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About 109jb

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109jb's Activity

  1. 109jb added a post in a topic Which is the Widest cockpit and useful load   

    NO, NO, NO. 
    The useful load is the maximum gross weight - empty weight. The maximum gross weight is dictated by many things that all interact together. For more gross weight you might need more wing area, or more horsepower or both, but then you also have to address the structure to carry the additional weight. If you don't know what you are doing, then you could actually make a heavier airplane that has even less useful load. Or worse yet, you could go fly and find out the hard way that the structure isn't up to the task. Unless you have engineering knowledge on how to do this, then you are best off finding an existing design that already fits your needs and has the useful load required rather than trying to redesign one.
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  2. 109jb added a post in a topic Rotax 447 vibration diagnosis   

    So I was able to fly it again after changing the mounts, balancing the prop, and fixing the prop tracking issues. Vibration is still there but definitely much less. On inspection I see that one of the started bolts can touch the firewall with very little effort. I'm thinking this may be the issue and will address.
    I do have a question though. When flying yesterday, operating at about 4000 rpm descending from downwind, the EGT on the front cylinder got much too hot for my liking. Wound up chopping it, descending, and then bringing in power but with more load on the prop to get it down. The descent was not unloading the prop much at all, and on my 582 powered Kitfox would not have been an EGT issue.  After flying I lowered the clip one notch on the jet needle and will try that, it is now at the lowest notch, but I remember on my 582 I went from 11G2 needles to 11K2 needles to correct the midrange lean spot in the 582. Is there a similar change for the 447? It currently has a 15K2 stock needle and stock 2.70 needle jet. perhaps I need a 2.72 needle jet?
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  3. 109jb added a post in a topic Rotax 447 vibration diagnosis   

    Yes. I have a balancer I made for GSC props. One 1/4" washer 6 inches from center can be detected. 
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  4. 109jb added a post in a topic Rotax 447 vibration diagnosis   

    Well, vibration is better, but still there to some extent. I took the prop off and re-varnished the blades, checked balance and set pitch on very flat table. Prop flange checks good on dial indicator and tracking with prop installed is within 1/16". Through all of this, I found that the initial tracking was off 3/4", and balance was a little off but brought into balance using a few additional washers on the hub. Ordered new engine mounts, and it looks like the aluminum angles bolted to the engine block have been rubbing the steel tube mount bolted to the firewall.  I will take a burr and die grinder and put a little relief in when I replace the rubber mounts and see what happens.
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  5. 109jb added a post in a topic Rotax 447 vibration diagnosis   

    The current prop is 60 inches and the ground clearance is marginal in my book. Another reason for slightly larger tires. 64" would be 2" close to ground and would not work IMO. 
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  6. 109jb added a post in a topic Rotax 447 vibration diagnosis   

    Thanks. I will check those things out.  Overall I'm really happy with the airplane. It flies really well although it does have a couple little quirks. Visibility over the nose is fantastic on the ground requiring no s-turns at all, but the flat attitude has a drawback. It sits flat enough that a full stall landing would really "hook" the tailwheel and slam the mains on. I'll just have to figure out how tis airplane "wants" to be landed. It wheel lands really well and the ground handling is a piece of cake. In-flight it handles really well except has a lot of adverse yaw which may be due to the non-plans aileron design, but it is easily manageable. Overall I'm really pleased with the airplane because I got it pretty cheap. I'll do what I can with the 447, but eventual plans will be to put a 1/3 Corvair engine on it. I happened to have a Corvair engine project that was for another airplane that didn't pan out, so I'm going to use the Ultravair plans available online and build the 1/3 Corvair for the J3Kitten. I'll be flying it with the 477 until then though.
    Thanks again for the tips. I will let you know what I find.
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  7. 109jb added a topic in Rotax and other engines   

    Rotax 447 vibration diagnosis
    Not really Kitfox or Avid Flyer related because it isn't either but you guys have helped before with tuning on my 582 powered Kitfox so thought I would give this a go here.
    I sold my 582 powered Kitfox 4 and in its place I bought a Rotax 447 powered Hipps J3 Kitten that I've nicknamed "Patches" because of all of the fabric patches I had to put on to make it what I consider airworthy.
    Enough introduction, now to the problem. The engine seems to be running well except that it vibrates. Power is good and getting 6200 RPM in a comfortable climb. The vibration happens at pretty much all RPMs but it is more noticeable at mid-range RPMs. This Rotax 447 is a single carb and the new digital EGT gauge I installed shows the EGTs are running in the 1000 to 1100 deg F range at everything above low speed. The EGT spread between the 2 cylinders when cruising and vibrating is only about 20-30 deg F, and CHTs are about 350 (analog gauge) and appear to be very even. These things have been done or are just other information. New BPR8ES plugs (inverted engine) gapped to 0.015", 2 blade ground adjustable GSC propeller 60" diameter.
    This is what I plan to check next:
    Both prop blade pitch anglesProp balanceProp trackingCylinder compressions for good and evenAny other ideas?

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  8. 109jb added a post in a topic Kitfox 4 1050 for sale   

    Sold.  The Kitfox went to a new home today.
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  9. 109jb added a post in a topic Kitfox 4 1050 for sale   

    Price reduced to $27,000
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  10. 109jb added a topic in For Sale and wanted, you got it, I want it   

    Kitfox 4 1050 for sale
    FAA finally got the registration to me, so I'm selling the Kitfox 4 1050.  Asking $29,000. Details in the pdf at this link. https://drive.google.com/file/d/1GEExdq3N1pKNp7ydmuPsxSQTRP219fHe/view?usp=sharing

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  11. 109jb added a post in a topic Ideal Idle RPM   

    Not a 670, but on my 582, with stock jets I could never get idle below about 2200 rpm without it hammering and running rough. It was way too rich. If I remember right stock idle jets are 55.  After re-jetting I can idle down to about 1700 before it gets rough and that is with 40 or 45 idle jets. I set idle to wherever it will not quit or run too rough on the ground. Right now it is set about 1600 rpm which is fine and smooth until the last part of roll-out on landing and then it starts to hammer a bit and I just bring the throttle in enough to smooth it out.
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  12. 109jb added a topic in For Sale and wanted, you got it, I want it   

    WTB Rotax 582 Ignition coil
    EDIT:  Never mind. I found one an hour away from me.
    Went to fly and the ignition check showed one side dead. I switched the 2 coils around and the problem followed the coil, eliminating the stator, pickup and ignition switch. So, my Kitfox is in need of an ignition coil. If anyone has a good used ignition coil for a Rotax 582 they would be willing to sell, let me know. Would like to get it quick because I go in for a surgery on July 11th and would like to get some flights in before I am laid up.  Alternately if someone would loan me one until I can get one elsewhere I'd go for that too.
    John Brannen
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  13. 109jb added a post in a topic 109JB got another wrecked Kitfox   

    This airplane has a 10 gallon header tank behind the instrument panel that the gauge is hooked to. It only has a 6 gallon wing tank in the right wing. That one has a sight gauge.
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  14. 109jb added a post in a topic 109JB got another wrecked Kitfox   

    Some pictures while flying today.

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  15. 109jb added a post in a topic 109JB got another wrecked Kitfox   

    Got some pictures of the airplane in the sunshine yesterday.

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