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Thread: KF IV Support Tube Break

  1. #31

    Join Date
    Aug 2013
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    Angola In
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    89

    Default Re: KF IV Support Tube Break

    Hi Paul,
    Might I suggest placing a reinforcing tube on the inside of the original tube.
    If it's 049 it might be a little loose but easy to install. Angle cut to fit,drill a pair of small holes thru the original tube at each end. Tach weld the gap,weld thru the end holes flush,then finish weld the gap. Easy and stronger than stock.

  2. #32
    P Morel's Avatar
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    Jun 2008
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    Locust Grove, GA
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    122

    Default Re: KF IV Support Tube Break

    Quote Originally Posted by Dave Holl View Post
    Anyone know if the gasket remover would work on the protective covering on the flaperons?
    This doesn't have anything to do with the thread but this is how I removed the protective covering on the flaperons. Jasco paint stripper for $11 @ Lowes

    https://www.youtube.com/watch?v=pvTJyIaatCQ
    Paul Morel
    912 Speedster

  3. #33

    Join Date
    Oct 2011
    Location
    Canada
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    187

    Default Re: KF IV Support Tube Break

    Quote Originally Posted by HighWing View Post
    Sorry here too. My guess is that the tubing is .049" wall thickness.

    I have see similar damage after hard landings. As I understand it, one problem with typical welding techniques is the concentrated heat that will often result in hardening of the metal near the weld.

    From "Bearhawken"
    "Since the transition temperature required for hardening carbon steels is always less than the melting temperature, there is always a region near the weld where the "hardening" temperature was reached. A quick and precise weld, like TIG or MIG, will heat a narrow zone quickly to the molten point. Since the heated region is very small, it also cools quickly, by radiation, by conduction to the air, and by conduction into steel a short ways away from the weld that was NOT heated. This rapid cooling near the weld acts line a quench and causes a narrow hardened region to form alongside the actual weld. This region is quite brittle and will easily crack unless the weld itself is "normalized."

    I seriously doubt the welds on our fuselages are normalized. I wonder whether the fuselage was welded up in winter or summer.
    Lowell is correct - MIG welding works well but without normalization hardness will happen and cracking likely.

    This is why I like to oxy.acet welding 4130 especially in joint and cluster areas. he biggest laugh is the guys with 120V MIG home welders that are welding 4130 . Actually quite scary as they go fly these

  4. #34

    Join Date
    Aug 2013
    Location
    Angola In
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    89

    Default Re: KF IV Support Tube Break

    Quote Originally Posted by Dave F View Post
    Lowell is correct - MIG welding works well but without normalization hardness will happen and cracking likely.

    This is why I like to oxy.acet welding 4130 especially in joint and cluster areas. he biggest laugh is the guys with 120V MIG home welders that are welding 4130 . Actually quite scary as they go fly these
    I guess I don't understand why a 120 volt mig won't do a good job on tubing
    We commonly use in aircraft? And as far as worrying about hardness caused
    by rapid cooling. Just preheat the area too hot to touch 160/200degrees,
    before welding and let it cool slow. Cover if necessary.
    I have very good 120 and 220 mig welders and a very nice tig setup,
    I think pre and post welding prep has more to do with success than the type
    Of welder.?? Just my 2cents

  5. #35

    Join Date
    Oct 2011
    Location
    Canada
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    187

    Default Re: KF IV Support Tube Break

    Quote Originally Posted by Xengineguy View Post
    I guess I don't understand why a 120 volt mig won't do a good job on tubing
    We commonly use in aircraft? And as far as worrying about hardness caused
    by rapid cooling. Just preheat the area too hot to touch 160/200degrees,
    before welding and let it cool slow. Cover if necessary.
    I have very good 120 and 220 mig welders and a very nice tig setup,
    I think pre and post welding prep has more to do with success than the type
    Of welder.?? Just my 2cents
    Exactly -- what I see is the 120V welders go home and the user thinks he is a pro over night and never welder before

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