08 nov 2017 16:50
Så skal du da ikke snydes for MotoCalc beregningerne (jeg er selv nysgerrig).
MotOpinion - Volksplane VP-1
50m above Sea Level, 101,3kPa, 14,7°C
Max speed: 13.5 m/s, kan ikke flyve ved 65% throttle.
Motor: Himax HC3522 990; 990rpm/V; 2,2A no-load; 0,027 Ohms.
Battery: FlightPower 3700 (20C); 3 cells; 3700mAh @ 3,7V; 0,0037 Ohms/cell.
Speed Control: Dualsky XC-40-MR; 0,0042 Ohms; High rate.
Drive System: Volksplane VP-1; 12x5 (Pconst=1,31; Tconst=0,95) direct drive.
Airframe: Volksplane VP-1; 45dm²; 2685g; 59,7g/dm²; Cd=0,054; Cl=0,42; Clopt=0,66; Clmax=1,2.
Stats: 162 W/kg in; 129 W/kg out; 9,3m/s stall; 12,5m/s opt @ 95% (21:00, 44°C); 15,7m/s level; 1,02m/s @ 4,7°; -1,32m/s @ -6°.
Warning:
MotoCalc was unable to determine a throttle setting for hands-off cruise airspeed, so the best lift-to-drag ratio airspeed and throttle setting will be used instead.
Inability to determine a throttle setting for an airspeed usually means the model is not capable of reaching the required speed with the given power system, or the airfoil information has not been specified correctly.
Possible Power System Problems:
The full-throttle motor current at the best lift-to-drag ratio airspeed (16,4A) is lower than the motor's maximum efficiency current (29,7A). A higher current level would improve system efficiency.
The static full-throttle current (41,6A) exceeds the capability of the specified speed control (40A), which will most likely damage it.
Current can be decreased by using fewer cells, a smaller diameter or lower pitched propeller, a higher gear ratio, or some combination of these methods.
Current can be increased by using more cells, a larger diameter or higher pitched propeller, a lower gear ratio, or some combination of these methods.
Due to the conflicting suggestions to both increase and decrease the current, this particular combination of power system components is not ideal (but not necessarily unusable).
Possible Aerodynamic Problems:
The static pitch speed (18,5m/s) is much less than 2,5 times the stall speed (9,3m/s), which may result in reduced performance at typical flying speeds and a low maximum speed. This situation is usually acceptable for an electric sailplane.
Pitch speed can be increased by using a higher pitched and/or smaller diameter propeller, a higher cell count, or some combination of these methods.
The model's maximum level flight speed (13m/s) is less than one and a half times the stall speed (9,3m/s). With such a narrow range of flying speeds, the model will require careful piloting in order not to stall.
Maximum speed can be increased by using a higher pitched and/or smaller diameter propeller, a higher cell count, or some combination of these methods.
Stall speed can be reduced by reducing weight, increasing the wing area, or using a thicker and/or more cambered airfoil.
The diameter (12,0in) to pitch (5,0in) ratio is greater than 2:1, which will result in reduced propeller efficiency at flying speeds. An appropriate smaller diameter, higher pitched propeller would improve this.
Aerodynamic Notes:
Due to some of the potential problems listed above, this model may require an experienced pilot.
The static thrust (1963g) to weight (2685g) ratio is 0,73:1, which will result in very short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and steep climb-outs.
At the best lift-to-drag ratio airspeed, the excess-thrust (284g) to weight (2685g) ratio is 0,11:1, which will give slow climbs and low acceleration. Some piloting experience would be beneficial.
General Notes:
This analysis is based on calculations that take motor heating effects into account.
These calculations are based on mathematical models that may not account for all limitations of the components used. Always consult the power system component manufacturers to ensure that no limits (current, rpm, etc.) are being exceeded.
Har crashet både det ene og det andet, men er efterhånden gode venner med de fleste af mine fly.
Medlem af EFK87.