Broken Wing Stringer-Options?

[fathom]

Going through the Classic IV kit I just purchased last weekend and noticed the lower stringer on the left wing is broken and about a foot of it is missing. John at Kitfox said it’s unavailable at this time but could possibly use aluminum. Anyone done this? If you go the aluminum route do I need to alter the right wing to match? Could I use the wood for the fuse stringer that I have and use aluminum on the fuse?

Thanks for the help..
-David

[jiott]

I think you could certainly use aluminum tube like the newer SS7 kits. But if you do, it would require filling in part of the square holes in the ribs and probably redoing where the false ribs rest on the tube; sounds like too much work to me. I would just replace the broken area of the wood stringer with a same sized piece of spruce or whatever with good strong scarf joints. This stringer is not of much structural importance. It is only there to stabilize the ribs, and support the aft ends of the false ribs. The aluminum spars and cross braces are where the structural strength lies.

[Dave S]

Fathom,

The classical way to repair this is use the same material do a tapered scarf joint and epoxy the overlap together. Alternatively, a person can bond a doubler on each side after squaring off the broken end if they don't do a scarf joint.

For the material, it is spruce - which can be purchased from, well, Aircraft Spruce - http://www.aircraftspruce.com/catalog/wppages/capstrip.php I believe Wicks also will have the material.

What you can do is get a strip which either matches the cross section of the part you have or get one slightly thicker and trim it on your table saw. The crown on the one side can be shaped with a small plane.

Check AC 43.13B on acceptable repairs for wood
Sincerely,

[dholly]

I think your plan to use the available wooden side stringer material on hand for the wing repair and substituting tubing for the side stringer is doable, but I've always wondered why the side stringers are wood vs. 4130. Possibly ease of install and more forgiving to an inadvertent bump/push on the ground? Or, maybe safety engineering as a designed in crumple zone? If the side stringer tubing is pooh-poohed by experts here, your plan would buy you some time to source new material while you get on with the repair. Keep moving forward!

[jiott]

The side stringer on the SS7 kits are aluminum tubing. They are non-structural, just for aesthetics to get away from the slab-sided look. So yes, I think using the tubing on the side would be fine. Repair the broken wood stringer with similar wood as has been described.

[Jfquebec]

Hi...i have some falses ribs if you want it let me know...
I will ship you That for Christmas 😜