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Thread: Jim's Kitfox 1 build of pristine kit from 1988

  1. #1

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    Default Jim's Kitfox 1 build of pristine kit from 1988

    I purchased an unstarted model 1 kit a few years ago and have made moderate progress. I am hoping That if I create a build log, I can stay motivated to work on this project. When I bought this kit I made an inventory. Everything was included except the wheel hubs, a couple bolts, window plastics and patterns, Then ext step was to clean off a very light layer of rust from the fuselage, stabilizers, engine mount and struts. This required long hours of scrubbing with scotch brite pads and then spraying a coat of epoxy primer on the tubing before it could rust again.
    I then studied the various bulletins and directives to get a list of items that would need replacement, upgrades or modification. Kitfoxaircraft.com was very helpful because they have a service bulletin page that seems to cover everything from 1987 to present. These are the bulletins I think apply to model 1:
    #1 plastic spinner - NA , this kit has an aluminum spinner.
    #2 fuel valve , line modification - I am modifying the fuel system to use wing tanks and a rear header tank.
    #3 VNE and flaperons counterweights - I will either purchase the counterweights or add metal bar to the inside leading edge of the flaperons to balance them.
    #4, cracking near elevator control horn - I have welded .060 triangular gussets to the elevator as recommended.
    #5, main tank cap vent - I am not installing the main plastic tank.
    #6A , left control column pivot , Special procedure, has been followed.
    #9, Flaperons rib hanger reinforcement - I have made the 20 aluminum brackets that will be glued and riveted to the 10 ribs with flaperons hanger extensions.
    #10 - replace aluminum wing tanks - This is a some sad requirement, The set of two tanks are still in their original boxes. Seems like a waste. I was wondering if I could put a few layers of fiberglass around these tanks and use them anyway.
    #11 Rotax 532 car air vent tubes. - I will be installing an HKS 700e instead of the 532. Care will be taken to route vent tubes correctly.
    #20 flaperons mass balance mandatory - I will either purchase the counterweights or add metal bar to the inside leading edge of the flaperons to balance them as is done in the UK.
    #21 flaperons hinge bearing stop points. I have not starter end the wing assembly yet.
    #45 - elevator bel rank bolt inspection. I modified this bel crank to be like model 5 thru 7.
    Additionally I welded a second layer of metal to the strut where it attaches to the fuselage and triangular gussets to the rudder pedal stand posts.

    I will post this and then grab some pictures from my archives. I hope anyone interested can make suggestions and encourage me to stay motivated.
    JDB building KF1 SN#111

  2. #2
    Senior Member
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    Default Re: Jim's Kitfox 1 build of pristine kit from 1988

    Sounds like you are off to a good start on the plane. Stay busy and stay motivated, and it will fly one day. Then it will all be worth it. Keep us updated as your progress. JImChuk

  3. #3

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    Default Re: Jim's Kitfox 1 build of pristine kit from 1988

    pileOfStuff.jpgrustyBeginning.jpgprimingParts.jpg
    This is where I started after hauling the project home I had a large pile of parts and not a lot of room to work on anything. I was able to clean off the rust and put primer on the metal parts before I decided that I would need more space to work.

    I took two years off and built a workshop that I could build build in.
    workshopBuild.jpgnewWorkshop.jpeg

    With a place to build, I set up tools and tables and bought a middle grade TIG welding machine and got started.

    diffAileronMix.jpgelevatorPushTubeHanger.jpg
    Here are pictures of modification I thought were needed to make the plane fly better. After reading about the adverse yaw I put together a design for differential aileron/flap mixing, using an article I found online from cfisher.com from 2005. It is the basis for the modern Kitfox flaperon mixer. You can also see the linear electric push rod that will be used to set flap position in place of the manual linkage. I am missing a left hand so I am trying to make the controls more automated. I will program the positions for takeoff, cruise, and landing into a controller for the pushrod so that I can just push a button for the phase of flight I'm in.
    The other picture shows a modification I made for the elevator push rod swing arm. This will be tighter and stronger than the one sided hanger mount that it came with. (along with the service bulletin to check the bolt every 50 hours)

    Next I welded on 8 seat pan hanger tabs and two panel mount tabs.
    seatPanTabs.jpeg
    Moving forward I strengthened the rudder pedal stand tubes by welding on triangular gussets. I then made better rudder pedals out of some 4" aluminum square tubing cut in half.
    rudderPedalMod.jpegrudderPedals.jpg
    From what I gathered in my reading, It seems that it is correct practice to use stainless sheet for firewall material. The original KF1 came with aluminum. I found some .018 stainless sheet at a local metalMart and made the firewall.
    firewall.jpeg
    Next post, I'll cover Upgrades/mods made for landing gear and tail feathers.
    Have a nice day everyone.
    JDB building KF1 SN#111

  4. #4
    Senior Member bbs428's Avatar
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    Default Re: Jim's Kitfox 1 build of pristine kit from 1988

    Great start on a cool bird! Glad you have the skills to tackle the mods. I'll be following along on your journey.
    Somebody said that carrier pilots were the best in the world, and they must be or there wouldn't be any of them left alive. — Ernie Pyle

    Brett Butler
    Flying: 1998 Model 5 Outback, 912ul Zipper 110hp, G3x avionics, ss7 upgrades

  5. #5

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    Default Re: Jim's Kitfox 1 build of pristine kit from 1988

    I have finished the welding on my horizontal stabilizer and elevator. I added 4 inches to the width and 4 inches to the elevator cord. I added a trim tab and made the tips of the elevator into aerodynamic counter balancing tips. (Don't really know the technical term for that) I also welded on the corner gussets that are recommended for adding strength surrounding the elevator control crank.
    image.jpgimage.jpgimage.jpg
    JDB building KF1 SN#111

  6. #6

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    Default Re: Jim's Kitfox 1 build of pristine kit from 1988

    I cut out a set of symmetric air foils for the horizontal stab and elevator. I used a plot from an NACA thin airfoil but after getting them all cut and fit I'm thinking the thickness is too much. About 2 inches thick at the hinge line. Too bad I drilled them out because now I don't have enough material to narrow them down. I wanted the higher effectiveness of the foiled tail compared to a flat tail surface. Maybe I'll cut out a new set of narrower ones.
    .image.jpgimage.jpg
    JDB building KF1 SN#111

  7. #7

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    Default Re: Jim's Kitfox 1 build of pristine kit from 1988

    I finished welding the new landing gear. I have the shock rods set to hold the gear legs at a 50 degree angle at gross weight. The springs are 250 pound per inch with a 5 inch compression. If I load them with 1 inch of compression they should support the static weight of the airplane and compress about one additional inch at gross weight. That will leave 3 inches of additional compression before hitting the end of travel. To hit the end of travel the landing would be have to produce a 3G force. Before committing to these springs. I am looking at some mountain bike shock absorbers in a doubled configuration, similar to the monster shock layout.

    image.jpgimage.jpg
    JDB building KF1 SN#111

  8. #8
    Senior Member bbs428's Avatar
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    Default Re: Jim's Kitfox 1 build of pristine kit from 1988

    Nice work Jim. Interesting build for me as I'm only familiar with the IV, V, VII models. Great pics!
    All the best!
    Somebody said that carrier pilots were the best in the world, and they must be or there wouldn't be any of them left alive. — Ernie Pyle

    Brett Butler
    Flying: 1998 Model 5 Outback, 912ul Zipper 110hp, G3x avionics, ss7 upgrades

  9. #9

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    Default Re: Jim's Kitfox 1 build of pristine kit from 1988

    Since my last post, I have finished the landing gear and spayed epoxy primer and base coat enamel on all of the metal parts. I faired out the vertical stabilizer so that it has a symmetric airfoil shape. I made a fiberglass end cap for the rear of the vertical stabilizer and put it all together with Hysol epoxy. The challenge now is to make the gap as small as possible with the original hinges, or to change the hinges to use the extended rod ends as used in the newer kit fox design.

    LayupTailPost.jpgTailpostCure.jpgInstalledTailPost.jpg
    JDB building KF1 SN#111

  10. #10

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    Default Re: Jim's Kitfox 1 build of pristine kit from 1988

    I have moved on to a challenging task of making a cowling that will fit over the HKS-700 engine. I put on the firewall and engine mount and then mounted the engine. I then covered the engine and areas of the firewall that might get resin stuck to it. I then chopped up two sheets of pink insulation foam and built it up around the engine. I used a hand saw and a sure form to rough out the shape of the cowling and then smoothed it up using drywall mesh sandpaper. After I was satisfied with the shape I coated everything with drywall mud. I have sanded and applied 3 layers so far. after it is smooth I will use some high build primer to Seal the surface and tune it all up with bondo and primer. I will use a bunch of left over cans of spray paint and make a fine shiny finish. I can then wax it all and apply 6 layers of fiberglass. Once cured, I can remove the fiberglass shell and it will become the cowling.
    3CoatMud.jpgIHKS-700Mounted.jpgInitialFoamShape.jpgAddingPinkFoam.jpg
    Attached Images Attached Images
    JDB building KF1 SN#111

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