damaged wing skin repair

[lgn98868]

I’ve bought a project that has a crumpled wing skin secondary to ground loop. Wondering if taking it to a machine shop and having it flattened as much as possible would be acceptable. Then rebend and rivet into place to hopefully maintain predrilled holes. Alternative is probably doing the same and transferring hole pattern into a fresh piece of aluminum.

concern is just the multiple bending of aluminum and if it would affect the strength of the metal.

thanks

[BravoGolf]

Probably not going to work out the way you hoped. The skins are fairly thin and with repeated bending will most likely crack. Additionally it won't every be as flat as a new piece of aluminum which affects the airflow over the airfoil. Really the best solution is to reskin the that section. There are methods to finding the existing rivet holes, there are hole finder tools or perhaps you could fabricate a drill jig that matches the existing rivet holes. Have you inspected the wing structure? What do the ribs and spars look like? It is possible you will need to replace one or two ribs. Is it just the tip region of the wing? Can you reach past the damaged area through the rib lightening holes? Perhaps you could post a photo of the damage. A patch might be possible opposed to replacing the entire skin section.

You did not ask, but there are other areas that would be important to inspect as well. But you may already have that under control.

[lgn98868]

Here are some photos. A rib will need to be replaced. Spar has some damage but a&p before me had started to repair per 172 repair manual instructions.

Wanted to hire out the repairs but the most viable option turned me down due to “started repairs not meeting standards which equates to more time and more money”

I feel like the started repairs are appropriate, advice on other things to inspect?

[jaredyates]

I would recommend checking with Bob, or an A&P experienced with sheet metal. My hunch is that you'll need to replace it but I'm certainly not qualified.

[lgn98868]

Thanks Jared. I’m happy to replace it but the simplicity of not repainting and not re drilling would be nice. I think I’m fairly close to you (little south of Burlington NC) and might reach out for advice and some training recommendations once it’s airworthy. Thanks for the help

[kestrel]

That wing skin is structurally compromised and can not be restored to original strength. Replace it.

[svyolo]

I will second the wing skin needs replaced. Zero chance of saving it. I am not in love with the spar repair, but not enough detail to go into detail. I do think it is very repairable.

[lgn98868]

svyolo front or rear spar? I assume his plan on the front spar was to also sandwich it between two pieces of plate and rivet as was done on the rear spar. Let me know what you want to see and I will get some pictures. Thank you

[svyolo]

There are lots of folks more knowledgeable than me. AC does a great job on repairs. The damage to the spars is near the tip. This is far less critical than near the root, or the strut attach point. If you have a good local A&P that does structural repairs I would trust him. If not, Bob in the past seems very open to help. I know enough to know it is repairable. I also know enough to not give advice on how to repair it.

[lgn98868]

Will do! Thanks for the advice

[lgn98868]

Not related to title, but another more detailed look of rear spar

[AZBearhawk272]

I am assuming this is a Patrol, correct?

Replace the skin.
Photo and talk to Bob.
Do a very detailed hidden damage and alignment assessment.
build a wood fixture or strong back to hold alignment.
Proceed thoughtfully with excellent craftsmanship. Nothing is riskier than a bad repair…..
Avoid locking in the spar slices until all the other elements have been vetted and repaired.
You might tackle the aileron first to assure mate to wing.

Kevin D
# 272
KCHD

[lgn98868]

Yes patrol.
Definitely going to replace any skins now. Looked up the rivet hole finding tool mentioned above and that will be a game changer.
I’m planning on calling Bob and sending him some really good pictures of current state weather email or mail.
Intend to order a few new parts and thought would be better to just order a new aileron than try to repair it. But agee, would be more ideal to fit the wing to a perfect aileron. Thank you for your advice.

[marcusofcotton]

Perhaps use some clear ~.020" mylar or polycarbonate film to lay over the wing to make accurate hole pattern for skins? Drill and cleco in place and then remove and put onto the skin to predrill all the holes.

https://www.ebay.com/itm/234703750271?chn=ps&mkevt=1&mkcid=28&srsltid=ASuE1wSCfWgiashCUIjvfLPmUGKHBX3krxwI0SPGvT079FwuFi6QbyIyuB4

https://www.mcmaster.com/products/polycarbonate-sheets/clear-impact-resistant-polycarbonate-film/

[Ed.Meyer]

I would think you could use the original skin as a template for cutting and drilling the new one. Hammer as flat as practical and if there is concern about being deformed too much, cleco back in place to check fit. If it fits the rivet holes should line up as good or better than using a hole finder.

[fairchild1934]

It would be nice to see that rear spar area BEFORE the scab plate was added---- do you have pics of that ? I wonder if either of the spars has an upward bend now ? I would think that would be an important thing to check. Otherwise you risk have a badly out of rig wing when you are done.

[lgn98868]

Don’t have any before pics. Bought it in that condition with plate riveted on. Think if a straight edge lines up flush with the top edge of the spar where skins are removed it is ok?