Is this a Crack or A scratch on the Varnish of Wood Spar

Asking for a friend, and of course will be looked at by qualified A&P but just picking the brains of the collective group.

the Spar is smooth over the mark/line/scratch and it doesnt catch a nail but I don’t know how cracks in wooden Spars present themselves.

IMG_5851 by https://www.flickr.com/photos/joeycostanza/, on Flickr

IMG_5850 by https://www.flickr.com/photos/joeycostanza/, on Flickr

I’d say scratch. From rib hole burr. But need better pictures


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mike mcs repair said:

I’d say scratch. From rib hole burr. But need better pictures


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Click to expand...

Ask and you shall receive lol. Embedded high resolution ones

I agree with Mike. In my limited experience cracks don't run that straight for that far and it doesn't really look like a delamination of a glue joint. If you follow that line does it end at a nail hole in a rib flange? If it does Mike is right.

It does appear to end at a nailhole/flange from what I can tell.

Here is another angle

Untitled by https://www.flickr.com/photos/joeycostanza/, on Flickr

If the wing's on a plane grab the tip and flex it up and down. Wood wings can move some. Look for change of wood layer spacing along those lines. Is there evidence or record of prior tip damage or repairs? Was the spar inserted and replaced from factory original at some point?

Edit: Posted prior to the above reply.

Gary

We see a lot of scratches from sliding ribs. But from your first pictues - early J3 spars were often laminated, both vertically and horizontally. Properly cared for, these 75 year old glue joints are surprisingly strong.

horizontal cracks are to be watched, not panicked over. The deadly ones are compression cracks, and they manifest vertical. Check out a Citabria forum for photos of those. Really hard to spot, and a failure can be fatal.

Thanks Bob!

Scratch from sliding rib on. Have built two wood spar J-3 wings. Go fly!

Blue Skies

I got into this over a Great Lakes a few years ago. Insurance adjuster had me go inspect supposed 4 cracked spars. They were scratches like posted above from the nail hole dimple when the ribs were slid down the spar. Cracks will follow the grain of the wood which is not generally exactly straight. Owner wanted the airport owner to line me out, guess he wanted the insurance company to pay for new spars and recover. Probably pissed him off when I was asked how 4 spars could get cracked and I replied that I did not know but probably from a ham fisted fighter pilot trying to do aerobatics. The CAPs never had any cracking issues from aerobatic pilots, only foreign militaries. I found out he was a former military fighter pilot.

Sorry for all that, just reminded me of the whole experience.

My old T-craft spars made excellent saw horses, light and strong. I still have a scaffold plank made from the rears, good mojo in that wood! Various little scraps of the spar remnants are used in various places on my S-7, wood lined baggage area, the window sill I rest my arm on, more good mojo. I have a 6' length left for future needs. I remember those exact same type scratches from the ribs, chewing and defecating mice are the bigger problem.

This came out of a flying chief. It was parked outside in the winter and had a snow load on the wing



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