need your experience

[Richard31]

Hi team,

I am interesting in a 2nd hand kitfox from 1996. i visit the airplane last week end and i take 2 pictures of something strange regarding the left root rib. here attach the pictures. have you already see this detachment of the bonded joints between wing ribs and spars ?. thanks for your help. does it exist a way to resolve the issue or does it means something more critical.

regards and thanks for your help !

[avidflyer]

At first glance, I wonder if the wing was swung into the overhang on the skylight part of the windscreen? Is there a wrinkle in the fabric by that rib? It's handy that there isn't a fuel tank in that wing, can you see if the other ribs are loose as well? If you were to decide to install a wing tank, it would be fairly easy to remove and replace that rib then when you had the fabric pulled back. JImChuk

[Dave S]

Richard,

There are probably several ways this could have happened - inadequate preparation on assembly, trailering the plane with the wings folded if the wings were not braced; and, there is one question (but not an answer) related to flox vs microbaloons per service bulletin 7 which relates to kits shipped around 1991.

http://www.kitfoxaircraft.com/images/servicebulletins/SB-7.pdf

No matter the cause, looks like further investigation is in order to determine if other ribs are separated and how extensive the problem may be and what might be necessary to effect a repair.

[avidflyer]

Dave, did you ever hear of any follow up information to that link you posted? JImChuk

[Dave S]

Jim,

As far as I know - the original SB 7 was the only information posted by the previous kit manufacturer ownership - I don't think there was any follow-up.

I am thinking somewhere there was some list discussion - and it would have been back a while; but, that may have been on the old Matronics list.

Sorry

[Bluebird19kf]

Pretty sure I read a follow up to that SB and it basically said that either flox or microballoons were fine to use.

[Guy Buchanan]

Doesn't look like the root rib braces are installed correctly. There are supposed to be some internal aluminum tube braces coming from the front and rear spars to the root rib top and bottom to make sure the fabric tension doesn't bend the root rib. Are they there? Are the root ribs straight fore and aft?

You've got some repair work on your hands there. First you'll have to stabilize the rib with some temporary braces, then grind all the existing epoxy off the forward and aft attachments, then prep the wood and aluminum for epoxy, then epoxy the forward rib break, then straighten the root rib using additional permanent internal braces, then epoxy the rib to the spars, then do cosmetic clean-up.

The big problem will be if the builder didn't install the braces, then bowed the heck out of the root rib during fabric shrink. You'll never be able to straighten it and will have to re-cover the root bay or the entire wing. (Probably just the root bay.)

PS. Check both sides. Probably the same inherent problem.

[avidflyer]

In the first picture, it looks like there are 2 aluminum tubes attached to the rear spar, maybe about a foot in. I figured they were the rear braces for the butt rib. Would have been nice to see the complete end of the wing to see if there were any pop rivets showing that would have been holding those braces in place on the rib. Fabric does pull pretty hard when shrunk, no doubt about it. JImChuk

[jiott]

Those braces visible in the picture look like the spar cross bracing tubes; they don't support the center of the rib against the pull of the fabric. What Guy is asking is are there additional support tubes not visible in the photo that go to the center of the rib, similar to what is done on the opposite wing tip end. With a fuel tank in the root bay we put small wood blocks from the tank side wall to the rib for support, but with no tank and if no support tubes, that could easily explain the damage that we see.

[Esser]

It is a concern and you could have a whole wing repair on your hand. I would offer him what ever for the plane he is asking minus 4 or 5 thousand if you are willing to repair it

[PapuaPilot]

I agree with Esser, it could be a bigger job then it looks. I would also make sure the spars are perfectly straight and don't have any kinks or bends in them.

[Richard31]

Thanks all for your reply and investigations !!!!!, i am going to see the Minifox (it is the name on the ID card, a kitfox with 10meter wing span to have 15m² surface... in 1996 it was the regulation).

i note to the following:
>check if wing was swung into the overhang on the skylight part of the windscreen?
>wing brace or not during transportation?
> other wings ? (see pictures attached)
>job to do if i bought the plane :)
>negociate price :)

i attach other pictures that could help you. Left hand wing, seams to have no trooble, and a picture of internal Right hand wing.

thanks again for your help.

regards,

richard

[avidflyer]

Were you able to see if there was a wrinkle or at least looser fabric just out from the front of the cracked rib? If it did get broke by hitting the skylight, you could maybe just clean the epoxy and paint off the end of the rib where it meets the spar, make a 1/4" plywood doubler for each side of the front 2" or so of the rib, and epoxy and clamp it all back together. Also remove the epoxy off the rear rib/spar junction and reglue it back together. What I described would not be a real hard job. Looks like the braces that are supposed to be in the wing are there. My Kitfox 4 manual shows 2 braces going from the rear spar to the butt rib and one in the front. That is on the drawing where a person doesn't use a wing locker or fuel tank. That pattern was probably the same on a Kitfox 2. My suggestion on the rib repair is worth what you paid for it, and you will have to determine if it makes any sense or is legal in your country. Use at your own risk. :-) JImChuk

[Richard31]

Hi all,

ì could make another visit beginning of the week and i understand what happen thanks to you :
> the wing was swung into the overhang on the skylight part of the windscreen (see photo), we clearly see the looser fabric and the crack rib also on the fuselage side.

thanks again for your contribution.

regards,

richard