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Passenger ferry consumption

Discussion in 'Technical Discussion' started by JMestre, Aug 29, 2006.

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  1. JMestre, Aug 29, 2006
    #1
    JMestre

    JMestre New Member

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    I'm studying the fuel consumption of a passenger ferry (47 meters) that is propelled with water jets and is used to cross a river in a distance of about 8.2 km.

    Do you have suggestions of how do I calculate the most efficient velocity for that ferry?

    Is it possible that this particular vessel consume more fuel (per distance) travelling at 22 knots than at 28-29 knots?

    Thanks
    J Mestre
  2. AMG, Aug 29, 2006
    #2
    AMG

    AMG YF Moderator

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    It depends on hull shape and on the top speed. Is it making 40 knots or more, it can happen that 28 knots is better economy than 22, but if top speed is closer to 28, like 32 knots, I think 22 can be a good economy speed.
  3. K1W1, Aug 29, 2006
    #3
    K1W1

    K1W1 Senior Member

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    Hi,

    Owing to the large number of variables that can effect fuel consumption the best way to determine the most economical speed is to do some actual runs.

    I take it this is an existing vessel so I would suggest that if you can do some measurements with calibrated flow meters( 1 in each supply and return line) you will have the most accurate results.

    Bear in mind that the longer you can hold a set speed the more accurate figures you will end up withbe. That boat should be able to cover 8kms in about 7 mins at 22knots so as you will ave acceleration and slowdown times you will need a few runs to get all the air out and an average consumption that is accurate.

    Good Luck and let us know how you get on.
  4. JMestre, Aug 30, 2006
    #4
    JMestre

    JMestre New Member

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    Thanks for your replies but it's not possible for me to install flow meters or to do those runs.

    I’ve looked in this forum for measures to improve energy efficiency in passenger ferries but I only found out measures for smaller boats. And I’m trying to find out measures that could be paid in the short-medium run for monohull and catamaran ferries with a capacity of around 500 passengers. For example, finding the optimal speed or reducing the weight. Can anyone help me in this subject with general measures or with references to previous studies?

    I’m also trying to find companies that operate in similar river crosses (2 km and 8.2 km) (1.24 and 5.1 miles) and with similar vessels to possibly start a benchmark process. I would be very happy if anyone could give me this information.

    If you need I can give more details about the boats.

    Thanks,
    JMestre
  5. K1W1, Aug 30, 2006
    #5
    K1W1

    K1W1 Senior Member

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    Hi,

    That's a pretty big ask.

    For someone to even attempt to calculate the consumption you would need to post at least the following.

    Waterline Length

    Displacement

    Engine Make, Model and Output

    Water Jet and exact tech specs

    With that someone should be able to determine the aproximate fuel consumption but it won't be anything set in stone.

    What are the guys who are running this service now saying it burns?
  6. JMestre, Aug 31, 2006
    #6
    JMestre

    JMestre New Member

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    Thanks K1W1

    I’m working on that, today I’ll see if I can get someone to work on that.

    But what about measures to reduce the boat’s consumption? And studies about this subject? This is my main objective!

    Here’s a list of possible measures:
    - Proper hull and propeller maintenance
    - Better antifouling paint
    - Optimal speed
    - Better routing
    - Optimal trim
    - Minimum ballast
    - Optimal rudder
    - Teaching economical navigation

    Thanks,
    JMestre
  7. Innomare, Sep 5, 2006
    #7
    Innomare

    Innomare Senior Member

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    yes, it is possible

    Olá,

    is this boat a monohull or a multihull?
    And if it's a multihull, is it a semi-displacement or a displacement type?
    A displacement type will almost be at the same trim at whatever speed. If it's a semi-displacement, the nose will come up 2-4 degrees when sailing at higher speeds.

    If it is a displacement multihull, the slower it goes, the cheaper it is. As long as the engines are running at a proper rpm....
    If there is some planing involved, it's more complex. It is indeed possible that fuel consumption is lower at e.g. 28 knots than at 22 knots.

    You should be able to get this info from the designer (the range versus speed graph is what you're after).

    All the measures you propose are also valid. Minimising the weight is important, so you may want to look at optimising the tankage intervals (maybe daily instead of weekly for example).

    Boa sorte!

    Bruno

    Naval Architect
  8. JMestre, Sep 5, 2006
    #8
    JMestre

    JMestre New Member

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    Olá,

    It's a catamaran and I believe it's a semi-displacement one because it can almost reach the 40 knots. But I'm just allowed to go aboard to collect speed, rpm, depth and consumption. I can’t ask the boat driver to go at the speed I want.

    I must get the range vs. speed graph!

    Obrigado pelo conselho:)

    José