Post by cwilliamrose on Aug 16, 2012 13:56:07 GMT -6
This is a design that originated with Ed Fisher and I at Sun 'n Fun in 1984. Ed has asked that I post this photo and talk a bit about how this project got its start. First things first, here's the photo;
This is actually about the third generation of this design, it wasn't quite as nice to look at in Gen1 form. It did however look good in Ed's early sketches which were done on bar napkins from more than one adult establishment in the Lakeland area.
It really started when I was watching the daily airshow and two different ultralight manufacturers were participating by doing aerobatics in their products. For the most part I was not impressed. Both airplanes were marginal in terms of control (especially roll rate) and inverted performance. I thought I could do better and the seeds of what would become Polecat took hold. By the time we were destroying napkins in dimly lit rooms I had already chosen a biplane design with large wings, symmetrical airfoils and big ailerons. Big wings to get the stall speed down to Part 103 specs even using an airfoil not designed for high lift. And big ailerons because it was clear to me that the airplanes in the airshow needed more roll rate than they were getting from their machines flying at fairly low speeds.
Of course, mentioning something like "new airplane design" to Ed will get you an immediate response and before I knew it we were designing an airplane. We were no strangers to using bar napkins for design work but the scantily-clad females I vaguely remember were a new distraction which we mostly ignored (really!). We had a number of details in those sketches that we actually remembered the next day, some we're still not sure about.... We had elephant ear balances on the ailerons, a mixer for drooping the full span ailerons to get a better coefficient of lift, a big slow-turning prop for good static thrust, rigid main landing gear, etc, etc....
If you look at those sketches and the actual airplane that came from them there's not a lot of difference. And it flew better than either of the airplanes that inspired the design effort by a large margin. But it was not 103 legal so we cheated in that regard. Close, but not strictly legal. What you see in the above photo is a EAB airplane with an N-number not a an ultralight.
Specifications:
All-metal, fabric covered single seat aerobatic biplane. Intermediate level aerobatic capabilities. Four full span ailerons on swept symmetrical wings (NACA 0012 airfoil) with no stagger and no dihedral. Wing incidence is 0° top and bottom. No aileron differential motion.
Fuselage is welded 4130 tubing, fixed tail surfaces are welded aluminum tubing with formed aluminum ribs, control surfaces are aluminum tube spars with formed ribs and trailing edges. Wings are aluminum tube spars with press-formed aluminum ribs all bonded with aluminum castings at the structural attach points. All control surfaces feature ball bearing hinges. Aileron and elevator controls are pushrod operated, the rudder is cable operated.
All flying and landing wires are fixed length wire rope with swagged fittings. Tension is provided by the interplane struts which feature left and right hand threads allowing them to be length adjusted to tension the wires. This design allows for easy disassembly and reassembly and rigging for trailer transport between airshows.
Various engines including Rotax 532 and Kawasaki 750 Turbo running a 100" diameter prop through an integral 5:1 gearbox. Fuel tank is wedge-shaped (like a section of a watermelon) welded aluminum with a flop tube for inverted flight. Rigid main landing gear, no brakes, tailskid (later with swiveling/locking tailwheel and brakes). BRS eqiupped.
Wing Span: 18 feet
Empty Wt: 278# for first flight, 425# with larger engines and other mods
Gross Wt: 525# with Rotax, later 700#
Top Speed: 80mph (uncowled Rotax 532)
Stall Speed : ~40mph
Roll Rate: 180°/sec @ 80mph
Fuel: originally 3 gallons, now 6 gallons
Endurance: Approximately 30 minutes
Structure: ± 6g (Limit)
This is actually about the third generation of this design, it wasn't quite as nice to look at in Gen1 form. It did however look good in Ed's early sketches which were done on bar napkins from more than one adult establishment in the Lakeland area.
It really started when I was watching the daily airshow and two different ultralight manufacturers were participating by doing aerobatics in their products. For the most part I was not impressed. Both airplanes were marginal in terms of control (especially roll rate) and inverted performance. I thought I could do better and the seeds of what would become Polecat took hold. By the time we were destroying napkins in dimly lit rooms I had already chosen a biplane design with large wings, symmetrical airfoils and big ailerons. Big wings to get the stall speed down to Part 103 specs even using an airfoil not designed for high lift. And big ailerons because it was clear to me that the airplanes in the airshow needed more roll rate than they were getting from their machines flying at fairly low speeds.
Of course, mentioning something like "new airplane design" to Ed will get you an immediate response and before I knew it we were designing an airplane. We were no strangers to using bar napkins for design work but the scantily-clad females I vaguely remember were a new distraction which we mostly ignored (really!). We had a number of details in those sketches that we actually remembered the next day, some we're still not sure about.... We had elephant ear balances on the ailerons, a mixer for drooping the full span ailerons to get a better coefficient of lift, a big slow-turning prop for good static thrust, rigid main landing gear, etc, etc....
If you look at those sketches and the actual airplane that came from them there's not a lot of difference. And it flew better than either of the airplanes that inspired the design effort by a large margin. But it was not 103 legal so we cheated in that regard. Close, but not strictly legal. What you see in the above photo is a EAB airplane with an N-number not a an ultralight.
Specifications:
All-metal, fabric covered single seat aerobatic biplane. Intermediate level aerobatic capabilities. Four full span ailerons on swept symmetrical wings (NACA 0012 airfoil) with no stagger and no dihedral. Wing incidence is 0° top and bottom. No aileron differential motion.
Fuselage is welded 4130 tubing, fixed tail surfaces are welded aluminum tubing with formed aluminum ribs, control surfaces are aluminum tube spars with formed ribs and trailing edges. Wings are aluminum tube spars with press-formed aluminum ribs all bonded with aluminum castings at the structural attach points. All control surfaces feature ball bearing hinges. Aileron and elevator controls are pushrod operated, the rudder is cable operated.
All flying and landing wires are fixed length wire rope with swagged fittings. Tension is provided by the interplane struts which feature left and right hand threads allowing them to be length adjusted to tension the wires. This design allows for easy disassembly and reassembly and rigging for trailer transport between airshows.
Various engines including Rotax 532 and Kawasaki 750 Turbo running a 100" diameter prop through an integral 5:1 gearbox. Fuel tank is wedge-shaped (like a section of a watermelon) welded aluminum with a flop tube for inverted flight. Rigid main landing gear, no brakes, tailskid (later with swiveling/locking tailwheel and brakes). BRS eqiupped.
Wing Span: 18 feet
Empty Wt: 278# for first flight, 425# with larger engines and other mods
Gross Wt: 525# with Rotax, later 700#
Top Speed: 80mph (uncowled Rotax 532)
Stall Speed : ~40mph
Roll Rate: 180°/sec @ 80mph
Fuel: originally 3 gallons, now 6 gallons
Endurance: Approximately 30 minutes
Structure: ± 6g (Limit)
