Hi, My yel-o-sub is about 37" inside dia. I would not want it any smaller! No room to add internal ribs. Anybody know what dia. the K-subs are? Jon Charles Samardza wrote: > I'm curious as to what diameter hulls are common among the personal > submarines being built. I've found some possible designs in Th. 40 to > 52 inch diameter range and I'd appreciate some input.