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Thread: A much faster Kitfox?

  1. #61
    Senior Member HighWing's Avatar
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    Default Re: A much faster Kitfox?

    Paul, actually my stall was the 40 mph one. I hope my tendency to mix numbers didn't occur here.

    My first Model IV stalled at 43 and I flew it for nine years so that number was pretty much verified as I piled on the hours - 900.

    The ASI might not be accurate at low speeds, but I did check it with a water manometer when building and it followed the theoretical curve quite closely - image of the spreadsheet attached. If there is an error, I suspect it would be common across the fleet using the factory supplied pitot tube.

    I find this thread very interesting and it brings to mind some more things I might want to try on my current airplane. Thanks to all who have contributed and hope for more ideas in the future.
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    Lowell Fitt
    Goodyear, AZ


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  2. #62
    Senior Member av8rps's Avatar
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    Default Re: A much faster Kitfox?

    Lowell,

    I guess I should have known you did a scientific test of your ASI. I'd be disappointed at anything less from you .

    So, maybe, just maybe... the advertised stall speed of the newer planes are a bit optimistic? Or just maybe, they are being tested with an aft cg and a very light load?

    Either way, our Kitfoxes generally speaking still have a really nice speed range from slow to fast. And since I am overall ok with the low speed end of my Kitfox (how slow does one really need to land anyhow?), I'm still curious how much a little more aerodynamic clean up might help our airplanes.

    Since our Kitfoxes generally resemble the old Monocoupes of the past, why can't they go as fast? I think they can...

    Paul

  3. #63

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    Default Re: A much faster Kitfox?

    I find this topic fascinating. It would be interesting to hear some more specifics on some of the mods. For example, the wide-body mod on the model IV's. I read on another post somewhere that some believe this mod actually improves cruise speed? Any data to back this up?

  4. #64
    Senior Member av8rps's Avatar
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    Default Re: A much faster Kitfox?

    This is still a great thread as there was a lot of great info shared here.

    There is info earlier in this thread about the Kitfox 4 tri gear that had the wide body mod that would go 140 mph. So yes, there is something about what that does to the drag on the stubby little Kitfox 4 fuselage. Unfortunately it will take someone with a better knowledge of aerodynamics than me to explain why that would make sense.

    But knowing that I am beginning to wonder if the bubble glass doors on my Model 4 amphib might be attributing to the extra speed I seem to enjoy. Maybe those doors are having a similar effect as the wide body mod? I've never flown it with conventional doors, so I can't compare.

    All good food for thought...

  5. #65
    Super Moderator Av8r3400's Avatar
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    Default Re: A much faster Kitfox?

    Short, Stubby and really, really FAST...

    Venture.jpg
    Av8r3400
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  6. #66

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    Default Re: A much faster Kitfox?

    Isn't the best fineness ratio for subsonic about 6:1?

  7. #67
    Guy Buchanan's Avatar
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    Default Re: A much faster Kitfox?

    I couldn't find that anyone's mentioned a great book on drag reduction: Speed With Economy, by Kent Paser. (Probably available at EAA.) He does major mods to a Midget Mustang to gain dramatic speed improvements. (64mph top speed improvement.)
    Guy Buchanan
    San Diego, CA
    Deceased K-IV 1200 / 912uls / 70" Warp 3cs

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  8. #68
    Senior Member jrevens's Avatar
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    Default Re: A much faster Kitfox?

    Quote Originally Posted by Guy Buchanan View Post
    I couldn't find that anyone's mentioned a great book on drag reduction: Speed With Economy, by Kent Paser. (Probably available at EAA.) He does major mods to a Midget Mustang to gain dramatic speed improvements. (64mph top speed improvement.)
    I've known Kent for many years, and his book is filled with good hints and ideas. His airplane was pretty drastically modified - it's a Mustang II by the way - and many of the things he did probably wouldn't be copied by most builders (like the tiny little canopy and other mods in that area). It sure was/is? a fast airplane, but I don't think he has flown now for quite awhile... I hope he's still around. I haven't seen him for a few years. He admitted at one time that some of the things in that book didn't prove to be beneficial like he thought... for instance the inversion cones in the exhaust system. It is an interesting book, worth having.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
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  9. #69
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    Default Re: A much faster Kitfox?

    Hi guys, it's been a while sence I have posted on the forum but as I saw this discussion on cleaning up our kitfoxes for more speed I wanted to post what I did to get more performance from my model 7SS with 912uls.
    I have to admit I took the easy way out but much more expensive way as I changed props from a ground adjustable to a 3blade electric constant speed by
    Full Torque propulsion. Now I am getting full rated power on take off "5600 rpm" With much higher climb angle at 55kt and about 50' shorter take off. As far as cruise speed I am seeing 10kt,s better at 5200 rpm and 28"mp, at 6000' and 5150 rpm and 24.2 mp,"wot" I am indicating 103kt with a true air speed of114kts as computed by the garmin g3x. Also I am running 850x6 tires so there is a drag penalty there. I got about 20 hrs on it and am really happy with it, I will try to post a video of the g3x in testing at 6000'

  10. #70
    Senior Member av8rps's Avatar
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    Default Re: A much faster Kitfox?

    http://www.sportclass.com/jeff-lavel...-at-reno-2013/

    Stubby and fast is nice, but I'd prefer the 400+mph Glasair 3 that races at Reno regularly. Tom Hamilton (Glasair 3 designer) told me that guy is making his Glasair 3 faster every year, so he reminded him that the G3 has only been tested to 523 mph for flutter, so be careful in shallow dives


    Quote Originally Posted by Av8r3400 View Post
    Short, Stubby and really, really FAST...

    Venture.jpg

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