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Thread: engines

  1. #1

    Default engines

    can you guys suggest which are good 4 stroke engines for standard mk 3 kitfox , cheers

  2. #2
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    Default Re: engines

    Without a doubt the Rotax 912. Super reliable and light weight, great performance and low fuel burn, there's no better choice.

  3. #3
    Administrator DesertFox4's Avatar
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    Default Re: engines

    I concur with James. I had a model 3 with 80 hp. Rotax. Really performed great. Very short take offs. Cruises easily 85 mph. plus if you need to.
    Back it down to 65mph or so and burn 1.8 to 2.3 gals. per hour. I put 900 hours on mine in 3 years. Loved it,


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  4. #4
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    Default Re: engines

    I've had good success with a Jabiru 4 cylinder in my Avid Flyer MK IV, which is very similar to a Kitfox 3, although with a higher gross weigh. I've put about 600 hrs on it. That being said, the 912 is probably better suited for our planes. Jabiru is actually a bit lighter and quite a bit simpler. Not quite the reliability overall compared to the 912 though. JImChuk

  5. #5

    Default Re: engines

    ok thanks for your input, was also wondering about vw or any other such as 3 cylinder light auto engines

  6. #6
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    Default Re: engines

    Neither the Jabiru or the V.W. engine will be nearly as exciting performance wise as the 912. The 2200 Jabiru is closest to the Rotax
    582 two stroke in power output. The V.W. is direct drive and heavy.

    The 912 and an Ivo 3 blade adjustable prop will put you into a whole other performance level. Do a Big Bore conversion to 105 hp and go again into a whole other performance level.


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  7. #7

    Default Re: engines

    thanks for that , my only other concern is once I have this nice smooth power what sort of cruise will the airframe put up with as here we are given a vne of 100mph and a max cont cruise of 80mph so what is the truth because I know that in the UK things are always under rated.

  8. #8
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    Default Re: engines

    80 mph cruise is no problem. The 80 hp with the Ivo prop can cruise faster but the model 3 likes 75 to 80 mph cruise. With in-flight adjustable prop ( which may not be legal in the UK, not sure) I could red line the airspeed in level flight but trimming at that speed is difficult.


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  9. #9

    Default Re: engines

    hi , yes 75-80 mph is what I cruise at now but I was wondering if it was given more throttle what would be a good safe max cruise. I wonder about this as on youtube I have seen two, one was a mk2 and the other a mk3 being flown at 95-100 mph in the cruise and thought as that is our vne here is it safe structurally to fly the plane for any length of time at that speed.

  10. #10
    Administrator DesertFox4's Avatar
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    Default Re: engines

    With the engine and prop combination I had on my model 3, it would exceed maximum operating speed slightly before full open throttle in level flight. I only approached these speeds in very smooth air. Even at 95 mph you are very close to the “red line”.
    Not much safety margin left if turbulence is encountered but in smooth air mine could spend all day at close to max. operating speeds. The issue was always not being able to trim the aircraft for these speeds. The nose up forces on the stick are somewhat uncomfortable as the only trim available on most model 3s in stock configuration is to input flaps to counteract the increased stick forces at higher than designed cruise speeds. At 95 mph you are way above the maximum flap use speeds. The model 3s were designed to cruise in the 70- 80 mph speed range comfortably so of course be careful when flying at the top end of the speed range.

    *** Warning.*** One time I did have flutter in the control system in my model 3 in smooth air while operating in the 95 mph cruise speed range. After immediately reducing the throttle it stopped but was a little disconcerting. I never could duplicate that flutter in flight at that speed in several attempts.
    After not being able to duplicate that control surface flutter event, I restored the entire rather convoluted control mixer to like new condition by replacing the aluminum pivoting blocks and bolts that allow the wings to fold without disconnecting the flapperon push pull tubes as designed into later model control mixers. I also looked for and eliminated any play in the stick mounts along with push pull tubes for both elevator and flapperons. I never had a repeat of the flutter issue but it was always on my mind at speeds above 85 mph.

    The model 3 Kitfox is a blast to fly. It’s under cambered wing makes for exciting take offs especially with the 80 hp. Rotax . I miss it’s incredible STOL capabilities and the ridiculously low fuel burn per hour. The reduced cruise speed and lack of cargo space is why I decided to build my model 4 and sell the 3.


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