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Thread: Air Vent Scoop

  1. #1
    Yellow Baron's Avatar
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    Default Air Vent Scoop

    Quick one: I noticed some have and some have not got a little square scoop around their round air vent inlets.

    The pic i found here has them on two:



    How much improvement in airflow and volume or cooling efficiency does this little mod yield? Versus just the plain round hole?





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  2. #2
    Stephen's Avatar
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    Default Re: Air Vent Scoop

    Isn't one heater and one carb heat? Mine is different. Also, no air scoop for carb air inlet.
    "You can only tie the record for flying low."

  3. #3
    Yellow Baron's Avatar
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    Default Re: Air Vent Scoop

    I know what is connected to them but I was wondering about the little square scoop around the round 2" hole.

    I was thinking of increasing flow and pressure through my muffler for cooling/heating but wanted to know if it was worth the effort.

    Also I see on the pic attached the square opening is smaller than the surface area of the circle behind it - I would try and match the opening areas to get optimum flow - i.e. i would make the scoop a little less flat.

    Area=2"/2 squared x 3.14 = the area the square opening should be: 2" wide by 1.57" high - right?

  4. #4
    Gilbert Pierce's Avatar
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    Default Re: Air Vent Scoop

    I went from the little scoop on the bottom of the cowl to a 2” round hole in the baffle behind the nose bowl and in front of #1 cylinder. I picked up a lot more air in the heater outlet.
    Last edited by Gilbert Pierce; 04-10-2018 at 08:07 AM.

  5. #5
    Administrator Steve Pierce's Avatar
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    Default Re: Air Vent Scoop

    Piper used the small scoop around the hole. Can't remember if it was cabin or carb heat. Should show in the parts manual.

  6. #6
    Rick-CAS's Avatar
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    Default Re: Air Vent Scoop

    The cowl hole normally was cabin heat inlet. The carb heat came from the right rear baffle above #3 cylinder.


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    Default Re: Air Vent Scoop

    Air scoop technology was being optimized for jet aircraft by NACA, the precursor to NASA, in the mid to late '40's. They are in use today in cars and aircraft due to the gain in efficiency over simple holes or simple scoops over simple holes, as you are considering for your plane. I don't know about legalities, but I know the a NACA duct design in a high shear environment such as the bottom of you cowl would give superior volume and speed of flow as compared to the design in the picture. The scoop in the picture might, or might not improve flow through the hole, but we know it will also increase drag to some small extent. Legalities and approvals aside, if you want better duct flow and no increased drag, look at a NACA design in that location.

  8. #8
    Yellow Baron's Avatar
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    Default Re: Air Vent Scoop

    Quote Originally Posted by Subsonic View Post
    Air scoop technology was being optimized for jet aircraft by NACA, the precursor to NASA, in the mid to late '40's. They are in use today in cars and aircraft due to the gain in efficiency over simple holes or simple scoops over simple holes, as you are considering for your plane. I don't know about legalities, but I know the a NACA duct design in a high shear environment such as the bottom of you cowl would give superior volume and speed of flow as compared to the design in the picture. The scoop in the picture might, or might not improve flow through the hole, but we know it will also increase drag to some small extent. Legalities and approvals aside, if you want better duct flow and no increased drag, look at a NACA design in that location.
    Thx - saw interesting comparisons between the two, NACA scoop it is then ... if I can source a metal one.


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