8KCAB Possible wood spar crack

reconaviator

reconaviator

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Joined
Apr 14, 2025
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6
Location
KSAC
1975 Decathlon 150hp.

I think I may have found a crack in the spar. Its longitudinal on the right wing. I would like to get somebody that really knows the 8kcab and this issue to look at it. I am in Northern California. Anybody know where I could take it. I also have some pics I could send.

Any help would be greatly appreciated

Scott
 
There are occasionally scratches in the varnish that can be alarming. You need someone with good eyes who has worked with wood structures. Just having an A&P license is not enough. If we are to help, really, really good pictures . . .
 
If you can get someone to grab the wing tip and twist wile you look it may show itself better. But it doesn’t look good from your pictures, next if you can reach it with something thin and push into what appears to be a crack might give you a definite answer. Do you know if it’s had a ground strike on that wing? Either way it leave’s concerns. Good luck on whatever you discover, and good photos
 
Good photos. You won't do any better until you remove the white paint spatter.

What I would do, since now you do have questionable areas, is remove all coatings down to bare wood, and then re-take the photos. The short "crack" around the rib nail may be an actual crack due to that nail, and the first thing before removing the spar would be to check to see if such a crack is allowable, either via Bellanca documents or 43-13.

My now obsolete copy of AC 43.13 is at the hangar - I will try to check. You can pull up the current version on the internet, free.
 
total time on the airframe and have any of the spars been replaced? Also, where along the span are those ribs?

😬
 
Bartman said:
total time on the airframe and have any of the spars been replaced? Also, where along the span are those ribs?

😬
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Bartman,
TT is 1400, no spar replacement. I can't see where there has been any damage to the wings (no indication of rebuild of wing structure ) The Logs indicate the wings were stripped in 2008 minor repairs to (nail replacement etc), the spars were fully inspected then, then recovered. Those ribs are at the strut attachment point with the plywood dubler.
 
Bruce said:
If you can get someone to grab the wing tip and twist wile you look it may show itself better. But it doesn’t look good from your pictures, next if you can reach it with something thin and push into what appears to be a crack might give you a definite answer. Do you know if it’s had a ground strike on that wing? Either way it leave’s concerns. Good luck on whatever you discover, and good photos
Click to expand...
Bruce,
I will do both those "tests". Thanks
 
reconaviator said:
Bartman,
TT is 1400, no spar replacement. I can't see where there has been any damage to the wings (no indication of rebuild of wing structure ) The Logs indicate the wings were stripped in 2008 minor repairs to (nail replacement etc), the spars were fully inspected then, then recovered. Those ribs are at the strut attachment point with the plywood dubler.
Click to expand...
don't tell me, right wing
 
I found loose nails only on the right side of the Decathlon I bought last fall. My theory is that most people will roll left with an engine that rotates to the right (viewed from the cockpit) so the right wing is doing all the work every time someone cranks into a rolling maneuver. The outboard third of the wing is hinged at the strut attach points so there's some flexing and bending that goes on +/- one or two ribs from the strut attach points. Rainbow Ron will tell you the spars get a little wiggly under g loading but I'm betting that right front spar gets the most abuse from all the left rolls the planes will do. Probably the rear spar too from that big aileron being forced to max deflection at higher airspeeds.

great place to spend time inspecting when doing a pre-purchase!
 
Ugh! That's a major bummer! I'd be interested in how you tackle this. I could be one inspection away from the same thing anytime.

I'd probably just do ACA wings but have my local fabric aircraft restoration shop cover and paint them. Then I'd keep the plane a lot longer than I originally planned to and enjoy the new wings.
 
The Decathlon is almost immune - according to Ron. Still have to do the inspection, but very few reported spar problems.

The problem child is the Scout.
 
David Johnson said:
Don't forget snaps.
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not good but a snap is a pull of the elevator followed closely by full rudder deflection, right? ailerons are neutral? i guess that yaw to the left is forcing the right wing into the wind more than the left so it's pretty quickly seeing more lift but without the twisting of the aileron deflection. similar but different?
 
Hey gents,
I am in working with Rainbow Ron to get this addressed. His assessment is the uneven "drying" of the wings around the plywood reinforcement is what caused it. The plywood bonded over the spar does not allow the spar to shrink appropriately. He described it exactly without even showing him. I will get it replaced this winter. Not sure on the route I am going, but I will work with Ron, wether it be he build me a new wing, rebuild the current one, or he stated he has a wing he could sell me.

Thanks,
Scott
 
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