"Incident" repair advice

[maplebud]

Recently purchased a kitfox model 2 with some damage. Plane was last flown by the builder in 1992 from what I can gather reading the flight log he had a 'hard landing'. He put the plane in storage. In 2008 he sold the plane the buyer took the plane home with thoughts of repairing the damage and putting in back in service. His dreams were never realized and I purchased it from him in the exact condition as it was in when he bought it.

The damage is as follows: front cowl, left wing damaged 3 ribs, fuselage bent tubing, broken tubing lh side at strut attach area.

Front cowl has been repaired. Moving on to the wing I stripped the fabric back to the 4th rib and it looks good no damage. My plan is to remove damaged ribs and braces, the 3rd rib is o ly cracked so was going to use it as a template for 3 new ones. Reinstall 3 new ribs and braces and recover overlapping the 4th rib out to the tip.

Here are some pics I took today.Any thoughts on repair would be appreciated as l am a newbie.

[Norm]

I am sure there will be some with much more detailed repair tips but I would pull all the covering off the wing. Then you can make sure nothing else is broken in the wing. It is probably easier to recover the whole wing than to try and patch what is there. Depending on the damage to the fuse it may be ok to patch but.......
Good luck The KitFox is a great airplane to fly.

[avidflyer]

I agree on stripping off all the fabric on the wing. If one diagonal brace popped loose, quite likely others have also. Or got an S curve in them. I've seen it before, and with less damage than what I see on your wing. Could easily be damage you can't see till it's uncovered. The Kitfox wings are actually real easy to recover. Rounded tips like Avids have are way harder to get the tapes to look good. JimChuk

[efwd]

Hmm, interesting. No rib stitching. Wonder why Kitfox recommends it, As well as Poly Fiber. That fabric seems to have held.
Eddie

[Norm]

Could be the early kitfox was a 70mph airplaine but after the model IV it was more of a 100mph plus airplane.

[maplebud]

Thanks for all the advice. I ended up stripping all the top off to check for more damage and you guys were right. Found another brace had broken. I plan to recover the whole wing once repairs are made.

[Clark in AZ]

Good job! Nothing short of your life is on the line. Not worth guessing... verify!

[efwd]

Wow, If this isn't a testament to being a member on this site I don't know what is!
Eddie

[avidflyer]

Good that you found the damage. Better safe than sorry. Just out of curiosity, I wonder what difference you would find if you measure diagonally on the spars before and after you remove the bent parts. With the S curve in the one diagonal brace, the wing is racked. It should go right back to where it's supposed to be when the braces are removed. It would be nice to know how much difference in measurement you find as a way of checking other wings in the future. If the wing is sitting up side down, you could push a bolt or pin up through the holes in the fuselage end of the wing to hook a tape on. Make a mark on the ends of each spar center to measure to. I never thought about this when I first answered your question about your wing damage. It probably would have told you there was damage inside the wing even before you uncovered it. JImChuk

[maplebud]

Hey Jim, I will measure the rack in the wing and post it. Got another question while we're talking about bracing. When I unrivit the damaged bracing and have to install new how would you go about attaching it as far going back in original holes with rivits.

Robert

[avidflyer]

The fewer holes in the spar the better I'm sure. Newer Kitfoxes use a steel bracket that rivits to the spar, and slides inside the aluminum diagonal brace. That would be probably easier to use and drill to fit the existing holes. Then you only have to line up 4 holes instead of 8. With very carful measuring it can be done though. Might give Kitfox a call and see what they suggest. Jim Chuk

[avidflyer]

Just happened to look at your first pictures and see that your spars have the internal extruded verticle stiffener. I would personally be less worried about some extra holes in these spars than ones without that type of stiffener. I would think they are stronger than the .065" spars used now on Kitfoxes. Just my opinion though. Another question to throw by John at Kitfox if you call him. Jim Chuk

[efwd]

I was thinking that Jim's idea was great and I would think drilling the holes to accommodate the next size up rivet would take care of a sloppy install of the same size. To place the holes in the brackets you can use a Hole Duplicator-Bushing Type available from Aircraft Spruce.
Eddie

[kiwi3]

Photo of drag tube bracket on Model 3, S/n 1013 which was built in 1991.
Hope this helps.Felt there was a Service Letter, or similar update information put out on forum, but am unable to locate it. Ian

[avidflyer]

Looking at the brackets, it looks like it would be hard to hit the old holes using them. The old holes would probably be under the welded tube somewhat. There are 6 holes in them however, so maybe intentionally not hitting the old holes and still using the original style aluminum tubes isn't so much of a concern. Jim Chuk

[dholly]

Hi Robert,

I would not bother with installing the new drag tube brackets, probably just replicate a new diagonal brace per the manual and attach with Hysol and next upsize rivet. First end is easy to fit to the existing mounting hole in the spar, make a simple D.I.Y. hole duplicator for the other (attached pics of one I used for locating spar bushing holes). You can temporarily rivet the hole replicator into the existing hole with the original rivet size called for in the manual, locate the hole position on the drag tube end tab, then drill out the temp rivet. Drill out spar hole for next upsize rivet and final mounting. Also, I recommend adding corner gussets between the diagonal bracing and spar. Coat ply gusset with Hysol to prevent water infiltration.

[Wheels]

while your there you could add rib stitching. No weight, no time like the present.

[maplebud]

Good that you found the damage. Better safe than sorry. Just out of curiosity, I wonder what difference you would find if you measure diagonally on the spars before and after you remove the bent parts. With the S curve in the one diagonal brace, the wing is racked. It should go right back to where it's supposed to be when the braces are removed. It would be nice to know how much difference in measurement you find as a way of checking other wings in the future. If the wing is sitting up side down, you could push a bolt or pin up through the holes in the fuselage end of the wing to hook a tape on. Make a mark on the ends of each spar center to measure to. I never thought about this when I first answered your question about your wing damage. It probably would have told you there was damage inside the wing even before you uncovered it. JImChuk




Jim, checked rack in the wing it's 5/16 ".

Robert

[avidflyer]

Thanks for the follow up info Robert. If the wing was built square to begin with, that would be a way to determine if there was damage on a wing then. Are all wings built square to begin with? Maybe not. Probably most are pretty close though. When you remove the braces, please measure the wing to see if it goes back to square. Take care, Jim Chuk

[Jfquebec]

Ya ..the square... Start to mesure from spar end on fuselage side,and from there Mark two line to the end (wingtips side) im not sure , i think it is 156''.and after you can take mesurement for the square

[avidflyer]

I'm on several other aircraft forums, and just now read a post from a guy on an "airchair" group. Look up red goat glider on utube if you want to see an airchair in action. Anyway here is what an engineer had to say about holes in the center section of an aluminum spar. Take it for what it's worth, I can't say he's right or wrong, but figured I would pass along what he said. Jim Chuk

I'm Richard Lamb - engineer and draftsman for the Texas Parasol project.
The TP is basically a "fat" ultralight. A few have been built under 254 pounds but most run 320 or more.*
*We sorta pioneered using extruded aluminum angle for fuselage construction, but my remarks today are about the wing we finally settled on.
*We operated at higher weights and speeds than the air chairs will EVER see.
And we have had NO failures due to rivet holes in the spar tubes with over 100 airplanes built.
*Our wing was actually designed by (the late) Paul Hammond of San Antonio, Texas,
It uses tube spars with bent sheet-metal compression ribs at each airfoil rib location to form an all-metal "ladder". The drawings specify .058 wall tube spars, but they have been built as light as .035.* The ,049 wall tubes cost more than the .058!
*The thing is to locate the holes on the spar tube neutral axis.
The front and back centerline of the tube.
Anything in an arc +/- 45 degrees from the neutral axis had negligible* impact on spar tube strength.*

[avidflyer]

The reason I posted the last message was to perhaps remove some worry about some extra holes in the center of the spar where the diagonal braces are riveted on. That is if you believe what that guy says. Come to think about it, the rear spar has a hole drilled in it big enough for the airspeed indicator/pitot tube line to go through to feed back to the cockpit. 5/16" or maybe 3/8" in size. How many 1/8" rivet holes would that equal. Jim Chuk

[maplebud]

Repair update, put the wing aside for now.Brought the fuse into the shop. Here are some pictures of damage.1192111922 I have started to straighten the 3 bent tubes in this area.
11923 This has put the longeron back together. What would you guys suggest for further gussets or braces in this area.