Maori Minesweeper Concepts

[Valles]

At the moment, I'm turning over two different possibilities for this role.

First:

MS-1920, Maori Minesweeper laid down 1916

Displacement:
   200 t light; 209 t standard; 251 t normal; 284 t full load

Dimensions: Length overall / water x beam x draught
   201.42 ft / 196.85 ft x 19.69 ft x 4.92 ft (normal load)
   61.39 m / 60.00 m x 6.00 m  x 1.50 m

Armament:
      1 - 2.95" / 75.0 mm guns in single mounts, 13.23lbs / 6.00kg shells, 1916 Model
     Quick firing gun in a deck mount with hoist
     on centreline aft
      1 - 1.38" / 35.0 mm guns in single mounts, 1.65lbs / 0.75kg shells, 1916 Model
     Anti-aircraft gun in a deck mount with hoist
     on centreline amidships
   Weight of broadside 15 lbs / 7 kg
   Shells per gun, main battery: 500
   2 - 20.7" / 525 mm above water torpedoes

Machinery:
   Oil fired boilers, steam turbines,
   Electric motors, 2 shafts, 5,626 shp / 4,197 Kw = 25.60 kts
   Range 2,500nm at 14.00 kts
   Bunker at max displacement = 74 tons

Complement:
   30 - 40

Cost:
   £0.043 million / $0.172 million

Distribution of weights at normal displacement:
   Armament: 2 tons, 0.7 %
   Machinery: 127 tons, 50.5 %
   Hull, fittings & equipment: 61 tons, 24.1 %
   Fuel, ammunition & stores: 51 tons, 20.2 %
   Miscellaneous weights: 11 tons, 4.4 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     57 lbs / 26 Kg = 4.5 x 3.0 " / 75 mm shells or 0.1 torpedoes
   Stability (Unstable if below 1.00): 1.10
   Metacentric height 0.5 ft / 0.2 m
   Roll period: 11.4 seconds
   Steadiness   - As gun platform (Average = 50 %): 52 %
         - Recoil effect (Restricted arc if above 1.00): 0.10
   Seaboat quality  (Average = 1.00): 0.53

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.460
   Length to Beam Ratio: 10.00 : 1
   'Natural speed' for length: 14.03 kts
   Power going to wave formation at top speed: 68 %
   Trim (Max stability = 0, Max steadiness = 100): 99
   Bow angle (Positive = bow angles forward): 5.00 degrees
   Stern overhang: 3.28 ft / 1.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      14.76 ft / 4.50 m
      - Forecastle (15 %):   13.12 ft / 4.00 m
      - Mid (20 %):      13.12 ft / 4.00 m (4.92 ft / 1.50 m aft of break)
      - Quarterdeck (15 %):   4.92 ft / 1.50 m
      - Stern:      4.92 ft / 1.50 m
      - Average freeboard:   6.66 ft / 2.03 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 174.7 %
      - Above water (accommodation/working, high = better): 57.1 %
   Waterplane Area: 2,492 Square feet or 232 Square metres
   Displacement factor (Displacement / loading): 56 %
   Structure weight / hull surface area: 16 lbs/sq ft or 77 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 0.71
      - Overall: 0.52
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is cramped
   Caution: Lacks seaworthiness - very limited seakeeping ability

2 tons torpedoes
9 tons minesweeping gear

A DD-framed mini-sweeper, 0.2 BP and a little under 1/4 a $ per hull, and useful for other stuff too, but... certain obvious problems.

MS-1920-C, Maori Minesweeper laid down 1916

Displacement:
   500 t light; 515 t standard; 693 t normal; 835 t full load

Dimensions: Length overall / water x beam x draught
   221.25 ft / 216.54 ft x 22.97 ft x 9.84 ft (normal load)
   67.44 m / 66.00 m x 7.00 m  x 3.00 m

Armament:
      1 - 2.95" / 75.0 mm guns in single mounts, 12.87lbs / 5.84kg shells, 1916 Model
     Quick firing gun in a deck mount with hoist
     on centreline aft
      1 - 1.38" / 35.0 mm guns in single mounts, 1.65lbs / 0.75kg shells, 1916 Model
     Anti-aircraft gun in a deck mount with hoist
     on centreline aft
   Weight of broadside 15 lbs / 7 kg
   Shells per gun, main battery: 200

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.39" / 10 mm   0.39" / 10 mm            -
   2nd:   0.39" / 10 mm   0.39" / 10 mm            -

Machinery:
   Oil fired boilers, complex reciprocating steam engines,
   Electric motors, 2 shafts, 3,699 ihp / 2,760 Kw = 20.00 kts
   Range 5,000nm at 14.00 kts
   Bunker at max displacement = 320 tons

Complement:
   66 - 87

Cost:
   £0.081 million / $0.326 million

Distribution of weights at normal displacement:
   Armament: 2 tons, 0.3 %
   Armour: 1 tons, 0.2 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 1 tons, 0.2 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 220 tons, 31.7 %
   Hull, fittings & equipment: 267 tons, 38.5 %
   Fuel, ammunition & stores: 193 tons, 27.9 %
   Miscellaneous weights: 10 tons, 1.4 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     935 lbs / 424 Kg = 72.6 x 3.0 " / 75 mm shells or 0.5 torpedoes
   Stability (Unstable if below 1.00): 1.34
   Metacentric height 0.9 ft / 0.3 m
   Roll period: 10.0 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.09
   Seaboat quality  (Average = 1.00): 2.00

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.496
   Length to Beam Ratio: 9.43 : 1
   'Natural speed' for length: 14.72 kts
   Power going to wave formation at top speed: 57 %
   Trim (Max stability = 0, Max steadiness = 100): 35
   Bow angle (Positive = bow angles forward): 5.00 degrees
   Stern overhang: 3.28 ft / 1.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      16.40 ft / 5.00 m
      - Forecastle (15 %):   16.40 ft / 5.00 m
      - Mid (50 %):      16.40 ft / 5.00 m (8.20 ft / 2.50 m aft of break)
      - Quarterdeck (15 %):   8.20 ft / 2.50 m
      - Stern:      8.20 ft / 2.50 m
      - Average freeboard:   12.30 ft / 3.75 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 106.9 %
      - Above water (accommodation/working, high = better): 117.2 %
   Waterplane Area: 3,300 Square feet or 307 Square metres
   Displacement factor (Displacement / loading): 149 %
   Structure weight / hull surface area: 33 lbs/sq ft or 163 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.81
      - Longitudinal: 6.08
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is adequate
   Room for accommodation and workspaces is adequate
   Ship has slow, easy roll, a good, steady gun platform
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

10 tons paravanes and other sweeping gear

500t/Light = 2/BP x4 for merchant construction = 8/BP

Unlike the smaller design, this one will be a deathtrap if anybody shoots at it, and it's really only good for minesweeping and maybe customs work, but boy, you can't beat that price. My only qualm is whether or not it falls under the constraints of 'designed to skirt the rules'. Because, in one way, it absolutely is - it's a purely military ship built under the civilian rules. But on the other, it's that way because it's intended to be utterly expendable.

So I dunno. What do you think?

[Sachmle]

For a sweeper, in all seriousness, drop the speed even more and cut the cruising speed to ~8kts. 15-18kts is plenty fast for a sweeper, and 8kts is probably faster than you'll actually be moving while sweeping.

[Ithekro]

I would agree that minesweeping is something that is done slowly and thus the most efficient use of your engine would be for when your two sweepers work together to clear paths in the minefields.

Of course the question comes up....is this a defensive minesweeper or an doffensive mine sweeper?  For use in you own coastal waters and rivers or in hostile coastal areas and rivers?   If these are for home waters than you won't need all that much range unless you think they will need to trawl for days on end to clear a field without stopping.  If it is for offensive action, then they will need range and speed to get in and out (under darkness more than likely) when not sweeping mines.

Fortunately mines (if I remember correctly) can only be used in 600 feet of water.

[Guinness]

Actually, the Brits during and after WW1 developed high speed sweeps culminating in the TSDS (Two Speed Destroyer Sweep), which had an upper speed of 25 knots. The idea being that DDs would sweep out in front of high-value ships, for instance while implementing the main fleet to Singapore strategy.

So relatively fast minesweepers aren't all that far-fetched. It makes sense to me that one might combine high speed sweeping and DD roles though.

[Valles]

This is very definitely an 'offensive' type ship, intended to screen the main battlefleet on 'overseas operations'. Fourteen knot cruise and twenty knot max is the standard for my existing fleet support ships, my oilers and colliers and so on. Slower operation regimes are 'legacy' designs, not a standard for new construction. Refitting clearing ability - and ASW, for that matter - onto my actual destroyers is 'on the wish list', so to speak, but at this point even warships that small are only relatively expendable. I'd rather keep them away from something as dangerous as minesweeping, if I could.

[Ithekro]

Since all offensive operations will have to cross oceans to get to any enemy territory, it might be best if they were at least seaworthy enough to get there when you need them and the range to get around if things go badly for you (like say your tenders get attacked and sunk, but the minesweeper is still intact but now can't get home because it doesn't have the fuel).

Also if you are thinking Swiss targets, you might want to consider either better guns to engage their gunboats, or serious night training to avoid their patrols.  Even an expendible ship needs to be able to survive long enough to do its job.

[Desertfox]

I also have this nasty habit of leaving very shallow draft gunboats smack-dab in the middle of a minefield, just waiting for any unwary minesweepers to come along...

[Sachmle]

I also have this nasty habit of leaving very shallow draft gunboats smack-dab in the middle of a minefield, just waiting for any unwary minesweepers to come along...

*NOTE TO SELF* In all future Anti-Swiss minesweeping operations, just bombard the field from a distance with BB caliber guns, wait 20mins, do it again. Then send in the sweepers escorted by DDs.

[damocles]

Dutch doctrine already.  8)

[Desertfox]

Ohhhhh! Nice big targets! *droooling*

[damocles]

For a man who is about to lose his whole navy and air force that is  tall talk. 

[Desertfox]

My Air Force is perfectly intact. And the crack units of my navy are perfectly sa... err I am extremely vulnerable and am about to crack, an attack by someone on my SLOC to Africa could destroy the Swiss Military.

[Valles]

*restrains inflammatory wisecrack*

MS-1920-D, Maori Minesweeper laid down 1916

Displacement:
   333 t light; 352 t standard; 418 t normal; 472 t full load

Dimensions: Length overall / water x beam x draught
   257.20 ft / 252.62 ft x 22.97 ft x 4.92 ft (normal load)
   78.39 m / 77.00 m x 7.00 m  x 1.50 m

Armament:
     1 - 3.94" / 100 mm guns in single mounts, 33.07lbs / 15.00kg shells, 1916 Model
     Quick firing gun in a deck mount with hoist
     on centreline aft
     1 - 1.38" / 35.0 mm guns in single mounts, 1.65lbs / 0.75kg shells, 1916 Model
     Anti-aircraft gun in a deck mount with hoist
     on centreline amidships
   Weight of broadside 35 lbs / 16 kg
   Shells per gun, main battery: 500
   2 - 20.7" / 525 mm above water torpedoes

Machinery:
   Oil fired boilers, steam turbines,
   Electric motors, 2 shafts, 6,964 shp / 5,195 Kw = 25.60 kts
   Range 3,000nm at 14.00 kts
   Bunker at max displacement = 121 tons

Complement:
   46 - 60

Cost:
   £0.070 million / $0.282 million

Distribution of weights at normal displacement:
   Armament: 4 tons, 1.0 %
   Machinery: 200 tons, 47.8 %
   Hull, fittings & equipment: 118 tons, 28.2 %
   Fuel, ammunition & stores: 85 tons, 20.4 %
   Miscellaneous weights: 11 tons, 2.6 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     141 lbs / 64 Kg = 4.6 x 3.9 " / 100 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.20
   Metacentric height 0.8 ft / 0.2 m
   Roll period: 11.0 seconds
   Steadiness   - As gun platform (Average = 50 %): 75 %
         - Recoil effect (Restricted arc if above 1.00): 0.20
   Seaboat quality  (Average = 1.00): 0.83

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.513
   Length to Beam Ratio: 11.00 : 1
   'Natural speed' for length: 15.89 kts
   Power going to wave formation at top speed: 62 %
   Trim (Max stability = 0, Max steadiness = 100): 90
   Bow angle (Positive = bow angles forward): 5.00 degrees
   Stern overhang: 3.28 ft / 1.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      14.76 ft / 4.50 m
      - Forecastle (15 %):   13.12 ft / 4.00 m
      - Mid (45 %):      13.12 ft / 4.00 m (4.92 ft / 1.50 m aft of break)
      - Quarterdeck (15 %):   4.92 ft / 1.50 m
      - Stern:      4.92 ft / 1.50 m
      - Average freeboard:   8.71 ft / 2.66 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 166.6 %
      - Above water (accommodation/working, high = better): 105.2 %
   Waterplane Area: 3,912 Square feet or 363 Square metres
   Displacement factor (Displacement / loading): 74 %
   Structure weight / hull surface area: 19 lbs/sq ft or 92 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 0.81
      - Overall: 0.52
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is adequate
   Ship has slow, easy roll, a good, steady gun platform
   Poor seaboat, wet and uncomfortable, reduced performance in heavy weather

2 tons torpedoes
9 tons minesweeping gear

Perhaps y'all'll like this better? I'm not going to go for less than three-per-BP no matter what people think they need by way of capabilities, though. If that means that they need escorts, well, they are a support element.

[damocles]

Thank you for that NS. There are interested parties who would be happy to know that you are so careless.

The NRDN.  

[Ithekro]

Hmmmm...

"*NOTE TO SELF* In all future Anti-Swiss minesweeping operations, just bombard the field from a distance with BB caliber guns, wait 20mins, do it again. Then send in the sweepers escorted by DDs."

A practical use for the old Dynamite Guns?  Relatively quiet delivery system for a large explosive.  Short ranged though...no more that maybe a mile and a half.  But at night, that might be useful...though it could put one dangerously close to the minefield and the Swiss warship.