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    FW: Barrels was DR thread from Nov-Dec '04
    From: Doug Royer
    Date: 2005 Feb 1, 10:42 -0800

    Doug
    
    George posted a plausible explanation of the cube method, but I have not
    seen your posting on how a merchant marine would solve the problem.
    
    Any hope I will see another way to skin the cat from you?
    
    Bill
    
    
    
    Here you go:
    
    s = old speed
    S = new speed
    c = old consumption
    C = new consuption
    w = pld displacement
    W = new displacement
    r = rpm at s
    R = rpm at S
    Ve = calculated speed by rpm
    Vo = observed speed
    De = calculated distance by rpm
    Do = observed distance
    
    Slip
    - slip = vessel speed outruns screw speed
    + slip = screw speed outruns vessel speed
    
    by speed
    % slip = ((Ve - Vo)/Ve) x 100
    by distance
    % slip = ((Do - De)/De) x 100
    
    Fuel Consumption
    
    by displacement
    log C = (log c + 2/3 log W)- 2/3 log c
    by speed
    C =(c x S cubed)/s cubed
    
    Speed by RPM
    speed in Kts = (60 x rpm x pitch x (1 - % slip))/6080
    rpm at given speed
    rpm = 6080/((pitch/1 + % slip) x 60) x speed in Kts
    rpm needed for new speed
    rpm = (r x S)/s
    
    
    

       
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