Trailing edge sraightness: what's the tolerance range?

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cattflight

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Joined
Dec 31, 2010
Messages
47
Location
Spokane, WA
Hi Folks,
Been many months since I visited HBA as I have been happily working away on my Glastar project. I purchased an in-progress kit from the original builder so I have been doing my best to pick up where he left off on various elements. On the ailerons in particular, he had labeled the spar and rib locations and pre-drilled all the rib rivet holes, including matching up the trailing edge joggles and match-drilling through the factory holes into the lower skin. Everything lines up end-to-end and the trailing edges match, but there is a discernable "wave" down the length of the trailing edge now that it is riveted. Not to the point where you can see it from a few feet away, but when sighting down the line, it's noticeable. (+/- 3/32" over a foot of length in one section). I am not concerned about the construction integrity. It's otherwise square, plumb, untwisted, etc.

So here's my question: what's the tolerance for that kind of wave for the ailerons and how will it manifest itself in flying qualities? (typical cruise is 130-135 KTAS) Part of me wants to just order replacement parts and rebuild the ailerons purely from a pride standpoint. The other part of me thinks, once I am in the air, with the exception of a perfectly still day, I'll be wiggling the ailerons for straight n' level flight anyway! :ponder:

Thoughts? I'll see if I can gather some photos.
 

Head in the clouds

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Joined
Mar 11, 2012
Messages
1,983
Location
Gold Coast, East Coast of Australia
Hi Folks,
Been many months since I visited HBA as I have been happily working away on my Glastar project. I purchased an in-progress kit from the original builder so I have been doing my best to pick up where he left off on various elements. On the ailerons in particular, he had labeled the spar and rib locations and pre-drilled all the rib rivet holes, including matching up the trailing edge joggles and match-drilling through the factory holes into the lower skin. Everything lines up end-to-end and the trailing edges match, but there is a discernable "wave" down the length of the trailing edge now that it is riveted. Not to the point where you can see it from a few feet away, but when sighting down the line, it's noticeable. (+/- 3/32" over a foot of length in one section). I am not concerned about the construction integrity. It's otherwise square, plumb, untwisted, etc.

So here's my question: what's the tolerance for that kind of wave for the ailerons and how will it manifest itself in flying qualities? (typical cruise is 130-135 KTAS) Part of me wants to just order replacement parts and rebuild the ailerons purely from a pride standpoint. The other part of me thinks, once I am in the air, with the exception of a perfectly still day, I'll be wiggling the ailerons for straight n' level flight anyway! :ponder:

Thoughts? I'll see if I can gather some photos.
A couple of years ago I sold my old C172 which was a 1960 'A' model, and a great little plane I might add.

It had had a very arduous life, it is one of the first of the BP registered craft, which was registered by the Bush Pilots Assoc. those planes lived a hard life in the bush delivering mail, groceries and all stock and station needs. After twenty or so years of that it went to a flying school and had loads of knocks and several serious crashes, it was written off several times, and rebuilt one time more than the write-offs...

The only original remaining parts of the wings was the port side aileron and flap. So on the starboard side are two perfect trailing edges and the port side has more dents, knocks, ripples, tears and buckles than you can point a stick at and you could never tell by the aircraft's inflight handling. And as far as pride goes... well the port wing has history!
 

TFF

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Joined
Apr 28, 2010
Messages
15,419
Location
Memphis, TN
It should fly fine. At most it will have a little more trim drag and possibly a fixed trim tab to keep it all level. Most planes have deviations of some sort.
 

Battson

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Joined
Jan 30, 2012
Messages
610
Location
New Zealand
Perfection is the enemy of completion.
You can fix some mightly ugly problems with rigging, and yours is the kind of problem that only you will ever notice...
 

autoreply

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Joined
Jul 7, 2009
Messages
10,765
Location
Rotterdam, Netherlands
How are the ailerons hinged? If it's two hinges, no worries at all, otherwise I'd check if it can freely rotate under G-load (put a guy under the tip and lift it, while you test aileron).
 

Dan Thomas

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Joined
Sep 17, 2008
Messages
6,201
A distorted aileron can cause wing heaviness. A little wave downward can act like a small trim tab and lift the aileron, making the airplane want to roll to that side.

The Cessna uses those corrugated skins on their ailerons and flaps and elevators. People preflighting the airplanes can get rough with them, either whacking the aileron up or down or even pinching it, and the top or bottom skin can get pushed inward a bit. That will make the airplane want to roll. I had a nifty little tool for working those out; it was easier and better than rerigging the wing.

Dan
 
Joined
Dec 1, 2012
Messages
10
Location
Holland
It has not so much to do with the speed, more with the airfoil that is used. A NACA 4415 is a "forgiving" airfoil but the GA(W)-2 airfoil less. For the correct answer check specialist.
 

dirtstrip

Well-Known Member
Joined
Dec 18, 2008
Messages
64
Location
Conde, SD. on the farm
Hi Folks,
Been many months since I visited HBA as I have been happily working away on my Glastar project. I purchased an in-progress kit from the original builder.... Everything lines up end-to-end and the trailing edges match, but there is a discernable "wave" down the length of the trailing edge now that it is riveted. Not to the point where you can see it from a few feet away, but when sighting down the line, it's noticeable. (+/- 3/32" over a foot of length in one section). I am not concerned about the construction integrity. It's otherwise square, plumb, untwisted, etc.

So here's my question: what's the tolerance for that kind of wave for the ailerons and how will it manifest itself in flying qualities? (typical cruise is 130-135 KTAS)


Thoughts? I'll see if I can gather some photos.

I have been away for more than a few months myself. I saw your question and thought I could help. I have my Tundra flying and it is close to the same cruise speeds as yours. The ailerons are alway self centering in flight. If one is down at the back slightly the other will just move up canceling it out and leveling again. You might find that the stick will not be quite centered during level flight. If that is an issue it can be adjusted to be centered again. A little imperfection on the trailing edge will not cause the plane to roll. If the plane has a slight roll then likely the washout needs adjusting on one wing or other to make the same lift on each wing. If the plane flies in a crab, likely there is more drag on one side or the other and the culprit is usually that one flap is a little lower than the the other causing more drag and a crab. That can be easily adjusted out.

If you look at most Cessnas, they are worse than you describe.
Have fun and fly safe
 
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