DESIGN CONSIDERATIONS FOR STABILITY OF DRILL SHIPS

When stability is neglected as a serious constraint in the preliminary and contract design of drill ships, the possible inadequacies in the intact and damaged stability are not recognized till relevant calculations have to be submitted to classification societies, or governmental agencies. Usually, this occurs when a ship is nearly complete and ready for delivery. Invariably, solutions to stability problems at this state are costly. They can involve expensive modifications to the ship and/or reduced operating KG. Principal dimensions of the ship, arrangements and outboard profiles, must be chosen with stability as one of the major considerations. A parametric analysis is presented to exhibit the influence of the variation of beam and depth of ships from 250 feet to 600 feet on the allowable maximum KG and the range of righting moment curves. Stability considerations related to arrangements and outboard profiles are also treated.