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Richard Pike
Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee
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 Posted: Wed Mar 31, 2010 9:37 am Post subject: Reinforcing the tip rib |
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Enclosed are some pictures I took this morning of the tip rib of the damaged FSII wing. Between the original wings and the donor wings, 3 out of 4 of the tip ribs were damaged in this same fashion. (One wing was destroyed, so maybe we shouldn't count that one)
You are looking at the top of the wing, notice how the thin aluminum web and 5/16" tube buckles in between the angles - that is consistent, and I think a weak spot. The aluminum angles along the top and bottom of the rib transmit the overload into that unreinforced area and it buckles under the load.
What I will do before I close these wings up is add additional angles to attach to the front and rear upper angles and which tie directly into the main spar, I expect the spar can handle the torque load, because even on the destroyed wing, the main spar was undamaged.
When I get to that point, will add more pictures.
Richard Pike
MKIII N420P (420ldPoops)
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williamtsullivan(at)att.n
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| Posted: Wed Mar 31, 2010 10:52 am Post subject: Reinforcing the tip rib |
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Richard- The damage to the tip rib looks like crash damage, and not wear and tear. Are you sure that reinforcing it would be worthwhile? If it was hit again, wouldn't a reinforcement only transfer the damage to a more expensive part? Also, what keeps the wires from moving around and chafing inside the main spar?
Bill Sullivan
Windsor Locks, Ct.
FS 447
[quote][b]
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frank.goodnight(at)att.ne
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| Posted: Wed Mar 31, 2010 2:38 pm Post subject: Reinforcing the tip rib |
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Hi Richard,
The pictures could have been a snapshot of my wing tip a couple of weeks ago. The damage is almost
identical. In my case it was caused by a rather hard ground loop, where the rear of the wing tip and the
aleron hit and was drug along the ground.Not because of any weakness ,just pilot error.fwiw.
Frank Goodnight
Firestar 2
Brownsville TX
From: Richard Pike <richard(at)bcchapel.org>
To: kolb-list(at)matronics.com
Sent: Wed, March 31, 2010 12:37:15 PM
Subject: Reinforcing the tip rib
--> Kolb-List message posted by: "Richard Pike" <richard(at)bcchapel.org (richard(at)bcchapel.org)>
Enclosed are some pictures I took this morning of the tip rib of the damaged FSII wing. Between the original wings and the donor wings, 3 out of 4 of the tip ribs were damaged in this same fashion. (One wing was destroyed, so maybe we shouldn't count that one)
You are looking at the top of the wing, notice how the thin aluminum web and 5/16" tube buckles in between the angles - that is consistent, and I think a weak spot. The aluminum angles along the top and bottom of the rib transmit the overload into that unreinforced area and it buckles under the load.
What I will do before I close these wings up is add additional angles to attach to the front and rear upper angles and which tie directly into the main spar, I expect the spar can handle the torque load, because even on the
[img]cid:1270074850909(at)dclient.mail.yahoo.com[/img]
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Richard Pike
Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee
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| Posted: Wed Mar 31, 2010 5:11 pm Post subject: Re: Reinforcing the tip rib |
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I guess it depends on what each persons definition of weakness is. IMO, dragging a wingtip and aileron ought to result in damage to the aileron and the back corner of the wingtip at the trailing edge, not bend the tip rib. (Because if you bend the tip rib, then you also bend the trailing edge and aileron tube, and probably the tip braces, or at least that's how these were.)
Richard Pike
MKIII N420P (420ldPoops)
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Richard Pike
Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee
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| Posted: Wed Mar 31, 2010 5:45 pm Post subject: Re: Reinforcing the tip rib |
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[quote="williamtsullivan(at)att.n"]Richard- The damage to the tip rib looks like crash damage, and not wear and tear. Are you sure that reinforcing it would be worthwhile? If it was hit again, wouldn't a reinforcement only transfer the damage to a more expensive part? Also, what keeps the wires from moving around and chafing inside the main spar?
Bill Sullivan
Windsor Locks, Ct.
FS 447
Oh, yeah, crash damage for sure. But the wing tip from the donor wing looked just like it, and (supposedly) all it was involved in was a ground loop. The wing tip in the previous tip reinforcement pictures smacked the ground a passing lick as the airplane was otherwise flailing around destroying itself.
My thinking is (and I reserve the right to be wrong) that the spar can absorb WAY more abuse than the rest of the wing without damage. The other wing on 2EF was totaled, (the wing pictured in this post) all the ribs, both the leading and trailing edges and the aileron, bent the compression strut, sheared the rivets off that hold the compression strut to the main spar, broke the steel root rib, bent the steel compression braces from the spar to the compression strut, snapped the wingtip bow, -but the spar is fine.
Maybe if the tip rib braces had been well tied to the spar, then the spar would not have survived? Maybe. Don't plan to find out... In this particular case, it probably wouldn't have mattered.
(Anybody need a FSII spar? As soon as this project is over, we are giving away a boatload of leftover FSII parts)
The wires - Can't remember if I was the one who put them there like that or ...? You got me curious, went downstairs and pulled them out. Some very minor chafing, not bad. But it's a moot point, they will be going somewhere else next time, and no chafing will be allowed. Thanks!
Richard Pike
MKIII N420P (420ldPoops)
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Eugene Zimmerman
Joined: 10 Jan 2006
Posts: 392
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| Posted: Wed Mar 31, 2010 6:12 pm Post subject: Reinforcing the tip rib |
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Yeah, but it saved the spar and or the steel root rib.
You simply trade one weakest link for another. And the plane is still
not designed for cartwheels.
Next time more expensive repairs will be needed.
Gene Z
On Mar 31, 2010, at 9:11 PM, Richard Pike wrote:
| Quote: |
I guess it depends on what each persons definition of weakness is.
IMO, dragging a wingtip and aileron ought to result in damage to the
aileron and the back corner of the wingtip at the trailing edge, not
bend the tip rib. (Because if you bend the tip rib, then you also
bend the trailing edge and aileron tube, and probably the tip
braces, or at least that's how these were.)
Richard Pike
MKIII N420P (420ldPoops)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=292590#292590
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jbhart(at)onlyinternet.ne
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| Posted: Wed Mar 31, 2010 6:24 pm Post subject: Reinforcing the tip rib |
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At 06:46 PM 3/31/10 -0700, you wrote:
| Quote: |
My thinking is (and I reserve the right to be wrong) that the spar can
absorb WAY more abuse than the rest of the wing without damage. The other
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wing on 2EF was totaled, (the wing pictured in this post) all the ribs, both
the leading and trailing edges and the aileron, bent the compression strut,
sheared the rivets off that hold the compression strut to the main spar,
broke the steel root rib, bent the steel compression braces from the spar to
the compression strut, snapped the wingtip bow, -but the spar is fine.
Richard,
If you are in a mishap, such as the aircraft you are repairing, it is a good
thing that the extremities crumpled and adsorbed energy. If the structure
had been stronger and more rigid, the pilot may have experienced much higher
G loads. The aircraft may look bad, but it does not feel pain.
My new propeller blades came today, and I remounted a re configured voltage
regulator and magneto kill switch assembly today. Could not finish up as I
ran out of Spider Wire (woven fish line) that I use to access the switch.
Jack B. Hart FF004
Winchester, IN
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Thu Apr 01, 2010 4:13 am Post subject: Re: Reinforcing the tip rib |
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Richard wrote:
....My thinking is (and I reserve the right to be wrong) that the spar can absorb WAY more abuse than the rest of the wing without damage....
When I flipped my early FS one wing was undamaged but the tip of the other was damaged a bit worse than what you showed in the photos with the deformed 5/16" tubes and separation from the main spar end plate. On mine, those tubes were bent a good bit more as the bow tip tube was crumpled and some of the loads were transfered to the end of the main spar resulting in a small bit of the tip of the spar bending inwards. No cracks or anything like that and only the end of the spar tube was affected an only a little. I replaced the end rib and all the tip tubes and angles, a couple false ribs and spliced in about 18" of new leading edge tube after pounding out the slight indention in the tip of the main spar.
My point is that the loads did transmit to the main spar with very minor damage to it and only on the very tip which was easy enough to repair. As someone said, crumpling metal absorbs energy before it gets to our fragile flesh and blood bodies and THAT is important for surviving crashes.
do not archive
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| bent wing tip with fabric removed |
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_________________
Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
- Anonymous |
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