wing spar wiggle giggle

[N74DV]

on preflight today I grabbed the ends of the wings and pushed up and down on them with a little force and as I wiggled them I sighted down the leading edge and I noticed that they flex and sort of make a wet noodle "s" shape. Not much but noticeable. Both wings did it the same amount.

The ends of the lift struts don't give at all and are secure... it's the wing spar itself that has a little give.

I'm assuming this is due to the long span and wood spars. They shouldn't be super rigid should they? Should I be concerned about this?

[VictorBravo]

Re: wing spar wiggle giggle

You are listening for noises and cracked wood on that kind of test. The first thing you look/listen/FEEL for is metallic clunking, which would show worn steel fittings (been there).

Once that test is passed, then when it is completely quiet and calm, lift several times again where you are listening and feeling for creaking, snapping, and groaning sounds coming from the wood spars themselves. If there is any such noise you have to look further.

While you are doing these tests, have someone with very good hearing listen through all the inspection plate holes, which have to be all open.

If you find something suspicious, then track down where the sound is coming from, and have someone look in with a flashlight and mirror while you are loading the wings.

[N96337]

Re: wing spar wiggle giggle

If they don't give, things tend to break... so from what I've read of your situation, I'd say it's ok... like Bill says...listen for a clunk, crack, or any sign of something moving and then stopping...then I'd be worried. The wing will always flex a bit, that's why your leading edges are in more than one piece.
When we pulled my Tcraft apart, the old glue in the spars had deteriorated and for the most part wasn't holding anything, and you could hear things moving inside there when you'd do a shake like you're talking about. Now I have NEW wood and not a whole bunch of scarfed splices and pieces.
JH

[Forrest Barber]

Re: wing spar wiggle giggle

Impart a wee twist out there too and listen for twanging of things. It is indeed an artform. Remember if you pick up hard on the outer tips of the spars , you have put more strain on the spars than you will ever get in flight... come to a fly-in sometime, we do a demonstration of this part of the pre-flight.

[Robert Lees]

Re: wing spar wiggle giggle

Also, do a fore & aft wiggle occasionally. It might indicate elongation of the holes in the spar fittments at the fuselage.

[flyguy]

Re: wing spar wiggle giggle

To directly answer your question: Yes you can set up a wavy motion in the wing by wiggling the tip up and down. Much the same as you would get if you did the same with a long flat board with one end supported by the ground. Otherwise all the stuff that you don't want to see or hear is well listed in the previous replies.
DC
Oh yeah, I really enjoyed your helicam video. I have just acquired a new Media center computer and it really played fine. Like the music also. Good luck on the business.

[N74DV]

Re: wing spar wiggle giggle

we opened up all the inspection hole and did the lift twist test. My dad lifted up and twisted while I listened. Sounded fine with the exception of a couple very slight cracking sounds. it wasn't a crunch nor was it long lasting, just a coupel small crackly sounds that only lasted for an instant.

Is it supposed to be completely silent when performing this test or will you hear some very slight noises?

[Forrest Barber]

Re: wing spar wiggle giggle

RE: the "crackly" sounds. When a lot of ships are rebuilt, some mechanics forget that the leading edge is attached with "slots" in them for the screws to go through into the ribs so they canmove in relation to the one next to it. This buckling sound may be what you are hearing.
Yes they have to move in and out under the fabric a wee bit with change in loads or temperature. Another story sometime would be the all Black ship we built one time , We had to go back inside and beef up the leading edge with little stringers between the ribs to get it back out into place on a hot day.... prevents "tin-canning"

[alwaysoar]

Re: wing spar wiggle giggle

I have a little tin-canning in the leading edge of my left wing. IA noticed it at annual, so I went to the spot and held the leading edge down with my pinky. I suppose I could nail it through the fabric, but depending on temps, it may not tin can so I let it go. The bigger concern frequently mentioned on the forum is clunk-clunking of bolts moving in elongated holes. Scares the hell out of you! I replaced the aft adjustment screws and that took care of that. I've put slippage marks all over the wing structure so I can make easy checks. So far no slippage. Lots of wear in 60-year-old airplanes, some may be serious, some may not. Always be alert.

Ed@BTV VT
TF 527

[N96337]

Re: wing spar wiggle giggle

RE: the "crackly" sounds. When a lot of ships are rebuilt, some mechanics forget that the leading edge is attached with "slots" in them for the screws to go through into the ribs so they canmove in relation to the one next to it. This buckling sound may be what you are hearing.
Yes they have to move in and out under the fabric a wee bit with change in loads or temperature. Another story sometime would be the all Black ship we built one time , We had to go back inside and beef up the leading edge with little stringers between the ribs to get it back out into palce on a hot day....

Or the people that try a one piece leading edge on the wing... talk about a mess!!
JH