Planing hull analysis using Savitsky

Discussion in 'Powerboats' started by wharris87, Apr 16, 2011.

  1. wharris87
    Joined: Apr 2011
    Posts: 2
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    Location: Plymouth

    wharris87 New Member

    I recently built my own speedboat, and as part of my dissertation, I am trying to analyse why it performs the way it does; in particular the high trim angles during acceleration onto the plane; As shown in the attached video.

    I have built a spreadsheet based on Savitsky's calculations, and have used similar spreadsheets (including Dingos)to validate it.

    However, can someone confirm the graphs shown in the attached word document look vaguely right?

    The resistance graph in particular seems to have a pretty extreme 'hump'?

    I understand that Savitsky assumes a prismatic hull form and flat (not warped) planing surfaces, however im just not convinced that my results are correct, even after using those reasons to justify the differences.

    Or am i getting myself confused?

    any help or advice would be greatly appreciated!

    Cheers,

    Will
     

    Attached Files:

  2. tom28571
    Joined: Dec 2001
    Posts: 2,470
    Likes: 113, Points: 63, Legacy Rep: 1728
    Location: Oriental, NC

    tom28571 Senior Member

    I can't confirm you calculations but the trim angle looks a bit too low for what the video shows at low speed. Of course, your position in the boat has a great effect on that.

    The power curve looks well off and may be steady state power required for constant speed while the video shows acceleration. Thus the actual power developed is higher at all but the top end of the speed range. Certainly there is a lot more power being developed in getting over the hump than the graph shows.

    Or I could be wrong.
     
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