Broken rib tail repair

9 posts in this topic

Posted

Hi all,  been working on the Avid some more, brought a wing up to the garage where I have some heat.  (It's supposed to be +2 F for a low tonight)  I have two broken rig tails on that wing, and so have worked on them after I ripped the fabric off.  I bought a 2' x 4' sheet of 1/4" 12 ply plywood from ACS  a while back and cut out some rib tails.  Here is how I'm fixing them.  I know Brett had a repair where he replaced the whole rib behind the rear spar, but I'm going a different way.  I built a few jigs so I can cut more tails with the table saw easy if anyone wants some.   A heat gun will soften the glue, I think they used T88 on the ribs and it does soften up with heat.  Careful cutting with a saber saw to get most of the rib out of the way, then heat and gently pry the rest off of the rib cap strips.  I am going to put a scab on each side of the rib (second picture)  that will be glued in to make it stronger than before.  (I think)  Any way, if anyone sees anything wrong, other than the messy workshop, fire away!  Jim Chuk

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Posted

Jim,

That looks really good!

What caused them to break originally? Was it the cracking at the trailing edge and flaperon horn? Or was it inside the wing covering?

Thanks,

Ron

P.S. That isn't a messy shop...you weren't standing on anything or using vehicle top to hold your wing level! :)

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Posted (edited)

Hi Ron, that is my Avid that had an oil cooler line blow on the Jabiru engine. Not the fault of the engine though. After the cockpit filled up with smoke and I thought we were on fire, I landed in the first field I could get to, and the field ended up being a few hundred feet short. The ditch and fence at the end of the field caused me to flip over. The crash bent some tubes in the fuselage and broke these two rib tails in the wing. Nothing bent or broke on me at the time, other than my wallet. Jim Chuk

PS the tails broke off just inside of the flaperon hangers. Last 1 1/2" or 2" broke off

Edited by Jim Chuk

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Posted

Jim, since I haven't built an Avid from a kit, I'm having a little trouble understanding how the new tail portion fits into the existing rib. Did you cut the existing rib vertically (90 degrees to chord line) to be able to break out the damaged piece? Does the new replacement part butt up against the cut edge of the existing rib?

 

Thanks for the photos, I have one broken rib  tail on my aircraft and I may have to repair it for a buyer.

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Posted

I don't like square butts, I cut mine on a 45 or better. The square butt with a piece scabbard to each side should be fine though.

:BC:

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Posted (edited)

No reason that shouldn't work. Nitpicking now, I may have chosen to continue the scabs a bit further rearward, butt them as close as possible to the spar and epoxy a few alum large head rivets on each side of the joint.

[edit] I would rough cut/shape the hanger end before gluing in place, but then, nothing looks glued yet in your pics so I assume that's your plan. Going with the white paint scheme again? I thought it looked real sharp!

Edited by dholly

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Posted (edited)

Hi all, thanks for the comments.  Leni, I agree a scarf joint is better, but my reasoning was I will have 1 1/2" overlap on each side of the joint with the scabs (one on each side of the rib) and they are both 1/4" thick just like the rib.  It's also hard to do the scarf joint and get it exact with the angles on the replacement rib, top and bottom.  Doug, I figured the scabs were big enough being as how they were on both sides of the rib.  Also, once they are glued in place, I will use a straight edge from the original surviving ribs across the new ribs to mark them for cutting.  That way things should end up straight.  (I hope :-)  )  Bill, I saved you for last, cause I have some pics of how the ribs are made, and how I once repaired a busted rib tail without messing with the fabric.  First three pics show a standard rib.  The top and bottom capstrips are 1/8" plywood, and the center (verticle part) is 1/4" plywood.  As you can see in the pictures, the bottom capstrip is slotted so that it goes on each side of the center section for the last 5 inches or so.  I cut the 1/4" verticle part of the rib with a saber saw as close to the cap strip as I dared, and cut it off about 2" vertically from the spar.  Then I went after the slivers that were left with a heat gun and a chisel and a Stanley knife to get the rest of the center part of the rib removed.  However..... if all you have is a busted rib tail, usually at the inner bolt hole where the flaperon hanger mounts, you might want to try what I did in the next three pictures.  I didn't mess with the fabric, but cleaned up the paint on the sides of the exposed tail part of the rib, and glued on two 1/4" thick pieces, one on each side.  I trimmed them just a tiny bit so the flaperon hanger could slide between them and the reglued in the piece of the busted off rib tail.  Glued them all together and put a few 10/32 truss head machine screws in to hold while the glue (T88) set and for a bit of extra holding afterwards, and flew it for probably 300 hrs afterwards.  It survived the crash that busted off the other two on the same wing.  Actually I'm debating whether to mess with it or leave it the way it is.  I think it's stronger than the original single piece, and it's out at the tip of the wing where it's more  likely to get bumped then the rest of them.  Hope this makes sense.  Didn't mean to write a book when I started this reply, but Orielly isn't on for another hour anyway! :-)    Jim Chuk

 

PS  On the rib I repaired with the doublers on each side, it was cracked off probably half way between the inner hole for the flaperon hanger, and the truss head machine screw in front of that open hole.  When I looked at the pictures, I don't see nuts on one side, so maybe I might have tapped the holes and glued the screws in while it was clamped together.  That was probably 7 or 8 years ago, and I'm not a teen ager any longer.... LOL

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Edited by Jim Chuk
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Posted

Are those reinforcing plates held on with wood screws?

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Posted

The plates were epoxied together and the machine screws were epoxied in as well.  That was a repair I did without uncovering the wing.  JImChuk

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