WesWorld

Proposed design for refit of existing older destroyers

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Z203 class German Destroyer - Refitted As Light Minelayer (Originally laid down 1924)

Displacement: 1,507 t light; 1,554 t standard; 1,680 t normal; 1,780 t full load

Dimensions: Length overall / water x beam x draught

350.07 ft / 350.07 ft x 35.10 ft x 11.81 ft (normal load) [106.70 m / 106.70 m x 10.70 m x 3.60 m]

Armament:

2 - 4.13" / 105 mm guns in single mounts, 35.32lbs / 16.02kg shells, 1936 Model Dual purpose guns in deck mounts on centreline, all forward, 1 raised mount
4 - 1.46" / 37.0 mm guns (2x2 guns), 1.55lbs / 0.70kg shells, 1938 Model Anti-aircraft guns in deck mounts on centreline, all aft, all raised mounts – superfiring
8 - 0.79" / 20.0 mm guns (4x2 guns), 0.24lbs / 0.11kg shells, 1928 Model Machine guns in deck mounts on side, evenly spread, all raised mounts
Weight of broadside 79 lbs / 36 kg
Shells per gun, main battery: 300
3 - 21" / 533 mm above water torpedoes

Armour:

Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.98" / 25 mm 0.39" / 10 mm -
2nd: 0.59" / 15 mm 0.39" / 10 mm -
3rd: 0.59" / 15 mm - -

Machinery:

Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 34,364 shp / 25,636 Kw = 33.56 kts
Range 4,500nm at 12.00 kts
Bunker at max displacement = 225 tons

Complement: 130 - 170

Cost: £0.570 million / $2.280 million

Distribution of weights at normal displacement:

Armament: 10 tons, 0.6 %
Armour: 6 tons, 0.3 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 6 tons, 0.3 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 881 tons, 52.5 %
Hull, fittings & equipment: 510 tons, 30.4 %
Fuel, ammunition & stores: 173 tons, 10.3 %
Miscellaneous weights: 100 tons, 6.0 %

Overall survivability and seakeeping ability:

Survivability (Non-critical penetrating hits needed to sink ship): 555 lbs / 252 Kg = 15.7 x 4.1 " / 105 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.39
Metacentric height 1.8 ft / 0.6 m
Roll period: 10.9 seconds
Steadiness - As gun platform (Average = 50 %): 52 %
- Recoil effect (Restricted arc if above 1.00): 0.06
Seaboat quality (Average = 1.00): 1.05

Hull form characteristics:

Hull has a flush deck and transom stern
Block coefficient: 0.405
Length to Beam Ratio: 9.97 : 1
'Natural speed' for length: 21.63 kts
Power going to wave formation at top speed: 67 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 20.67 ft / 6.30 m
- Forecastle (20 %): 14.76 ft / 4.50 m
- Mid (50 %): 14.76 ft / 4.50 m
- Quarterdeck (15 %): 14.76 ft / 4.50 m
- Stern: 14.76 ft / 4.50 m
- Average freeboard: 15.24 ft / 4.64 m
Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 180.8 %
- Above water (accommodation/working, high = better): 139.9 %
Waterplane Area: 7,874 Square feet or 732 Square metres
Displacement factor (Displacement / loading): 69 %
Structure weight / hull surface area: 34 lbs/sq ft or 165 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.54
- Longitudinal: 2.08
- Overall: 0.62
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is excellent


Breakdown of miscellaneous weight:

Mine rails port and starboard (10-tons per; total 20 tons)
Eighty mines (each 1-ton)

Not particularly a good idea for such a ship, considering it has a transom stern.

Why is a transom stern bad for mine laying?

It would cause the mine to be sucked back in towards the stern due to the wierd...current pattern that's caused by transom sterns....or something like that. Brock explained it to me a while back.

Quoted

Originally posted by TexanCowboy
It would cause the mine to be sucked back in towards the stern due to the wierd...current pattern that's caused by transom sterns....or something like that. Brock explained it to me a while back.

A transom stern creates a space of slack water aft of the transom.

Quoted

Originally posted by TexanCowboy
Not particularly a good idea for such a ship, considering it has a transom stern.

Thank you for pointing out the potential problem. It is something to which I will give deep thought.

There are though, I think, several possible schools of thought. While the design shortcomings of HMS Adventure are well known - and seem to form the basis of the "Transom Stern=Bad Minelayer" dictum, the US Navy, for its part, was confident enough to convert a dozen Sumner hulls for the destroyer minelayer role.

I also speculate whether laying mines over stern rails - which would project somewhat beyond the stern itself - and laying mines through stern chutes, as in HMS Adventure - might also be a factor.

All these elements are one reason why peer review is a good thing. Were I designing a minelayer from the keel up, I might eschew a transom stern; in the case of these conversions the transom stern is an existing design feature. This proposal is one possible way of playing the hand that I have been dealt.

Length: 10.97 metres
Beam: 3.20metres
Draft: 0.90 metres aft
Light Displacement: 20 tons

Powerplant: One Maybach diesel engines, 220 hp; one shaft
Maximum speed: 9 knots; cruise speed 7 knots; radius 100 nm at 7 knots.
Capacity – Up to 4 tons of cargo and vehicles or up to 36 troops or combination thereof
Armament - Pintle mounts for two machineguns

Fitted with bow ramp for loading or unloading

Quoted

Originally posted by exigeant
While i do not want to be the cause of any trouble, can you please clarify if 550 mm torpedoes are now standard for Germany?
The above designs and the encyclopedia 'Paderborn class Fleet Destroyer (Zerstorer Typ 1940 Rev B)' all refer to them.
Is it intended as the replacement of existing 533 and 600 mm torpedoes as future weapons?

Thank you for calling to my attention an inadvertent error. The torpedoes refitted to the Z203 class should be 21-inch.