Resitance Prediction for Buoy tender vessel

Discussion in 'Boat Design' started by engine_afiq86, Mar 7, 2009.

  1. engine_afiq86
    Joined: Mar 2009
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    engine_afiq86 Junior Member

    Hi...

    I have an assignment regarding the prediction of power for buoy tender vessel..
    Does anyone here know what is the method suitable for the power estimation?

    the ship particulars are:

    Lwl = 37.98m
    B = 10m
    T = 2 m
    Displacement = 483.40 tonnes

    Please!!..I need your help..
    u can email me at engine_afiq86@yahoo.com
     
  2. Guest625101138

    Guest625101138 Previous Member

    The most accurate readily available method is to use Michlet. The hull is not ideal for this analysis but I expect it will be closer than most other methods and the software is free.

    You need a reasonable idea of the hull shape so you can create a suitable input file. Do you have the hull in a 3-D electronic format or a table of offsets?

    There are other methods but again you need some hull shape parameters.

    Rick W
     
  3. engine_afiq86
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    engine_afiq86 Junior Member

    I want to do it by calculation..
    without using any software..
    do you know Rick W?
     
  4. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    Not a simple task but some (old) methods are intoduced in the Elements of Yacht Design by Norman L Skene ISBN 1-57409-134-4 Chapter XV, allmost 30 pages so too much to quote here esp without knowing anything more specific about your boat..
     
  5. Guest625101138

    Guest625101138 Previous Member

    The linked ppt presentation gives a reasonably good explanation of the drag on a yacht. Some of the components shown are not applicable to your calculation. So you will not need to understand all components:
    http://academic.amc.edu.au/~gthomas/yacht/yacht_lec34_hydrodynamics.ppt

    You will find it a very tedious process and begin to understand why people use proven software for the calculation. It will pay you to set up a spreadsheet anyhow.

    If nothing else this presentation may give you more references to search for. The viscous resistance is not too difficult to get a good result. Calculations for wave drag can have large errors using the empirical formulas but at least you will get an answer.

    Rick W.
     
  6. Guillermo
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    Guillermo Ingeniero Naval

    I'll send you a calculator based on the Holtrop & Mennen prediction system, which may work for you if parameters are within limits.

    Cheers.
     
  7. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    engine_afiq86

    From your figures you've got a Cb of 0.62. This is rather low for such a vessel. Unless of course you have selected a finer form vessel deliberately?

    As for doing it by hand, you'll really need more than just what you have presented.

    1) Quick method using Froude skin friction, Rt = fSV^1.825, and the "old " Circular (C) method. But again you still need a bit more data, such as a rough WSA and a value for "f". You may find some decent tabulated values for vessel in PNA or similar (My books are all packed up ready for moving, so i haven't got them to hand..otherwise i could scan in some figures for you).

    2If you can find again from some sources, a similar hull form that you want, with either some model test data and/or a spot on a curve giving a resistance at a given speed, either model or ship. If so, then it is a straight forward calculation.

    But either way, you'll need more data than just that provided above...
     
  8. engine_afiq86
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    engine_afiq86 Junior Member

    ok...
    Ad Hoc....
    where could i find the similar hull form for the vessel?could you tell me?
     
  9. engine_afiq86
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    engine_afiq86 Junior Member

    Ship Model
    Scale Ratio 15.20 1.000
    LOA (m) 40.00 m 2.632 m
    LBP 37.00 m 2.434 m
    LWL 37.98 m 2.499 m
    Beam 10.00 m 0.658 m
    Design Draft 2.00 m 0.132 m
    Displacement 483.40 tonnes 134.300 kg
    Wetted Surface Area, 405.35 m2 1.755 m2
    LCG (from amidship) 1.39 m 0.092 m
    KG 2.40 m 0.158 m

    VS
    (knots)
    10.00
    11.00
    12.00
    13.00
    14.00
    15.00
    16.00

    The question are....We need an estimation of the hullform given using any suiable method that fits our hullform..

    40m Buoy Tender Vessel

    Please All of the senior and junior..
    help me!!
     
  10. bit
    Joined: Feb 2008
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    Location: Trieste

    bit Student

    Approximate...
    Regards
     

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  11. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    engine _aqfiq86

    Do you have access to a library?...if so, then you should be able to get any "standard" series, be it NPL or other. Or, try some of the usual books for data, PNA or similar.

    failing that, I've dug out an old file, luckily on top of my packed box, where i have 2 different sets of data, one basic one more detailed. It depends upon the level of detail you're required to work out the power requirements.

    However, when i geosim the data it is not as close to the hull form you have. So given this and possible speed range you're looking at, these may not be ideal. But, if all you are required to do is demonstrate resistance calc's by hand then this may suffice??

    1) model basic data
    speed (ms-1) Resistance (N)
    0.7 5.70
    0.9 9.00
    0.97 10.30
    1.04 11.90
    1.10 13.40
    1.25 18.40

    model Lwl = 5.0m, Den. FW 1000kg/m3
    viscosity 1.139x10-6 m2s-1, and WSA 5.9m2

    2 More detailed data
    Model
    Lwl = 0.47m, Displ 0.453kg, Ca = 0.0002, Den. = 1000kg/m3
    viscosity 1.6594x10-6 m2/s-1, with 6 pins for flow = 9x10-6 m2 each
    appendage= 3x10-4m2 with a Cf 0.0094, WSA laminar 0.0067m2 L= 0.09m, Turbulent 0.0456m2 L =0.37m:

    speed (ms-1) Drag (kg)
    1.134 0.0500
    1.346 0.0642
    1.446 0.0785
    1.628 0.0785
    1.853 0.0925

    This is just some basic raw data.

    I never use software to calculate resistance. Always by hand. But I'm lucky that we have many different hull forms and model test data to select data from. Having a database of hulls over the past 20~30years. Where no hull form exists, we just make a model and tank test it ourselves.
     
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