The great size of the boats (compared to their predecessors) led to control and depth-keeping problems, particularly as efficient telemotor controls had not yet been developed. This was made worse by the estimated maximum diving depth of being much less than their overall length. Even a 10-degree angle on the 339-foot-long hull would cause a difference in depth of the bow and stern, and 30 degrees would produce , which meant that while the stern would almost be on the surface, the bow would almost be at its maximum safe depth. The submarines were made more dangerous because the eight internal bulkheads were designed and tested during development to stand a pressure equivalent to only , risking their collapse if the hull was compromised at a depth below this figure.