Wing Rebuilding

[jrd4198]

I am looking at purchasing a KFII that has been ground looped. Part of the repairs insclude rib replacement and compression strut repair. My question is this. How diffucult is it to replace the ribs and repair the struts. Is this something that can be completed with a high degree of strength and reliability. I don't believe the current owner has photos of the repair. With out removing fabric this seems a little trusting. Any thoughts on this.

They also mentioned repairing the landing gear which I would most likely upgrade anaway so I am not to concerned with this.

Are there any other points, tweeks or repairs to look for in this situation?

[Mark]

I have replaced ribs on wings following a ground loop. The ribs and drag/antidrag tubes can be removed and replaced fairly easily. HOWEVER, if the spar was bent, it is trash. It may be very difficult to determine the integrity of the spar with it being covered. You can view inside the wing with the wingtip removed but could only see major damage that way.

The FAA 43.13 is a great source of information, but useless if the builder / repairer doesn't follow it.

[jrd4198]

Thanks for the replies.

I wasnt sure how you would re attach the ribs to the spar. are they mechanically fastened or are they epoxied or?

[mclayton]

I am in the middle of rebuilding a KitFox II that was pretty badly trashed in a departure stall. The damage to the wings was very severe on one side, and bad on the other side. After salvaging the good ribs, I am building a new wing, with a new spar, and many new drag/anti-drag braces, as well as new trailing edge and leading edge.

To properly repair the damage, any broken ribs will have to be replaced. If any drag/anti-drag braces are damged, they will also have to be replaced. If the spar is buckled, it will have to be replaced for sure. If it is only very slightly bent, you may be able to straighten it out successfully. The ribs are epoxied to the spars, and so you will need to use a heat gun to loosen the epoxy, then it has to be cleaned from the spar, and a new undamaged rib installed. If the damaged rib is surrounded by good ribs, you will either have to disassemble the wing, or remove and replace ribs. Effectively, if the damage is very severe, you will have to build a new wing. None of this is difficult to do, but you have to be careful to end up with a structurally sound wing, and one that has the proper amount of washout.

I purchased some needed ribs, a copy of the KitFox II manual, and the spar and the internal stiffener from John McBean. He has also been really helpful in helping me to understand what needs to be done.

As far as the landing gear goes, mine was trashed, and I have replaced it with the Bush Gear from John as well.

[SkyPirate]

here is a trick some of you might of heard of ,..first make sure the inside of the spar is clean,..then take some fine metal dust,.. and dump them down the wing spar,..take a strong magnet and drag the metal shavings all the way around and down the wing spar from the outside,..in doing this flex your wing,..have someone lift slightly and pull down slightly on the wingtip end,..if there is a crack,..the metal dust will go into the crack and stay there,..you will see a faint line on the inside of the spar where the metal was sucked in and stuck,..it's a rather tedious method of looking for a crack ,..but it does work,..if you do see a fine line ..clean the inside of the spar again..taking note of the area the dust stayed,..then try to apply it again in the same area,.. working the magnet all around that area ,..and someone flexing the spar,..it will define the crack again in the same area if there is a crack,..this is on a wing that is coverd of course..

[jrd4198]

What if a center rib is broke. Do you have to remove the preceding ribs to fix it or can it be fixed by removing and replacing that rib only?

[SkyPirate]

if I've got the fabric off the wings,..and I see broken ribs,..I'd be replacing them,..and anything else that was broke,..wood is not like steel,..where as if you weld a crack,..it's suppose to be stronger if welded properly,..wood ..if it has a fracture,..you see the fracture,..but you do not see where the ply's of the rib where stressed during the fracture,..if the ply's were stressed and not visible to the naked eye ,..that is a potential place for moisture to inhibit the rib,..

[Steve]

Does anyone have any experience in fixing wing struts? I have the two long beams that are bent and I guess need eigher replaced or welded. Any have one forsale?

[Skybolt]

Steve.

Very important....Replace them with new.
Get the side you want from Kitfox aircraft.

Eric

[SkyPirate]

Steve ..although 4130 is a very strong material,..in the application of a wing strut I wouldn't trust straightening it ,..especially if it has a split in it and you want t oweld it ,..in flight it doesn't only support your wing ..but it supports your life,..let me ask you this ..when it bent the strut ..what damage did it do to the wing spars at the point where they meet the fuselage..the aluminum being softer,..I'd expect it elongated the holes by stretching the material,..this would also have to be inspected and repaired if it is damaged,. you can not weld this area either ,..but you might be able to insert a smaller tube and attach it to the spar..never attach or rivet on top or bottom of the spar ...attach front and back,...ie the sides,..you might have to file the fuselage attach points to fit the smaller tube,..the other option is to replace it completely.
The reason for this repair being crucial ..if you ever went with a negative G load,..and this point is elongated ,..your wing could seperate from the fuselage at that point.
Since the strut was bent ..drawing the wing down,..chances are there is something that got stressed at that point where the wing meets the fuselage.