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I've taken this discussion to Warhips1 before, but those who know don't tell and those who were dong the most talking clearly didn't have any clue. I don't expect much information to come of this but thought I'd kick it out there. Anyone know what is a typical speed that a modern D/E boat can make snorting all the way, assuming they are 'floating the load' as one individual once put it to me? Basically I'm looking for absolute upper transit speed, disregarding 'indiscretion'. Has some bearing on what countries could afford what kind of boat to deploy over what range--for instance the Soryu and Collins seem like much longer range animals than their PLAN or European cousins. WWII Fleet boats had four diesels and a hull optimized for surface running; they could do 20 knots indefinitely. Simple back of the envelope calculations on modern European and Kilo type boats seem to indicate they couldn't do anything close to this with their power plants; a dozen knots seems as the upper limit...further more I've been told a more typical transit speed is ~6 knots, but I assume that is with occasional snorting, not constant. Without knowing more math and having values like the efficiency and hotel load there's little conclusion an amateur can deduce, though I assume anyone who operates a Kilo/212/Gotland/Song/etc has a very good idea of the limitations. They seem to be roughly in the same tonnage and power range and the non-linear relationship of power to speed (cube rate?) for a boat should make anything but a major difference in power yield a similar speed. Another thing, does anyone know if/what is the upper limit a snorkel or other mast type could actually withstand the pressure of being raised during snort? I assume all boats have some upper limit on what masts can take what speeds without incurring damage; I can't see a nuke fan tailing water off its search scope at 30 knots even if anyone thought it was a good idea. I know the Collins class boats were built with several diesels and a large battery bank but no AIP on the assumption (so I've heard) that AIP didn't generate the power density to really aid in transit times compared to more engines running during quicker snorts. I assume the trade off is a larger snorkel and less fuel efficiency combined with increase mechanical complexity and cost.