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Thread: Kitfox Mk IV 1050 speedster vs 1200 lbs

  1. #1

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    Default Kitfox Mk IV 1050 speedster vs 1200 lbs

    Hello,

    I have the opportunity to purchase a MK IV Speedster 1050lbs version built 1992 model. I really wanted the 1020 version, the MAUW isn't an issue, I just like the idea of a stronger aircraft with bigger rudder.

    So I guess me question is, would you let this put you off buying it all..?

    If you had identically equipped and conditioned MK IV Speedsters (1050lbs and 1200lbs) what money value difference would there be between the two.

    Many thanks,


    Ryan.

  2. #2
    Administrator DesertFox4's Avatar
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    Default Re: Kitfox Mk IV 1050 speedster vs 1200 lbs

    Ryan, welcome aboard. Just had a buddy pick up a nice 1050 model 4. They are great flying aircraft. It’s nice to have the extra 150 lbs. of useful load but many have flown the model 4/1050’s for years and gotten by just fine. My 20 plus years of flying Kitfox aircraft seems to be about 85% of flights are solo so I seldom get very near gross weights even on long cross country trips.
    I did own a model 3/1050 for 3 years and only got to gross with full fuel and an adult passenger and light baggage.


    DesertFox4
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  3. #3
    Senior Member Norm's Avatar
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    Default Re: Kitfox Mk IV 1050 speedster vs 1200 lbs

    Seems to me the rudder is the same size on the 1050 speedster and the 1200 speedster. One of the speedster's advantage was the better rudder. Maybe DF4 can confirm.
    Norm
    Airdrie Ab, Can
    North of Calgary
    Flying SuperFox Model IV

  4. #4
    Senior Member 109JB's Avatar
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    Default Re: Kitfox Mk IV 1050 speedster vs 1200 lbs

    All I have to say is that as a new owner of a 1050 with 490 lb useful load, I have no complaints at all. I don't see many occasions were 490 useful would be limiting.

    Before I go further let me say that I am not advocating anyone else doing what I am contemplating doing. These things I'm about to talk about are my thoughts and what I may or may not do.

    The manual for my airplane says it is stressed for ultimate loads of +5.7 g, -2.85 g at 1050 lbs. So if we ran this airplane at 1200 lbs without any mods it would be good for an ultimate load of 5.7*1050/1200 = 4.99 g and with a 1.5 safety factor it would be good for 3.325 g. Slightly below what the FAA considers a "normal" category airplane which is 3.8 g. Another way to look at it would be to say it is still good for 3.8 g, but with a 1.3 safety factor rather than 1.5.

    The other consideration is performance which could be the limiting factor on gross weight, but from my little flying of a Kitfox with just 65 hp I just can't see this as an issue.

    So what?? Well, those number don't scare me at all, so from a airplane capability standpoint I would not have a problem going to 1200 lbs for the very few flights where I would need to. However, there is the legal standpoint which is that the airplane certification from the original builder is set at 1050 lbs. That is actually pretty easy to change by re-entering Phase I testing, flying it up to 1200 lbs and then making a logbook entry stating that everything worked hunky dory at that weight. That is what I am contemplating doing so that if I need to exceed 1050 I would be legal doing it.

    I have my fire suit on
    Last edited by 109JB; 10-16-2019 at 08:00 PM.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

  5. #5
    Senior Member 109JB's Avatar
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    Default Re: Kitfox Mk IV 1050 speedster vs 1200 lbs

    Quote Originally Posted by Norm View Post
    Seems to me the rudder is the same size on the 1050 speedster and the 1200 speedster. One of the speedster's advantage was the better rudder. Maybe DF4 can confirm.
    I'm not sure about the speedster, but last week I measured the vertical an rudder on my non-speedster 1050 and a friends non-speedster 1200 and found that the 1200 fin and rudder are 6" taller and the rudder is 2" wider compared to the 1050.
    Last edited by 109JB; 10-16-2019 at 08:00 PM.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

  6. #6

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    Default Re: Kitfox Mk IV 1050 speedster vs 1200 lbs

    I have the 1050 model 3 (smaller tail) with the 4 wing. I recently added gap seals with clear 2" wide Gorilla tape (center 3/4" double taped so it is not sticky).
    Really improved the elevator and especially rudder for landings. This may help you if you buy a 1050 model.
    IMG_7564.jpgIMG_7563.jpg
    Kirby Cramer
    Kitfox 4, Built 1993
    NSI/Subaru 98HP, Warp Drive 70" three bade tapered ground adj. @ 22 deg. 90MPH cruise @ 3700 RPM.
    Elison throttle body, Dynon D3 VSI, ForeFlight/Ipad 10",
    uAvionix ADS-B in/out, Narco AT150 transponder, Icom 1220 VHF.
    460 Hours

  7. #7
    Senior Member
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    Default Re: Kitfox Mk IV 1050 speedster vs 1200 lbs

    It's been said, there has never been an in-flight breakup of any Kitfox. Sure, many have suffered broken fuse tubes by landing hard while over weight, but the wings falling off due to being over gross does not seem to occur. However, having said that, if you crash while operating over weight the FAA won't be happy, and your air-frame insurance is probably nullified.
    Roger

  8. #8
    Senior Member 109JB's Avatar
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    Default Re: Kitfox Mk IV 1050 speedster vs 1200 lbs

    From what I understand the broken and bent fuselage tubes during hard landings can occur whether or not the airplane is over or under gross weight. I have read several accounts of it happening when not at or over max gross weight. Besides, as far as I know, none of the changes from the 1050 to the 1200 had anything to do with the landing gear, or landing gear mounting to the fuselage. So from a landing gear standpoint they are the same anyway..

    if you crash while operating over weight the FAA won't be happy, and your air-frame insurance is probably nullified.
    The question here is over what weight? If I were to validate 1200 lbs during re-entered phase 1 testing and make the appropriate logbook entry then 1200 becomes the new maximum gross weight for my airplane. At that point the operating limitations, POH, and whatever else would reflect that. FAA and insurance can't really argue that because it follows the regulations. My insurance policy doesn't have a stated maximum gross weight that I cannot exceed, so as long as I am within the "legal" weight limit of the airplane I am ok.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

  9. #9

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    Default Re: Kitfox Mk IV 1050 speedster vs 1200 lbs

    I have a recently completed Model 4 1200 with the Subaru engine, what is the empty weight of your bird?
    Scot Trueblood
    Bonita Springs, FL

    Kitfox IV in Phase 1 Flight Testing

  10. #10
    Super Moderator Av8r3400's Avatar
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    Default Re: Kitfox Mk IV 1050 speedster vs 1200 lbs

    I have over 500 hours in my first Kitfox, a IV-1050. They are a great flying airplane and highly under-rated. I wouldn't walk away from a good deal on one.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
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