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Thread: Bent Fuselage opinions, solutions, thoughts...

  1. #1
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    Apr 2010
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    Bryan, Texas
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    Default Bent Fuselage opinions, solutions, thoughts...

    My old KF 4 that I sold was involved in an on the ground loss of control. I believe one brake was accidentally applied, causing the loss of control on landing and the plane verred off to the right, basically ground looped, and the grove landing collapsed. I have gotten it back to finish the repairs that were already started. (finishing wing tip repair, and flaperon replacement) There is an area under the passenger door that apparently had some wrinkled fabric, that was being worked on prior to me getting it. It was believed that something ripped the fabric, but when I look at it, it appears that there is some bent tubing, including the Longeron tubing that caused wrinkled fabric.

    Couple of questions for folks who have dealt with this.....

    There is no kinked tubing but there are 2 areas that the paint chipped off in a ringlike fashion around the tubing at both ends. Looks like these were areas that may have flexed. There is a slight arch in the bottom of the door frame that is parallel the arch in the longeron tubing so my thought is that when the landing collapsed, it torqued against the longeron and arched both lengths of tubing. The original builder reinforced the area around the landing gear so it held up but essentially moved the stress farther back.

    Looking for Thoughts on.....is it necessary to cut out this tubing with the rings of paint missing on each end and replaced them?

    What are the odds that I could straighten this area as a unit, like using hydraulics to pull the slight arch out of both pieces of tubing at the same time.

    Any other words of wisdom on dealing with this? I have seen posts about this but none with just minor bends like this.

    Here are some pics:
    IMG_4574.jpgIMG_4573.jpgIMG_4576.jpgIMG_4572.jpgIMG_4577.jpgIMG_4575.jpg

  2. #2

    Join Date
    Dec 2009
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    Lawrenceville, GA
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    180

    Default Re: Bent Fuselage opinions, solutions, thoughts...

    If the tube isn't kinked it can be straitened. I've made a tool which is just a metal saddle and steel strap that can fit around and use a cheater bar. This is cold forming so work carefully.

    The area with missing paint/power coat should be checked for cracks. It can be welded if need be.

    I would peel the fabric back from the areas that need work rather than cut it. After the other repairs the fabric can be glued back on in the same order it came off. You can minimize the amount than needs recover and paint.

    And yes the cheap hydraulic frame tool from harbor freight is helpful to get a tube to move a little at a time.
    Building a KF IV Classic

  3. #3
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    Default Re: Bent Fuselage opinions, solutions, thoughts...

    So tried to straighten, and put 4 tons on it. It would straighten out and then come right back to being bent. In addition, I discovered that the truss under the front seat is bent up and back about 1/4"-1/2". I am thinking it's time cut out bent pieces and weld new pieces in. This is gonna be more involved than than I or the owner has time for. Anyone interested in a project? Fairly Easy fix if you have the time and skills.

  4. #4

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    Lawrenceville, GA
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    Default Re: Bent Fuselage opinions, solutions, thoughts...

    Quote Originally Posted by Jerrytex View Post
    So tried to straighten, and put 4 tons on it. It would straighten out and then come right back to being bent. In addition, I discovered that the truss under the front seat is bent up and back about 1/4"-1/2". I am thinking it's time cut out bent pieces and weld new pieces in. This is gonna be more involved than than I or the owner has time for. Anyone interested in a project? Fairly Easy fix if you have the time and skills.
    Did he actually hit something or is this all from the force of the ground loop?
    Building a KF IV Classic

  5. #5
    Senior Member
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    Apr 2010
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    Default Re: Bent Fuselage opinions, solutions, thoughts...

    The right side landing gear (grove) collapsed back at 45 degree angle under the belly of the plane. The gear never made contact with the plane but it torqued the reinforcement plate that was added in the past to accommodate the grove landing gear. This caused the bend in the tubing. Sad part is, this is will be less than $100 worth of tubing to repair.

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