Inclining an stability length less than 24 m ship

Discussion in 'Stability' started by Adarsh Edakkote, Nov 8, 2019.

  1. Adarsh Edakkote
    Joined: Dec 2015
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    Adarsh Edakkote Junior Member

    Hi Can anyone advise the requirement of conducting inclining experiment for a crew boat with length less than 24 m?
    Regards
    Adarsh
     
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Adarsh, could you perhaps elaborate a bit more please re the requirements you are worried about?
    The basic method of carrying out an inclining experiment on a crew boat would be the same as for any other type of boat generally re the procedures to follow and the measurements that have to be taken.
     
  3. Adarsh Edakkote
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    Adarsh Edakkote Junior Member

    Sir,

    Normally Every passenger ship regardless of size and every cargo ship having a length (L) of 24 m and upwards, shall be inclined upon its completion

    My doubt is do we need to conduct inclining of a 16 m crew boat?

    Hope you understand my doubt
     
  4. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    If the vessel needs to have a stability booklet then you will have to do an inclining experiment.
    Is there a requirement for your 16 metre crew boat to have a stability booklet?
     
  5. gonzo
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    gonzo Senior Member

    Who is the certifying authority? They should be able to provide the information.
     
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  6. Alik
    Joined: Jul 2003
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    Alik Senior Member

    The problem with inclining such as small boat is accuracy of measurements. Say, one might not be able to measure displacement from draft survey, as 1cm if draft on this boat could be 5% of displacement.
    Other than that, 16m boat can be inclined, we did it many times.

    However, Class can raise questions regarding the accuracy. They might ask to incline every boat in the series as displacement deviation between the boats might seem to them more than 2% :) If class does not have common sense (and some of them don't), one has to do such stupid things.

    Keys for success are:
    - deal with reasonable classification society and find reasonable surveyor to handle Your case
    - incline on flat water, better in pond
    - mooring ropes loose when You take measurements - always have person on charge ON SHORE.
    - measure draft by measurement tape from tender, not by draft marks!
    - in addition to pendulum, use 2 U-tubes - this is more accurate and less effected by craft's motions
    - attach tubes to bulwarks, and attach paper tapes parallel to the tubes. Use pencil to mark position of water level each time You shift weights.
    - minimize free persons on board during test, for small boats! There will be few persons on board to take measurements anyway, mark position of every person on deck. Let surveyor and others watch from pier.
    - we often use persons instead of weights, say, on catamarans. This allows us to move the 'inclining ballast' fast, also no damage to FPR or teak deck. Assign each group of persons, check their weight, mark their position on deck, explain them how to stand.
    - process the results in specialized software (we use HST, they have inclining test module), not class spreadsheets where 'vertical sides' assumption used.
     
  7. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    What does the spec of the boat say?
    And as Gonzo notes, who is the statutory/flag authority?

    Since the inclining experiment is a statutory requirement and you need to establish what their procedures are for such. Most are the same, such as MCA here.
    But best check to avoid any ambiguity. Since some Flag States allow Classification societies to oversee this role and/or they have insufficient manpower to do so themselves; hence being differed to Class - contractual certification between the shipyard and the authorities, will note this - who is doing what. In which case Class tend to be a bit more strict and less willing to negotiate, as they are representing the Flag sate and have no veto power on the methodology.

    I recently completed an inclining expt where LR was the surveying body as the shipyard contracted the Classification society to do all statutory checks. Thus you need to find out who is doing what.

    In addition, whatever the statutory rules state, these may be overridden by the Spec. for a higher standard, thus must be checked.
     
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  8. Adarsh Edakkote
    Joined: Dec 2015
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    Adarsh Edakkote Junior Member

    Thanks all for your valuable informations
     
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