False rib problem

[kitfoxrk]

The 7SS kit I acquired had been in storage for several years. It has the quick build wings. When I was inspecting the wings, a number of the false ribs literally fell off in my hand when I touched them. I have several questions for the group:

Has anyone else experienced this problem?
Any ideas on what may cause this type of problem?
Any suggestions on how to repair(other than just hysolling them back on)?

I have attached a couple of pictures of the ribs. They came off very clean with no apparent damage to the ribs or the structure they were attached to.

Any suggestions and/or advice would be appreciated.

[Dick B in KY]

I suggest you clean them off, prep the area where they install good , and reinstall with proper Hysol mixture. Check all the other glue joints for security and if OK, no harm no foul.

Dick B

[PapuaPilot]

Make sure you scuff up the parts or powder coating that these ribs will adhere to. Before you glue them wipe all the mating surfaces down with MEK, acetone, etc. so that there is no oil, grease or finger prints on the parts.

[jtpitkin06]

This appears to be a classic case of bond failure due to surface oxide. Before bonding to the spar you must mechanically clean the aluminum. Wiping alone will not remove aluminum oxide. A Scotch Bright pad is good for getting the surface oxide off. Avoid aggressive sand paper that could scratch the spar. Then clean up with alcohol. Do your bonding immediately. If you wait a day, you must clean it again as aluminum oxide will form very quickly.

I would sand or grind away all of the hysol from the loose ribs to get a clean wood bonding surface

Grab all of the remaining ribs and false ribs then give them a good tug. Nothing should fall off.
.

Jp

[HighWing]

The 7SS kit I acquired had been in storage for several years. It has the quick build wings. When I was inspecting the wings, a number of the false ribs literally fell off....

Wow! In my mind you just might be the lucky one. I can't imagine finishing an airplane and subsequently finding the false ribs banging around inside the wing bays.

The cause? In my mind, improper preparation of the mating surfaces at the time of assembly.

Repair? Good suggestions already. When I built my original wings it was Alodine and Alumaprep. Alodine being an etching solution and alumiprep which also has corrosion preventive properties. Both commonly used on aluminum aircraft and recommended as a surface preparation for paint and adhesives.

A note on the why's. Some might think long term storage might be the issue. But consider the range of conditions found inside a wing during routine use and storage. I always think of Don Smythe a contributor in the early Kitfox email list days. He was an engineer at the Newport News Submarine construction facility in Virginia. His specific task was to ensure the submarines sent out on line didn't kill our sailors by things breaking or "falling off". He once found some light showing through his wings at the edges of the pinked finish tapes. Being the engineer, he needed reasons and since heat shrinks the fabric, he put some thermocouples in his wing and put it out in the sun to check internal temps. In his white wings, he found temps near the lower end of the shrink temps - approaching 250°. I can only imagine the internal temps in dark blue or black wings.

[ken nougaret]

This leads me to wonder if your strut attach brackets have the same issue, if they are installed. You wouldnt know if the bond was good because they are riveted.

[jiott]

Since these are factory quick build wings, I wonder if the false ribs were factory installed? I can't believe the factory would have been so lax on surface prep. I know the bottom false ribs are optional and customer installed, but I believe the top false ribs are factory installed except in the lift strut bracket bay. I guess my question is: which false ribs are falling off?

[Dave S]

The clean separation is indicative of inadequate prep of the spars or contamination of the surface prior to applying the hysol. The joints, properly done, are extremely strong and this should never happen. I don't see how the storage would possibly affect the bond.

For the false ribs that fell off in your hands, I am going to speculate that they are the ones located in the lift strut bracket bay. I believe that the factory installs all the false ribs on the QB wings in the factory except the ones in the bracket bay - leaving that to the builder. If that is the case, the original builder may have messed up with the prep for the false ribs in the lift strut bracket bay.

If this ends up being an issue with the person's technique who had the kit before you...I'd go through the manual and parts and double check anything else the original purchaser may have done.

Dave S
Kf 7 Trigear

[dcsfoto]

make sure to read the instructions on scuffing the spar

D Kelm SS7

[kitfoxrk]

Thanks for all the replies guys.

The ribs that came off are from the far outer bay toward the wingtip. The ribs to be installed by the builder are still in a bundle in the boxes of "stuff".

Bob