National Shipbuilding Research Program. Limitations of Computerized Lofting for Shell Plate Development.

摘要

Some shipyards are not satisfied with the current computer aided lofting (CAL) shell development systems that they use. This dissatisfaction manifests itself in fit up problems and the need for excess material ( green or stock ) to be left on some butts and seams to allow corrections to be made at erection. Most shipbuilders desire a cut to neat size approach. This is obviously to eliminate labor intensive fitting cutting in and edge preparation for welding, on the assembly plattens or building berth. On the other hand, most CAL developers recommend that stock material be left on one seam and one butt for each shell plate block with significant curvature. They claim that this is to take care of inaccuracies due to the platers skill level and limitations of the forming machinery, rather than inaccuracies in the shell development systems. This study was undertaken to help put the shell plate development problems in their correct perspective and to determine if the shipbuilders goal of cutting all shell plates neat is reasonable. The study was performed in two phases to suit funding restrictions. Phase I developed the Problem and Solution Description and Phase II covered the development of the Shell Plate Test Cases and the preparation of the Ship Designers Manual.