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Pitts Challenger II Plus Ultimate = Ulti pitts

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Pitts Challenger II Plus Ultimate = Ulti pitts

Old 05-04-2015, 07:19 PM
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Default Pitts Challenger II Plus Ultimate = Ulti pitts

So I had a Pitts Challenger II that I could not get off the ground with out the "P" factor kicking my but and U turning into the ground. Played with CG and wing incidence to no success. On the four attempt I ended up with this. The wings, interplane struts and cowl were in tacked. I was able to save this from the fuse. After doing some thinking and wonder why I couldn't fly this bird ( flown many Ultimates and other bipes)I did some math. Whether or not it is correct I came to the conclusion the an Ultimate of the same top wing span was 4" longer, prop plate to rudder post. With a few more inches in the fin and rudder So being a scratch builder out came the paper and a set of .40 size ultimate plans. Measuring and multiplying I came up with a set of plans for the fuse and tail. Here are some pics of what I came up with. She is complete now and has been flown 4 times with smoke and I must say it will do more than I can. So It was crashed and rebuilt but with a few changes. Lots of fun to fly!!!. I wil get some pics of the finished bird.
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Old 05-09-2015, 07:12 PM
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P-factor can really bite you, bin there and done it. But what your pic's show, it look like a good plan, and congratulations on the 4 flights.

Just a bipe lover

Cheers Bob T
Old 05-12-2015, 08:43 AM
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Here she is finished. It is a little pitchy so I check my incidences and found the wings were a little to the positive. Hoping to get her out this week end a see how it has changed. Really look nice with "Smoke on"
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Old 05-12-2015, 05:35 PM
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Looks great, but I have to ask what are your incidences setting's compared to the horizontal thrust line ? Just asking

cheers Bob T
Old 05-13-2015, 06:30 AM
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After the first few flights and knowing it was a bit pitchy, certain that the cg was right. I put the meter back on it. My research discovered that it should have the lower wing and stab at 0 degrees with a -1 to 1.5.
What I found was the lower wing had 1 degree + to the stab and the upper wing had 1.5+ to the stab. They have been corrected to the specs found through research and is waiting on the weather to have a maiden again.
I'm sure the pitchy condition will be gone with what I found. She really does fly well and with the corrections more predictable. If your a bipe lover and have first hand knowledge, what do you think? The ailerons have also been extended to the what you see now, I extended them into the center 2 rib bays and added 2 servos to the top wing, they were driven from the bottom wing with rods.
Old 05-13-2015, 06:33 AM
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-1 to -1.5 was the top wing
Old 05-13-2015, 08:09 AM
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Hi, my experience comes from full size bipe's after WWII Stermans PT-17 and N 3 N's don't remember the # , So when ever I have built a Bipe I have followed what I learned with them assuming the horizontal thrust line is at 0, the horiz/stap +.5 to +1 this allows the plane to fly with the tail hi, lower wing at 0 to +.5 depending on the airfoil, the upper wing at a -1 1/2 to -3 the reason for this is it lets the upper wing stall last that is how I have set up both of my Weeks Specials and they fly great with no bad habits, flying buddy has his Pitts and Eagles set up the same way. It's just the way we do ours and not intended to advise any one to do other than the drawings.

If your bird flies fine I would not mess with it


Cheers Bob T
Old 05-13-2015, 08:51 AM
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Thanks Mr. Bob T
Sounds like I should be in the window of where it needs to be, very close to what you have presented. Thanks for the info and I will let you know how the new maiden turns out.

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