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Thread: Prop choice

  1. #11
    tommg13780's Avatar
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    Nov 2008
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    Guilford, NY
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    156

    Default Re: Prop choice

    We just had an incident (Friend) that involved a GSC 2 blade with some VW derived engine in a direct drive situation. The blades were trimmed short to stay within 80% mach 1 tip speed at around 3600, full throttle RPM. Unfortunately the blades separated form the hub after about 4 hours flying.
    Fortunately both blades left the engine simultaneously. The motor mount fractured at one point but three points did not fail. The engine stayed with the airplane revving way high with no load until ignition was killed.
    The pilot (300+hour student) was able to return to the field and dead stick land without damage to the Kitfox 1. As I understand it when the engine separates from the airplane the resulting imbalance will make the airplane hopelessly uncontrollable. This incident has pretty much killed my interest in direct drive VW engines along with GSC Propellors. Pobably there is an equation out there that could have told these experimenters that this was going to be risky business. Perhaps the inertia value was exceeded?
    Nick's comments caught my attention because "shedding blades" is such a harmless sounding expression.

  2. #12
    Senior Member
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    May 2011
    Location
    MN
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    469

    Default Re: Prop choice

    Okay, you guys have just convinced me that to remount the GSC prop to this plane could be hazardous to my health. The prop looks like new and was only test run for a couple of hours so I doubt it would have any issues but my life and the well being of the plane are more important than keeping the prop on the plane.
    Since I have two other props I can use I will 'flip a coin' and see which one I will use. Most likely the 70" Whirlwind will win.

  3. #13
    Senior Member Av8r_Sed's Avatar
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    Feb 2010
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    10C Greenwood, IL
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    671

    Default Re: Prop choice

    Quote Originally Posted by tommg13780 View Post
    This incident has pretty much killed my interest in direct drive VW engines along with GSC Propellors. Pobably there is an equation out there that could have told these experim
    Tommy,
    I understand your personal choice to avoid a risk. On the other hand, It wouldn't be appropriate to reject all VW direct drive derivatives and all GSC props due to one incident with a combination of the two on a Kitfox. There have been many postings here indicating direct drive VW derivatives might not be a good match for a Kitfox, while there are others like Sonex drivers who wouldn't have anything else. Many Kitfox pilots have flown behind GSC props for many hours. With good maintenance and storage they can be very reliable and smooth.

    The upshot is, it would be best to work with the prop manufacturer and heed their advice on good and not so good engine/prop combinations.
    -- Paul S
    Model III SN910
    582 IVO Med

  4. #14
    tommg13780's Avatar
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    Nov 2008
    Location
    Guilford, NY
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    156

    Default Re: Prop choice

    Paul, I can appreciate your point of view. I've had many (200-300) trouble free hours flying with GSC on a rotax 2 stroke/gearbox application.
    For some reason, possibly a naturally occurring fracture of 1 blade, I made an inquiry for replacing that one blade and the GSC representative advised me to order 3 new matching blades as the only feasible option. Of course that would cost equal or greater than a new Warp, or IVO.

    I believe this "shedding of blades" incident was somewhat disturbing to me because it could be something I probably would have tried myself. Those blades were both retrieved and they both looked like they were in a vise and someone carefully ran a chainsaw vertically from the inboard end down to the thru bolt slot. I found that mental image to be rather emotional. It was kind of a "foxhole" moment when the guy next to you takes a head shot.

    I'm sorry if my preference here seems irrational but to some extent perhaps it is. I really get a lot of pleasure from the Kitfox buying, selling, building and flying activities and would hate to see the whole thing spoiled by a senseless incident.

  5. #15
    Senior Member
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    Feb 2011
    Location
    wilmington nc
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    201

    Default Re: Prop choice

    want to weigh in on this topic and give my 2ct worth. have 250+ hrs on the keiv prop with no problems and very happy with the performance on our ss7 with 912 uls and 850 tires. routinely see 1200 to 1300 ft per minute climb and 113 mph ias, at 5300 rpm and very smooth. Ted Bryant at b&b and i have become good friends and I am going to be doing some testing on the new keiv electric veritable pitch hopefully soon and will post the results here when done. that said the w/w wins the sex appeal contest hands down, best looking prop out there.

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