Shipbucket

Whatever makes you happy...

I think it's quite spiffy

With the end of the war, the few surviving Japanese destroyers (to give an example of exactly how few, only Yukikaze survived out of all the pre-war DDs) continued in service, but it was obvious more destroyers would be needed. As a result, two designs were approved, one of which improved on the Akizuki-class. The main armament layout of four twin Type 98 3.9-inch turrets was retained, but the new ships were given the upgraded Mark II design, which solved the problem of the short barrel-life of those guns mounted on the preceding Akizuki-class. The antiaircraft guns were also upgraded; the 25-mm. mounts were scrapped in favor of twin-mount 40-mm. Bofors and 20-mm. Orelikons. The bridge structure was enlarged, and the newly-designed Type 26 surface-search radar was mounted on the foremast, with the also-new Type 23 air-search radar mounted on the mainmast. The quadruple torpedo mount was removed; these were the first Japanese destroyers to not carry the infamous 'Long Lance' torpedo, but by the time these ships would be ready for service, it was obvious to even the Imperial Japanese Navy that Solomon Islands campaign-level surface actions were a thing of the past. Instead, a second funnel and more boilers were added, along with the same engines installed in the Umigiri-class DDs. The result was an improved Akizuki-class ship with the speed of an Umigiri-class ship. In the end, it was found that with the lighter gun mounts and no torpedo tubes, the ships achieved speeds faster than the Umigiris, with Yamazuki achieving an incredible 43.7 knots on acceptance trials.

There would be sixteen ships of the class in all; laid down between February 1947 and June 1951, launched between January 1948 and May 1952, and commissioned between November 1948 and March 1953, with numerous upgrades to their equipment throughout their service lives, these vessels would serve the IJN well into the early 1980s.

I'd be highly entertained to see you present a brief Springsharp chart that would support a 43.7 knot speed at any displacement.

The lack of any ahead-throwing ASW armament, or sonar whatsoever, is odd.

erik_t wrote:I'd be highly entertained to see you present a brief Springsharp chart that would support a 43.7 knot speed at any displacement.

Yes this seems highly dubious.

Best I could do in Springsharp was 38 knots, though its not well suited to smaller designs. Super high speed is rather dubious anyhow. Didn't help Shimakaze survive.

Yamazuki, Japanese Destroyer laid down 1947

Displacement:
3,153 t light; 3,262 t standard; 3,997 t normal; 4,585 t full load

Dimensions: Length overall / water x beam x draught
440.31 ft / 433.00 ft x 40.00 ft x 14.50 ft (normal load)
134.21 m / 131.98 m x 12.19 m x 4.42 m

Armament:
8 - 3.94" / 100 mm guns (4x2 guns), 30.51lbs / 13.84kg shells, 1947 Model
Dual purpose guns in deck mounts with hoists
on centreline ends, evenly spread, 2 raised mounts - superfiring
4 - 1.57" / 40.0 mm guns (2x2 guns), 1.95lbs / 0.89kg shells, 1947 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
8 - 0.79" / 20.0 mm guns (4x2 guns), 0.24lbs / 0.11kg shells, 1947 Model
Machine guns in deck mounts
on side, all amidships
Weight of broadside 254 lbs / 115 kg
Shells per gun, main battery: 200

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.50" / 13 mm 0.50" / 13 mm -

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 99,541 shp / 74,258 Kw = 38.00 kts
Range 8,000nm at 18.00 kts
Bunker at max displacement = 1,323 tons

Complement:
250 - 326

Cost:
£3.370 million / $13.481 million

Distribution of weights at normal displacement:
Armament: 32 tons, 0.8 %
Armour: 10 tons, 0.3 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 10 tons, 0.3 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 2,331 tons, 58.3 %
Hull, fittings & equipment: 749 tons, 18.8 %
Fuel, ammunition & stores: 844 tons, 21.1 %
Miscellaneous weights: 30 tons, 0.8 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
692 lbs / 314 Kg = 22.7 x 3.9 " / 100 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.33
Metacentric height 2.1 ft / 0.6 m
Roll period: 11.6 seconds
Steadiness - As gun platform (Average = 50 %): 48 %
- Recoil effect (Restricted arc if above 1.00): 0.18
Seaboat quality (Average = 1.00): 0.47

Hull form characteristics:
Hull has rise forward of midbreak
and transom stern
Block coefficient: 0.557
Length to Beam Ratio: 10.83 : 1
'Natural speed' for length: 23.47 kts
Power going to wave formation at top speed: 72 %
Trim (Max stability = 0, Max steadiness = 100): 100
Bow angle (Positive = bow angles forward): 18.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 22.50 ft / 6.86 m
- Forecastle (15 %): 16.50 ft / 5.03 m
- Mid (50 %): 16.50 ft / 5.03 m (10.50 ft / 3.20 m aft of break)
- Quarterdeck (19 %): 10.50 ft / 3.20 m
- Stern: 10.50 ft / 3.20 m
- Average freeboard: 13.85 ft / 4.22 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 195.3 %
- Above water (accommodation/working, high = better): 132.1 %
Waterplane Area: 12,669 Square feet or 1,177 Square metres
Displacement factor (Displacement / loading): 77 %
Structure weight / hull surface area: 37 lbs/sq ft or 180 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.50
- Longitudinal: 0.67
- Overall: 0.51
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is excellent
Caution: Lacks seaworthiness - very limited seakeeping ability

Oh, I've got no doubts that high-30s are possible.

Although installing 25% more power than a Sprucan on a ship half the size sounds like a fun maintenance nightmare.

The LCS could reach speeds of more than 45 knots, but the two LCS designs feature propulsion and hull form that allows that.

Then again, Springsharp and destroyers doesn't agree very well. They do better in the last Beta(which CanisD didn't use), but it's still a nightmare trying to make something fairly small(or anything were you limit yourself in size, really) reach speeds above 33 knots and still retaining acceptable seakeeping.
Also, the speed given in Springsharp is the "Service speed", in other words their normal max. Those 43,7 knots were for acceptance trials, when you push the ship to it's limits.

seahawk, of 15 years later, required 90MW to get it to top speeds of about 39 knots on double the displacement. if we ignore the displacement problem for now, that means for 44 knots you will require AT LEAST 121 MW, which ignores wave resistance (which will most likely put that required power to about 150-200 on good weather conditions)
this puts you on an powerplant similar in size to that of an essex class carrier or bigger. you might even require an forrestal sized plant
the smaller size of the ship might let you cut that back to 100-150 MW.

the way out is an planing, swath or semi-planing hull, which has less wave resistance, which allows you to go to 45-55 knots on an frigate sized hull, or ground effect ships. none of these are available with WW2 tech.

the steam powered seahawk proposals had 18% of their weight submitted to propulsion, 28% to hull weight and only 1% for arnament. you are not getting close to these numbers on your design.
if trial speed is with just enough fuel to make one run and without the arnament fitted, you might reach near 40 knots max, but I don't see that ship getting over 30-35 otherwise.