 45 turns of 2 in hand and that should be fine with a stator about 5/8 thick and working in a 3/4" air gap.
This should handle a 12ft prop as long as you furl it below 1kW. I wouldn't try to push the peak power any higher but you will gain over the 10ft machine all the way up the speed range so total energy capture should be well up.
Flux