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Thread: 109JB's Kitfox IV rebuild

  1. #11
    Senior Member
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    Default Re: 109JB's Kitfox IV rebuild

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

  2. #12
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    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.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

  3. #13
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    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.

    20200404_130238.jpg

    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.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

  4. #14
    Senior Member Dusty's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    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

  5. #15
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    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.

    20200404_153202.jpg

    This one shows how far past you have to go the account for spring back of the tube.
    20200404_153820.jpg

    Here it is after releasing the tension on the screw
    20200404_153947.jpg

    Here is a sight picture of the top longeron showing how much it bent during the mishap.
    20200404_154818.jpg

    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.
    20200404_155334.jpg
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

  6. #16
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    As a reminder, this is what the airplane looked like before I started straightening this morning:
    20200401_170336.jpg

    This is what it looked like just before I put it away this evening.
    20200404_160632.jpg
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

  7. #17
    Senior Member Dusty's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    Thanks for the photos, now it all makes sense.

  8. #18
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    I have a question for all the more experienced Kitfoxers out there. This airplane has a little problem. Now that the fuselage is straight to where it needs to be I find that the leading edge of the flaperon on the right wing when folded will hit the horizontal tail. This happens when you rotate the flaperon into the vertical position next to the vertical stabilizer.

    It must have been built this way because when I got the airplane it came with a set of the wing trailering supports and the one that connects from the aft fuselage to the wing strut had been lengthened to keep the wing out far enough that the flaperon didn't need to be rotated to the vertical position. I know the 2 previous owners but not the original builder of the airplane. and will ask them if it was always this way but based on what I see it must have been.

    I didn't get a picture of this and I have since taken the wings off of the airplane.

    It obviously didn't affect the flight performance of the airplane because the 2 previous owners and others I know that have flown the airplane said it was a really nice flying airplane.

    If possible I would like to correct this because as it is the airplane would never be a candidate for an enclosed trailer since not being able to completely fold that wing makes it too wide.

    What do you guys think? Can it be rectified?
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

  9. #19
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    Default Re: 109JB's Kitfox IV rebuild

    Are you saying that the wing is lower at the tip then it should be? Looking at old pictures of my Kitfox 4 with the wings folded, the flaperon clears the elevator by about 3" with the flaperon tight against the vert. stab. My first thought would be to measure from the rear spar bolt hole to the lift strut attachment bracket. If that dimension is longer then it should have been, the wing tip would be lower. (less dihedral then it should have had) Compare both wings. Other then that, is the elevator level/parallel in relation to the wing carrythroughs? Or maybe I didn't understand your question. JImChuk

  10. #20
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    With the wings folded the right wing tip is lower in relation to the left wing tip. Not by much, but enough that you can't fold the right wing fully without the flaperon leading edge touching the fabric on the horizontal stabilizer. It clears the spars on the H-stab, but with the airfoil ribs it touches the fabric. Since I was recovering anyway, I did fold it all the way by cutting the fabric out of the innermost bay on the top of the H-stab. If I remember right the left wing clears by an inch or 2 but not more than that. Dang it. I should have taken pictures.

    Looking at the build manual I have, the placement of the wing strut brackets on the spar is different for the speedster. They are placed 1 inch farther outboard. This would mean less dihedral on the speedster which would lessen the clearance to the stab on the folded position.

    Measuring the geometry, the struts would have to be extended about 3/8" to get clearance when folded. I'll install them as built first and use a laser to see what the dihedral is on each side and if it matches first before making any decisions, but I think 3/8" might be doable on the strut heim joints.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

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