isvana
Dec 02, 2003, 11:06 PM
Greetings SPADers. Despite this being in the glow n gas department, I thought I'd ask away here as I contemplate my first SPAD, and an eSPAD at that.
From the SPAD Gnat plans (http://www.spadtothebone.com/SPAD/gnatplans.jpg) on spadtothebone, scaled down to 80% to match the locally available coroplast size (27" for the wing span). 3/4" stick for the fuselage, with a GWS A or B box at the end. LiPolys either stuck on the wing per the plans, or maybe IN the wings if I use 2 packs.
Motocalc claims this would work OK...
MotOpinion - ESpad-HiMaxx-Etec3S2P-Agearing
Sea Level, 29.92inHg, 59°F
Motor: Himaxx 2025-4200; 4166rpm/V; 0.75A no-load; 0.075 Ohms.
Battery: E-Tec ET-1200; 3 series x 2 parallel cells; 1200mAh @ 3.7V; 0.033 Ohms/cell.
Speed Control: Castle Creations Phoenix 25; 0.0065 Ohms; High rate.
Drive System: GWS GW/EPS-300C-AS; 9x5 (Pconst=1.31; Tconst=0.947) geared 3.75:1 (Eff=95%).
Airframe: SPAD E-Gnat; 260sq.in; 20.6oz; 11.4oz/sq.ft; Cd=0.07; Cl=0.43; Clopt=0.53; Clmax=1.1.
Filter: 20A max; 25A max (ESC).
Stats: 142 W/lb in; 109 W/lb out; 17mph stall; 24mph opt @ 62% (53:22, 72°F); 26mph level @ 67% (49:40, 73°F); 1597ft/min @ 49.9°; -320ft/min @ -8.8°.
Power System Notes:
The full-throttle motor current at the best lift-to-drag ratio airspeed (16.5A) falls between the motor's maximum efficiency current (9.5A) and its current at theoretical maximum output (60.6A), thus making effective use of the motor.
Aerodynamic Notes:
The static pitch speed (45mph) is within the range of approximately 2.5 to 3 times the model's stall speed (17mph), which is considered ideal for good performance.
With a wing loading of 11.4oz/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 (26.3oz) to weight (20.6oz) ratio is 1.28:1, 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 (14.9oz) to weight (20.6oz) ratio is 0.72:1, 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.
From the SPAD Gnat plans (http://www.spadtothebone.com/SPAD/gnatplans.jpg) on spadtothebone, scaled down to 80% to match the locally available coroplast size (27" for the wing span). 3/4" stick for the fuselage, with a GWS A or B box at the end. LiPolys either stuck on the wing per the plans, or maybe IN the wings if I use 2 packs.
Motocalc claims this would work OK...
MotOpinion - ESpad-HiMaxx-Etec3S2P-Agearing
Sea Level, 29.92inHg, 59°F
Motor: Himaxx 2025-4200; 4166rpm/V; 0.75A no-load; 0.075 Ohms.
Battery: E-Tec ET-1200; 3 series x 2 parallel cells; 1200mAh @ 3.7V; 0.033 Ohms/cell.
Speed Control: Castle Creations Phoenix 25; 0.0065 Ohms; High rate.
Drive System: GWS GW/EPS-300C-AS; 9x5 (Pconst=1.31; Tconst=0.947) geared 3.75:1 (Eff=95%).
Airframe: SPAD E-Gnat; 260sq.in; 20.6oz; 11.4oz/sq.ft; Cd=0.07; Cl=0.43; Clopt=0.53; Clmax=1.1.
Filter: 20A max; 25A max (ESC).
Stats: 142 W/lb in; 109 W/lb out; 17mph stall; 24mph opt @ 62% (53:22, 72°F); 26mph level @ 67% (49:40, 73°F); 1597ft/min @ 49.9°; -320ft/min @ -8.8°.
Power System Notes:
The full-throttle motor current at the best lift-to-drag ratio airspeed (16.5A) falls between the motor's maximum efficiency current (9.5A) and its current at theoretical maximum output (60.6A), thus making effective use of the motor.
Aerodynamic Notes:
The static pitch speed (45mph) is within the range of approximately 2.5 to 3 times the model's stall speed (17mph), which is considered ideal for good performance.
With a wing loading of 11.4oz/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 (26.3oz) to weight (20.6oz) ratio is 1.28:1, 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 (14.9oz) to weight (20.6oz) ratio is 0.72:1, 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.