WesWorld

Heres my first crack at a mine sweeper, any comments? I'm not fond of the figure for the light displacement!!!

MS-9 Class, Atlantis minesweeper laid down 1923

Displacement:
666 t light; 683 t standard; 749 t normal; 798 t full load
Loading submergence 116 tons/feet

Dimensions:
210.00 ft x 26.00 ft x 7.50 ft (normal load)
64.01 m x 7.92 m x 2.29 m

Armament:
1 - 3.00" / 76 mm guns
2 - 1.57" / 40 mm AA guns
4 - 1.00" / 25 mm guns
Weight of broadside 19 lbs / 9 kg

Armour:
Main gun shields 0.78" / 20 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 1,756 shp / 1,310 Kw = 16.00 kts
Range 3,500nm at 12.00 kts

Complement:
71 - 93

Cost:
£0.098 million / $0.391 million

Distribution of weights at normal displacement:
Armament: 2 tons, 0.3 %
Armour: 1 tons, 0.1 %
Belts: 0 tons, 0.0 %, Armament: 1 tons, 0.1 %, Armour Deck: 0 tons, 0.0 %
Conning Tower: 0 tons, 0.0 %, Torpedo bulkhead: 0 tons, 0.0 %
Machinery: 59 tons, 7.8 %
Hull, fittings & equipment: 455 tons, 60.7 %
Fuel, ammunition & stores: 82 tons, 11.0 %
Miscellaneous weights: 150 tons, 20.0 %

Metacentric height 0.7

Remarks:
Hull space for machinery, storage & compartmentation is excellent
Room for accommodation & workspaces is adequate
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable and able to fight her guns in the heaviest weather

Estimated overall survivability and seakeeping ability:
Relative margin of stability: 1.03
Shellfire needed to sink: 1,955 lbs / 887 Kg = 144.8 x 3.0 " / 76 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 1.2
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 71 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.05
Relative quality as seaboat: 1.82

Hull form characteristics:
Block coefficient: 0.640
Sharpness coefficient: 0.40
Hull speed coefficient 'M': 7.07
'Natural speed' for length: 14.49 kts
Power going to wave formation at top speed: 51 %
Trim: 39
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)

Estimated hull characteristics & strength:
Underwater volume absorbed by magazines and engineering spaces: 50.9 %
Relative accommodation and working space: 114.1 %
(Average = 100%)
Displacement factor: 261 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 1.84
(Structure weight / hull surface area: 70 lbs / square foot or 340 Kg / square metre)
Relative longitudinal hull strength: 3.78
(for 10.50 ft / 3.20 m average freeboard, freeboard adjustment 1.48 ft)
Relative composite hull strength: 1.98

...
Yes, what on Earth were you thinking when you created this ship?
But since this ship has a lot of hull strength left, I think you left it this way on purpose.
:-)

Walter

"But since this ship has a lot of hull strength left, I think you left it this way on purpose."

*chokes on his drink*

I was basically shooting for a certain armament speed and set of dementions for this little ship, unfortunately the original speed of 22 knots seriously effected the stability and i didn't check the CT rules to see just what the speed limit was for mine sweeper size vessels. Any inprovements I can make to the design to make her more balanced? I would think that extra hull strength would come in handy in the Atlantic.

Quoted

unfortunately the original speed of 22 knots seriously effected the stability and i didn't check the CT rules to see just what the speed limit was for mine sweeper size vessels.

According to the treaty (currently looking for the scrapping stuff regarding the sale of war prizes, so slightly shifting to the limitations is not much of a problem), speed limit for that category of vessel is 24 knots (Part 3, Chapter G, Article I-b).

Walter

... also, increasing speed improves stability, so yes it seriously effects the stability, but not negatively. But increasing speed does have a negative influence on that 'steady gun platform' and 'excellent seaboat' rating of your design.
For 22 knots, you'll get something like this (note that I slightly increased the range to get rid of that figure for the light displacement that you 're not fond of):

MS-9F Class, Atlantis Minesweeper laid down 1923

Displacement:
657 t light; 674 t standard; 749 t normal; 806 t full load
Loading submergence 116 tons/feet

Dimensions:
210.00 ft x 26.00 ft x 7.50 ft (normal load)
64.01 m x 7.92 m x 2.29 m

Armament:
1 - 3.00" / 76 mm guns
2 - 1.57" / 40 mm AA guns
4 - 1.00" / 25 mm guns
Weight of broadside 19 lbs / 9 kg

Armour:
Main gun shields 0.79" / 20 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 6,531 shp / 4,872 Kw = 22.00 kts
Range 4,000nm at 12.00 kts

Complement:
71 - 93

Cost:
£0.162 million / $0.647 million

Distribution of weights at normal displacement:
Armament: 2 tons, 0.3 %
Armour: 1 tons, 0.1 %
Belts: 0 tons, 0.0 %, Armament: 1 tons, 0.1 %, Armour Deck: 0 tons, 0.0 %
Conning Tower: 0 tons, 0.0 %, Torpedo bulkhead: 0 tons, 0.0 %
Machinery: 218 tons, 29.2 %
Hull, fittings & equipment: 286 tons, 38.2 %
Fuel, ammunition & stores: 92 tons, 12.2 %
Miscellaneous weights: 150 tons, 20.0 %

Metacentric height 0.8

Remarks:
Hull space for machinery, storage & compartmentation is cramped
Room for accommodation & workspaces is excellent

Estimated overall survivability and seakeeping ability:
Relative margin of stability: 1.08
Shellfire needed to sink: 763 lbs / 346 Kg = 56.5 x 3.0 " / 76 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 0.4
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 52 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.04
Relative quality as seaboat: 1.05

Hull form characteristics:
Block coefficient: 0.640
Sharpness coefficient: 0.40
Hull speed coefficient 'M': 7.07
'Natural speed' for length: 14.49 kts
Power going to wave formation at top speed: 68 %
Trim: 50
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)

Estimated hull characteristics & strength:
Underwater volume absorbed by magazines and engineering spaces: 118.9 %
Relative accommodation and working space: 124.9 %
(Average = 100%)
Displacement factor: 123 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 1.03
(Structure weight / hull surface area: 43 lbs / square foot or 208 Kg / square metre)
Relative longitudinal hull strength: 2.63
(for 11.50 ft / 3.51 m average freeboard, freeboard adjustment 2.48 ft)
Relative composite hull strength: 1.13

So the question would be: do you actually need the 22 knots speed for it to perform its job? I think that, compared with this design, your original design is not too bad.
Perhaps something somewhere in between the two versions?

Walter

As long as she can match with the fleet's cruising speed. 20 kts is plenty. But you could probably do with a bit more range, and you've got excess hull strength to allow for that. So here's what I'd suggest:

Mine Warfare Ship, Atlantean Mine Warfare Ship laid down 1923

Displacement:
582 t light; 599 t standard; 749 t normal; 866 t full load
Loading submergence 116 tons/feet

Dimensions:
210.00 ft x 26.00 ft x 7.50 ft (normal load)
64.01 m x 7.92 m x 2.29 m

Armament:
1 - 3.00" / 76 mm guns
2 - 1.57" / 40 mm guns
4 - 1.00" / 25 mm AA guns
Weight of broadside 19 lbs / 9 kg

Armour:
Main gun shields 0.78" / 20 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 3,919 shp / 2,923 Kw = 19.50 kts
Range 8,000nm at 12.00 kts

Complement:
71 - 93

Cost:
£0.119 million / $0.474 million

Distribution of weights at normal displacement:
Armament: 2 tons, 0.3 %
Armour: 1 tons, 0.1 %
Belts: 0 tons, 0.0 %, Armament: 1 tons, 0.1 %, Armour Deck: 0 tons, 0.0 %
Conning Tower: 0 tons, 0.0 %, Torpedo bulkhead: 0 tons, 0.0 %
Machinery: 131 tons, 17.5 %
Hull, fittings & equipment: 288 tons, 38.5 %
Fuel, ammunition & stores: 167 tons, 22.3 %
Miscellaneous weights: 160 tons, 21.4 %

Metacentric height 0.8

Remarks:
Hull space for machinery, storage & compartmentation is excellent
Room for accommodation & workspaces is adequate
Good seaboat, rides out heavy weather easily

Estimated overall survivability and seakeeping ability:
Relative margin of stability: 1.09
Shellfire needed to sink: 1,232 lbs / 559 Kg = 91.3 x 3.0 " / 76 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 0.7
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 61 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.04
Relative quality as seaboat: 1.23

Hull form characteristics:
Block coefficient: 0.640
Sharpness coefficient: 0.40
Hull speed coefficient 'M': 7.07
'Natural speed' for length: 14.49 kts
Power going to wave formation at top speed: 62 %
Trim: 50
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)

Estimated hull characteristics & strength:
Underwater volume absorbed by magazines and engineering spaces: 83.1 %
Relative accommodation and working space: 114.1 %
(Average = 100%)
Displacement factor: 169 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 1.13
(Structure weight / hull surface area: 44 lbs / square foot or 215 Kg / square metre)
Relative longitudinal hull strength: 2.39
(for 10.50 ft / 3.20 m average freeboard, freeboard adjustment 1.48 ft)
Relative composite hull strength: 1.22


Adequate speed, decent seakeeping, a bit of extra hull strength, and plenty of range. What's not to like?

Simple change with good results. Thanks for the input guys.

"So the question would be: do you actually need the 22 knots speed for it to perform its job? I think that, compared with this design, your original design is not too bad."

I depends on the misson of your minesweeper, i f she just is a minesweeper you don't need 22kts, but if she also is sailing as a subchaser(like the swedish ww2 Bremön) for the mainforce you will need the speed.