My Powerboat plan (Take II)

Discussion in 'Boat Design' started by adrocha, Nov 4, 2014.

  1. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    The parameters of your hull seem to be compatible with the F-L method, though you have a hard-chine hull and the F-L method is for round-bilge hulls. However, the slenderness ratio of your hull is 5.9, so the error might not be very big - though it's value is actually unknown. You could also try to make a run with the Mercier-Savitsky method, which was made for hard-chined hulls and accounts for dynamic lift too - and see if and how much will the results change.
    Cheers
     
  2. adrocha
    Joined: Oct 2014
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    adrocha Junior Member

    In attachment are the results of this method.
    Do you know where I can find some documentation about this method to study the results?
     

    Attached Files:

  3. daiquiri
    Joined: May 2004
    Posts: 5,373
    Likes: 247, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    As you can notice, the two method give very similar results up to 12 kts approximately. The Mercier-Savitsky then diverges and indicates there might be a resistance hump soon after. You can find the paper by Mercier and Savitsky here: http://www.dtic.mil/dtic/tr/fulltext/u2/764958.pdf

    For the planing speed ranges, the Savitsky method is pretty much the norm: http://shoxs.com/images/uploads/sit...n_of_Planing_Hulls_in_Smooth__Rough_Water.pdf

    Finally, this paper hints that the Lahtiharju method can give better results for certain hull shapes: http://www.hrbi.hr/sorta2012/files/rad55.pdf . You should check out which one is your hull similar to and decide which method to apply. You can find the paper by Lahtiharju et al. here: http://www.boatdesign.net/forums/education/i-need-paper-lahtiharju-wave-resistance-44771.html

    Cheers
     

  4. adrocha
    Joined: Oct 2014
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    Location: Lisbon

    adrocha Junior Member

    Thanks daiquiri.
     
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