How to repair fuel tank rib?

[JackScott]

While prepping my left wing for recovering after fuel tank replacement, I noticed a crack in the glue joint between the fuel tank rib and the rear spar, please see attached pictures. Is there a way to fix this, preferably without taking the wing apart?

This picture shows the bottom of the wing. I put a few pounds of force on the rib trailing edge to make the crack more visible.

7F69B87D-7A81-4506-8E41-94EDC4772A5E.jpg

This picture shows the top of the wing, the crack seems to only go half way around.

A52E72B8-F456-4819-9800-B193150AD05F.jpg

Both pictures show the inboard side of the rib. The outboard side is affected as well but doesn’t appear as bad. I checked the right wing fuel tank rib, it looks normal.

Thanks in advance for all your help,

Jack

[jiott]

I would carefully apply heat (it will soften the Hysol) with a heat gun to the old Hysol and scrape out as much as possible all the way around, without scratching or nicking the aluminum spar. Clean thoroughly, and apply new Hysol to the joint. The spar is the item that needs the most care to avoid damage. The ribs are not so critical since they are not really structural items, but only serve to space apart the spars and provide the correct airfoil shape to the covering.

[alexM]

That looks more like the old 3M adhesive than Hysol. I found it took a lot more heat to loosen (enough to burn the wood).

Also, the issue with heating up that specific rib is that you risk also loosening the steel reinforcements at the root.

[avidflyer]

Back around 1994 when my Kitfox 4 kit was produced, it got the factory built wing option. I bought it barely started from the original buyer, and got all he had with it. There was a letter from Kitfox (skystar really) saying that there had been some issues with their glue joints on some of their prebuilt wings. They supplied some crazy glue and the instructions to drip it into the cracks and it would be a satisfactory repair. That would probably be the simplest solution I would think. Glue it up, and leave it a day or so, and see if the crack opens when you try to flex it. Pretty simple, and if it doesn't work, you are no worse off than now.. YMMV... use at your own risk. Just telling you what I read in the letter from Kitfox. Maybe someone else will remember that after reading this post.

[JackScott]

This is a model 4 speedster wing, built with 3M 2216 epoxy mixed with cotton flox.

Jack

[airlina]

I used the scotchweld (2216) adhesive when building my Series 5, 20 years ago. There was a time or two I had to remove some dried adhesive. It was doable with a high quality heat gun with a known heat output ( i.e.controllable) and as I recall it was near 400 degrees to get it soft enough to scrape. As others have said , don't scratch or nick the spar in the process. Bruce N199CL

[Eric Page]

If those joints have been together for many years, your chance of getting the Scotch-Weld off using heat without damaging the attached parts is probably nil.

I got a damaged elevator push-pull tube with my second-hand Series 5 kit (assembled with Scotch-Weld) and needed to remove the turned aluminum end fittings to re-use on a new tube. I tried everything up to a propane torch and they absolutely would not budge. I had to buy new parts.

[JackScott]

I picked up a heat gun from the local home and aircraft supply depot and gave it a try. I removed a bit of the epoxy, enough to show it’ll work, but it’s going to be a slow process.

I’d like to find a scraping tool hard enough and heat resistant enough to remove the epoxy, but soft enough to not damage the spar. Does such a thing exist? I’m going to try making some scrapers from wood, but I’m not sure they’ll work.

Jack

[JackScott]

Success! A heat gun, putty knife and sharpened piece of wood did the trick. I found a piece of hard wood tapered on the end did a good job of scraping epoxy without damaging the spar, but needed retapering often. I ordered hysol from the factory for the repair, that starts next week.

Thanks for all your help.