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Thread: Kitfox IV `project fifty`

  1. #11
    motortommy's Avatar
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    Default Re: Kitfox IV `project fifty`

    so today I wanted to learn more regarding the "batwing design" of my horizontal. Very uneven look although I like the slightly speedster styled tails.
    Look at the trim tab area

    IMG_4969a.jpgIMG_4976a.jpg


    Insight shows a mess of thin, unattached ribs, hold in place only by PVC electric tape. Some housebuilding insulation foam was added for "strength"
    IMG_4977a.jpgIMG_4979a.jpg

    OK. steelframe is good, w/o corrosion. I think, I like to have a slightly shaped tail again (hope that`s not naughty!). At the moment vertical is flat while horizontal was with profile. Where to find a suitable pattern/shape? My manual shows only an outline of a horizontal rib with 1.25 height? What about the elevator? Further 6pcs. are mentioned, but if you check 1st pic. there are many more. So how to proceed?

    Next there is a trim servo labeled with 8V or alike. It`s still working, but I have only 2 wires and there is no end stop (elctronic/mechanic). Should I keep this item or is there a more modern one nowadays standard?
    Marc
    rebuilding IV-1200
    `Kitfox fifty`

  2. #12

    Default Re: Kitfox IV `project fifty`

    I don't even know what to say..... I can't believe there are builds like this out there. Good thing you decided to take it apart. This will be a good one to watch you work through!
    Building Model 6
    912 IS
    Garmin G3X
    http://northernfox.build
    C-FKLO

  3. #13
    Senior Member
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    Default Re: Kitfox IV `project fifty`

    Whoever owned and flew this before had a death wish. That “workmanship” you’ve uncovered is appalling. Go well with the restoration.
    David
    SS7 Builder

  4. #14
    Senior Member HighWing's Avatar
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    Default Re: Kitfox IV `project fifty`

    When I ordered my first Model IV, I wanted the trim tab option so ordered the "Speedster" elevator with the trim tab cut-out and ribs. I found it curious that the ribs sent were similar to what you show in the pictures. I was not too pleased with the rib design that provided separate airfoils on the horizontal stabilizer and elevator - sort of like an hour glass shape on its side. I opted to do something a bit different by providing a coordinated airfoil shape from leading edge to trailing edge - typical on most airplanes. The airfoil shape was not "engineered" but laid out by placing the stabilizer elevator assembly on a flat surface, putting blocks under leading and trailing edges to level and then placing a piece of wood inboard to outboard that provided the lift where I wanted it. Thin aluminum, strips placed fore and aft and secured with clamps to the leading edge and trailing edge tubing gave an airfoil like shape that could be copied to ribs. For weight saving, I chose 1/4" urethane foam for the ribs that were then covered each side with a single layer of light weight fiberglass cloth and resin. After cutting and sanding to the desired shape, the edges between the glass surfaces was then covered with epoxy resin thickened with micro-balloons and finish sanded. Due to the tight hinge line - welded tube hinge - designing the gap closure resulted in some challenges. The attached diagram explains what was done to solve that problem. The full chord ribs also gave the needed spacing for a smooth transition to the trim tab on the elevator.

    On build number 2 in the hope of saving a little weight, I made some patterns from which I made some fiberglass shapes that could then be bonded to the ribs on either side of the hinge line to provide the gap seal. The last photo shows the geometry of the needed shapes. Both ideas take a bit of time, but in practice, I never felt a need for gap seal tape to gain maximum elevator authority.

    On the vertical stabilizer - rudder gap, the rod end bearing hinges gave sufficient spacing that the gap closure was more typical and didn't require the complex shapes needed on the elevator hinge area.
    Attached Images Attached Images
    Last edited by HighWing; 04-21-2019 at 03:11 PM.
    Lowell Fitt
    Cameron Park, CA
    Model IV-1200 912 UL

    My You Tube Channel

  5. #15
    motortommy's Avatar
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    Default Re: Kitfox IV `project fifty`

    First, thanks for your comments!
    I‘d like to clarify that it isn‘t my concern to blame former owners or builder of my plane. Especially the original builder did a great job in 1995 and realized nice details which are still here today - 25 years later! Me so far, I did only tear down things to see and certainly learn to get a reasonable rebuilt done- someday! Not in position to point at somebody...

    Thanks Lowell for the insight into the world of tail-airfoiling! I will check and see what I could adapt/realize. Overall I‘m in need to save some weight, means the plane is too heavy at the moment...
    Marc
    rebuilding IV-1200
    `Kitfox fifty`

  6. #16
    motortommy's Avatar
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    Default Re: Kitfox IV `project fifty`

    going on with the horizontal, I ask myself if the elevator horn is initially straight or some kind angled sideways? (pls. see pic)
    Would be kind if someone could confim, I was already close to straighten out both elevator surfaces as I found the important information in the builders manual that there is some deliberately misalignement...

    So what about the horn?
    IMG_5042.jpg

    Thanks!
    Marc
    rebuilding IV-1200
    `Kitfox fifty`

  7. #17
    motortommy's Avatar
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    Default Re: Kitfox IV `project fifty`

    I´m still here…in case some have imagined the newbie quit already!

    More disassembly is going on. Each section has its surprises
    Hoping that I could complete and partly renew existing stuff, (e.g. like wiring) it turned out that cleaning up the mess is better…
    IMG_5332.jpgIMG_5333.jpgIMG_5337.jpg
    Marc
    rebuilding IV-1200
    `Kitfox fifty`

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