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mikemike -> RE: Proto-Shokaku (8/9/2011 7:56:13 PM)
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quote:
ORIGINAL: FatR
I've already put up idea of building a DD and a dedicated APD on the same hull when we were discussing RA. Then it was pointed to me, that type 1 APDs were significantly large than Matsus. They are closer in size to Shiratsuyus. And APD of a pre-war design will inevitably be less downgraded for simplicity, particularly in terms of engine power and speed. Also, building destroyers so small makes litte sense, when you primarily need to increase the number of frontline combatants, not escorts.
That is a pertinent objection. I've checked the data again, and, you're right, the T1 has roughly the same beam and draught as the Shiratsuyus, it's just about ten meters shorter, but definitely closer in size than to the Matsus. And, incidentally, all the British War Emergency destroyers were quite a bit bigger than the Shiratsuyus, at least in full load displacement, not so much in hull dimensions. So a repeat Shiratsuyu would seem to be a plausible choice if you want to go for numbers, provided they can really be built faster than a Kagero, where the yards would just extend a running program instead of retooling for a different design. If Shiratsuyus, what should the armament be? 127/50s, leaving away the awkwardly-placed single mount?
The APDs: The T1 design is already not that much smaller than a Shiratsuyu. On a platform of that size, if you switch to a two-shaft plant with more power than the T1 had, you would be cutting deep into the cargo space. In fact, just going to the full Matsu plant would probably eliminate most of it. Taking half the Shiratsuyu plant for a single-shaft design, you would need to use the Shiratsuyu size hull to get enough interior cargo space. How about a Shiratsuyu-sized hull with the kind of modifications the T1 had, especially that roller ramp at the stern for smooth launching of loaded Daihatsus, and a two-shaft plant with 15000-16000 HP, not in unit arrangement to save space. Should be good for about 25 kts.
quote:
ORIGINAL: FatR
Seeing its stats there is a reason - its gun weight is about 10% less than of 120/45 10th Year, but shell weight is about 30% less, with the bursting charge being almost 50% less.
Seeing as 120/45 10Y and hand-operated Type 88 version of 127/40 were quite close in terms of weight (and their complete rounds had practically the same weight, making no difference in manual operation), I see no reason why 127/40 shouldn't be produced instead of 120/45 and used in all the same roles.
If there is a potential alternative here, it is using 120/45 tubes as a part of Type 89 flak system, and therefore utilizing 120/45 in all places where 127/40 was used historically. 120/45 has a little better ballistics and a little lesser weight than 127/40, while the bursting charge of their shells is practically equal. If placed in modern mountings, with modern fire direction equipment, it, in all likelyhood, could produce superior performance. But the increase is small enough, and I'm not convinced that it is worth using two calibres instead of one.
The thing about the 100mm is correct. I hadn't looked at the weights. Strange that the 120/45 doesn't have better ballistics in comparison to the 127/40, with a longer barrel and 20% more propellant, although navweaps remarks that initially, the charge didn't combust completely before the shell left the barrel - which was remedied later by using a different grain to the powder. But really, the odd man out here is the 127mm/50 used on all the fleet destroyers - everything else has fixed ammunition and sliding breeches, while the 127/50 has separate ammo with bagged propellant and a Welin breech. Maybe somebody just scaled down a Vickers-type 6incher to the 127/50 design, while some other team designed the 120/45 10th year, the 127/40 Type 88/89, the 100/50 Type 88 ... If the navweaps data is precise, the two 127mm guns seem at least to have used the same shells. Anyway, the design date of the 127/50 is straddled by those of the 120/45, which was earlier, and the 127/40, which was slightly later. So why didn't they just design the 127/50 in the same style? Because it was intended as anti-surface, not as a DP gun like the others? Technically, I don't think there would be any obstacle to designing that gun with a sliding breech and cased propellant, fixed or separate. The longer gun would have needed a larger charge than the 127/40, meaning that the round for the 127/50 wouldn't have fitted the shorter gun. This way, the Type 1/Type 5 design would have been an evolutionary development from the original 127/50, and, using your intended timescale, I can't see much of a difficulty having it come into service around 1940. The sort of ballistic performance the Type 1 had would, of course, have made yet another new type of round necessary.
Wait a minute. You want to drop the 120mm Tenth Year, so the 127/40 would need to come out first, in 1926. Call it the Type 86. And then you want another gun for the Special Type DDs. As you have just lost one size of ammo, the DD gun (call it Type 88) could use a heavier shell. The Type 1 had a 27kg shell, the US Mk12 a 25kg shell, the German SK C/34 a 28kg shell. Go for 25 or 27 kg? A serious DP gun (Type 98) developed from this New DD gun could possibly use the same ammo.
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