Help with Kort No. 19A/37 Ordinates

Discussion in 'Props' started by Samuel Neves Jocas, Mar 20, 2020.

  1. Samuel Neves Jocas
    Joined: Dec 2019
    Posts: 7
    Likes: 0, Points: 1
    Location: Brasil

    Samuel Neves Jocas Junior Member

    Dear,

    I would like to know if any member of the forum could assist me (or guide, at least). I am looking for the points/coordinates of Kort No. 19A and 37. The materials where I found them were:

    1. CARLTON, J. Marine Propeller and Propulsion (pages 114 ~ 117);
    2. Principles of Naval Architecture;
    3. The attached image (GIF).

    I tried to develop a spreadsheet with [1], and I will be attaching it, in case anyone can verify it (I translated it).

    a. If everything is correct, by then, how can I progress to generate a 3D model of the ducts?
    b. I am trying to plot the points using the SolidWorks¹ "XYZ Curves" tool. Is there another way, or perhaps another, more efficient program?
    c. In the spreadsheet I am attaching, in the "Calculations" workbook, I am marking two cells in yellow. Could anyone explain the difference between Tip Clearance and Clearance only, which are explained in these worksheet cells?

    ¹The use of this tool is giving headaches, because the profile of the curves is not good.
    ²Feel free to change the propeller diameter (D) and gap if you want.
     

    Attached Files:

  2. jehardiman
    Joined: Aug 2004
    Posts: 2,695
    Likes: 319, Points: 83, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    FWIW, SNAME PNA lifted those figures from van Manen's '54, '57, and '59 works.
    I'm not sure if "XYZ Curves" is beizer or NURBS, but what ever you use, you need to ensure that the tangents at 0.4L and 0.6L are parallel to the thrust axis to set the cylindrical tip sweep area or you will have problems. Generally we used Rhino because it gave better shape control than solidworks.
    Tip clearance is a complicated matter; performance increases then decreases as the gap between the prop and nozzle inner face approaches zero. I think the stated 1% is too much but is based on the realities of fabrication without significant methods to close it.. The gap should be approximately the thickness of the blade tip.
     
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