Any idea about New hull Shape Prismatic Coef ?

[Erwan]

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

[Ad Hoc]

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?

[Erwan]

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.

[Questioner]

Originally Posted by Erwan

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.

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

[Questioner]

Originally Posted by Erwan

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.

EK

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

[Erwan]

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