RE: Throttle curve
Jim.
The relationship between engine rpm and
1. static thrust and
2. power
are not proportional, nor are they the same. (Power=rpm^3, static thrust = rpm^2, while pitch speed is proportional with rpm.) This means that increasing the rpm from one value to an other value gives you a certain increse in power. It will also increase the thrust, but not by the same percentage value.
Taking the above example as a case, (post #5) OS 160 with APC 17x12.
Based on Pe Reivers power calculator: (Pe is the Dutch supplier of MVVS engines.)
Idle, 1700 rpm, 0,03 Hp, 0,39 kg thrust, 31 km/h pitch speed.
Mid range, 6000 rpm, 1,34 Hp, 4,91 kg thrust, 109 km/h pitch speed.
Full, 8300 rpm, 3,56 Hp, 9,4 kg thrust, 152 km/h pitch speed.
To have "half power", (i.e. 3,56 Hp/2= 1,78 Hp) would require 6600 rpm, where the static thrust would be 5,93 kg, and the pitch speed is 120 km/h.
To have "half static thrust", i.e. 4,7 kg, would require 5900 rpm, which is 1,28 Hp and give a pitch speed of 108 km/h.
If you set up the throttle linearly, you will only gain a few hundred rpm's from mid-stick to full stick, but those few hundred rpm's make a lot of power, not so big increase in static thrust, and almost no increase in pitch speed.
Magne