109JB's Kitfox IV rebuild

[109JB]

Did you fly that beast home with all the bent tubing etc? I like the floppy windscreen. Duct tape might have been appropriate

Fortunately it was only 20 miles from my house and I won the auction for it. Trailered it home.

[Dusty]

That spring setup is a bit suboptimal!
can you post a photo of your tube straightener in action as I can't quite picture how it operates.
cheers

[109JB]

The weather looked a little iffy this morning, but cleared up so I was able to pull the airplane out and do a good bit of straightening of the tubes. Still a little more to go but I'm taking it slow. Here are some pictures of the tool I made in action:

This one shows it loaded onto the lower longeron. The screw is on the bottom and when you crank it it draws the straps and the center light coloerd plywood block toward the dark colored backbone board.

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This one shows how far past you have to go the account for spring back of the tube.
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Here it is after releasing the tension on the screw
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Here is a sight picture of the top longeron showing how much it bent during the mishap.
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This is after about 10-15 minutes using the straightener. I go real slow because you don't want to overbend it back the other way. So I go slowly and a lot of times you have to slide the yoke around to the high spot because it may not always be in the center and cna change as you slowly work th tube back straight. Just to note, this isn't straight enough but its getting very close.
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[109JB]

As a reminder, this is what the airplane looked like before I started straightening this morning:
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This is what it looked like just before I put it away this evening.
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[jrevens]

You’re right, John. I was obviously not thinking very clearly. If the 2 pivot points on the fuselage are not in exactly the same alignment with each other, comparing the right side to the left side, or the fuselage & tail structure isn’t straight, or the wing dihedral and washout isn’t exactly the same, etc., then the position of things when folded may not be in alignment & where you want them to be. You & I and everybody else knows this, so I don’t know why I was thinking the way I was. Sorry about that!

[Dusty]

From what I have seen this appears to be a speedster thing possibly to stop binding under high G.
I have only seen one speedster here, it also had an extra mass balance per side.

[avidflyer]

Page W-D-10 in my Kitfox 4 manual describes how to slot the flaperon for the speedster model. JImChuk

[109JB]

Thanks guys. That is exactly what my airplane has. The manual says it is for high load situations. If i were the original builder I don't think I would have put the slots in. Oh well. Not much I can do about it now. Thanks again for letting me know what they were.

[109JB]

Got a little more done. Last night I made a towbar because moving it in and out of the small space where I have it in my barn right now was a real pain with the wings folded. I was going to just buy one until I saw the prices. I spent a total of $14 for 2 wheels and the rest of it is a piece of 1/2" solid bar, a piece of 3/4" black gas pipe, a few washers an couple cotter pins and a piece of a can of rustoleum green paint I had lying around. about an hour of cutting and welding and I had this.

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This morning I went about making a tubing straightener. I wanted something easier to handle that the 2x4 setup I used on my other kitfox because you needed 4 hands to operate that setup. I had a hardwood picture shelf thing that was getting tossed that I used for the backbone. The clamp screw is made from a 6" carriage bolt and a couple 1/4" bolts I had on hand. this screws into a nut that is welded to the 2 straps that have a series of holes spaces about 2 inches apart From there are some 3/4" plywood blocks that I drilled a 1/2" hole through the edge and then cut done the center of the hole to straddle the tube. That's a piece of 1/2" bar in there where the longeron or other tube being straightened would go. The outer blocks can be moved closer together or farther apart depending on length needed.

20200404_130300.jpg

So I did some straightening that I'll talk about later, but while lying under the airplane working on straightening tubes, I saw this:

20200404_135940.jpg

Anyone see a problem with this picture?

Back to the tube straightening. I worked on it for about 1-1/2 hours and got things pretty straight. It is crammed into basically the size of a small 1-car garage so I couldn't get pictures too well, but all of the longerons are going to straighten fine, and I even got the 2 diagonals pretty straight but not quite straight enough. I will have to cut a section of those out and replace, but it looks like I will be replacing a total of about 12 inches of tubing to get the fuselage fixed. I'll see if I can get some pictures later.

[jrevens]

In analyzing this, one thing that would cause the "misalignment" when folded is a slight difference in the angle or position of the tube that is welded to the spar carry-through tube of the fuselage, that the spar attachment bolt goes through. Just the tiniest misalignment of that tube (the holes drilled in the carry-through for it) when it is installed/welded will result a considerable misalignment out at the wingtip when folded, regardless of how correct the dihedral is in the flying position.