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  1. #1
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    Default Changing the chord of a propeller while keeping the diameter and pitch constant

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    Hi everyone!

    I've an apc 8x3.8 propeller CAD file and I've to modify the chord length while maintaining the pitch and diameter but I'm not sure how to go about doing it. The airfoil used is the NACA 4412. Any ideas?


  2. #2
    Forum Deity Dana W's Avatar
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    This technique only applies to a 2D section of one of your propeller blades. Maybe it will give you a starting point.

    Since the chord length is the straight line width of the propeller blade in a given spot, (see attached image) changing the chord length will not affect the rotating diameter of the propeller, nor the pitch (angle of the blade in relation to the propeller shaft).

    However, just changing the chord length, and nothing else, will make the cross section of the blade either flatter or more curved, since the cross section will be either wider or more narrow respectively. This will destroy your (I assume) objective of retaining the original airfoil shape. However, there is an easy way to change the chord length in cross section view only without losing the correct airfoil shape.

    To do the above, you can simply use the Scale command, with the Reference sub-command. This will proportionally change the size of the airfoil overall, retaining the profile shape.

    First, draw a new line (different color) at the desired length directly over your original chord length line starting at one exact end of the original line.
    Now execute SCALE.
    Click the common end of your two chord length lines as your Base Point.
    Type R(for reference).
    Click the Base Point again. Then, click the other end of your original chord length line.
    Now click the other end of your new chord length line and exit (esc) the Scale command.
    erase the new line you drew for the reference.

    You now have a new chord length, and the original airfoil profile has been retained.

    Now, changing the overall chord length in 3D is out of my league.
    Attached Images
    The S197 gen Ford Mustang, and the F-4 Phantom both prove the same theory. "With enough power applied, a school bus will fly."

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