# Resistance prediction

Discussion in 'Software' started by souravsandesh, Sep 30, 2014.

1. Joined: Aug 2014
Posts: 8
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Location: INDIA

### souravsandeshJunior Member

Hello all,

I need a small clarification as to what the below text actually mean

1 {0.93 ( / )
0.521448 0.6906
0.92497
1 13 12
C C lcb
k c c B L
P P
R
− − +
+ = +

In this formula, CP is the prismatic coefficient
based on the waterline length, L and lcb is
the longitudinal centre of buoyancy forward
of 0.5L as a percentage of L??

Please kindly tell me what the highlighted text means

My vessel is a catamaran and am calculating resistance for a demi hull...

My vessel length is 18m...and my LCB demi hull is 8.9m from aft

thank you

2. Joined: May 2004
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Location: Italy (Garda Lake) and Croatia (Istria)

### daiquiriEngineering and Design

Longitudinal centre of buoyancy expressed as a percentage of L, measured from the mid-ship (0.5 L). If it is forward of the mid-ship, then it is a positive value - otherwise it is negative.

For example:
L = 80 m
Xlcb = 3 m aft of the midship​
gives:
LCB = -3/80 = -0.0375​
or, in percentage:
LCB = -3.75%.​
The value is negative because it is aft of the 0.5L.

Another example:
L = 60 m
Xlcb = 2 m forward of the midship​
gives:
LCB = 2/60 = 0.0333​
or, in percentage:
LCB = 3.33%​
The value is positive because it is forward of the 0.5L.

Hope it helps.

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