WesWorld

This is the data for the mine sweepers currently under construction for the Greek navy. Personally I think it’s a good design, my only reservation is that it may not have the deck space to fit two 76.2mm guns.

Eventually I will draw it up and answer that question for myself, so for the time being would any one like to take an educated guess.



mnswp21f, laid down 1921

Length, 47.0 m x Beam, 8.0 m x Depth, 1.8 m
375 tonnes normal displacement (274 tonnes standard)

Main battery: 2 x 7.6-cm
AA battery: 3 x 4.0-cm
Light battery: 4 x 1.3-cm

Weight of broadside: 15 kg

Hull unarmored

Maximum speed for 1366 shaft kw = 17.30 knots
Approximate cruising radius, 4700 nm / 14 knots

Typical complement: 43-55


Estimated cost, $219,000 (£55,000)

Remarks:

Ship has slow, easy roll; a good, steady gun platform.

Good seaboat; rides out heavy weather easily.

Magazines and engineering spaces are roomy, with superior
watertight subdivision.

Ship is roomy, with superior accommodation and working space.


Distribution of weights:
Percent
normal
displacement:

Armament ......................... 4 tonnes = 1 pct
Machinery ........................ 63 tonnes = 17 pct
Hull and fittings; equipment ..... 147 tonnes = 39 pct
Fuel, ammunition, stores ......... 112 tonnes = 30 pct
Miscellaneous weights ............ 50 tonnes = 13 pct
-----
375 tonnes = 100 pct

Estimated metacentric height, 0.3 m

Displacement summary:

Light ship: 264 tonnes
Standard displacement: 274 tonnes
Normal service: 375 tonnes
Full load: 455 tonnes

Loading submergence 254 tonnes/metre

+++++++++++++++++++++++++


Estimated overall survivability and seakeeping ability:

Relative margin of stability: 1.17

Shellfire needed to sink: 367 kg = 59.9 x 7.6-cm shells
(Approximates weight of penetrating
shell hits needed to sink ship,
not counting critical hits)

Torpedoes needed to sink: 0.6
(Approximates number of 'typical'
torpedo hits needed to sink ship)

Relative steadiness as gun platform, 70 percent
(50 percent is 'average')

Relative rocking effect from firing to beam, 0.08

Relative quality as a seaboat: 1.21

+++++++++++++++++++++++++


Hull form characteristics:

Block coefficient: 0.55
Sharpness coefficient: 0.41
Hull speed coefficient 'M' = 6.53
'Natural speed' for length = 12.4 knots
Power going to wave formation
at top speed: 64 percent


Estimated hull characteristics and strength:

Relative underwater volume absorbed by
magazines and engineering spaces: 78 percent

Relative accommodation and working space: 124 percent


Displacement factor: 179 percent
(Displacement relative to loading factors)


Relative cross-sectional hull strength: 0.87
(Structure weight per square
metre of hull surface: 167 kg)

Relative longitudinal hull strength: 3.60
(for 3.13 m average freeboard;
freeboard adjustment +0.74 m)

Relative composite hull strength: 1.00

+++++++++++++++++++++++++


[Machine-readable parameters: Spring Style v. 1.2.1]

154.16 x 26.24 x 5.90; 10.27 -- Dimensions
0.55 -- Block coefficient
1921 -- Year laid down
17.30 / 4700 / 14.00; Oil-fired turbine or equivalent -- Speed / radius / cruise
50 tons -- Miscellaneous weights
++++++++++
2 x 3.00; 0 -- Main battery; turrets
Central positioning of guns
:
0 -- No secondary battery
3 x 1.57 -- Tertiary (QF/AA) battery
:
4 x 0.51 -- Fourth (light) battery
0 -- No torpedo armament
++++++++++
0.00 -- No belt armor
0.00 / 0.00 -- Deck / CT
0.00 -- No battery armor


(Note: For portability, values are stored in Anglo-American units)