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Old Jun 24, 2005, 11:46 PM
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Stuttgart, Germany
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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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Old Jun 25, 2005, 12:07 AM
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ecologito's Avatar
near UNC Charlotte, NC
Joined May 2003
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That is a really good looking plane, that is awesome, great job...
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Old Jun 25, 2005, 12:15 AM
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Joined Oct 2004
789 Posts
Very nice plane!!! Do you have design plans available for others? Or did you use someone's plans? Of course we are looking forward to see flight pictures and video

Have fun flying it!
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Old Jun 25, 2005, 12:16 AM
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JayJay76's Avatar
Stuttgart, Germany
Joined Oct 2004
944 Posts
ecologito,
Thanks for the compliment! So many people buy kits, and when you figure in the time to make a model yourself, kits are really atractive. But the one thing that will never come installed with an ARF is the pride of owning and flying an aircraft that you built with your own hands. And the knowledge that its only about $8 worth of materials for the airframe is a bonus. I consider building to be my hobby, and the flying is only justification for the time spent.

J
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Old Jun 25, 2005, 12:18 AM
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Stuttgart, Germany
Joined Oct 2004
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Quote:
Originally Posted by MadDuc
Very nice plane!!! Do you have design plans available for others? Or did you use someone's plans? Of course we are looking forward to see flight pictures and video

Have fun flying it!
I used Chris3D's micro pitts plan, layed out in photoshop to fit on 11x17 paper. The only changes were omitting the ribs and simplifying the landing gear. I also have a micro pitts of balsa that I fly with my RFFS-100 setup.

J
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Old Jun 25, 2005, 12:39 AM
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Thank you very much, it's a very nice plane indeed. I just found the plans and must say I have not seen such detailed FREE building plans before.

Thumbs up for Chris as well.
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Old Jun 25, 2005, 09:48 AM
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Stuttgart, Germany
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Quote:
Originally Posted by MadDuc
I have not seen such detailed FREE building plans before.
Be sure to pick up his micro moth plan as well, they are both excellent models at any scale. I hope he will release more models of this type soon, I would like something like a spitfire.

J
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Old Jun 25, 2005, 03:38 PM
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Stuttgart, Germany
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im off to the field, I'll try to get some flight photos but it might be difficult to hold the camera while im flying!
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Old Jun 25, 2005, 11:10 PM
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Stuttgart, Germany
Joined Oct 2004
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Quote:
Originally Posted by jlepinske
im off to the field, I'll try to get some flight photos but it might be difficult to hold the camera while im flying!
okay didnt get to go to the park, went to the taste of chicago instead. i will fly tomorrow morning before the pride parade starts and the neighborhood becomes a zoo.
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Old Jun 26, 2005, 12:31 PM
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Lincoln, NE
Joined Dec 2003
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That is one of the best looking foamies I've seen in quite a while..great job!
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Old Jun 26, 2005, 02:45 PM
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Stuttgart, Germany
Joined Oct 2004
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Quote:
Originally Posted by shakysticks
That is one of the best looking foamies I've seen in quite a while..great job!
Thanks! Its only my second attempt at building with foam. I usually scratch build with balsa and tissue, but the anxiety of wrecking all that hard work keeps me from flying. Foam lets me build and fly cheap, quick, and carefree! My other flyable model is a profile bird dog ala TOG, and I have a 25" micro moth, a 28" depron version of fiddler's green GeeBee R1, and a parkflyer pete on the board.

J
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Old Jun 26, 2005, 03:27 PM
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Lincoln, NE
Joined Dec 2003
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I would like to see that GeeBee - I've thought about doing that myself. I really enjoy this "nicer" style of foamy construction. I'm not much into profile planes, although I did build a pete and it flew great.
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Old Jun 26, 2005, 06:39 PM
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Stuttgart, Germany
Joined Oct 2004
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Went flying, disaster averted........

Hey fellas,

I took my bird dog and 5 fresh packs out to the park, did a quick pre-flight and launched. I took it up to safe altitude and immediately noticed that something wasn't right. Either the wind was playing tricks or something was very wrong! It turned left sluggishly, but wouldnt turn right at all! The pre flight showed the rudder moving okay, but under flight loads it would not deflect to the right. I was trying to bring it around I lost it, augering in from 30' tearing the nose out and trashing the landing gear. Looking over the wreckage I found that some foamed gorilla glue had crept into the rudder hinge, and only by flexing of foam was there any deflection. I was fuming because we had just got there and now I had nothing to fly. My wife was very consoling, and suggested I run home and grab the Pitts Special. Angrily I walked home and retrieved it, and by the time I reached the park again, I was over the bird dog, and excited to fly. I pre-flighted her (thoroughly this time) and went out to the middle of the field to launch. One more radio check and my elevator stopped responding!! I was really disappointed that I wasnt going to get to fly today, and upon inspection i discovered a servo wire had become disconnected from the receiver board, it failed right above the solder joint. I was packing it up and really steeming about the whole mess. I kept thinking, 'why wasn't it the rudder servo that failed? I could do without the rudder, its only mixed 15% to the ailerons anyway.' HEY! WAIT A MINUTE! what if I plugged the elevator servo into the rudder port, and slaved rudder to elevator? Then when I applied up elevator, the rudder would deflect (which was now actuating the elevator) And so without any tools, I was able to switch the plugs, program the strange mix into my trusty Futaba 7CAP, and BAM! I had correct elevator! Even the elevator dual rates were functional! I knew with a lot of side area I would be fighting the wind vaning effect without rudder, but I had solid bank-and-yank control! I launched and immediately got a feel for this type of flying (this is my first aileron model, and only my second time flying it) The first few laps were hairy, I had the ailerons at high rates, but it still felt like there was little response until I applied full stick, then it was twitchy. I landed it and adjusted the exponential from -50 to -15, and relaunched. Immediately it felt better. I could now make nice shallow turns without losing any altitude, and could bank it over and pull back for a very sharp turn. I didnt want to be too daring with my hokey makeshift mixing, but couldnt resist a loop! It stalled at the top in the wind and only pulled out at the bottom about 2' above the grass WHEW! almost dumped it! After the throttle started to sag, I landed for a new pack and noticed that the pack was puffed up a little and quite hot. I propped down to an 8x4.3 and launched again. This time everything was smooth, and I was able to use a little less throttle. I think at full throttle, the 9x4 prop was pulling more amps than the pack could sustain, and the voltage was sagging, reducing thrust output, and the overload caused the pack to swell. After running another pack the battery was quite hot but not swollen, leading me to think that I need to re-wind my GBx double. it currently has 9 turns of double strand 26ga wire, and using my cheapo E-tec 1200mAh classic 2 cell lipos, it seems to be pulling too much current for these packs. any suggestions? maybe I need to make the jump to 3 cell packs, but that means a new charger, and my brushless speed controller is only rated for 10amp service. The plane weighs 11oz with the current setup. Overall, the plane flew great, needing no trimming to transition from pretty, slow flybys to high speed passes and pylon style turns. What a great design, very impressive looking in the air and a real pussycat to fly at low throttle, but handles like a racer at full throttle. And wouldn't it figure I forgot the camera and couldn't get a decent shot with my cell phone. I think I'll head back to the field tomorrow.

J
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Last edited by JayJay76; Jun 26, 2005 at 06:55 PM. Reason: spelling
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Old Jun 26, 2005, 09:24 PM
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Stuttgart, Germany
Joined Oct 2004
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my flying field is right next to lake shore drive just behind the diversey harbor driving range. It was distracting me looking at the people slowing on LSD to watch me fly. Strangely, not a single person in the park came over or even acknowledged my activities. I love that. Nothing makes me nervous like an audience.

J
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Old Jun 27, 2005, 10:34 AM
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Stuttgart, Germany
Joined Oct 2004
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I think i'm going to add ailerons to the upper wing to increase roll authority. Its gentle right now which is great for learning but I want someaerobatic capability. Dual rates will make both possible. Any potential pitfalls in setting up linked upper and lower ailerons on a staggered wing biplane? Input appreciated.

Thanks,
J
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