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Folded Aerobird wing in flight today

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Old 12-09-2003, 12:56 AM
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shams42
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Default Folded Aerobird wing in flight today

I folded a reinforced Aerobird wing in flight today. I was probably 75-100 feet high doing loops. I did a loop at full throttle and then gave full down elevator trying to make the plane fly upside down. Of course it didn't work, and the plane picked up a lot of airspeed. I've never seen the plane move so fast. When I've done this before, I've actually had the plane be uncontollable for a few moments doe to excessive airspeed. I didn't think I was at risk for a wing fold, though, since I had reinforced the center section on the wing. I gave it some up elevator to pull out of the inverted dive and the wing folded. The plane fell out of the sky in an uncontrollable spiral and smacked the ground hard. No damage was done to the plane. The wing folded just past the reinforced area.

This plane is very tough. It's taken a tremendous amount of abuse from me over the past several weeks and never missed a beat.

Anyway, this goes to show that reinforced wings CAN fold if you abuse them enough. The wing had taken a few crashes but had no visible creases prior to the incident today.

Matt
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Old 12-12-2003, 09:40 PM
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Default RE: Folded Aerobird wing in flight today

I have never had an undamage wing fold in the air.

How did you reinforce it and why did you reinforce it?
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Old 12-13-2003, 11:55 AM
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Default RE: Folded Aerobird wing in flight today

i believe they come reinforced with a piec of carbonfiber rod in the top to the wing. the one on my firebird xl does
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Old 12-13-2003, 12:48 PM
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Default RE: Folded Aerobird wing in flight today

The Firebird XL is the only one in the line that has that rod. None of the others have any kind of reinforcing rod or plate in them. They are made to flex. If you put a short reinforcement on one, it is likely to fold at the edge of the reinforcement as you create a concentration point for stress.

I have reinforced damaged wings, but then I never use them for any kind of agressive flying or in high winds.
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Old 12-13-2003, 01:31 PM
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Default RE: Folded Aerobird wing in flight today

Aeajr,

I've already thrown out the damaged wing, or I'd take pictures and post them here. But I'll try to describe what I did to reinforce it. I got a pack of bamboo skewers at the grocery store. I took two of them and trimmed them to about 5" in length. I then taped these to the bottom of the wing with packing tape at the leading and trailing edges of the wing. This had the net effect of lifting the entire wing up by about 1/8", but it did not change the angle of attack of the wing.

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Old 12-13-2003, 04:05 PM
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Default RE: Folded Aerobird wing in flight today

I am curious what these skewers were intended to do? Were they taped to the underside of the wing?

When the wing folded, where did if fold? Near the tips? In the center? Perhaps somewhere near the edge of the skewers?

I have heard of wings folding, but it has normally been a wing that was damaged. Someone had tried to fix it with packing tape or the like. I myself have had a few wings fold, but they had already been patched or taped to repair crash damage.

I may not be as agressive a flyer as you, but there is at least one pilot who goes wild with his Aerobird and I am not aware that he has ever folded a wing. So I was interested as to what and how a wing would fold.
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Old 12-13-2003, 05:41 PM
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Default RE: Folded Aerobird wing in flight today

The skewers prevent the wing from folding at the center where they are anchored to the body. The skewers themselves are probably easier to break than the foam of the wing. However, when they are taped to the underside of the wing, they are positioned so that they would have to stretch as well as bend in the case of a wing breakage. They resist this deformation very well. When the skewers are properly taped to the wing, the reinforced section is almost impossible to bend.

The fold happened just past the reinforcement point. The problem with reinforcing the wing in this way is that the aerodynamics of the reinforced section are totally destroyed. Making the skewers longer would result in a stronger wing, but also in a wing that produces less lift. I do not know what the optimal balance point is. I do know that there was no noticable difference flight characteristics after I reinforced the wing.

This wing had been through some tought times but had no visible gouges, holes, or creases in the wing when it folded.

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Old 12-13-2003, 06:12 PM
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Default RE: Folded Aerobird wing in flight today

Note where the fold occured, just past the reinforcement point. A stress concentration point is created and the wing folds there.

If you really want to reinforce the wing, the reinforcement needs to go out almost to the tips. You can use thin clear plastic, of hte type the make hanging displays out of. You need to shape it to the underside or the top of the wing. It needs to resist folding. It is not stretch tat gets the wing, it is a fold point.

Another way to do this is to take a thin wood strip and either tape it to the top of the wing, or cut the wing and embed it in the wing. That is how the T-Hawk does it. Visit this page and you will see what I mean.
http://www.readytoflyfun.com/thawk3chrtf.html

Look for the shot of hte wing reinforcement. If you were to check it out you would see that the reinforcement is flexible, not rigid like the skewers, and it is flat so that pressure is spread across it, not narro like the skewers.

I hope I am making myself clear.

I don't recommend reinforcing a good Aerobird wing, but if you are going to do it, it needs to be done in a certain way or it can actually be the cause of the failure.
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