Compton Semiplaning 1986 method - Typo in the article?

Discussion in 'Boat Design' started by Vincent G, Jan 25, 2006.

  1. Vincent G
    Joined: Sep 2004
    Posts: 14
    Likes: 1, Points: 3, Legacy Rep: 12
    Location: France

    Vincent G Junior Member

    I am trying to use the paper from Roger H. Compton 'Resistance of a Systematic Series of Semiplaning Transom-Stern Hulls' from Marine Technology Oct. 1986 (and also enclosed on SNAME small-craft CD-ROM). I know, this is corresponding to old fashion hull lines...:)

    Based on model test results, a regression formula is given to compute residuary resistance coefficient Cr in function of Froude number Fn for both round bilge and hard-chine hulls.

    An example is given in the article with vessel characteristics and the corresponding EHP from model test and difference with regression computation - showing good agreement - unfortunately, no detail of the computation is given.

    Unfortunately, when using the regression method, I find Cr coefficients which are quiet different from what they should be.
    I double-checked the maths manually, and my application of the method is correct.
    I am now wondering if the regression coefficients given in the article are correct. Does anybody have any experience with this ?

    The example model particulars are:
    LOA 108.0ft
    LPP 101.2ft
    Ref draft 6.0ft
    BWL 21.4ft
    L/B 4.719
    Disp. 163.2LT
    LCG 4.47ft aft of amidship
    WSA 2377ft2
    LWL 101.7ft

    From these particulars, I computed the following parameters needed by the regression formula:
    LPP/BX 4.729 (I supposed that BX=BWL)
    DLR 157.46
    LCG/LPP .4558
    Round Bilge

    My results are:
    Fn = { .1 .15 .2 .25 .3 .35 .4 .45 .5 .55 .6 }
    CR = { .01324346406 .0130523335 .01355796833 .01564463618 .01876070302 .02054304344 .02177314384 .02635984895 .02779758948 .02411864564 .01987043872 }

    Can somebody knowing the method check my results?
    Do you have any correction that should be applied that I am not aware of?

    Best regards

    Vincent
     
    Vincent G, Jan 25, 2006
    #1
  2. symfoni
    Joined: Mar 2006
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: sweden

    symfoni New Member

    Hi Vincent
    Did you find the typo?
    I have the same problem…
    LCG/LPP = 0.4558 ?????
    I’m using LCG/LPP = 0.044, then later multiply it with 100 in the regression equation.

    Apart form this we doing the same thing… And I can’t Implement the method in the same way as Compton in Fig.36 and Table 3.

    Any Ideas, Anyone…?
    /Anders
     
    symfoni, Mar 3, 2006
    #2
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