# Estimated Block Coefficient for Catamaran Vessel

Discussion in 'Boat Design' started by 07MAM, Aug 7, 2018.

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### 07MAMJunior Member

Is there anyone can refer me a Cb for Catamaran Ferry. Just for estimation or a standard one if there is a standard Cb for Catamaran Vessel.

Details:
LOA 100FT
TYPE Passenger Vessel with 3 deck on top

Thank you in advance for opinions and suggestion

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### bitStudent

Approx 0.42

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### TANSLSenior Member

Is Cb the block coefficiente?. In addition to the number of decks, we would have to introduce some other variable in the formula that, if it existed, would allow us to deduce an appropriate block coefficient for your boat. But, as far as I know, answering your question, there is no standard value for 3-deck passage catamarans.

P.S. Deleted a comment for being consequence of an incorrect interpretation of the question.

Last edited: Aug 8, 2018
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### 07MAMJunior Member

Thank you for all your inputs. Well appreciated.

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### rxcompositeSenior Member

Designed operational speed?

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### 07MAMJunior Member

20 knots sir

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### rxcompositeSenior Member

Is this a student thesis project or a design estimate? We need to know so we can tailor our response to you.

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### 07MAMJunior Member

Design Estimate sir

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### BlueBell. . . . .

"Sir", that's rather presumptuous of you isn't it?

How many passengers?
Cars?
Seas?
Travel distance.
Seasons.

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### 07MAMJunior Member

100 passenger
no car
Davao Gulf
47.27km
No season.

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### rxcompositeSenior Member

You are outside the range. To realize that you need a 300 ft hull. for 20 knots you are designing around a very slim hull, NPL type, destroyer type, overdriven, with poor fuel economy.

#### Attached Files:

• ###### Ship coefficient and ratios Sample.xlsx
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### Mr EfficiencySenior Member

He is talking catamarans, plenty of them 100 feet long doing 20 knots.

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### rxcompositeSenior Member

The table is not limited to mono. Just speed to length ratios or Froude number. Resistance and powering formulas will analyze the efficiency of the hull.

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### Mr EfficiencySenior Member

So what range is he out of ?

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### 07MAMJunior Member

100ft hull only. Based on the presentation sir the sample ratios that I can used is ranging form 0.67-0.73. Well noted of this sir. Thank you so much

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