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tc1917(at)hughes.net
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 Posted: Tue Apr 10, 2007 1:52 pm Post subject: wing bounce |
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flying with the new warp three blade and have something different from the
IVO. Using an E box on a 582 slingshot. Engine is elevated in order to
fold wing. With warp drive prop I have a definate vibration or what I would
rather call a wing bounce on the left wing when I reach about 86 indicated.
Only the left wing. I can see the wing actually go up and down, occilate
and when I slow the engine, it quits. I can make it do it climbing,
straight flight and turning. If I am descending, without the engine imput,
it is okay past 90. My thought is buffet on the wing cause the blade is
coming up on that side. Wonder if I put about 3/4 to 1" spacer between the
box and the blade, maybe that would be enough. Going to try it when the
bolts come in. Another slingshot is just about that far with its big spacer
with a C box. No problem there. What say? Am I on the right track. Dont
want to space it very much cause that move weight back and I cant afford
that. Ted Cowan, Alabama
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Tue Apr 10, 2007 2:15 pm Post subject: wing bounce |
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Ted C:
Off the top of my head I do not thing the prop is creating wing
bounce/occilation. If it was, the IVO or any prop would likely cause
the same problem.
Ronny Collins had a bad vibration problem with his SS. After a lot of
investigation we found that the rib stitching the builder used,
instead of recommended fabric rivets, had pulled loose back in the
inboard wing areas around the front of the prop. I flew on Ronny and
saw the fabric ballooning up. He fixed the fabric and the problem
went away.
Be sure you fabric is not pulling up back near the prop on top of the
wing.
I was not hesitate to fly the SS with a 4" extension on the prop. Do
not think it will create an aft CG problem. I'm not telling you it is
alright to do that, but if it were my airplane, I'd try it.
john h
mkIII
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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JetPilot
Joined: 10 Jan 2006
Posts: 1246
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| Posted: Tue Apr 10, 2007 3:14 pm Post subject: Re: wing bounce |
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The prop is so close to the CG on a Kolb moving it back even 4 inches with a spacer is a non issue. Moving the prop back several would have such miniscule effect on CG that it would never make a bit of difference in the way it flys, stalls, or anything else.
JettPilot
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"NO FEAR" - If you have no fear you did not go as fast as you could have !!!
Kolb MK-III Xtra, 912-S |
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jb92563
Joined: 23 Mar 2007
Posts: 314
Location: Southern California
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| Posted: Wed Apr 11, 2007 6:48 am Post subject: Re: wing bounce |
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Sounds like a harmonic vibration from the engine and/or prop.
The way to stop it is to stiffen the wing rigidity or change the engine mounting by perhaps softening the engine/airframe interface. Also check prop balance.
Perhaps the rubber lord mounts are getting old and hard and need replacement?
Its possible that the proximity of the prop to the wing has an effect.
Make any one of those changes and it should change your bounce speed or perhaps eliminate it altogether.
I would definately check the integrity of the wing and all attach points for wear though as a first step......that bounce can't be good for it and if things get looser as a result you could get wing flutter, which is a life threatening event.....make sure your chute is in good working order.
Ray
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Ray
Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider
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