On the bottlenose: a what if

In 1930, the U.S. Navy's Bureau of Construction & Repair (later Bureau of Ships) saw their latest fleet sub, Dolphin, laid down at Portsmouth. About a third smaller than the previous design, Narwhal & Nautilus, she was also about a third bigger than the next, Cachalot & Cuttlefish. Cachalot & Cuttlefish proved too small, as would the next class, the Porpoises. It would be 1936 before BuShips hit on a fleet boat design truly suited to Pacific operations, & 1954 before Darter even approached Dolphin's size again.

So: what would it take for BuC&R to standardize on Dolphin in 1930? How much difference would it make to the Pacific War, if any? How much difference to USN sub design?
 
Well for starters Dolphin's range wasn't good, its internal tanks only allowed it 4,900 nmi (nautical miles) range at 10 knots, compared to Cachalot's 11,000 nmi. Of course that could be extended to nearly 19,000 nmi, but that required filling the main ballast tanks. You'd also have to work on the drive-system, which seems to be overly complex to my mind., and was probably the reason for the limited endurance and relatively poor armament (18 torpedoes, vs 16 for Cachalot)
 
MattII said:
Well for starters Dolphin's range wasn't good, its internal tanks only allowed it 4,900 nmi (nautical miles) range at 10 knots, compared to Cachalot's 11,000 nmi.
Without The Fleet Submarine in front of me, I can't say for sure, but that should be easily fixable.
MattII said:
You'd also have to work on the drive-system, which seems to be overly complex to my mind
Agreed. Bear in mind, there was quite a bit of experimenting with drive systems in this period, even throught the Salmons & Tambors. It wasn't really until the Gatos, & the war, a standard was fixed.
MattII said:
probably the reason for the limited endurance
That I'm less sure of.
MattII said:
and relatively poor armament (18 torpedoes, vs 16 for Cachalot)
That's about what you'd expect: 4 bow tubes =12 fish; 2 stern tubes =4 fish. (Why Dolphins had 18, IDK; something in the equipment layout, perhaps the drive, perhaps more forward; there was room in the Gatos, but the extra two were rarely carried.)

The hull form astern had space for more reloads, but the equipment in the aft room never took advantage of it; I suspect this was partly due to a need to change the ballast & trim tankage to account for the added weight.
 
What really killed the Dolphin design was that it ran afoul of the submarine size limits imposed by the 1930 LNT- 2 planned sisters were cancelled before they were even authorized because they'd be too big both individually, and in terms of the aggregate tonnage restrictions, which was why the USN developed the Cachalot as another prototype, to try to get similar performance on a more reasonably sized 1100-1200 ton standard displacement platform, but was unsatisfactory as a little too small, but more importantly, only having 2 engines was seen as a major weakness for Pacific operations. (both designs were basically attempts to develop an Americanized & updated version of the WW1 German U-135 as a mobilization prototype.)

According to Friedman's, the third attempt, the slightly larger Porpoise, which was designed just as some major advances in welding & diesel propulsion tech became ready, corrected most of those faults, and it was the desire for heavier armament and greater surface speed that were the big drivers in the subsequent growth of the fleet boat over the next few classes, as well as a revision of fuel storage arrangements.
 
DD951 said:
What really killed the Dolphin design was that it ran afoul of the submarine size limits imposed by the 1930 LNT- 2 planned sisters were cancelled before they were even authorized because they'd be too big both individually, and in terms of the aggregate tonnage restrictions
She was under the 2000 ton limit. Or was that 2000 tons submerged? (I always understood not.)

As for staying under the 52,700 ton limit, why not surplus off or scrap the S-boats (which were obsolescent at best)? Or, at a minimum, dump the surviving O- & R-boats?:confused:

This has benefits in reducing operating cost & reducing manpower demands.

There's other arguments in favor: building new fleet boats means all-new ships in inventory. Plus building them creates jobs...

(Yes, you do end up having one *Dolphin for every 2 S-boats...:rolleyes:)
DD951 said:
the slightly larger Porpoise
She was close to the ideal, agreed; IMO, still a bit small (only 1300 tons).
 
She was under the 2000 ton limit. Or was that 2000 tons submerged? (I always understood not.)

As for staying under the 52,700 ton limit, why not surplus off or scrap the S-boats (which were obsolescent at best)? Or, at a minimum, dump the surviving O- & R-boats?:confused:

This has benefits in reducing operating cost & reducing manpower demands.

There's other arguments in favor: building new fleet boats means all-new ships in inventory. Plus building them creates jobs...

(Yes, you do end up having one *Dolphin for every 2 S-boats...:rolleyes:)

That has to do with the specifics of the treaty- submarines could only be replaced by new construction once they were more than 13 years old, except in the event of accidental loss, while submarines under 600 tons (which would include both the O & R boats), which meant that during the period the LNT was in effect, the US would be permitted to replace 25,800 tons of submarines, & would still have the V-boats & 11 S-boats left as underage.

As Dolphin displaced about 1560 tons standard, that'd allow for 16 & a half submarines if they were exact copies, which was too few; by allowing unit size to fall to 1200 tons, which the designers thought would be just doable for the U-135 knock-off they were going for as the minimum useful submarine, they could get 21 & a half units on that displacement, which even then would be a loss of over a third in total unit numbers, as whatever replacement submarines were built would have to do the same work as the 35+ S-boats eligible for replacement in that timeframe (at a point where USN planners figured that at least ~60 long-range modern submarines to fulfill all the requirements for a war against Japan, & the US submarine fleet was grossly outdated compared to that of Britain or Japan.)

The big reason the S-boats survived until WW2 was that the LNT had an escalator clause that allowed the signatories to retain or build extra tonnage in retaliation for other signatories having too large a fleet, and the US invoked this after only a handful of S-boats were disposed of after Japan kept some 16k tons worth of excess submarines, & the whole treaty structure started collapsing soon afterwards- as the submarine building plant was fairly limited (as well as what Congress would buy), the antiques got to stick around for a while longer.
 
DD951 said:
while submarines under 600 tons
Looks like you missed a thought, here.;)
DD951 said:
That has to do with the specifics of the treaty- submarines could only be replaced by new construction once they were more than 13 years old, except in the event of accidental loss
For a start, then, that gives you three for the S-boats lost to accidents, plus S-50. Assuming you replace these, & through S-10, at the rate of one or two per yard per year (which was about the going rate), you're no earlier than 1933 when you've built out your first 14 (max prewar build in any one year was 7, IIRC).

This also presumes the S-boats are retained... They were demonstrably too slow for operation with the fleet (in keeping with the doctrine under development), & too small for the Pacific. (Not to mention damned uncomfortable for work in the Tropics.:eek:) So what happens if PotUS declares them surplus & sells them to Bolivia or the Vatican or somebody?:p I can't imagine the Treaty refuses to allow replacement in that instance.

So replace with Bottlenoses:p (8 tubes {4+4? 6+2?}? 10 tubes (6+4? 8+2?}? 2x4"/50cal? 4 Fairbanks-Morses or Wintons) at 4/yr til 1936, then see Japan renounce the treaty, quit it, & increase the build rate to 2-3/yard/year in '36 or '37. Then in '39, surplus off the remaining S-boats to RN & RCN.;)
DD951 said:
they could get 21 & a half units on that displacement, which even then would be a loss of over a third in total unit numbers, as whatever replacement submarines were built would have to do the same work as the 35+ S-boats eligible for replacement in that timeframe (at a point where USN planners figured that at least ~60 long-range modern submarines to fulfill all the requirements for a war against Japan...)
This is the hardest argument to answer. At the time, I doubt anybody really anticipated a major war against Japan's commerce. Loss of the P.I., Guam, & Wake had long been anticipated, tho, so retaining the S-boats should have been self-evidently a bad idea: fine if you work out of Manila, not if you have to base in Midway or Pearl Harbor (never mind Dago or San Pedro:eek::eek:)

They were right about the number: a sustained force of 65 was about what Nimitz got. Truth is, it was possible to do the job with fewer...but that required more imagination, which is another POD entirely.
 
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