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Thread: "Speed" Pacer.

  1. #11
    cook11's Avatar
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    Default Re: "Speed" Pacer.

    Quote Originally Posted by Steve Pierce View Post
    Do you think the thrustline modification will work on a short wing? Because of the difference in the angle of incidence of the wing and my experience Super Cubs with a higher angle of incidence that the modification did not work on I am curious to see.
    Steve this is a topic I have seen pop up from time to time.....I am not 100% sure whether the modification is even feasible or worth the re-engineering ....It seems that Piper is the only one "I'm probably wrong" that uses nose down on their mounts. I don't think Aeronca, Cessna, Funk, Luscombe, Taylorcraft, Rearwin, Monocoupe, Interstate had negative down thrust on their mounts. I am curious to know whether wing rigging will need to be modified due to the modified engine angle.

  2. #12
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    Default Re: "Speed" Pacer.

    Quote Originally Posted by andya View Post
    IMHO - a level flight 170 mph will take a wing other than the clark Y of the piper heritage and no struts for starters
    It would be interesting to know how well a shortwing would go with the Taylorcraft NACA 23012 airfoil rather than the Pipers USA 35B airfoil. The Monocoupes were quiet efficient and fast with the Clark Y but again they had a small frontal area to them. I would be interested in talking to Callbie Wood the designer of the CF-4 Four Runner an enlarged four seat Tailwind which used the same airfoil and get an idea of what was involved with his design process.

  3. #13
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    Default "Speed" Pacer.

    Quote Originally Posted by Steve Pierce View Post
    Do you think the thrustline modification will work on a short wing? Because of the difference in the angle of incidence of the wing and my experience Super Cubs with a higher angle of incidence that the modification did not work on I am curious to see.
    Yeah, don't think changing the thrust line will work if speed is what the builder is looking for. I think...ouch....decreasing the vertical axis to zero does the same thing on a Pacer or Tripacer as it does on some of super cubs modifications with a positive thrust line like we see at the Valdez short field competition. Like Cessna the Pacer/Tripacer horizontal thrust line is off set to the right overcome torque. For instance the 207 offset is three degrees. The Bearhawk has a zero zero thrust line, to compensate for torque the off set of the leading edge on the vertical stabilizer is 3/4" to the left. The Bearhawk also flys with a 2 degree nose down angle when light...heavy she flys level.


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    Last edited by mmoyle; 12-08-2015 at 02:21 PM.

  4. #14
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    Default Re: "Speed" Pacer.

    Quote Originally Posted by andya View Post
    IMHO - a level flight 170 mph will take a wing other than the clark Y of the piper heritage and no struts for starters

    Actually the Maule does close to it but with a whole lot more horse power.

  5. #15
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    Default Re: "Speed" Pacer.

    What was the 60's mantra? No substitute for cubes. Actually though on an experimental speed at altitude would be assisted by turbo normalizin plus you can ditch the muff.
    Last edited by rsrguy3; 12-08-2015 at 04:06 PM.

  6. #16
    cook11's Avatar
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    Default Re: "Speed" Pacer.

    Wittman BIG X
    http://spirit.eaa.org/apps/magazines/eaa_articles/1965_01_18.pdf

    http://spirit.eaa.org/apps/magazines/eaa_articles/1980_07_14.pdf


    The BIG X looks very similar in profile to the Pacer yet its larger. Wittman airfoil with "V"struts, raked back windshield, no wheel fairings and cruises @ 150mph...on 130-150hp


    CF-4 Four Runner
    http://spirit.eaa.org/apps/magazines...1974_08_11.pdf

  7. #17
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    Default Re: "Speed" Pacer.

    Quote Originally Posted by cook11 View Post
    CamTom12 did Roger install a zero thrust mount on the Racer for the RV-6 cowling to work?
    Quote Originally Posted by CamTom12 View Post
    I'm not sure, but I'll email him and ask.
    No email back yet, but I did some rough measuring with a digital level today and it looks like there's a 3 deg nose down angle on the engine when compared to the bottom of the inboard wing rib.

  8. #18

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    Default Re: "Speed" Pacer.

    There's a big X in the Hanger next to me it was thought to been used for drug running and was purchased cheap

  9. #19
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    Default Re: "Speed" Pacer.

    Quote Originally Posted by CamTom12 View Post
    No email back yet, but I did some rough measuring with a digital level today and it looks like there's a 3 deg nose down angle on the engine when compared to the bottom of the inboard wing rib.
    Confirmed with Roger, he kept it as close to the stock engine angle as possible.

  10. #20
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    Default Re: "Speed" Pacer.

    What limits the Pacer to a VNE of 170mph?

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