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1

Friday, April 25th 2008, 4:58am

Minelayers...?

His Majesty's Royal Siamese Navy (for reasons that will be explained at the end of finals next week) is currently investigating mine warfare vessels. Currently one such ship is on order from Denmark (a Humelbi II clone) but Siam wishes to build further vessels of their own. The question being posed is this:

Capacity or Number?

Should Siam 1.) build a smaller number of larger vessels capable of laying large minefields alone but are expensive to loose, or should we 2.) build many smaller vessels which cannot carry as many mines but are less of an investment if lost?

Advice is sought on the matter from those wiser and more experienced than Siam.

2

Friday, April 25th 2008, 5:12am

Bulgaria's plan:

- The German Z-214 destroyers we're going to start building in late 1936 are going to come equipped with mine rails. By 1940, that gives me at least six modern, fast destroyers that can serve as minelayers.
- Purchase or build numerous small boats in the 50-60t range used for laying small coastal minefields. Realistically, a large part of my mine-warfare will be defensive in nature, so this is the primary focus of my MW group.
- Converted merchant ships, and using my minesweepers as minelayers.

Some of my personal madboy ideas:
- Make a floating mine as the warhead of a long-range torpedo: have a ship launch them from out of sight, have them run at slow speed into the target area, then deploy the mine when the torpedo sinks.
- Mines laid by airship/aircraft.

3

Friday, April 25th 2008, 6:40am

If I were Siam I'd invest in destroyer designs capable of acting as minelayers in addition to some smaller classes. A few dedicated types may be possible but as you say more costly to loose than a DD capable of fullfilling the role occastionally.

Atlantis currently has no DD's that can lay mines, some of the older DD designs may be converted to act in this role but untill then the current purpose built designs are sufficient.


4

Friday, April 25th 2008, 7:07am

This is one of the designs that Siam has been considering. It comes in at only 500 tons and carries a large amount of mines for it's size (160 mines @650 kg/1433 lbs each). It's a small minelayer/sweeper for setting up and maintaining defensive fields in friendly waters... as can clearly be seen from it's top speed. Its advantages are that it's cheap and relatively easy to construct, and can lay a rather nice field on it's own; it's disadvantage is- as you pointed out- is that it uses up almost as much material as a small destroyer.

Art will be forthcoming if I adopt the design.

Quoted

Minelayer, Small #1, Siamese Minelayer laid down 1936

Displacement:
500 t light; 515 t standard; 583 t normal; 637 t full load

Dimensions: Length overall / water x beam x draught
164.04 ft / 164.04 ft x 29.53 ft x 9.02 ft (normal load)
50.00 m / 50.00 m x 9.00 m x 2.75 m

Armament:
1 - 3.00" / 76.2 mm guns in single mounts, 13.23lbs / 6.00kg shells, 1936 Model
Dual purpose gun in deck mount
on centreline forward
4 - 1.46" / 37.0 mm guns (2x2 guns), 1.65lbs / 0.75kg shells, 1936 Model
Dual purpose guns in deck mounts
on centreline, all aft, 1 raised mount - superfiring
Weight of broadside 20 lbs / 9 kg
Shells per gun, main battery: 300

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 1.57" / 40 mm 164.04 ft / 50.00 m 8.20 ft / 2.50 m
Ends: Unarmoured
Main Belt covers 154 % of normal length

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

- Armour deck: 1.57" / 40 mm, Conning tower: 0.98" / 25 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 1 shaft, 500 shp / 373 Kw = 12.38 kts
Range 5,000nm at 12.38 kts
Bunker at max displacement = 122 tons

Complement:
59 - 77

Cost:
£0.113 million / $0.454 million

Distribution of weights at normal displacement:
Armament: 2 tons, 0.4 %
Armour: 178 tons, 30.6 %
- Belts: 78 tons, 13.4 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 4 tons, 0.6 %
- Armour Deck: 95 tons, 16.3 %
- Conning Tower: 1 tons, 0.3 %
Machinery: 14 tons, 2.4 %
Hull, fittings & equipment: 190 tons, 32.5 %
Fuel, ammunition & stores: 83 tons, 14.3 %
Miscellaneous weights: 115 tons, 19.7 %
160 mines @650 kg/1433 lbs each

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
2,467 lbs / 1,119 Kg = 182.7 x 3.0 " / 76 mm shells or 1.9 torpedoes
Stability (Unstable if below 1.00): 1.14
Metacentric height 1.0 ft / 0.3 m
Roll period: 12.2 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.03
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.467
Length to Beam Ratio: 5.56 : 1
'Natural speed' for length: 15.49 kts
Power going to wave formation at top speed: 45 %
Trim (Max stability = 0, Max steadiness = 100): 35
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: 14.76 ft / 4.50 m
- Forecastle (20 %): 11.48 ft / 3.50 m
- Mid (50 %): 10.66 ft / 3.25 m
- Quarterdeck (15 %): 10.66 ft / 3.25 m
- Stern: 10.66 ft / 3.25 m
- Average freeboard: 11.21 ft / 3.42 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 34.4 %
- Above water (accommodation/working, high = better): 114.1 %
Waterplane Area: 3,257 Square feet or 303 Square metres
Displacement factor (Displacement / loading): 171 %
Structure weight / hull surface area: 35 lbs/sq ft or 170 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.83
- Longitudinal: 4.87
- Overall: 1.00
Hull space for machinery, storage, compartmentation is excellent
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


Alternately, I could convert my ancient ex-Italian destroyers to fulfill the duty. This is a very likely possibility, as they are virtually useless in their original role at this point in time, and the refits for 2 of them would be about the same amount as trying to build a single new ship.

5

Friday, April 25th 2008, 7:13am

To me converting the Italian DD's to fill the role would be cost effective. You gain minelayers and extend the life of existing ships.

Kaiser Kirk

Lightbringer and former European Imperialist

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6

Friday, April 25th 2008, 7:26am

Quoted

Originally posted by Brockpaine
Some of my personal madboy ideas:
- Make a floating mine as the warhead of a long-range torpedo: have a ship launch them from out of sight, have them run at slow speed into the target area, then deploy the mine when the torpedo sinks.
- Mines laid by airship/aircraft.


I may be misremembering, but I think the Dutch did have the torpedo mine...aha they did! Well, kinda- it wasn't a floater it was a ground mine. Two mines would substitute for one torpedo and could be laid via the torpedo tube, intended to be laid in 5-60fathoms (which covers much of the Java sea). Rather inefficient way of laying a field of course, but could make a choke point interesting.

7

Friday, April 25th 2008, 9:19pm

Quoted

Originally posted by thesmilingassassin
To me converting the Italian DD's to fill the role would be cost effective. You gain minelayers and extend the life of existing ships.


Here's a quick design for that; the bow and waist guns are replaced by Siamese 76mm DP guns, and the deck aft the midbreak is cleared, has mine rails added and an enclosed (and unarmored) mine hanger installed. Other than that, it's a standard life-extension refit @ 15%.

Total refit cost - 96.15 tons per ship

Quoted

Ratanakosin, Siamese Minelayer laid down 1915

Displacement:
641 t light; 667 t standard; 774 t normal; 860 t full load

Dimensions: Length overall / water x beam x draught
242.78 ft / 239.50 ft x 23.95 ft x 11.81 ft (normal load)
74.00 m / 73.00 m x 7.30 m x 3.60 m

Armament:
1 - 3.00" / 76.2 mm guns in single mounts, 13.23lbs / 6.00kg shells, 1936 Model
Dual purpose gun in deck mounts
on centreline ends, evenly spread
2 - 3.00" / 76.2 mm guns in single mounts, 13.23lbs / 6.00kg shells, 1936 Model
Dual purpose guns in deck mounts
on side, all amidships, all raised mounts - superfiring
4 - 1.46" / 37.0 mm guns (2x2 guns), 1.55lbs / 0.70kg shells, 1936 Model
Dual purpose guns in deck mounts
on centreline, all aft, all raised mounts - superfiring
Weight of broadside 46 lbs / 21 kg
Shells per gun, main battery: 300

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.79" / 20 mm - -
2nd: 0.79" / 20 mm - -
3rd: 0.79" / 20 mm - -

Machinery:
Oil fired boilers, steam turbines,
Direct drive, 2 shafts, 16,115 shp / 12,022 Kw = 30.00 kts
Range 3,000nm at 15.00 kts
Bunker at max displacement = 194 tons

Complement:
73 - 95

Cost:
£0.120 million / $0.481 million

Distribution of weights at normal displacement:
Armament: 6 tons, 0.8 %
Armour: 6 tons, 0.7 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 6 tons, 0.7 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.0 %
Machinery: 396 tons, 51.1 %
Hull, fittings & equipment: 214 tons, 27.7 %
Fuel, ammunition & stores: 133 tons, 17.2 %
Miscellaneous weights: 20 tons, 2.6 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
217 lbs / 98 Kg = 16.1 x 3.0 " / 76 mm shells or 0.2 torpedoes
Stability (Unstable if below 1.00): 1.25
Metacentric height 0.9 ft / 0.3 m
Roll period: 10.7 seconds
Steadiness - As gun platform (Average = 50 %): 71 %
- Recoil effect (Restricted arc if above 1.00): 0.14
Seaboat quality (Average = 1.00): 1.10

Hull form characteristics:
Hull has rise forward of midbreak
and transom stern
Block coefficient: 0.400
Length to Beam Ratio: 10.00 : 1
'Natural speed' for length: 17.90 kts
Power going to wave formation at top speed: 70 %
Trim (Max stability = 0, Max steadiness = 100): 65
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 3.28 ft / 1.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 18.04 ft / 5.50 m
- Forecastle (20 %): 18.04 ft / 5.50 m
- Mid (30 %): 18.04 ft / 5.50 m (9.84 ft / 3.00 m aft of break)
- Quarterdeck (15 %): 9.84 ft / 3.00 m
- Stern: 9.84 ft / 3.00 m
- Average freeboard: 12.30 ft / 3.75 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 174.5 %
- Above water (accommodation/working, high = better): 106.2 %
Waterplane Area: 3,664 Square feet or 340 Square metres
Displacement factor (Displacement / loading): 60 %
Structure weight / hull surface area: 24 lbs/sq ft or 118 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.50
- Longitudinal: 3.84
- Overall: 0.61
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

This post has been edited 2 times, last edit by "Carthaginian" (Apr 25th 2008, 10:38pm)


8

Friday, April 25th 2008, 10:32pm

Two things. 1st, why DP for the 37mm? 2nd, that 0.49 cross-sectional strength is under limit, I believe.

9

Friday, April 25th 2008, 10:36pm

Quoted

Originally posted by Sachmle
Two things. 1st, why DP for the 37mm? 2nd, that 0.49 cross-sectional strength is under limit, I believe.


1.) All my 37mm are on DP mounts. For this ship, it allows firing at mines in the water that cannot be recovered... saving valuable main gun rounds. It also allows the ships to engage MTB's with the 37mm guns- something that the MTB's find rather nasty.

2.) Dammit... don't you just love it when that happens.
A revised design fixing that will be up shortly!

EDIT: Revised design posted.

This post has been edited 1 times, last edit by "Carthaginian" (Apr 25th 2008, 10:38pm)