Iberian Minesweeper

[miketr]

More diesel suppor craft, Mine-Sweeper / Layers.  Figure to build two groups of 4 each to start.

Thoughts?

Michael

Mine-1, Iberia Mine-Sweeper/Layer laid down 1915 (Engine 1912)

Displacement:
   400 t light; 416 t standard; 495 t normal; 559 t full load

Dimensions: Length overall / water x beam x draught
   196.85 ft / 196.85 ft x 26.25 ft x 5.41 ft (normal load)
   60.00 m / 60.00 m x 8.00 m  x 1.65 m

Armament:
      2 - 4.13" / 105 mm guns in single mounts, 35.32lbs / 16.02kg shells, 1915 Model
     Breech loading guns in deck mounts
     on centreline ends, evenly spread
      4 - 0.49" / 12.5 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1915 Model
     Breech loading guns in deck mounts
     on side, all amidships
   Weight of broadside 71 lbs / 32 kg
   Shells per gun, main battery: 150

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.98" / 25 mm         -               -
   2nd:   0.98" / 25 mm         -               -

Machinery:
   Diesel Internal combustion motors,
   Direct drive, 2 shafts, 2,000 shp / 1,492 Kw = 17.40 kts
   Range 2,450nm at 14.00 kts
   Bunker at max displacement = 143 tons

Complement:
   52 - 68

Cost:
   £0.047 million / $0.190 million

Distribution of weights at normal displacement:
   Armament: 9 tons, 1.8 %
   Armour: 5 tons, 1.0 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 5 tons, 1.0 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 80 tons, 16.1 %
   Hull, fittings & equipment: 191 tons, 38.6 %
   Fuel, ammunition & stores: 95 tons, 19.2 %
   Miscellaneous weights: 115 tons, 23.2 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     886 lbs / 402 Kg = 25.1 x 4.1 " / 105 mm shells or 0.5 torpedoes
   Stability (Unstable if below 1.00): 1.19
   Metacentric height 0.9 ft / 0.3 m
   Roll period: 11.4 seconds
   Steadiness   - As gun platform (Average = 50 %): 61 %
         - Recoil effect (Restricted arc if above 1.00): 0.13
   Seaboat quality  (Average = 1.00): 1.22

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.620
   Length to Beam Ratio: 7.50 : 1
   'Natural speed' for length: 14.03 kts
   Power going to wave formation at top speed: 56 %
   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:      13.12 ft / 4.00 m
      - Forecastle (20 %):   10.66 ft / 3.25 m
      - Mid (50 %):      10.17 ft / 3.10 m (7.87 ft / 2.40 m aft of break)
      - Quarterdeck (15 %):   7.87 ft / 2.40 m
      - Stern:      7.87 ft / 2.40 m
      - Average freeboard:   9.39 ft / 2.86 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 91.6 %
      - Above water (accommodation/working, high = better): 127.6 %
   Waterplane Area: 3,850 Square feet or 358 Square metres
   Displacement factor (Displacement / loading): 141 %
   Structure weight / hull surface area: 33 lbs/sq ft or 163 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.92
      - Longitudinal: 2.03
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is adequate
   Room for accommodation and workspaces is excellent
   Good seaboat, rides out heavy weather easily

Miscweight: 115 tons total
Long range radio 25 tons, minesweeping gear 25 tons and mines 65 tons

[The Rock Doctor]

Seems a little fast and heavily armed for a sweeper/defensive layer.  Knock her down to ~15 knots and you could probably increase the sweeping gear weight to 50 t or more, along with more mines.

[ledeper]

Two different designs: First is for coastal operations,second for more open waters:
http://www.navalism.org/index.php?topic=2947.msg31548#msg31548,
and:
http://www.navalism.org/index.php?topic=2019.msg21552#msg21552

Some inspiration I hope ;)

[Korpen]

Seems a little fast and heavily armed for a sweeper/defensive layer.  Knock her down to ~15 knots and you could probably increase the sweeping gear weight to 50 t or more, along with more mines.

But the ship will be a much worse sweeper if slower, as 16-17 kts was kind of ideal to get maximum cutting effect and distance. Over 20kts did not bring greater sweeping width. Granted that other countries might have had different paravane parameters then Sweden.
Think the ship looks very fine, about the same kinds of speed and armament that historic sweepers had.

[miketr]

Rock I looked at historic examples...

http://www.german-navy.de/hochseeflotte/ships/minehunters/m1915/index.html

I tried to clone the above ship in rough detail in effect.  I went with whatever speed I got from 2,000 SHP (four 500 HP diesels on 400 light tons)

And some in game ones like Ledeper (yes I saw them and looked them over; good designs).

A question on weight for mine sweeping gear thing is fixed in the rules just whatever we feel like?

Korpen thanks for the comments and info on the historic examples.  Glad to know I picked a good one to clone.

Michael

[Guinness]

I don't think we have any hard figures. For one thing, real life MS gear seemed to vary widely. In WW2, for instance, US Gleaves class destroyers were converted for minesweeping, and lost 1 5inch gun and both sets of pentad tubes in the process. British TSDS had less of a price. It was designed to quickly replace just the after twin 4.7inch mounting in the tribals, for instance. It was significantly less capable though, not being designed for clearing mines in a field as much as detecting the presence of a field while in transit.

So it seems that we're making it up as we go along. In smaller RN ships, it would replace some combination of guns and depth charges and their facilities. Approximately 15 tons of our misc weight, I think. So maybe we can say something between 10 and 20 tons of Misc Weight for a basic paravane sweep, and something more for more capable systems? Certainly later on when we get into systems capable of sweeping magnetic mines, etc. sweeping systems will get larger.