Just wanted to solicited comments on my current build

rwdreams

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Hi I'm requesting comments on my current build. It is a gyro copter of dominator design.
Empty weight 360, flight weight 560. Yamaha engine , 138 hp at 8300 rpm, 94 ft lbs at 7100 rpm. Using a 3:1 reduction and a 69 inch 3 blade kool prop , clockwise pusher, sabre shape pure carbon for higher rpm on the top end. The hub adds 1 inch so actually a 70 inch prop. Using a 26 ft rotor from tango gyos, or a 26 ft from sport copter. Cruise speed 65 mph and takeoff altitude of 6000 ft. So do these numbers sound realistic, any suggestions ? Thank you for your time.
 

XXavier

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If you end up with that flight weight you will have an exceptional power to weight ratio.

wolfy

So exceptional, that –were it not for the need to compensate for the torque reaction– you might climb vertically just with the prop thrust...

If my simple calcs are right, 100 HP would be the power required for hovering with a mass of only 560 lbs, assuming a prop of 70" dia. with an efficiency of 70%.
 

Jean Claude

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I agree with Xavier that 135 HP on a 1.78 m propeller allows a vertical climb of 560 lbs wheight !
Too dangerous because then the rotor tends to come to a complete stop.

Xavier, how your prop. can have an efficiency of 70% in hover?
 

XXavier

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I agree with Xavier that 135 HP on a 1.78 m propeller allows a vertical climb of 560 lbs wheight !
Too dangerous because then the rotor tends to come to a complete stop.

Xavier, how your prop. can have an efficiency of 70% in hover?

It's a figure I gave 'at eye', thinking in usual props under cruise conditions. A stationary propeller has probably a lower efficiency...
 

rwdreams

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Well while I like the idea of a vertical takeoff, someone said to calculate the mach number at max engine rpm of 10000. The Yamahas like to rev high, if I take the prop to that, the mach would be more than .92. which I guess could do unfortunate things. So I guess I'll use a smaller prop with maybe 4 blades.
 

Vance

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Likely the 560 pound gyroplane will carry a pilot and fuel for a higher takeoff weight. It still should have lively performance even at higher density altitudes.
 

Jean Claude

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I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C
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About 500 h (FW + ultra light)
0.75 Mach is a limit not to be exceeded, but still acceptable while 0.92 Mach is not.
A stationary propeller has probably a lower efficiency...
Since the produced power is Speed * Thrust, the efficiency of a stationary propeller is exactly zero, Xavier
 

XXavier

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0.75 Mach is a limit not to be exceeded, but still acceptable while 0.92 Mach is not.

Since the produced power is Speed * Thrust, the efficiency of a stationary propeller is exactly zero, Xavier

It depends on how do you define that efficiency. It can be considered as power of the accelerated mass of air/mechanical power delivered to the prop shaft
 
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