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Old Apr 29, 2015, 09:42 PM
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Question
CG for Sterling PT-17, 64" Wing Span, BARN FIND

Just got this old Sterling PT-17 from one of our local flyers who has had it hanging in his barn for the past 30 years. He is hoping we can get it to fly again,
The engine is already running great, I have replaced the old butterscotch 4 wire kraft servos. The tail feathers were warped but the covering shrunk tight and is so far keeping them straight.
What I am looking for now is if someone has the plans and can give me the correct CG location.
If she survives the test hop we will strip her down and recover her in the yellow and blue color scheme.
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Old Apr 30, 2015, 07:16 AM
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# Scale is a way of life
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Nice find,,,

on the plans
http://www.outerzone.co.uk/plan_details.asp?ID=3704

good luck
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Old Apr 30, 2015, 09:40 AM
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If you get really turned on, Robart made functional oleos for that model. You would have to tear open the belly, and modify a bit, but it does work. I did mine.
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Old Apr 30, 2015, 10:37 AM
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Again, Scale comes through, Thanks !
Great looking Stearman Les
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Old Apr 30, 2015, 11:14 AM
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Somebody will have the plan CG location, but actual location varies. A little nose heavy with tank empty is good advice for the maiden flight. Good tail-dragger technique is needed, be ready for pitch-up after lift off. A little right aileron up-trim and a little right rudder trim may help takeoff. Some up-elevator helps keep tail on ground for steering during start of takeoff, then let tail rise and steer with rudder during takeoff. Keep climb gradual at around 3/4 throttle. Forgive me if you already know all this.
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Old Apr 30, 2015, 11:51 AM
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Any advice it welcomed.
All the flyers here want the re-maiden to go well.
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Old Apr 30, 2015, 03:21 PM
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Gva: Thanks. Still got it hanging in my garage.

Got me to thinking, a lot. The reason I went to Robart for wheels, was that the stock Sterling were soooooo springy, I never knew which way the plane was going to go when I began to taxi for take off, and once it landed, the same was true. Hated it. Robart solved that problem.

Les
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Old Apr 30, 2015, 05:40 PM
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# Scale is a way of life
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My Royal Stearman was the same way,, had to land it like an at-6,, a little power on wheel landing,, if you tried a flair landing it was 1 in 10 that stuck,, the other 9 were bouncy

happy to help,,
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Old May 06, 2015, 05:56 AM
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Man oh Man ! That is nice ! It just has that 'look' of an Antique...I can't imagine recovering it, unless it's absolutely necessary......
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Old May 07, 2015, 08:59 AM
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I have this same question EXACTLY. I bought a 65" PT-17 at Perry this year. I'm unsure which kit it is but I'm ready to fly it. Got a radio in it, put an OS 91 4 stroke on it and now I need a CG for it. It balances right now 4.5" aft of the top wing leading edge. I'm thinking I need to move it forward to about 2.5", about 25% of the top wing chord. Is that at least a safe starting point? This plane appears to be several years old but was quite well built and has never been flown. I'm going to test run the motor today and fly it tomorrow if all goes well. Looking forward to flying it at our warbird event in a few weeks. Any help on this CG location will be appreciated. Thanks.

Rick H.
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Old May 07, 2015, 09:05 AM
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Les if you don't mind, which radial is that you have around that OS? It's one of the last things I need to finish this and that installation is very nice. I'm going to wait until I know it flies before getting one but will need to make a decision soon on it. Thanks.

Rick H.
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Old May 07, 2015, 09:06 AM
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# Scale is a way of life
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Again, the plan shows it,, it's more like 55% at the top wing,, 25% will be very nose heavy

http://www.outerzone.co.uk/download_...an.asp?ID=3704

good luck
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Last edited by scale_only; May 07, 2015 at 09:13 AM.
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Old May 07, 2015, 09:33 AM
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I took a bunch of Williams Brothers parts, and fabricated to fit. Cost more that it would have to put a two stroke engine in the plane:-)))))) But this looked a lot better.

Les
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Old May 07, 2015, 03:28 PM
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Guys- for most straight wing bipes-measure from the LEADING edge of the top wing, to the TRAILING of the bottom one.- Fuselage level, vertical lines drawn to the surface of the work bench... Treat that total length as your wing "Chord" and then 25% will be a nose heavy 'safe' starting point.
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Old May 07, 2015, 03:36 PM
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I also like that antique look on this plane but the covering is so brittle, I have already poked a hole in it. Plans are to test fly it this weekend.
This plane did come with a large piece of lead on the firewall but I still wanted to confirm it was enough.
What I have done was look at the Great Planes PT-17 with a 71" wing span and found their CG to be 5 1/2" back from the leading edge of the top wing.
I decided to look at 5 1/4" for this one and she was spot on with an empty tank.
I did add 4 oz to the firewall for good measure.
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