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Thread: Static RPM

  1. #1
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    Default Static RPM

    Just noticed yesterday max RPM I can get at take off is 2400. Any chance the cable may streatch or an adjustment on the Carb? Any insight would appreciated.

  2. #2
    Senior Member Pete D's Avatar
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    Default Re: Static RPM

    There are a lot of variables.

    Altitude? (is density altitude high enough you need to lean to get best power?)
    Which prop?
    What airspeed?
    What is the static RPM? (on the ground, no wind full power when stationary)

    You should be able to look in the cowl flap or take the air cleaner cover off the bottom of the cowl and verify that the throttle is hitting the stops.

    How many hours on the spark plugs? (They should be inspected for cleanliness and the gap checked every 100 hours. Older CCs from a few years ago don't have the iridium plugs and the gap opens up much quicker)

    2400 doesn't sound bad depending on some variables. Has it changed?
    Pete Dougherty
    R & D Shop Manager
    Cub Crafters Inc

  3. #3
    Senior Member randylervold's Avatar
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    Default Re: Static RPM

    In addition to Pete's comments, I recall from our prop testing that a low altitude 71 mph IAS (Vy) climb should yield about 2550 rpm so you might check to see if you're in the ballpark there.

    And yet another metric, in straight/level flight you should be able to exceed (overspeed) 2700 rpm at low altitudes but not once you climb up higher.
    Randy Lervold

  4. #4
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    Default Re: Static RPM

    I am getting around 2400 rpm on take off. I thought it use to be 2550. Must be dreaming. Am at about 1000 ft. here. Am able to exceed 2700 in flight. Static rpm must be around the 2400 mark? Thanks for the help.

  5. #5
    Senior Member Pete D's Avatar
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    Default Re: Static RPM

    Quote Originally Posted by t.c.williams View Post
    I am getting around 2400 rpm on take off. I thought it use to be 2550. Must be dreaming. Am at about 1000 ft. here. Am able to exceed 2700 in flight. Static rpm must be around the 2400 mark? Thanks for the help.
    That sounds like its about where it should be. Usually static RPM is around 2350-2400.
    Pete Dougherty
    R & D Shop Manager
    Cub Crafters Inc

  6. #6
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    Default Re: Static RPM

    Great thanks. I'll rest easy now.

  7. #7
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    Default Re: Static RPM

    Anybody else mind sharing their static RPM with 80x50 prop (with temp and altitude if available)?

    Thanks,

    Andrew

  8. #8
    Senior Member Dan L's Avatar
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    Default Re: Static RPM

    Quote Originally Posted by jasimmons View Post
    Anybody else mind sharing their static RPM with 80x50 prop (with temp and altitude if available)?

    Thanks,

    Andrew
    It took me a few trips to the hangar to remember to look for my notes on static rpm.

    I checked my static with the 80x50 twice. At 55 degrees and 2800 elevation I got an even 2400 rpm. At 17 degrees and 2800 feet it was 2390 rpm

    With my original 78x54 at 65 degrees and 2460 elevation static was 2520.

    I now have the 84x42.5 and static is 2280 rpm at 2800 elevation.

    All of of these are Catto props.
    Flying Carbon Cub EX #11 since 2011

  9. #9
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    Default Re: Static RPM

    Quote Originally Posted by jasimmons View Post
    Anybody else mind sharing their static RPM with 80x50 prop (with temp and altitude if available)?

    Thanks,

    Andrew
    Andrew, mine was 2400-2410 at 1500 ft. and 55 degrees.

    Tom R

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