Wing root bolt hole slop

[Bluebird19kf]

I inspected my wing root bolt hole and found the spare hole to be really sloppy. The fuselage hole is nice. What is the best way to fix this. My first thought was to rivet new steel backup plates in and re drill the holes. Tried searching but didn't see much info. Holes have probably 1/16 of play!!!!

[Esser]

I think you are on the right track with that idea. I would also put some hysol between the two plates so when you drill the hole, the old hole in the spare with slip is filled in. Best bet would be to call the factory.

[Bluebird19kf]

I talked to john at kitfox. He said AC 43.13....but the way the newer foxes are they put 2 steel doublers instead of 1 on the spars with hysol and micro balloons(controversial)and cherry max rivets . I feel like I am going to put 2 new doublers on with hysol and microballons out of 4130 with cherry max rivets and call it real. Now I just need to figure out the best way to line up and drill the holes perfectly. I'm liking the attach something to the fuselage carry thru tube with the hole and mimic that. Please comment with other words of wisdom. Thanks

[jiott]

I would suggest when you drill/line-up the holes in your new steel doublers you follow the same procedure in the manual as if this were a new build. Since your old holes are all wallowed out there is nothing there you can count on. Using the original rigging procedure will insure the wings are lined up (leading edges) and symmetrical (diagonal measurements from each wingtip to rudder post).

[WISDAN]

I agree with jiott, follow the rigging instructions to drill the holes correctly. I have re-inforcements that are completely circular and fit the inside I.D. Of the spar. I bought them from Blue Sky Aviation, don't think they are in business anymore. May be another optiion if you can find them. Two doublers should work out, good luck!

[redbowen]

Wisdan do you have any pictures of that set up?

[DesertFox4]

I have seen the stainless repair inserts WISDAN speaks of years ago. I also believe they were from Blue Sky Av.
I saw them at Murle Williams (Williams Aviation in Phoenix, AZ.)
Murle had a set but I am not sure if he used them or not in a spar repair. You might give him a call. 602-978-0553.
The spar repair inserts looked very high quality.

[airlina]

I believe these are the inserts you are talking about. When I was building back in the late 90's there was a guy in Colorado that made aftermarket stuff for the Kitfox and these SS wing spar root inserts were one of the items. i used them on my Series 5 . Was a slick setup as they were a nice tight fit in the spar and were glued and riveted in place. Weren't cheap though at 330 bucks and history has shown in the great safety record of the Kitfox that they were probably overkill and the current design has served well. Bruce N199CL

[DesertFox4]

Bruce, yes those are the ones I saw at Murle’s many years ago. Really they were overkill but a neet solution for a miss drilled hole or worn ones.

[WISDAN]

DesertFox 4 is correct, the inserts were designed to repair damaged or mis- drilled spar holes. Not really needed for a normal wing build as the kit supplied spar doublers are more than sufficient.

[WISDAN]

By the way, they were of high quality as airlina stated and fit and worked great for my wings. Unfortunately I don't have any photos but can take some in early April if you need them.

[Agfoxflyer]

I also used the stainless spar inserts on my 5 and was very happy with them.

[Bluebird19kf]

I wish they were still available. I guess I am just going to put two steel plates on the inside and 2 on the outside. I'm thinking I will go with ss rivets because that is what was in it. Can someone give me a link to the ones on aircraft spruce I need. I don't see where they say anything about "structural" I'm just nervous I will get the wrong thing and my wings will fly off. It looks like 2 .0625 plates and .049 aluminum wall thickness of the spar which is .174 plus hysol and micro balloons. I know there haven't been any issues with this setup but it just seems crazy my life is depending on pop rivets!

[jiott]

Why not just buy the plates and proper rivets from Kitfox? The plates come preformed to the radius of the spar tube. We need to support our manufacturer plus get the right stuff.

[Bluebird19kf]

Because my stuff I have on order is still not here after a month.

[Bluebird19kf]

15152 So I bought certified 4130 chromoly plate, built a die to bend a blank and made this. I copied the original steel doubler with the exception of making it wider in the rear to accommodate adding 4 more ss rivets. That way I can hopefully try to get the original 4 rivet holes lined up but if they aren't perfect have 4 new ones that will be right on because I will drill them with the plate attached. Do you guys agree with all this or have anything to add?

[jrevens]

I think that looks very good, Brandon. Nice job. Is your 4130 material annealed, or condition N (normalized)?

[Bluebird19kf]

Pic of the blank

15153

[Bluebird19kf]

It appears that it is annealed. Is that what I want?
15154

[jrevens]

There is a big difference in strength between the “A” and the “N” conditions. You can bring the annealed to a normalized state by heat treating & quenching. I am not sure what Kitfox specifies & uses for these pieces. Condition N is the standard for most 4130 used on aircraft.

[Bluebird19kf]

Called John at kitfox and they are made out of condition "N"

[HighWing]

15152 Do you guys agree with all this or have anything to add?

This I would add. This was discussed a lot in the old days. Sorry to bring up so much of the "antique" conversations all the time. but during one of the olden day conversations, the stresses put on the wing root during flight was discussed. The wisdom then was that the forces at the wing root of a lift strut suported wing are compressive. In other words the forces during flight would end to drive the wing root in to the fuselage rather than trying to tear it away - even on the forward spar. To illustrate this, one guy posted that once while trailering his Kitfox to the airport - nose forward, the attachment holding the wing back came loose and the air flow over the wing resulted in the wing swinging out into a normal flying position that unfortunately chopped down a sign on the side of the road.

What keeps me flying - when I can still hear, but that is another story - is the fact that about 3000 "Amateur" builders have completed Kitfoxes and there is still to be reported an accident due to a structural failure. I put the Amateur in quotes because there are builders from the perfectionists with tons of time holding tools and the guys who held a screwdriver in his hand for the very first time when he started his build. I think your concern is wise as are your questions, but my opinion is that you have thought it through and your solution is good.

[Bluebird19kf]

Thanks for the replies...I decided just to order the blanks and the rivets from kitfox. I know I wasted time and material but I learned something and that's part of the fun!

[WISDAN]

I've said before but I'll say it again, this form group is one of the many reasons to build or own a Kitfox. BTW I love my Kitfox!

[jrevens]

... The wisdom then was that the forces at the wing root of a lift strut suported wing are compressive. In other words the forces during flight would end to drive the wing root in to the fuselage rather than trying to tear it away - even on the forward spar...

Very true, except when you pull negative G's, perhaps during turbulence, limited aerobatics, or a hard landing.