Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Barrels was DR thread from Nov-Dec '04
    From: Doug Royer
    Date: 2005 Feb 2, 10:54 -0800

    Not clear what the old and new displacements are relative to a a couple of
    How many pounds in a ton for this formula (I am assuming with displacement
    we are not talking gross or net tonnage as a factor of square feet of cargo
    a.  Is there a baseline displacement based on the displacement of an empty
    vessel plus fuel etc?  which is already factored in before we add or
    subtract cargo, or
    As I understand it(I'm no mathematician)these formuli are based on ratio.As
    long as the units are kept squared away in each formula answers will give
    the needed info.
    That said these are the basic formuli.You manipulate them as needed.There
    are other steps or mutations of these formuli one adds or not(as in reguards
    to auxillary usage)as needed.There are also others that I didn't include.
    In real life the bridge or chartroom has volumes of gragh/plot books used
    for easy,speedy referance for the baseline info(such as rpm to speed or fuel
    consuption at a certain speed/g.t. weight).
    b.  Is the new displacement the total weight of the ship, fuel, cargo etc
    plus/minus the added or subtracted cargo?
    It is usually gross tonnage for all calculations. We know what the un-laden
    tonnage of the vessel is so by adding/subtracting the weights of
    cargo,consumables(fuel,fresh water etc)as they are loaded,discharged or
    consummed you have the displacement.The set-up of the data for some of this
    can get complex and time consumming.
    Tangentially, in practice does a captain run close to hull speed (assuming a
    non-perishable cargo and sea conditions permitting) to save time, or back
    off to decrease fuel cost?
    Put another way, is the earning capacity of the vessel per day so large that
    fuel cost be damned, only time is money; or is the margin slim enough that
    he has to calculate the cost/benefit ratio of speed (time is money) vs. fuel
    (oil is money)?
    This seems like an easy question but really isn't.There's so many
    variables(such as safety).I will say that time seems to be the over riding
    factor.These cargos are consigned to be picked up/delivered at specific
    times at specific places.One transit can have a vessel loading/offloading
    cargos at multiple ports along the baseline track.For example: scheduleing
    has the vessel in say San Pedro to pick up 3,200 tons of containers at warf
    B on 02-13-04 starting at 1300 hrs.At 1900 hrs it has to be at warf G to
    load 500 tons of frozen beef.The vessel is scheduled to leave S.P. by 0845
    02-14-04.Offloading the 500 tons of beef at the Port of Ventura by no later
    than 1600 hrs 02-14-04 and be underway to offload the 3,200 tons of
    containers at Warf 23 in S.F. by 1300 hrs 02-15-04 etc.
    I'd say time is the most important factor.
    The earning capacity of these vessels are enormous!
    It would stagger you the amounts of capital moved and made by just 1 vessel
    during a transit.The company I used to work for had a fleet of 17 vessels.

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site