Single pull macgregor type hatch cover.pdf - Cochin University of ...

3.2.2 Cover Stowage
Where a designer is attempting to obtain the largest possible hatchway openings, the
question of the hatch cover stowage is especially important. The width of the stowage
space is fixed by the hatchway width if the covers are stowed at the end of the
hatchway, but the height and length of the space can be varied. If the hatchways are to
be the longest possible in a given deck length, the length of the stowage space must be
kept to a minimum; this can be accomplished in a various ways depending on the type
of hatch cover employed. No special stowage space is required for simple pontoon
covers since these are usually stowed on adjacent hatch covers or on the quayside
when the hatch is open. Alternatively side rolling covers may be used if the hatchway
is not too wide in relation to the ships breadth.
3.2.3 Deck Openings
As deck opening becomes larger, the problem of ensuring adequate hull strength
becomes more complex. The necessary longitudinal strength of the hull girder can be
readily achieved, even for ships with hatch widths 80 percent of the breadth of the
ship, by the use of high tensile steels. But the provision of the adequate torsion
strength may require very detailed design and stress analysis, since the torsional
deflection of a ship with large hatchways give rise to high stress concentration at the
corners of the openings and to deformation of the hatchway.
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