Any idea about New hull Shape Prismatic Coef ?

Discussion in 'Multihulls' started by Erwan, May 7, 2009.

  1. Erwan
    Joined: Oct 2005
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    Erwan Senior Member

    Hi everybody,

    By new hull shape, I mean the new pierce-wave hull shape one can see on A-Cat for instance. Of course with one hull carrying the full load.

    In fact I would like to compare with more classic boats, in order to see if there is a trend.

    The only prismatic coef available for light Cat is the Tornado's I think ? It should be around 0.61 or 0.63. I need to check.

    Thanks in advance

    EK
     
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    can you explain a bit clearer what it is you are interested in, as your post title suggests a new hull shape, yet the body of the text suggests you're only after facts to establish a trend.
    care to elucidate?
     
  3. Erwan
    Joined: Oct 2005
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    Erwan Senior Member

    Yes I would like to see if Prismatic has increased over the last 40 years:
    (New A-Cat shape vs Tornado shape). I guess it has, according to what I see.
     
  4. Questioner
    Joined: Sep 2007
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    Questioner Junior Member

    Erwan,
    these numbers are based offsets from a laser scan of the hulls, one is Flyer, the other shall remain nameless, both are A-Class cats...hope this helps

    Flyer

    Length Units: m Origin Depth: 0.0000 Weight Units: kg


    Dimensions:
    L.O.A. 5.4864 L.W.L. 5.4755
    Immersed Length 5.4864
    Bmax. 0.3159 B.W.L. 0.3103

    Immersed Volume 0.16 cu.m.
    FW Displacement 157.79 kg SW Displacement 161.74 kg

    Centroids:
    LCB 2.9270 (46.6 % aft) LCF 2.9917 (45.5 % aft)
    TCB 0.0000 VCB -0.0686

    Coefficients:
    Block (Cb) 0.513 Prismatic (Cp) 0.633
    Midships (Cm) 0.810 Waterplane (Cwp) 0.754
    Volume (Cv) 0.961

    Areas:
    Water Plane 1.281 sq.m Wetted Surface 2.294 sq.m

    Ratios:
    L/B Ratio 17.644 D/L Ratio 26.73

    Immersion:
    Load Increment / Draft Increment 1281.15 kg/m

    Metacentre:
    Transverse Radius (BMt) 0.0458 m


    Nameless

    Length Units: m Origin Depth: 0.0000 Weight Units: kg


    Dimensions:
    L.O.A. 5.4864 L.W.L. 5.4196
    Immersed Length 5.4864
    Bmax. 0.3000 B.W.L. 0.3000

    Immersed Volume 0.16 cu.m.
    FW Displacement 158.08 kg SW Displacement 162.03 kg

    Centroids:
    LCB 2.9606 (46.0 % aft) LCF 3.0550 (44.3 % aft)
    TCB 0.0000 VCB -0.0687

    Coefficients:
    Block (Cb) 0.535 Prismatic (Cp) 0.696
    Midships (Cm) 0.770 Waterplane (Cwp) 0.755
    Volume (Cv) 0.993

    Areas:
    Water Plane 1.228 sq.m Wetted Surface 2.291 sq.m

    Ratios:
    L/B Ratio 18.066 D/L Ratio 27.62

    Immersion:
    Load Increment / Draft Increment 1227.69 kg/m

    Metacentre:
    Transverse Radius (BMt) 0.0431 m
     
  5. Questioner
    Joined: Sep 2007
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    Questioner Junior Member

    Erwan
    all these are at full load, the one posted here (new Geltek Flyer that Ashby sailed in the Aussie Nats) is an extrapolation from the original Flyer based on the description of the changes posted on catsailor...not sure how accurate it is, but if all the changes where described accurately, it will probably be close

    New Geltek Flyer

    Length Units: m Origin Depth: 0.0000 Weight Units: kg


    Dimensions:
    L.O.A. 5.4864 L.W.L. 5.4769
    Immersed Length 5.4864
    Bmax. 0.3159 B.W.L. 0.3090

    Immersed Volume 0.15 cu.m.
    FW Displacement 152.95 kg SW Displacement 156.78 kg

    Centroids:
    LCB 2.9470 (46.3 % aft) LCF 3.0275 (44.8 % aft)
    TCB 0.0000 VCB -0.0661

    Coefficients:
    Block (Cb) 0.514 Prismatic (Cp) 0.636
    Midships (Cm) 0.808 Waterplane (Cwp) 0.766
    Volume (Cv) 0.931

    Areas:
    Water Plane 1.297 sq.m Wetted Surface 2.254 sq.m

    Ratios:
    L/B Ratio 17.724 D/L Ratio 25.89

    Immersion:
    Load Increment / Draft Increment 1296.66 kg/m

    Metacentre:
    Transverse Radius (BMt) 0.0485 m
     

  6. Erwan
    Joined: Oct 2005
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    Location: France

    Erwan Senior Member

    Thank You So Much Questioner

    Hi Questioner,

    Thank you very much for all these datas and for taking time to answer. I am very curious about the software you use to get all these figures.

    Also, I am happy to notice that you are interested in A-Cat hull design, as I am.

    I was expecting higher figure for the Flyer

    You mentionned your data acquisition system with laser. On my side I have a few datas on the Flyer I, and according to these measures, the max beam seems to be around 290 mm, may be 296 mm but no more.

    May be it can help to adjust your modelization.

    I guess that new LR3 shape with very narrow hull will achieve a very hight prismatic.

    Do you have any design project on the back-burner?

    Thank you again

    Best regards

    EK
     
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