4.7 Pontoons

 The provisions given hereunder apply to seagoing pontoons. A pontoon is considered to be normally:

• .1 non self-propelled;

• .2 unmanned;

• .3 carrying only deck cargo;

• .4 having a block coefficient of 0.9 or greater;

• .5 having a breadth/depth ratio of greater than 3.0; and

• .6 having no hatchways in the deck except small manholes closed with gasketed covers.

  4.7.2.1 The following information is typical of that required to be submitted to the Administration for approval:

• .1 lines drawing;

• .2 hydrostatic curves;

• .3 cross curves;

• .4 report of draught and density of readings and calculation of lightship displacement and longitudinal centre of gravity;

• .5 statement of justification of assumed vertical centre of gravity;

• .6 simplified stability guidance such as a loading diagram, so that the pontoon may be loaded in compliance with the stability criteria.

  4.7.2.2 Concerning the performance of calculations, the following is suggested:

• .1 no account should be taken of the buoyancy of deck cargo (except buoyancy credit for adequately secured timber);

• .2 consideration should be given to such factors as water absorption (e.g. timber), trapped water in cargo (e.g. pipes) and ice accretion;

• .3 in performing wind heel calculations:

  • .3.1 the wind pressure should be constant and for general operations be considered to act on a solid mass extending over the length of the cargo deck and to an assumed height above the deck,

  • .3.2 the centre of gravity of the cargo should be assumed at a point mid-height of the cargo, and

  • .3.3 the wind lever arm should be taken from the centre of the deck cargo to a point at one half the mean draught;

• .4 calculations should be performed covering the full range of operating draughts;

• .5 the downflooding angle should be taken as the angle at which an opening through which progressive flooding may take place is immersed. This would not be an opening closed by a watertight manhole cover or a vent fitted with an automatic closure.

  4.7.3.1 The area under the righting lever curve up to the angle of maximum righting lever should not be less than 0.08 metre-radians.

  4.7.3.2 The static angle of heel due to a uniformly distributed wind load of 540 Pa (wind speed 30 m/s) should not exceed an angle corresponding to half the freeboard for the relevant loading condition, where the lever of wind heeling moment is measured from the centroid of the windage area to half the draught.

  4.7.3.3 The minimum range of stability should be: