How do I fix this?

[Alberta_Kitfox]

Hi guys,

Last summer I bought a Kitfox IV and trailered it home from Yellowknife, NWT for 1600km. Someone had advised me to support the rear of the fuselage with blocks to prevent stress on the tailwheel spring with the wings folded. Unfortunately, due to the rough roads in northern Canada, when I got home I found that the tailwheel spring was fine, but the tubes along the top of the fuselage were bent. Now I'm wishing I were just replacing a tailwheel spring.

I was busy with other things over the winter, but now that the weather is getting nice, I'm getting the itch to get this Kitfox in the air so I would like to repair the fuselage.

I am am pretty mechanically inclined and have taken the Polyfiber covering course so I am comfortable with fabric work.

I have attached a photo of the damage. What would be the best way to fix this? As you can see the fabric has some holes already, should I just strip all of the fabric off and straighten the tubing and re-cover the whole fuselage? Or is there a way I can do this repair without doing a full re-cover?

Thanks,
Randy (Alberta, Canada)

See photo's below:

[Jfquebec]

Sorry about that....look that...All is in that book

http://www.aircraftspruce.ca/catalog...clickkey=57647

[t j]

Okay, here's what I would do to begin with just based on what I can see in the picture.

You need to remove enough fabric to get access to do a good inspection of all the fuselage tubing in the section from about the handle in the rear to about the antenna.

Cut a rectangular section of fabric off the top only to begin. Cut the side about an inch or so below those top tubes that are bent and straight across the top preferably along tubing that you can make splices of the old and new fabric pieces to. Use a straight edge to cut along so you have a good straight fabric edge to attach new fabric to if you get lucky and only those top tubes are bent.

This should give you enough access to make a good inspection of the bottom and side tubing.

If you're lucky it's just the top and the fix for 4130 that is bent and not kinked is to cold bend it back into shape.

If you find evidence of more damage then more fabric may need to come off to repair it.

For what it's worth for anyone for future trailering. I saw damage like this from trailering once but it was a tri gear and they strapped the nose wheel down tight to the trailer and the tail tight to a support under the tail so the plane was level. The trailer flexed on the rough roads and bent the lower tubing in the same section yours is bent. He cold bent it back into shape without removing the fabric. I would have removed the fabric to inspect it better.

[Alberta_Kitfox]

Thanks for the advice, Tom, that's what I will do. Like you said, hopefully it is just the top tubes that are bent. I'm out of town right now but will get this done when I get back home, will keep you guys posted.

Thanks again,
Randy

[DesertFox4]

So sorry to see this damage.

Someone had advised me to support the rear of the fuselage with blocks to prevent stress on the tailwheel spring with the wings folded

The purpose of supporting the tail during transport has nothing to do with saving the tail wheel. Looking at your damage, you would have most likely broke your rear tail post and have a much bigger repair ahead of you if you had left it on the tail wheel the entire trip.

I would love to see a Youtube video made by a member that frequently and successfully trailers their Kitfox long distances with no damage, showing the proper trailer, securing techniques, aircraft preparation, ect. I hate seeing damage like this when it's completely avoidable.

[Esser]

That's a rough drive too Randy. I would have been tempted to take Canadian North up and fly it back but I can see a whole bunch of reasons why you wouldnt want to do that with a new to you homebuilt plane in pretty hostile territory.

[Alberta_Kitfox]

Yeah, I considered flying it home. If it had a 4 stroke engine I probably would have, but I was uncomfortable with the idea of flying a two stroke of the North-West Territories.

[Alberta_Kitfox]

Meant to say "over the NWT" - I don't have much experience with two stroke powered aircraft but didn't want to fly one I wasn't familiar with over a remote area of northern Canada.

Yeah, I considered flying it home. If it had a 4 stroke engine I probably would have, but I was uncomfortable with the idea of flying a two stroke of the North-West Territories.

[Geowitz]

So I've been pondering this post...

I tow my plane back an forth(with a tow bar hooked to the tail rolling on the mains) every time when I fly. I don't believe I have any towing induced damage yet, however after seeing this thread I am certainly more aware of the possibility. I remember when covering that those two exact tubes on my model IV had a slight inward bend after shrinking the fabric. I think that these tubes are strong enough to handle the compression force created by towing from the tail and lifting with all the weight shifted back by having the wings folded, BUT only if they are stabilized laterally much like trusses or rafters are in a roof. The distance between the nearest tube junctions is pretty long and therefore the tubing span is less rigid to resist the bend shown in this thread. If I had known this before covering I would have welded in lateral bracing at the mid span of these two tubes to prevent the compression force from potentially buckling them.

So here's what I plan to do. This could also be a viable repair for this condition and can be done WITHOUT FABRIC REMOVAL assuming no other major damage is detected. I suspect all you need to do is straighten out the top tubes and brace them and you would be fine. I believe the tubing is 1/2 inch. If so, I will be taking a short section of scrap tube(maybe 4 inches) with an inner diameter of 1/2 inch to create a saddle of sorts. Cut it in 1/3's lengthwise so it will cradle under the 1/2 inch tube. Epoxy and run a hardwood dowel(heck, you could probably use conduit - it's only there to laterally brace the load bearing tube) of significant diameter(maybe 5/8inch) from the closest bottom front most weld clusters diagonally to the underside of each prior mentioned cradle bracket(epoxied under the bent tubes) at the mid span point of each of the bent tubes. You may want to weld on some sort of "catch" to the cradle bracket to positively hold the dowel in place so the epoxy isn't taking all of the pushing force. This should laterally brace each of those top tubes and allow the force to continue through instead of buckling the tubes which are already biased in the inward direction from fabric shrinking.