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Thread: Fixed Pitch Props

  1. #11
    Super Moderator Av8r3400's Avatar
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    Default Re: Fixed Pitch Props

    Today I did put in calls to Catto and Prince in query to their fixed pitch props.
    Av8r3400
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  2. #12
    Senior Member PapuaPilot's Avatar
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    Default Re: Fixed Pitch Props

    My Catto prop is going to be $2750 plus shipping. It's a two blade with nickel leading edges.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  3. #13
    Super Moderator Av8r3400's Avatar
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    Default Re: Fixed Pitch Props

    May I ask what diameter and pitch you are getting?
    Av8r3400
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  4. #14
    Senior Member PapuaPilot's Avatar
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    Default Re: Fixed Pitch Props

    It is 74" x 47" for an IO-240. I asked for a cruise prop, not a climb prop.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  5. #15
    Senior Member av8rps's Avatar
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    Default Re: Fixed Pitch Props

    Larry,

    Another prop you might want to look at is the Sensenich 68 inch 3 blade. I personally think it will make an awesome prop for a Kitfox, especially considering that our Kitfoxes don't have a lot of ground clearance. Here's what one of the Highlander guys experienced from switching to a Sensenich 68-69" 3 blade from a Warp 72" 3 blade;

    "Hi guys,

    I recently upgraded my Highlander from a 72 Warp Drive to a 68 Sensenich. What I noticed was a slight speed increase of about 3-5 mph for the same rpm.

    The biggest improvement was for sure the smoothness of this prop. With the Warp Drive my windshield was shaking badly from the turbulence created by this prop. Now I barely notice my windshield shaking with the Sensenich. All in all, I would have liked to get 10 mph more speed obviously, but I'm more than satisfied with the result. Also, don't forget that this prop is much nicer, and most important much lighter than the Warp Drive. So it will save your engine sprag cluth on long term.
    ...Snip, snip"

    Note, this is on a 912uls Highlander, so even though he could have run a longer prop he chose the Sensenich for overall performance. And here is his response after I asked what the shorter prop did to his climb rate;

    "Good evening Paul,

    To answer your questions, with my Sensenich set up to 5650 rpm WOT at level flight just like my Warp Drive was, I lost about 50-100 fpm. So very negligible. I still climb between 1000 to 1200 fpm at 55 mph depending of the air density.

    About my landing gear, I didn't streamline the back of the gear when I covered it. Before covering the gear I was cruising at 101 mph at 5300 rpm with 8.50 tires. Now with the gear covered and ABW 29'' I cruise at 109 mph at the same 5300 rpm. This is an amazing improvement considering that I gained weight from the bigger tires and landing gear. What can I ask more??? I have a faster airplane with more STOL capabilities."

    I think the Sensenich with its scimitar shaped blades might be one of the more efficient props for planes like ours that can't run long props due to ground clearance. But it would be interesting to hear more about the Sensenich from other people using it. I've heard it is pretty popular with the Vans RV-12 LSA group, but haven't taken the time to investigate that claim. A few friends of mine are telling me if you have an RV-12 the Sensenich is "the prop to have". Granted, our Kitfoxes are more of a STOL aircraft that any RV-12 will ever be. But I'm guessing that unless you are looking for getting the most STOL out of your plane, the Sensenich just might prove to be a really good compromise for speed and climb.

    I would say he for sure has one of the faster Highlanders out there with big wheels and tires on a tall gear.

    Paul

    http://wingsforum.com/viewtopic.php?f=218&t=23571

  6. #16
    Super Moderator Av8r3400's Avatar
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    Default Re: Fixed Pitch Props

    This investigation is meant to gather information to offer an option over the bevy of ground adjustable props on the market. In a receint Kitplanes magazine there was an article on Catto propellers and their technology. They make the argument that many, one size fits all blades, in a ground adjustable prop are often operating Ineffeciently. At a given pitch, set by rpm, can be causing the center of the prop blade to pull well but the tips doing little or nothing, or vise versa. A properly designed fixed pitch prop will use the entire length to generate thrust.

    In my particular situation, I have mocked up an 80" diameter prop and still have more than adequate clearance with my custom, longer, Grove gear and 21" tires. Right now both prince and Catto are touting their 76" models for the Highlanders and Rans S7.

    I am still waiting call backs to discuss the particulars of a Kitfox design.
    Av8r3400
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  7. #17
    Senior Member av8rps's Avatar
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    Default Re: Fixed Pitch Props

    Yeah, I read that article and that makes a lot of sense. Unfortunately it is always a crap-shoot to get the right pitch and length. But when you do, I agree you are likely to have a better performing prop. I will most definitely keep following this thread.

    I am really surprised you have that much ground clearance. That must be one heck of an extended Grove gear. I remember seeing one like that years ago on a model 5 at oshkosh, but hadn't seen one since. So I wasn't aware they were still doing those.

    Sounds like you're going to have a really cool model 4 when you get that mangey fox done.

  8. #18
    Senior Member colospace's Avatar
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    Default Re: Fixed Pitch Props

    My understanding, from conversations with the Catto Props folks and Debra McBean at Oshkosh this past year, was that Catto was making some props to provide to John McBean for testing/evaluation. I have not heard how that may be going.
    - Gary
    S7 SuperSport Tri-gear
    w/Rotax 912, Oratex, Dynon

  9. #19
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    Default Re: Fixed Pitch Props

    On my plane with IO-240B, this is my experience:

    I went through several Sensenich props on N85AE and ended up with a 74"
    prop (can't recall the exact pitch at the moment). I get just under 2300
    rpm static, and the plane accelerates fast and gets off the ground quickly,
    in level flight firewalled I can hit VNE (140), and typically throttled back
    it pulls the plane along at 120 with no problem at all.

    Actually 120 is a very easy speed for the plane, it pulls along nicely with
    the 74" and the engine doesn't feel like it's working hard at all. The biggest
    problem with 120 or faster, is the plane is light and any and all bumps are
    VERY noticeable. It is not an airplane who's design is conducive to speed.

    I would say a consideration should be that these planes between 120-140 the
    drag ramps up so quickly, that a prop isn't going to make much difference ...
    On my plane the idea of climb/cruise prop for these reasons is I think a
    bit irrelevant. The drag builds so fast that I think the only real difference
    will be felt when you hit the gas for takeoff. After that they are all the
    same.

    So I'm perfectly happy with the prop I have now. The ONLY problem is I
    like flying in the rain on occasion, and it's like a sandblaster on that wood
    prop.

    A 912, or other engine may be totally different, this is strictly my experience
    over ten years flying with my IO-240B.

    Jeff

  10. #20
    Super Moderator Av8r3400's Avatar
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    Default Re: Fixed Pitch Props

    I have made the decision to go with Prince. Lonnie Prince and I had a long discussion and afterwards we came to the conclusion that the prop will be 78" in diameter x 50" pitch for the speed/STOL conditions I am forecasting, with the engine (105 hp zipper equipped 912 UL) I am using.

    I will report on the flight testing as the plane is finished and flown, hopefully by this fall.
    Av8r3400
    Kitfox Model IV
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