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Old 01-15-2007, 12:30 PM
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Mike Wiz
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Default RE: New Piedmont Focus 90/110

Here is the second set of numbers from Motocalc. It's a lighter and more affordable setup. I have a friend that used this system on his Dream 110 and he liked it quite well.

MotOpinion - Focus Sport
850ft above Sea Level, 29.92inHg, 56°F

Motor: E-Flite Power 60 Outrunner 400KV; 400rpm/V; 2.7A no-load; 0.06 Ohms.
Battery: Thunder Power TP2100 (ProLite) (15C); 6 series x 2 parallel cells; 2100mAh @ 3.7V; 0.018 Ohms/cell.
Speed Control: Castle Creations Phoenix 80; 0.001 Ohms; High rate.
Drive System: APC 16x12 Electric; 16x12 (Pconst=1.08; Tconst=1) direct drive.
Airframe: Focus Sport; 1100sq.in; 127.5oz RTF; 16.7oz/sq.ft; Cd=0.043; Cl=0.06; Clopt=0.42; Clmax=0.81.
Stats: 132 W/lb in; 104 W/lb out; 23mph stall; 33mph opt @ 50% (32:15); 87mph level; 2166ft/min @ 48.7°; -465ft/min @ -9.3°.

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.

Power System Notes:

• The full-throttle motor current at the best lift-to-drag ratio airspeed (55.3A) falls approximately between the motor's maximum efficiency current (29.4A) and its current at theoretical maximum output (161A), thus making effective use of the motor.
• The voltage (19.2V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.

Possible Aerodynamic Problems:

• The diameter (16.0in) to pitch (12.0in) ratio is less than 1.5:1, which will result in reduced propeller efficiency at low speeds (the propeller is stalled). Although this is not likely to affect flying characteristics, it may make take-off or hand launching difficult.

Aerodynamic Notes:

• The static pitch speed (72.3mph) is within the range of approximately 2.5 to 3 times the model's stall speed (23.5mph), which is considered ideal for good performance.
• With a wing loading of 16.7oz/sq.ft, a model of this size will have very sedate flying characteristics. It will be suitable for relaxed flying, in calm or very light wind conditions.
• The static thrust (140.3oz) to weight (127.5oz) ratio is 1.1:1, 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 (95.9oz) to weight (127.5oz) ratio is 0.752:1, 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.

General Notes:

• This analysis is based on calculations that do NOT take motor heating effects into account. This also means that no calculations were done to determine if the motor might overheat.
• 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.