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Old Jun 24, 2005, 11:46 PM
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Stuttgart, Germany
Joined Oct 2004
966 Posts
Pitts Special 26" from sturdyboard

Hey fellas,

I just got around to shooting some pics of my newly completed and maidened Pitts Special. Its based on enlarged micro pitts plans and constructed of peeled foamcore covered with packing tape. The paint job was accomplished with a red sharpie. The pilot is a carved chunk of pink foam painted in the likeness of my cat, Chewy. I added whiskers made of paint brush bristles glued in with tiny dabs of glue. The finished model ready to fly weighs a smidge under 11 ounces, and is powered by a GBx double with cheese, wrapped nine turns with a double strand of 26ga newbie wire; which spins a GWS 9x4 slowflyer prop. The power is supplied by a 2S1P 1250mAh li-poly pack which is fed intraveinously to the GBx by a BP-10A brushless speed controller. Guidance is provided by a lightened GWS R4-PII receiver through 2 pico servos for rudder and elevator, and a naro servo for the ailerons. I decided to leave off the wheel pants for now as I intend to actually use the landing gear; when I get good at landing her I might add them.

Construction:
I started with the pattern parts peeled and shaped, and accomplished the airfoil by creasing the udnerside of each wing panel with a triangular engineer's scale, adding tape to lock in the curvature. It was a gamble but it worked out extremely well. All the critical joints are reinforced with 3M Extreme bi-directionally reinforced strapping tape. The fuselage is covered in 3M glossy multi purpose tape, which worked really well and went on very easily. The engine cowl is stacked pieces of foam sanded to shape, and the spinner is a piece of pink foam carved and sanded to shape in the chuck of a cordless drill, then 'glassed with silkspan and polycrylic. It was my first attept at covering with this technique and it was much easier than I expected. The interplane struts have .125" cf tube backbones glued to a 1/16" ply profile, and filled with foam sheet sanded to an airfoil shape. I used gorilla glue exclusively, which is quickly becoming my new favorite adhesive. The motor mount is 4 CF tubes glued into holes in the firewall through a lite ply plate. the front half is removable with 4 screws, allowing thrust angle adjustments. In retrospect, the tube mount would have been a heck of a lot easier to use than the firewall mount I selected, but probably wouldnt offer the adjustability. the logos and numbers where whipped up in photoshop and printed on transpareny film. The registration numbers are on white paper to isolate them from the pinstriping in the background. The battery compartment is behind the firewall, and retains the battery with a patch of velcro, and a redundanyt velcro strap. I don't want to risk dropping the pack in a tumble maneuver and have to watch her self destruct. All the control horns are made of lite ply, and the pushrods are thin music wire. The wings contain no CF spars, as the curvature added so much stiffness; although the rigging wires are functional and adjustable, and really strengthen the assembly while supplying the needed washout.

First flight:
I was in indianapolis over fathers day weekend, and took it along to the field with my bird dog, not intending to fly it unless it was dead calm. After 2 packs on the bird dog in moderate winds, I couldnt resist a little taxi testing. The ground handling was very stable and easy to control, so with the encouragement of my wife and co-pilot, I took her out in the middle of the field and applying full throttle, gave her a firm toss at a 30 degree angle. She foundered for a second until up on step, then climed out at a 50 degree angle. The underbcambered wings supply a ton of lift and no reasonable amount of down elevator would tame the climb. I got her up to a safe height and got a feel for the sticks. She was very fast and responsive, and if not for the advanced probramming capabilities of my brand new Futabe 7CAP, she would have been a real handfull. I always maiden with full throws, with a lot of negative exponential curve so that the controls are smooth around the middle, but I have also have access to full throws to keep it out of trouble. I found that the high rates were necessary on the ailerons, but the pitch was better at low rates. The rudder was extremely effective, producing nearly pure yaw, and I mixed in a little to aileron for coordinated turns. After a few laps, a few rolls, and a loop or 3, I brought her in for a really undignified landing. roll sensitivity becomes an issue at slow speeds, and I was overcorrecting. She cartwheeled in the grass 2 or 3 times, but amazingly suffered not a scratch! I love this plane! My guesses as to the throws and rates were very close, but after a little tuning she was a real smooth operator. I was going to pop in a fresh pack, but decided that I was too shaky to get behind the sticks again. Below are some photos, I'm sorry no in flight pics yet.
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