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Brenner -> RE: 69" QQ Yak-54 (12/9/2007 5:34:32 PM)
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I just ran your specs through MotoCalc, and according to its results you should be very pleased wih this setup. This is what it says: Motor: Hacker C50 10XL; 1624rpm/V; 1.26A no-load; 0.0118 Ohms. Battery: FlightPower 2500 (20C); 8 series x 2 parallel cells; 2500mAh @ 3.7V; 0.0065 Ohms/cell. Speed Control: Castle Creations Phoenix 80; 0.001 Ohms; High rate. Drive System: Hacker Planetary 6.7:1 Gearbox; 20x10 (Pconst=1.16; Tconst=1) geared 6.7:1 (Eff=95%). Airframe: Yak 54; 950sq.in; 157.4oz RTF; 23.9oz/sq.ft; Cd=0.056; Cl=0.47; Clopt=0.66; Clmax=1.24. Stats: 213 W/lb in; 192 W/lb out; 23mph stall; 31mph opt @ 66% (56:45, 72°F); 37mph level @ 78% (41:21, 75°F); 3635ft/min @ 90°; -294ft/min @ -6.2°. Power System Notes: The full-throttle motor current at the best lift-to-drag ratio airspeed (64A) falls approximately between the motor's maximum efficiency current (54.6A) and its current at theoretical maximum output (1181.7A), thus making effective use of the motor. The voltage (27.5V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above. Aerodynamic Notes: The static pitch speed (61mph) is within the range of approximately 2.5 to 3 times the model's stall speed (23mph), which is considered ideal for good performance. With a wing loading of 23.9oz/sq.ft, a model of this size will have trainer-like flying characteristics. It would make an ideal trainer, for use in calm to light wind conditions. The static thrust (334.1oz) to weight (157.4oz) ratio is 2.12:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll. At the best lift-to-drag ratio airspeed, the excess-thrust (196.2oz) to weight (157.4oz) ratio is 1.25:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.
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