to be a constant and not a function of the thickne ss- radius ratio of the 

 sphere; this appears to be true at least for the range of thickness- radius 

 ratios from 0.10 to 0. 01 investigated by Krenzke. Tests with welded 

 hemispheres and tests of spherical caps (having included solid-angles 

 ranging from 5 degrees to a full sphere) are also presently underway at 

 the Model Basin. 



Although the overall shape of even present-day submersibles is that 

 of a general extended ellipsoid of revolution, (see the ALBACORE 

 (AGSS-569) hull in Figure 1), the main pressure hull structure is still 

 the ring- stiffened, right-circular cylinder. In the future it may be desir- 

 able to consider the use of doubly curved shells such as prolate spheroids 

 for the major hull structure. Such shells are superior to the circular 

 cylinder in hydrodynamic characteristics and may also possess signifi- 

 cantly greater structural strength for the same weight of hull. At 

 present, both analytical and experimental data on such shell structures 

 are rather limited. Two major problems which require attention are 

 those dealing with the axisymmetric stresses in and buckling of ring- 

 stiffened prolate spheroids. A general set of edge coefficients for a 

 spheroid of constant but different radii of curvature in the two principal 

 directions may serve as a basis for carrying out an analysis of the elastic 

 deformations and stresses in the ring- stiffened structure. Efforts should 

 also be directed toward an examination of available buckling analyses such 

 as those summarized in Reference 83. Structural models are required to 



130 



