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Just for reference, with a wooden, fixed pitch prop, I could get no more than about 2350 RPM for a sealevel takeoff and takeoff was a bit on the anemic side, to say the least. With the CS unit, I always get 2650-2700 RPM and the takeoffs are now quite sprightly affairs.
    Do the numbers; that's better than a 10% increase in takeoff horsepower
(HP = T x RPM / K [K is a constant around 5200 for these regimes]).
Nearly all of it is "excess power" needed to climb, which relates to
better takeoff performance.
    Cheers,
    Dan Schaefer
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             An addition to Dan Schaefer's response to Sven (SE-XOP) regarding     props.         The constant mentioned in the HP = T x rpm / k is fallout from the unit     conversions required:
    hp = 550 ftlb/s
    T = ftlb
    rpm = (2*pi rad/s)/(60s/min)
        put it all together and you get:
        HP [550 ftlb/s] = T [ftlb] x rpm [(2*pi rad/s)/(60s/min)]     HP = T x rpm /(550 ftlb/s x (60s/min)/(2*pi rad/s))
    HP = T x rpm / 5252
        With a CS prop, in addition to the engine putting out more horse power     at the higher take off rpm, more of the prop blade is flying and     providing thrust.  A fixed pitch cruise prop can have a substantial     portion of the blade in a stalled condition until sufficient forward     velocity is obtained.  If the pitch is too steep, enough of the blade     can be stalled such that the aircraft can't accelerate at all.  In     this case all of the horse power being generated is going into     stirring a lot of air and providing no thrust.
        Dan, your % thrust increase was probably much higher than your % power     increase.
        CS all the way.
        Chris Zavatson
    N91CZ