Joukowski airfoil as basis for hull form?

Discussion in 'Powerboats' started by barrelback, Feb 21, 2018.

  1. barrelback
    Joined: Feb 2018
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    barrelback Junior Member

    I want to build a planing inboard something along the lines of a vintage Chris Craft, but with a few changes to accommodate newer technologies and safety standards. I intend to use it for day-cruising around the local reservoir, maybe tow the grandkids on their tube or drop anchor and drown a worm. Basically I'm looking in the neighborhood of 18' with a 6' beam, and cruise around 35kn with as little HP as possible.

    Rather than trying to copy a Chris Craft Runabout line for line, I was thinking maybe I could work up my own lines based on http://airfoiltools.com/images/airfoil/joukowsk-il_l.png It seems to have served me better than the NACAs in turning out radially-symmetric fuselages for RC airplanes. But since air is compressible and water not so much, I wonder if there is a better shape.

    I'm thinking to start at the keel with a Joukowski of thin aspect and work upboard to a wider Joukowski at the chine, then wider still at the sheer clamp, truncate aft, and add a cutwater. Am I on the right tack or is my approach unsound?

    Also, in keeping with minimizing drag (and reducing wake at slower displacement speeds), should the sides of the cutwater be concave, flat, or convex? I ask this bc there are a few places marked NO WAKE, and one of them is frequented by a group of people that likes to troll everyone that passes by, so the faster I can zip past and not get into trouble with WP, the happier I am.
     
  2. TANSL
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    TANSL Senior Member

    I do not think that those types of aerodynamic profiles are the best for a planing boat. You need to have the largest possible breadth on the back of the hull and up to the mirror.
     
  3. philSweet
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    philSweet Senior Member

    Our Joukowski is Daniel Savitski.
     
  4. barrelback
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    barrelback Junior Member

    Yeah, compressible air vs incompressible water... this is what I was afraid of.
     
  5. barrelback
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    barrelback Junior Member

    AH!!!! THANK YOU VERY VERY MUCH!!! I figured there had to be some maths involved somewhere, just didn't know how to find it before. Savitsky (Savitski gave me a bunch of hits on something else entirely lol) has some recently published research papers to boot. Well, recent in the sense that some were published within the last 50 yrs.
     

  6. TANSL
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    TANSL Senior Member

    The boat moves in two fluids, water and air, and it is the interface between both fluids that gives more problems. The plane is immersed in a single fluid. A submarine looks more like what you propose.
     
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