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Thread: Welding and repairs used Kitfox

  1. #1

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    Default Welding and repairs used Kitfox

    I looked at a video on the Kifox web page and I saw a few seconds of the factory construction of the kitfox as they were putting one together. I was supprised to see they were mig welding the fuselage together or so it seemed. (It was not Oxy/Ac welded). Do they stress releive the fuselage after welding ? Is the fuselage especially the lower longerons oiled or not ?
    If I were to buy a used kitfox requiring some tube replacement can I do that or does it have to be done by an A&P mechanic? How about recovering? Can I do that? I can check with PolyFiber and see if they have envelopes for the kitfox. But if not, can I get envelopes from Kitfox for the older models or do they just cover using a blanket method?
    Just a few questions that I would like to have answered before I get involved with a project that will require a lot of that type of repair.

  2. #2
    Senior Member SkyPirate's Avatar
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    Default Re: Welding and repairs used Kitfox

    how much damage does this kitfox have? there is more to it then just replacing a tube here and there if the fuselage has excessive damage,..
    and the wings? what kind of shape are they in?

    Chase

  3. #3
    Super Moderator Av8r3400's Avatar
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    Default Re: Welding and repairs used Kitfox

    Quote Originally Posted by PA-17 View Post
    I looked at a video on the Kifox web page and I saw a few seconds of the factory construction of the kitfox as they were putting one together. I was supprised to see they were mig welding the fuselage together or so it seemed. (It was not Oxy/Ac welded). Do they stress releive the fuselage after welding ?
    MIG welding is the norm. No they are not stress relieved.


    Is the fuselage especially the lower longerons oiled or not ?
    No


    If I were to buy a used kitfox requiring some tube replacement can I do that or does it have to be done by an A&P mechanic?
    As the owner of an experimental aircraft you can do any repair, modification or maintenance you wish. You will need an A&P do the condition inspection (similar to an annual on a certified plane) for an amateur built experimental.


    How about recovering? Can I do that? I can check with PolyFiber and see if they have envelopes for the kitfox. But if not, can I get envelopes from Kitfox for the older models or do they just cover using a blanket method?
    You can do any of the covering or cover repairs. The blanket method is what is used on these. I know of no envelopes available. The blanket method is easier, anyway.
    Av8r3400
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    Senior Member SkyPirate's Avatar
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    Default Re: Welding and repairs used Kitfox

    If you opt to purchase this plane and repair it,..using a mig welder ..just preheat the joints first,..this will ensure that you don't get a cold weld and use a telescoping tube on the inside of the repair joint . use a 75/25 mix with .030 wire or a tri mix with 2 to 11% helium.
    the best way would be to tig weld it,..no perocity in the welds this way,..no perocity means less distortion end result ,less shrinking ,..
    with a mig,.. look at the tube like a clock,..weld from 4 oclock to 8 oclock first then 12 to 4 and 12 to 8,.welding the bottom first keeps the heat in the tubing for better welds.
    I'm curious how much damage is done first,..if the fuselage is out of square then you must square all crucial points first prior to any welding new tubes in.

    Chase

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    Default Re: Welding and repairs used Kitfox

    Av8r3400:
    It is good to know that the repairs can be done by the owner,including recover. I was not sure about that part. I did know that the original builder had the right to repair and inspect the aircraft but that was the end of my knowledge on the subject.Thanks for that information.

  6. #6
    Senior Member SkyPirate's Avatar
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    Default Re: Welding and repairs used Kitfox

    If this is a rust issue,.and not damage due to a wreck.I'd drill every tube that concerned me and check the thickness of the tubing wall at the bottom of the tube or where water might have been trapped. you can weld the holes after checking the tube.

    Chase

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    Default Re: Welding and repairs used Kitfox

    Chase:
    Plane not wrecked as far as I know. But it has been stored outside and looks like it. I would guess some tubing may be rusty. Bottom of rudder looks discolored in the photos. If the mice have not made it their home the tubing and spars may be all right. The price seems to good to be true and you know what they say about that.

  8. #8

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    Default Re: Welding and repairs used Kitfox

    Chase, Good idea about drilling 'small' holes in the bottom of selected tubes, then rewelding.
    Question: Do you guys ever use a back purge? How about filling up all the tubes with n2, co2 or argon, then welding to trap the gas inside? Sound like to much? - Lion8

  9. #9
    Senior Member SkyPirate's Avatar
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    Default Re: Welding and repairs used Kitfox

    Tom ,,I have done that with argon and I'm doing that now on the plane I'm building ,..Argon works best,. because I had planned on this I drilled every connection point prior to welding so all the tubes would be exposed to a charge,.at the nose of the fuselage will be an inject point at the tail a purge point,..to each his own as to do this or not,..I also do it on the strut tubes.

    P-17 if you plan on blasting the fuselage,..use the silycon bead blasting material,..don't use sand or high carbon based blasting materials,.. because 4130 is a low carbon material other then silycon blasting beads will eat the material away quick if held in one spot too long,.also carbon based sand blasting materials will put a slight magnetism to the fuselage which will raise havoc with your compass once your to that point .

    Chase

  10. #10

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    Default Re: Welding and repairs used Kitfox

    Chase:
    What documents should I get from the seller besides the Bill of Sale and the 2 log books?
    Is the operations and limitations a required document or can I get it from the group for the make and model I am considering?

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