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Stiff Ailerons

Damage

Mike Im not sure he mentioned it to them. The tail was completely replaced. Every inch of the fuse was examined for any hidden damage. The wings were not damaged in the hangar collapse. You can go back to my spar repair thread to see exacly what we did. Only the bottom skin was removed and it went back on perfectly. The wings are straight and not warped. But at this point anything is possible. Maybe if we all brainstorm long enough a cause and solution will be discovered. Im glad people show an interest in helping us out and not just talking trash.
 
Lightening holes

Arlie I went back and looked at your lightening holes and they are indeed big. Do they go all the way forward to the spar attach point for the an3? If so that could be the weak point. It is also be possible that the increase in speed is actually creating drag inside the aileron. Maybe it is ballooning instead of warping like was suggested. I believe that if wind speed is doubled then the force it creates on an object goes up seven fold. That is why cat 4-5 hurricanes although they are not much greater in wind speed compared to the cat 1-3 are much more devastating!
 
Jstov said:
Arlie I went back and looked at your lightening holes and they are indeed big. Do they go all the way forward to the spar attach point for the an3? If so that could be the weak point. It is also be possible that the increase in speed is actually creating drag inside the aileron. Maybe it is ballooning instead of warping like was suggested. I believe that if wind speed is doubled then the force it creates on an object goes up seven fold. That is why cat 4-5 hurricanes although they are not much greater in wind speed compared to the cat 1-3 are much more devastating!
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Since the ailerons are "hollow" and have no internal ribs the only parts preventing twist are the end ribs.

Removing the inner portion of the spar attach flange with an oversize access hole would certainly make the ailerons much more flexible and act in a unique way from all other RV-4s. Your test pilot's description of warped ailerons makes sense.

It probable wouldn't be too difficult to just replace the end ribs, but new ailerons would be better. :)
 
acam37 said:
Im glad people show an interest in helping us out and not just talking trash.
Click to expand...

This is why so many of us are on VAF and don't bother with other aviation forums. (try the AOPA Red Board. It's fun if you like Jerry Springer.)

I'm sorry you're having this problem, but it is a very interesting discussion that I'm sure lots of us will learn from. I now have more things to think about when I reassemble my rebuilt airplane.
 
Ailerons

Arlie I did get my aileron in from vans and was pleasantly surprised to find they are pre drilled so if you go that route it will be an easy assembly! You could also order the QB ailerons and they come assembled.
 
Thanks for the info. I'm not going to mess with the plane until after the holidays. I'm exhausted and need a break.
 
A temp plate on the end ribs would plug holes and stiffen the aileron. Could be done with blind rivets. If you are considering new end ribs or new ailerons anyway then you have nothing to lose. Say 0.032". That's what I would do. You would confirm if that is the problem or not.

I would say certainly it is a hinge moment issue i.e. the trailing edge shape of the aileron, either the shape it currently has is bad or it is deforming in flight. If all of the mechanical bits check out that's all it can be, that or the aileron gap seal and I don't think you snagged that.

I helped a guy fix his hummel bird. The elevator TE was rounded off and the airplane was horrible to fly. He just figured all hummels were like that. Maybe they are! But with a few mods it was a different airplane. We increased the tail area and the elevator hinge moment to give him higher forces. Sounds like you need lower forces.
 
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Aileron part numbers

Here are the part numbers for the ailerons if you decide to go that route. The slow build does come pre-drilled so it should be easy. The quick build parts actually come assembled so that is your quickest option. The only parts that I can see that are missing are the aileron hinges but you can use your old ones. It is the same part numbers as the -8 as they share the same ailerons.

QP8-8A aileron right or left: Parts only pre-drilled
Q8-8A aileron right or left: quick build option comes assembled

If my memory serves me correctly the quick build is just over $400 and the parts only is just under $200.
 
Today I was sitting in my hangar looking at my ailerons, asking the question "what would cause the aileron to balloon and flex in flight?" And then it dawned on me, The Stiffeners. So I went and took a closer look. What did I find? The stiffeners terminate approx. 3" from the trailing edge, so this could explain a lot. I went ahead and squeezed the trailing edge radius from 3/16" down to 1/8" which tightened the skin a little and straightened it up a bunch. Justin took it up and voila. He said that made a 100% difference in the stick forces. I am still going to build a new set of ailerons, but at least I think I finally solved this mystery.
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Another thought

Alternatively, you could drill your current skins off, remove and replace just the stiffeners, which can be easily made from bent sheet stock, and put it all back together. The little stiffeners require correct tapering and orientation, as they actually overlap at the trailing edge. Some people add a little proseal to the last inch to help prevent cracking of the skin, and keeping the AFT most rivet away from the radius are which is tricky to buck.
 
Kudos!

Arlie-

I know this puzzler was frustrating; lots of us were silently watching you work it.

Congrats on sticking to it!
 
acam37 said:
Today I was sitting in my hangar looking at my ailerons, asking the question "what would cause the aileron to balloon and flex in flight?" And then it dawned on me, The Stiffeners. So I went and took a closer look. What did I find? The stiffeners terminate approx. 3" from the trailing edge, so this could explain a lot. I went ahead and squeezed the trailing edge radius from 3/16" down to 1/8" which tightened the skin a little and straightened it up a bunch. Justin took it up and voila. He said that made a 100% difference in the stick forces. I am still going to build a new set of ailerons, but at least I think I finally solved this mystery.
5266396E-1065-4C8B-8DE8-8944A86C25BB_zpskrymci1t.jpg
[/URL][/IMG]
Click to expand...

It is amazing and non intuitive how much the trailing edge shape changes the flying qualities. I am sure some airplanes, particularly very small ones like the hummel bird, have been lost because of this.
 
Buy a set of plans, it is your plane, YOU are responsible for it!

Hello Arlie

Congratulation for you buying an RV-4 and rebuilding them.

It is not the first time here on VAF, that someone bought a plane and having difficulties with it. You found with the help of VAF and your testpilot the root cause.

I just can highly recommend to change all the important parts, so that they exactly are looking like the plans from Vans describe them. It is now your plane, you are responsible for it!

Flying an RV is one part, the community around another ... both are wonderfull! You are at the right place here on VAF!

Btw, there are not so many RV-4 crashes, but those that happend are often loaded to heavy, behind the rear CG limit and doing aerobatics! It is a cross country plane for two, but only a single aerobat machine.

Take care and enjoy!
 
acam37 said:
Today I was sitting in my hangar looking at my ailerons, asking the question "what would cause the aileron to balloon and flex in flight?" And then it dawned on me, The Stiffeners. So I went and took a closer look. What did I find? The stiffeners terminate approx. 3" from the trailing edge,
Click to expand...

Actually, the rivets terminate at that point, the actual stiffener continues a bit more toward the TE.
 
Maybe they do, maybe they don't...

Mike S said:
Actually, the rivets terminate at that point, the actual stiffener continues a bit more toward the TE.
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Maybe, maybe not! With the flex that Arlie was describing, I bet they don't go as far back as they SHOULD. :eek:

I looked at mine, the last rivet is about an inch from the TE. The stiffener goes back another .75" IIRC.
 
Actually, the rivets terminate at that point, the actual stiffener continues a bit more toward the TE.
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Mike, I don't think so in this case. As I described earlier, you can actually manipulate the entire trailing edge by hand. Even where the stiffeners are "supposed to be" in either case, it ain't right. I just don't know why I didn't notice this earlier?
 
Gregg Brightwell said:
Maybe, maybe not! With the flex that Arlie was describing, I bet they don't go as far back as they SHOULD. :eek:
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Gregg------I have no idea how far the stiffeners are designed to go, (notice I used the term "a bit" -----carefully chosen word to give me wiggle room;) ) I was just pointing out that the end of the stiffener and the location of the rivet are not necessarily relative.

Gonna take x-ray vision or a can opener to tell for sure.
 
Mike S said:
Gonna take x-ray vision or a can opener to tell for sure.
Click to expand...

Not necessarily...

It may be possible to do it a different way. If you can find a chest or walk-in freezer big enough, freeze the aileron. Then take it out and apply a warm rag a couple inches away from the stiffener on both sides (but don't cover it) just enough to warm the skin. Then breathe on the area. You may be able to see the outline of the stiffener where frost forms from your breath due to the larger thermal mass of the stiffener holding a lower temperature for longer than the thin skin.

Just a thought.
 
It doesn't really matter how long the stiffeners are
if there is no rivet near the aft end.
The stiffener effectively ends at the last rivet.
 
So, the moral of the story is when it comes to critical to flight systems, build to plans. This could have been a lot worse than just heavy ailerons. It could possibly lead to flutter at higher speeds. I am also an avid R/C guy and I have lost several planes to flutter. When it happens, it happens quick. And 90% of the time it's catastophic.
 
Good catch Arlie, another question...

Have you checked rudder and elevators for similar "build technique"?

They, of course are built very similar....

So glad you found this. You have a gorgeous airplane.

Gregg
 
Gregg, fortunately the entire tail section was replaced due to the hangar collapse damage. We got lucky and found a completed tail that was going on a Rocket. The skins are .020 and was built very well. So once I replace the ailerons all flight control surfaces will be new.
 
Awesome Arlie...

... That's good news. I've delivered a couple airplanes to Nac over the last several years. I want to make it a point to come see your airplane.

It's possible that I have an upcoming trip to Houston. I'll give you a heads up if I do.

Take care,

GB
 
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