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1

Wednesday, October 15th 2008, 6:13am

Irish ASW Escort

In 1937, the Irish Naval Service will continue growing its fleet. Continued emphasis will be placed on all-purpose, all-weather ASW vessels and on minesweeping/laying operations. Several vessels will be used for schoolship duties, and several ocean escort acquisitions will be made as well.

In 1938, the Irish Naval Service intends to field four Provinces-class destroyers: Connacht, Ulster, Munster, and Leinster. This four-ship flotilla will be the mainstay of the INS probably into the 1950s. However, another four-ship flotilla will be formed of smaller destroyers with less gunnery emphasis and more ASW emphasis: this class is tentatively named the Saints-class.

Gunnery on the Saints switches to 6x3.7" DP guns, which I feel are adequate to provide AA firepower and destroy surfaced submarines, as likelihood of surface encounters is deemed low. Number of torpedoes also drops. On the other hand, ASW loadout will be increased over the Provinces, with better hydrophones and improved antisub armaments, and range will be substantially increased to permit the ships to aid in convoy escort. Additionally, there will be some loss of speed compared to the Provinces, but the difference is deemed non-crucial (in fact, more my be dropped as the design continues). Also, as these vessels are meant to operate in particularly foul conditions, they will have some additional creature comforts to help morale. Seakeeping, stability, and steadiness are - as always - highly emphasized to let them survive the North Atlantic.

By 1940, with eight destroyers completed, the INS will turn to smaller and slower (23knots?) 500-900 ton ASW sloops and larger minesweepers.

Quoted

Saint Patrick, Irish ASW Escort laid down 1938

Displacement:
1,314 t light; 1,369 t standard; 1,600 t normal; 1,786 t full load

Dimensions: Length overall / water x beam x draught
368.37 ft / 360.00 ft x 34.50 ft x 11.00 ft (normal load)
112.28 m / 109.73 m x 10.52 m x 3.35 m

Armament:
6 - 3.70" / 94.0 mm guns (3x2 guns), 25.33lbs / 11.49kg shells, 1938 Model
Dual purpose guns in deck mounts with hoists
on centreline ends, majority forward, 1 raised mount - superfiring
3 - 1.46" / 37.0 mm guns (1x3 guns), 1.55lbs / 0.70kg shells, 1938 Model
Anti-aircraft guns in deck mount
on centreline aft, all raised guns - superfiring
8 - 0.79" / 20.0 mm guns (4x2 guns), 0.24lbs / 0.11kg shells, 1938 Model
Anti-aircraft guns in deck mounts
on side, evenly spread
Weight of broadside 159 lbs / 72 kg
Shells per gun, main battery: 250
6 - 21.0" / 533.4 mm above water torpedoes

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 1.18" / 30 mm 0.79" / 20 mm 0.98" / 25 mm

- Conning tower: 1.18" / 30 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 27,113 shp / 20,226 Kw = 32.00 kts
Range 6,200nm at 15.00 kts
Bunker at max displacement = 417 tons

Complement:
126 - 164

Cost:
£0.915 million / $3.661 million

Distribution of weights at normal displacement:
Armament: 20 tons, 1.2 %
Armour: 17 tons, 1.1 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 14 tons, 0.9 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 3 tons, 0.2 %
Machinery: 709 tons, 44.3 %
Hull, fittings & equipment: 516 tons, 32.2 %
Fuel, ammunition & stores: 286 tons, 17.9 %
Miscellaneous weights: 52 tons, 3.2 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
685 lbs / 311 Kg = 27.1 x 3.7 " / 94 mm shells or 0.4 torpedoes
Stability (Unstable if below 1.00): 1.30
Metacentric height 1.6 ft / 0.5 m
Roll period: 11.4 seconds
Steadiness - As gun platform (Average = 50 %): 71 %
- Recoil effect (Restricted arc if above 1.00): 0.31
Seaboat quality (Average = 1.00): 1.33

Hull form characteristics:
Hull has rise forward of midbreak
and transom stern
Block coefficient: 0.410
Length to Beam Ratio: 10.43 : 1
'Natural speed' for length: 21.84 kts
Power going to wave formation at top speed: 64 %
Trim (Max stability = 0, Max steadiness = 100): 53
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 23.00 ft / 7.01 m
- Forecastle (20 %): 19.00 ft / 5.79 m
- Mid (50 %): 19.00 ft / 5.79 m (12.00 ft / 3.66 m aft of break)
- Quarterdeck (15 %): 12.00 ft / 3.66 m
- Stern: 12.00 ft / 3.66 m
- Average freeboard: 15.82 ft / 4.82 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 156.8 %
- Above water (accommodation/working, high = better): 122.6 %
Waterplane Area: 7,983 Square feet or 742 Square metres
Displacement factor (Displacement / loading): 94 %
Structure weight / hull surface area: 33 lbs/sq ft or 162 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.50
- Longitudinal: 2.14
- Overall: 0.58
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily


Comments and criticisms?

howard

Unregistered

2

Wednesday, October 15th 2008, 7:04am

No depth charges, and no torpedo tubes.

H.

3

Wednesday, October 15th 2008, 10:11am

Odd, it has plenty of misc weight, and 6*21inch torpedo tubes

As far as the design goes, I'd question the use of the 3.7inch gun over the more reliable 4inch.

This post has been edited 1 times, last edit by "Earl822" (Oct 15th 2008, 10:12am)


4

Wednesday, October 15th 2008, 2:13pm

Quoted

Originally posted by howard
No depth charges, and no torpedo tubes.

H.

What's the point of an ASW escort if it has no ASW weapons, and what's it to do if an enemy destroyer shows up? What are you suggesting I replace them with, if you want them removed?

Quoted

Originally posted by Earl822
As far as the design goes, I'd question the use of the 3.7inch gun over the more reliable 4inch.

Rationale for that... the first Irish warships, the Deirdres, received 3.7" DPs via Britain (I think). Another two Deirdres will be built in 1937 with the 3.7", and several secondhand DDs will be refitted with 3.7". Basically I used it for caliber standardization purposes.

I did design a version of the Saints armed with three 5.1" DP singles, but at the moment I'm preferring the 3.7" DP twins as it gives me more guns with a better ROF. I expect the 3.7"s are better AA weapons in any case.

5

Wednesday, October 15th 2008, 2:19pm

So these will operate together with the RN? Or does WW Eire have a vastly greater merchant navy than OTL?

6

Wednesday, October 15th 2008, 3:03pm

Quoted

Originally posted by Vukovlad
So these will operate together with the RN?

That's the idea, yes. My theory is that Britain cannot and will not permit any third country to seize and hold Ireland, as it will cut their western approaches. It's not really worthwhile to arm against Britain, either, as they can build as much every three months as I can build every six and a quarter years. Hood also informed me he thinks Britain and Ireland would have a less antagonistic relationship in WW, which I'm amenable to. All this adds up to coast defense being of tertiary importance.

On the other hand, Ireland can make a difference if it needs to join Britain in any ASW campaign on the western approaches, as demonstrated in the Great War. Ireland is very well-placed to do this job, and thus intends to specialize in ASW and high seas patrol.

howard

Unregistered

7

Wednesday, October 15th 2008, 7:53pm

Quoted

Originally posted by Brockpaine

Quoted

Originally posted by howard
No depth charges, and no torpedo tubes.

H.

What's the point of an ASW escort if it has no ASW weapons, and what's it to do if an enemy destroyer shows up? What are you suggesting I replace them with, if you want them removed?


I missed the torpedo tubes at the first read, but I ask you this....up to now name me ONE destroyer that has been sunk in a single ship destroyer duel by torpedo? Maybe in WW by accident, but the RTL WW II events haven't happened yet. The torpedoes we have aren't that good YET, and they most certainly would need to be fired in spreads of at least four fish to have a prayer of hitting a 30 knot ship beyond 3000 meters.^1

I don't want them totally removed. You can remove two tubes and still have sufficient room to operate depth charges and get off a salvoe. Don't forget our discussions about torpedoes, Brock. Remember the future HT-3?

For now as far as ASW you need depth charge rails and throwers. And no, fifty two tonnes miscellaneous weights will not cover the depth bombs needed. Not when you consider that one pattern weighs 3000 kilograms. How many patterns can you lay? Take out half of the fifty-two tonnes for the launchers you install [ignore roll racks]. That leaves twenty-one tonnes. Seven patterns? You usually expect to see about twelve to sixteen patterns from a destroyer.

Quoted


Quoted

Originally posted by Earl822
As far as the design goes, I'd question the use of the 3.7inch gun over the more reliable 4inch.

Rationale for that... the first Irish warships, the Deirdres, received 3.7" DPs via Britain (I think). Another two Deirdres will be built in 1937 with the 3.7", and several secondhand DDs will be refitted with 3.7". Basically I used it for caliber standardization purposes
.

Nothing wrong with the 94 mm as a DP FLAK mount. Its actually better than the other more common 4.7 inch.

Quoted


I did design a version of the Saints armed with three 5.1" DP singles, but at the moment I'm preferring the 3.7" DP twins as it gives me more guns with a better ROF. I expect the 3.7"s are better AA weapons in any case.


Without any radar proximity shells, I approve of the more garbage in the air through which to fly is better argument proposed.

This post has been edited 1 times, last edit by "howard" (Oct 15th 2008, 7:56pm)


8

Wednesday, October 15th 2008, 10:16pm

- British F-class DD: 75 tons misc weights (4% of total)
- Russian Vinnitsa-class DD: 30 tons misc weights (1.8% of total)
- Iberian D142-class DD: 50 tons misc weights (3.5% of total)
- Atlantean K-class DD: 45 tons misc weights (2.2% of total)
- Italian Soldati-class DD: 70 tons misc weights (3.6% of total)
- Dutch Z81-class DD: 95 tons misc weights (3.2% of total)
- SAE Lizard-class DD: 15 tons misc weights (1.1% of total)
- Japanese Mutsuki-class DD: 125 tons misc weights (5.3% of total)
- Japanese Kasumi B-class DD: 50 tons misc weights (2.6% of total)
- Indian Allahabad-class DD: 58 tons misc weights (2.9% of total): 26 tons marked for DC and related equipment.
- American Fletcher-class DD: 80 tons misc weights (2.7% of total): 20 tons marked for DC and related equipment.
- Nordish 35-class DD: 55 tons misc weights (2.3% of total)
- German Z214-class DD: 30 tons misc weights (1.6% of total): 10 tons marked for DC and related equipment.
- French Le Terrible-class DD: 30 tons misc weights (1.9% of total)
- Greek Heracles-class DD: 30 tons misc weights (1.3% of total)
- Siamese Chao Phya-class DD: 36 tons misc weights (2.7% of total)
- Persian Vouruskasha-class DD: 50 tons misc weights (2.9% of total)
- Irish Saints-class DD: 52 tons misc weights (3.2% of total)

If we presume sixteen British Mark VII DCs used per pattern, that's 3,056 kg or 3 long (UK) tons/3.36 short (US) tons. To achieve sixteen patterns of sixteen bombs, that'd be 48 tons, with 256 191kg DCs carried. Would you call that sufficient?

How much is the weight of a Y-gun?

So yes, it appears I need to add some more weight for DCs.

howard

Unregistered

9

Wednesday, October 15th 2008, 10:34pm

You'll want to use a K-gun. The Y gun is a heavy center-line mount. The K-gunn is a perimeter mount, at least 200 kilograms, is much lighter, as it is a spigot mortar and not a standard Stokes type weapon.

You might also want to consult HEBCO as they have a few ideas about depth charge weapons for the INS.

http://www.navweaps.com/Weapons/WAMUS_ASW.htm

This post has been edited 2 times, last edit by "howard" (Oct 15th 2008, 10:36pm)


10

Wednesday, October 15th 2008, 10:46pm

Quoted

You usually expect to see about twelve to sixteen patterns from a destroyer.

Just curious. This is based on what?

Looking at various destroyers I see values between roughly 20 and 100 but haven't encountered anything higher than that. Now it should be noted that I did not look at all DDs and that some DDs don't have DC numbers but still 100 DCs is less than 40% of what Brock calculated that you say is "usual".

... so 100 DCs at ~ 200 kg per DC gives you ~19.7 tons...

... so yes, 52 tons will cover the DCs + rails and/or throwers and probably the TTs and Torpedoes as well.

This post has been edited 2 times, last edit by "Rooijen10" (Oct 15th 2008, 10:47pm)


11

Wednesday, October 15th 2008, 11:31pm

The pattern size depends on what equipment you have on board. A minimal pattern is five charges from one stern rack and two projectors. It consists of a diamond shape with a central charge. Add another two projectors and you have a pattern of seven with a hexagon and central charge. Double the amount and have the DCs set to different depths so you have two hexagons one on top of the other. A standard British DC weighs 191kg so patterns are 1ton 1.3tons or 2.6tons.

Asdic weighs about 9tons, but hydrophones would be less at around 5tons.

For the ship I think you're trying to fit too much into the hull. High speed, good seakeeping and range, heavy armament on a fairly small ship size. You're probably better off with something like a Black Swan Sloop with reciprocating engines (they're more efficient at low speed, cheap and easy for Ireland to manufacture)

howard

Unregistered

12

Thursday, October 16th 2008, 12:23am

Quoted

Originally posted by Rooijen10

Quoted

You usually expect to see about twelve to sixteen patterns from a destroyer.

Just curious. This is based on what?

Looking at various destroyers I see values between roughly 20 and 100 but haven't encountered anything higher than that. Now it should be noted that I did not look at all DDs and that some DDs don't have DC numbers but still 100 DCs is less than 40% of what Brock calculated that you say is "usual".

... so 100 DCs at ~ 200 kg per DC gives you ~19.7 tons...

... so yes, 52 tons will cover the DCs + rails and/or throwers and probably the TTs and Torpedoes as well.


12-16 patterns is based on what US warships of the period carried in the way of depth charges.

A standard 600 LB explosive fill charge is my base computation as the 300 pounders were/are just about WORTHLESS in light of submarine tech as it exists. I also submit that you did not add casing to charge weights so recompute everything by adding 25% to account for the can exploder and hydrostatic pistol. Then you have the launchers and rails themselves. None of that equipment is light.

You find yourself shooting and rolling off at a minimum of a ton of projectiles to get a six and one pattern as RA describes which is the minimum effective pattern with a 300 pounder fill bomb. A five shit requires the bigger bomb.

H.

This post has been edited 3 times, last edit by "howard" (Oct 16th 2008, 12:49am)


13

Thursday, October 16th 2008, 12:40am

Quoted

Originally posted by Red Admiral
You're probably better off with something like a Black Swan Sloop with reciprocating engines (they're more efficient at low speed, cheap and easy for Ireland to manufacture)

As a matter of fact, I have one right here, part of the 1940 program:

Quoted

Contae Thiobraid Arann (County Tipperary), Irish ASW Sloop laid down 1940

Displacement:
861 t light; 894 t standard; 1,003 t normal; 1,090 t full load

Dimensions: Length overall / water x beam x draught
230.00 ft / 230.00 ft x 36.50 ft x 11.00 ft (normal load)
70.10 m / 70.10 m x 11.13 m x 3.35 m

Armament:
3 - 3.70" / 94.0 mm guns in single mounts, 25.33lbs / 11.49kg shells, 1940 Model
Dual purpose guns in deck mounts
on centreline ends, majority forward, 1 raised mount
4 - 1.57" / 40.0 mm guns (2x2 guns), 1.95lbs / 0.88kg shells, 1940 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
8 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1940 Model
Anti-aircraft guns in deck mounts
on side, evenly spread, all raised mounts
Weight of broadside 86 lbs / 39 kg
Shells per gun, main battery: 250

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.59" / 15 mm 0.39" / 10 mm -
2nd: 0.59" / 15 mm - -
3rd: 0.59" / 15 mm - -

- Conning tower: 0.59" / 15 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 8,553 shp / 6,381 Kw = 23.35 kts
Range 5,000nm at 13.00 kts
Bunker at max displacement = 196 tons

Complement:
88 - 115

Cost:
£0.427 million / $1.708 million

Distribution of weights at normal displacement:
Armament: 11 tons, 1.1 %
Armour: 6 tons, 0.6 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 5 tons, 0.5 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 1 tons, 0.1 %
Machinery: 229 tons, 22.8 %
Hull, fittings & equipment: 535 tons, 53.4 %
Fuel, ammunition & stores: 142 tons, 14.1 %
Miscellaneous weights: 80 tons, 8.0 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
2,179 lbs / 988 Kg = 86.0 x 3.7 " / 94 mm shells or 0.8 torpedoes
Stability (Unstable if below 1.00): 1.13
Metacentric height 1.4 ft / 0.4 m
Roll period: 13.0 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.12
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has low quarterdeck
Block coefficient: 0.380
Length to Beam Ratio: 6.30 : 1
'Natural speed' for length: 15.17 kts
Power going to wave formation at top speed: 65 %
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: 23.00 ft / 7.01 m
- Forecastle (20 %): 19.00 ft / 5.79 m
- Mid (50 %): 19.00 ft / 5.79 m
- Quarterdeck (15 %): 12.00 ft / 3.66 m (19.00 ft / 5.79 m before break)
- Stern: 12.00 ft / 3.66 m
- Average freeboard: 18.27 ft / 5.57 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 92.1 %
- Above water (accommodation/working, high = better): 210.5 %
Waterplane Area: 5,119 Square feet or 476 Square metres
Displacement factor (Displacement / loading): 159 %
Structure weight / hull surface area: 48 lbs/sq ft or 232 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.76
- Longitudinal: 12.62
- Overall: 1.00
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

Breakdown of Weights
50 tons for Depth Charges
15 tons for Hydrophones
15 tons for growth


I was planning to build a number of these ships following the completion of the Saints, but I wanted a second flotilla of destroyers before building the above sloops.

14

Thursday, October 16th 2008, 12:46am

Actually that design was the cheapo design. I think this was the one I wanted.

Quoted

Contae Thiobraid Arann (County Tipperary), Irish Destroyer Escort laid down 1940

Displacement:
907 t light; 951 t standard; 1,065 t normal; 1,156 t full load

Dimensions: Length overall / water x beam x draught
230.00 ft / 230.00 ft x 36.50 ft x 11.00 ft (normal load)
70.10 m / 70.10 m x 11.13 m x 3.35 m

Armament:
6 - 3.70" / 94.0 mm guns (3x2 guns), 25.33lbs / 11.49kg shells, 1940 Model
Dual purpose guns in deck mounts
on centreline ends, majority forward, 1 raised mount - superfiring
4 - 1.57" / 40.0 mm guns (2x2 guns), 1.95lbs / 0.88kg shells, 1940 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
8 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1940 Model
Anti-aircraft guns in deck mounts
on side, evenly spread, all raised mounts
Weight of broadside 162 lbs / 73 kg
Shells per gun, main battery: 250

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.59" / 15 mm 0.39" / 10 mm -
2nd: 0.59" / 15 mm - -
3rd: 0.59" / 15 mm - -

- Conning tower: 0.59" / 15 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 9,036 shp / 6,741 Kw = 23.35 kts
Range 5,000nm at 13.00 kts
Bunker at max displacement = 204 tons

Complement:
93 - 121

Cost:
£0.495 million / $1.981 million

Distribution of weights at normal displacement:
Armament: 20 tons, 1.9 %
Armour: 9 tons, 0.9 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 8 tons, 0.7 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 1 tons, 0.1 %
Machinery: 242 tons, 22.7 %
Hull, fittings & equipment: 556 tons, 52.2 %
Fuel, ammunition & stores: 158 tons, 14.9 %
Miscellaneous weights: 80 tons, 7.5 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
2,109 lbs / 957 Kg = 83.3 x 3.7 " / 94 mm shells or 0.7 torpedoes
Stability (Unstable if below 1.00): 1.14
Metacentric height 1.4 ft / 0.4 m
Roll period: 12.9 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.22
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has low quarterdeck
Block coefficient: 0.404
Length to Beam Ratio: 6.30 : 1
'Natural speed' for length: 15.17 kts
Power going to wave formation at top speed: 66 %
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: 23.00 ft / 7.01 m
- Forecastle (20 %): 19.00 ft / 5.79 m
- Mid (50 %): 19.00 ft / 5.79 m
- Quarterdeck (15 %): 12.00 ft / 3.66 m (19.00 ft / 5.79 m before break)
- Stern: 12.00 ft / 3.66 m
- Average freeboard: 18.27 ft / 5.57 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 97.8 %
- Above water (accommodation/working, high = better): 201.5 %
Waterplane Area: 5,179 Square feet or 481 Square metres
Displacement factor (Displacement / loading): 145 %
Structure weight / hull surface area: 49 lbs/sq ft or 238 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.75
- Longitudinal: 12.31
- Overall: 1.00
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

50 tons for Depth Charges
15 tons for Hydrophones
15 tons for growth