This paper reports on a research effort involving design of a class of significantly complex products — nuclear submarines. It focuses on the use of features as a means of design abstraction, and it is found that a principal motivation for the use of features in this design environment is the convenience of the early stage submarine designer. To support this argument, a review of feature research is presented. Experiments in the development of feature catalogs are described, and implementation through two generations of feature based submarine CAD systems are discussed. The architecture of the feature based submarine CAD systems includes the use of Microsoft Foundation Classes (MFC), the ACIS geometric modeler, and user interfaces which store/recall hierarchical submarine feature information easily. Strong connections to object-oriented programming and object-oriented databases are recognized. Conclusions are drawn regarding the use of features for designer convenience and regarding support provided by hierarchical, parameterized features for other means of design automation.