my new dual rotor machine

[Devo]

Finally got my Stator done on my 12 mag dual rotor.

I went with 45 wraps of #15 wire 2 in hand , I still had some space & probably could have hit 50.

This gives me 12 volts at 120 -130 rpm.

I think If I redid it I could get 3 in hand at 30 wraps # 15  but the cut in would be higher.

I was wondering when you use a blade calculator for example on a 10 foot prop

at tsr 5 you get 60 watts at 10 mph at 140 rpm. if the prop was "unloaded" in a 10 mph wind would it exceed 140 rpm?

for example if you had a larger prop with a lower rpm like 80 watts at 120 rpm in a 10 mph wind would it speed up to the cut in in a 10 mph wind if the cut in was 140

& just produce a little less power ?

I had good luck when I put an oversized prop on my 8 mag dual rotor & I like to run like this to get all I can from the genny when I had a 5 foot prop I would get 5 to 15 amps , with an 8 foot it hit 25, amps regularly

I was going to put a 10 foot prop on this but was wondering if an 11 or 12 foot would be better to catch the low winds or way to big.

Devo  

[Flux]

Devo

I have never found the power output predictions from those calculators to be very useful. They are fine for working out the dimensions for a given size and tsr.

In low winds props will spin considerably above design tsr so if you needed tsr 8 to reach cut in at 8mph a prop with design tsr7 would do it with ease and tsr6 would also do it without being unduly stressed.

Choose your tsr for mid range say 15 mph and expect it to run fast in low winds.

I find that all my props run fast happily in low wind and also like to run slower than design in high wind which suits the real conditions quite well.

These blade calculators are based on very simple theory and at best treat them as a guide.

Flux