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Thread: 109JB's Kitfox IV rebuild

  1. #1
    Senior Member 109JB's Avatar
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    Default 109JB's Kitfox IV rebuild

    So I finally got a chance to get my project airplane home today. This is a Kitfox IV speedster powered by a 80 hp Rotax 912 UL that I bought from an insurance auction. It actually belonged to an acquaintance of mine and was located only about 30 minutes away. The airplane suffered a loss of engine power followed by a forced landing to a waist high bean field, which ended in a rapid nose-over. The vertical tail struck the ground and the aft fuselage got bent as did the vertical stab. The horizontal and elevator look OK as do the wings and struts. The plan is to rebuild the airplane while incorporating a few key modifications which will include these main mods but also a lot of little weigh next to nothing mods:


    1. Landing gear area reinforcement


    2. Tail spring mount reinforcement


    3. Fuselage widening (Murle Williams style)


    4. Provisions for future autopilot servo mounting


    5. Upgraded panel with only engine monitor, Garmin G5X, tablet computer for navigation, intercom, radio, and transponder.


    6. Upgraded baggage area.


    It will probably be a little while before I can really get into it as I have to clean out and sell my father's house since he passed away recently. He was a pilot too and I had wanted to get him airborne in the other Kitfox I have but his health never got well enough. I know he would have also loved to see the rebuild of this project airplane. I learned most of what I know about fabrication, welding, machining, and general mechanicing from him.


    Anyway, Here are some pics of it stuffed away in the storage part of my barn.

    20200316_165034.jpg
    20200316_165120.jpg
    20200316_165153.jpg
    20200316_165232.jpg
    20200316_165327.jpg
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)

  2. #2
    Administrator DesertFox4's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    Best of luck on the rebuild John. Sounds like some nice mods.
    A friend just installed a Garmin G5 in his Model 4 Kitfox and so far really likes it. The wide body mod is a nice addition too.

    Sincere condolences on the loss of your father John.
    So many of us here inherited our love for aviation from our dads and owe many of the very best times of our lives to their influence.


    DesertFox4
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    7 Super Sport
    912 ULS Tri-gear


  3. #3
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    Quote Originally Posted by DesertFox4 View Post
    Best of luck on the rebuild John...Sincere condolences on the loss of your father John.
    So many of us here inherited our love for aviation from our dads and owe many of the very best times of our lives to their influence.
    Thanks. What you say is so true. Even though we could butt heads like no other pair, it was because we were so alike. He is and will continue to be sorely missed. It has been 4 months since he passed away and Iíll still be doing something and think to myself ďI need to call Dad and Ö.Ē I then catch myself. Basically, it sucks!! Now clearing out his house I find things we worked on together from years ago and they bring up now bittersweet memories.

    On the airplane Iíve kept the list of structural modifications small because one of my goals is to keep weight down as much as possible. The logs for this airplane say it was 619 pounds empty and I want to keep it under 650 with the mods Iím adding. That would still give me 550 useful load to the 1200 gross. The structural mods I listed should only add a couple pounds and Iím considering covering with Oratex to keep weight to a minimum.

    I have looked at the Mangy Fox rebuild that Larry did and it looks great. Iím considering some tail enlargement, but I think Iíll put that decision off until later. I have a friend that has a long wing IV 1200 with a 912 so Iíll probably fly that airplane a bit this spring to check out the handling to decide if Iíll enlarge anything. I have a IV 1050 and on that one I do think it could use more vertical tail surface. I know the 1200 has a larger tail so maybe it is sufficient, or maybe I just need to increase the rudder chord to accomplish what I want to do.

    On that note I do have a question. Since this is a speedster it has the airfoiled tail surfaces. Since there is some tail damage, I was contemplating going back to the slab surfaces as it may be easier to do the repairs and eliminate the wood ribs. Can anyone who has flown both the slab and airfoiled surfaces relate if there is any handling or performance benefit to the airfoil surfaces? If there is, I would keep them but if it is only aesthetic then they may go depending on what I see when I pull the covering.

    The most major mod I want to do is eventually put in an autopilot to ease the workload on cross countries and a Grove gear. Beyond that there arenít really a bunch of mods I want to make. My experience so far with my IV 1050 indicates that it is a pretty decent airplane the way it is and I donít want to make it into something it isnít
    Last edited by 109JB; 03-17-2020 at 09:19 AM.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)

  4. #4
    Senior Member efwd's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    I bet Kitfox has the capability to cut new wood ribs for the IV. They are the simplest things to install. For the $ I would certainly aim to keep it a speedster. IMHO
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  5. #5
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    I have another Kitfox IV that has slab sided tail surfaces. Call me an odd duck but I actually prefer the aesthetic looks of them over the airfoiled speedster surfaces. I'm not at all worried about cutting ribs, most of the ribs are probably intact anyway. Even though I prefer the slab side surfaces I am more than willing to keep the airfoil surfaces for a benefit. In that vein, I have been reading past Kitfox articles and found one that said:

    "The vertical fin, rudder, stabilizer and elevator have a moresubstantial appearance with their newintercostal ribs and they do give the tailgroup a more effective feel in flight."

    So it sounds like there is a handling qualities benefit. Be nice to hear from anyone that has flown both to see the magnitude of this benefit.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)

  6. #6
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    Finally got some time to mess with this one and got the Rotax 912 running today. I know the guy this airplane used to belong to and it was a afternoon flight in late August last year when the engine quit when he was at about 1,500 ft agl. I didn't really do anything to get it running. I just ran a hose from the pump inlet to a gas can on the ground, put some run out blades in the prop hub and it started pretty much right away. The only things are:




    1. The temp and dew point (23/15 deg C) are right in the middle of the "moderate icing at cruise power"/"Serious icing at descent power", so I guess it is possible it was carb ice, but this Kitfox has the short filters back at the firewall which everyone say are not ice prone. I guess the reasoning is that with the carbs back there they are drawing in warm air from inside the cowl. I wonder about that theory though.


    2. The other thing I notice is that this airplane doesn't have a fuel return line as called for by this Rotax Safety Notice. I wonder if this could have been a case of vapor lock.


    Anyway, I'm happy it runs and for the price I paid I'm really happy. To let the cat out of the bag, I paid $5100 for the whole airplane and it looks like the only real problem is the little kink in the fuselage. It has a newish Garmin SL40 comm radio, a Terra transponder with encoder, and a flightcom intercom. I figure those are worth about $1500 all together.

    Here is a short video of the run today with flopping windshield and all.

    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)

  7. #7
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    Another day of playing with my new project. Here is the second run of the engine after getting it home. I ran it for about about 5 minutes this time. Just enough to get it warm enough to do a full throttle run. It ran great but I must have the prop pitched too high as I could only get about 4800 rpm. I'm very very very happy. I still have lots of checking and running to do but it is going perfect so far.


    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)

  8. #8
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    Here are some pictures of the fuselage damage from the nose over. Not as bad as I thought. Looks like the longerons can be straightened, except for maybe one in one bay. Only a couple diagonals will need to be replaced. I'll probably straighten everything and then decide which ones don't cut the mustard. The 2 diagonals I think are kinked so they will have to go, at least the kinked section. The one picture with the colored lines shows the tubes that are bent. The green ones are those I believe can be straightened. The yellow ones are the ones that are borderline and the red ones are the ones I think definitely need replaced. I'll see once I start working on it. I may try to do some straightening before stripping it down to a bare fuselage.
    Attached Images Attached Images
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)

  9. #9
    Senior Member 109JB's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    I was doing a little on the airplane today and came across something that puzzles me. The flaperons on this airplane appear to be multiple piece units with a joint at every hinge location. I forgot to take a close up but you can somewhat see it in this picture. Basically it has 4 short flaperons and they have about a 1/4-inch gap between them with a small tab at the trailing edge to keep them aligned there. The gap is covered with a bit of white duct tape. Not sure I'm too keen on this arrangement but apparently it works. I've tried searching both on the forum and on the internet but can't find anything on this. Anyone know about this? My other Kitfox IV has one piece flaperons.

    20200401_164924.jpg

    Edit: Zoomed in you can actually see it pretty well. Here are a couple cropped showing the joints. They still have some tape on then in these.

    Flaperon close up 2.jpg
    Flaperon close up.jpg
    Last edited by 109JB; 04-03-2020 at 07:54 PM.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)

  10. #10
    Senior Member Dusty's Avatar
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    Default Re: 109JB's Kitfox IV rebuild

    From what I have seen this appears to be a speedster thing possibly to stop binding under high G.
    I have only seen one speedster here, it also had an extra mass balance per side.

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