Dutch Escorts
The Dutch have long maintained purpose built escorts. Of the 80+ on hand, the 45-strong Frigate class 500 ton vessels are aging, and while refurbished once and spend most of their time in reserve.. will be due for the breakers ~1945 or so.
22 of the S19 class was built under the Cleito treaty as exempt vessels. In 1938, 4 improved versions, the S44 class, were built with the idea that the design could be tested, and then when the Capital ships were completed, produced en masse in the 1940s.
Parameters
Tonnage:
As small as possible.
At least <1,500 tons, preferably ~750tons.
Weaponry :
With Phillips Electronics, the Dutch were, OTL, ahead of the game in Radar and fire control in general. In early 1940, when Holland fell, radar-guided search lights were entering service, the early decimetric radar brought to England was in advance of the Brits own, and hastily exported Phillips tubes went into British Radars, etc. So I figure about 1 year behind the Americans. Prox fuses hit the South Pacific in May, 1942, so 1940 is when the Dutch prox fuses entered service. Early prox fuses needed specialty small vaccumn tubes, and 5" was about the smallest shell which could fit them. So the Dutch 125mm can be forecast as the main AA barrage gun. For mid range, they use 40mm guns in stacked Quad 'wirblewind' style mounts with Hazemeyer gyrostabilization gear, and are working on RPC in conjunction with the SAE. For close in defense they use the single or twin 23mm FN-Madsen.
a 1(TT) b
So... Desired weaponry A / B Q X / Y
c (TT)2 d
bah, spaces don't format right. "a" is behind and outside of B, "1" before and outside of "Q", "b" before and outside of "X" etc, with "2" aft and outside of "Q"
With A & Y being twin 125mm mount & hoist
With B & X being quad 40mm Hazemeyer mounts
With Q being the Searchlight/Torpedo Control Director tower
and
1 & 2 are Quad 40mm Hazemeyer mounts on a raised platform around the TCD 'en echelon' , with the triple tubes under the platforms
a,b,c,d are raised platforms for 2 single 23mm mounts each.
note : the wieght of the Hazemeyer gear is simmed as "other" armor on the mount - 21mm for Quads, 11mm for Twins. That puts the weight in the right place.
Ranges:
Dutch Capital ships are built for the "worst case" - the need to make an unrefueled run at 15knts from the Netherlands, around the UK, around Cape Horn to Jakarta. That's 16,500nm. Cruisers and Heavy Destroyers (Z77/Z81) are being built for the Netherlands-Kongo-DEI run. I'd like these new sloops to be able to make the Matadi, Kongo to Batavia, Java run... about 7,200nm, with a 20% reserve makes 8,650nm. Cruise speed only needs to be about 12kts, which gives freedom to move around the convoy.
Speed :
Desired top speed is 25-26kts. The Dutch should know the IJN subs are fast by now, but not know what their real top speed is, so there's no real OPFOR there, but with the Ijelsijk class small BBs at 23kts, the idea was they could be a core of a slow squadron of older BBs to counter the Bahrat fleet/serve as heavy convoy escorts/group with the older/slower BBs in a slow Squadron... at 25-26kts, the sloops can- barely- work with them in a pinch. Not desirable to do, but useful as an option.
Hull form & Seakeeping :
Over in Navalism it's been observed that DD freeboards were far less than we sim. Basically, DDs had "poor" seakeeping- they are small and have to slow down in high seas. Now on my Z77/Z81 heavy DDs, I went for good seakeeping anyhow- they are for midocean trips in any weather. Considering most of the life of these sloops is to escort convoys at lower speeds, 0.75+ seakeeping is acceptable. Shorter L:B is better for turning radius, which in turn is better for subhunting or dodging aerial torpedoes. A fairly beamy ship will be needed to host the twin mounts.
Result :
Well, the seakeeping is a bit higher than desired. Armor was added as an anti-strafing measure ala the Fletcher class. Size is ~100 tons more than desired. Would prefer 26kts. At 19% fuel percentage is about maxed. With 0.5 comp hull required, the 0.62 represents a 20% reserve, more than adequate for a strong hull. Aft is cut down, and is the depth-charge platform.
I can drop the armor and add a knot, making her 26kts and 0.91seakeeping and 0.75 comp hull, but in hindsight I kinda like the armor, and the South-Atlantic/South Indian ocean route can have rough seas. Plus the additional engine space turns below decks from Adequate to Cramped, I want Adequate for the long trip.
So.... what could I do to meet those parameters with a smaller ship? Do I actually need the various things I think I need? Smaller could be far cheaper- but would that be as suited to open-ocean work? The Dutch view these as 2nd tier combatants, not minimal vessels - more the USN Evart's class than the RN's Flower class.
Ideas/Comments/Competing designs?
S52, Netherlands Escort laid down 1941
Displacement:
1,099 t light; 1,175 t standard; 1,356 t normal; 1,501 t full load
Dimensions: Length overall / water x beam x draught
303.87 ft / 298.56 ft x 42.65 ft x 9.32 ft (normal load)
92.62 m / 91.00 m x 13.00 m x 2.84 m
Armament:
4 - 4.92" / 125 mm guns (2x2 guns), 59.52lbs / 27.00kg shells, 1926 Model
Dual purpose guns in deck mounts with hoists
on centreline ends, evenly spread
8 - 1.57" / 40.0 mm guns (2x4 guns), 1.94lbs / 0.88kg shells, 1936 Model
Anti-aircraft guns in deck mounts with hoists
on centreline ends, evenly spread, all raised mounts
8 - 1.57" / 40.0 mm guns (2x4 guns), 1.94lbs / 0.88kg shells, 1936 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
8 - 0.91" / 23.0 mm guns in single mounts, 0.37lbs / 0.17kg shells, 1926 Model
Breech loading guns in deck mounts
on side ends, evenly spread
Weight of broadside 272 lbs / 123 kg
Shells per gun, main battery: 300
6 - 21.0" / 533.4 mm above water torpedoes
Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 0.98" / 25 mm 229.66 ft / 70.00 m 8.01 ft / 2.44 m
Ends: Unarmoured
Main Belt covers 118 % of normal length
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.98" / 25 mm 0.20" / 5 mm 0.20" / 5 mm
2nd: 0.39" / 10 mm 0.83" / 21 mm -
3rd: 0.39" / 10 mm 0.83" / 21 mm -
4th: 0.20" / 5 mm - -
- Armour deck: 0.59" / 15 mm, Conning tower: 0.98" / 25 mm
Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 12,073 shp / 9,006 Kw = 25.00 kts
Range 8,650nm at 12.00 kts
Bunker at max displacement = 326 tons
Complement:
111 - 145
Cost:
£0.691 million / $2.763 million
Distribution of weights at normal displacement:
Armament: 34 tons, 2.5 %
Armour: 175 tons, 12.9 %
- Belts: 74 tons, 5.5 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 13 tons, 1.0 %
- Armour Deck: 86 tons, 6.3 %
- Conning Tower: 3 tons, 0.2 %
Machinery: 319 tons, 23.5 %
Hull, fittings & equipment: 470 tons, 34.7 %
Fuel, ammunition & stores: 257 tons, 19.0 %
Miscellaneous weights: 100 tons, 7.4 %
Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,468 lbs / 666 Kg = 24.6 x 4.9 " / 125 mm shells or 0.7 torpedoes
Stability (Unstable if below 1.00): 1.29
Metacentric height 2.2 ft / 0.7 m
Roll period: 12.1 seconds
Steadiness - As gun platform (Average = 50 %): 59 %
- Recoil effect (Restricted arc if above 1.00): 0.24
Seaboat quality (Average = 1.00): 1.04
Hull form characteristics:
Hull has low quarterdeck
Block coefficient: 0.400
Length to Beam Ratio: 7.00 : 1
'Natural speed' for length: 17.28 kts
Power going to wave formation at top speed: 60 %
Trim (Max stability = 0, Max steadiness = 100): 57
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: 16.34 ft / 4.98 m
- Forecastle (20 %): 14.70 ft / 4.48 m
- Mid (50 %): 14.70 ft / 4.48 m
- Quarterdeck (15 %): 6.69 ft / 2.04 m (14.70 ft / 4.48 m before break)
- Stern: 6.69 ft / 2.04 m
- Average freeboard: 13.63 ft / 4.15 m
Ship tends to be wet forward
Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 106.0 %
- Above water (accommodation/working, high = better): 133.5 %
Waterplane Area: 7,838 Square feet or 728 Square metres
Displacement factor (Displacement / loading): 114 %
Structure weight / hull surface area: 41 lbs/sq ft or 199 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.56
- Longitudinal: 1.62
- Overall: 0.62
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
This post has been edited 3 times, last edit by "Kaiser Kirk" (Jul 24th 2011, 11:16pm)