WesWorld

Overall it's looking more like I'll be building 3-4 classes of escort vessels ranging from 600-1800 tons.

In regards to the 600tons, they are replacing 589 ton vessels. I'm trying to explore what the bottom 'size' *should* be and getting some "hints" it should be larger

As RA points out the Flower class was to small...but my 3rd rate source says that the later Castle class was not only 90tons less, but "Once the Flower-class corvettes were in service it was clear they were too small and uncomfortable for thier crews, one of the problems being that their lenth did not fit with the normal distance between waves in the North Atlantic. Smith's Dock therefore suggested that the length should be increased significantly from 205 ft (62.5m) to 252ft (76.8m)".
So to fix the "Flowers" they slimmed the ship and increased the length. It's pretty much a coffee table book, but tends to simply not say anything rather such statements.

This is why I was thinking that going smaller might be viable if I provided adequate length, and I freed up more internal room with diesels rather than triple expansion. Replace the 4" mount and Squid mount of the Castles with the twin 100mm. Add a couple waist AA for the expected threat, keep a clear deck aft for DCs.

Quoted

Originally posted by Red Admiral
Its a really bad idea to use 600ton vessels to escort convoys through actual oceans. The 1000ton Flowers were proven to be too small.

Beware of hindsight! This probably is a lesson that still needs to be learned....

F30, Nordmark Frigate laid down 1930

Displacement:
592 t light; 630 t standard; 849 t normal; 1,024 t full load

Dimensions: Length overall / water x beam x draught
256.53 ft / 253.00 ft x 29.00 ft x 9.00 ft (normal load)
78.19 m / 77.11 m x 8.84 m x 2.74 m

Armament:
4 - 4.33" / 110 mm guns (2x2 guns), 40.61lbs / 18.42kg shells, 1930 Model
Dual purpose guns in deck mounts
on centreline ends, evenly spread
8 - 1.46" / 37.0 mm guns (4x2 guns), 1.55lbs / 0.70kg shells, 1930 Model
Dual purpose guns in deck mounts
on side, all amidships
8 - 0.79" / 20.0 mm guns (4x2 guns), 0.24lbs / 0.11kg shells, 1930 Model
Machine guns in deck mounts
on side, evenly spread
Weight of broadside 177 lbs / 80 kg
Shells per gun, main battery: 200

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 2.00" / 51 mm 1.00" / 25 mm -
2nd: 2.00" / 51 mm - -
3rd: 1.00" / 25 mm - -

- Conning tower: 1.00" / 25 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 3,372 shp / 2,515 Kw = 20.00 kts
Range 8,000nm at 15.00 kts
Bunker at max displacement = 395 tons

Complement:
78 - 102

Cost:
£0.224 million / $0.896 million

Distribution of weights at normal displacement:
Armament: 22 tons, 2.6 %
Armour: 27 tons, 3.1 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 25 tons, 2.9 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 2 tons, 0.2 %
Machinery: 102 tons, 12.0 %
Hull, fittings & equipment: 361 tons, 42.5 %
Fuel, ammunition & stores: 257 tons, 30.3 %
Miscellaneous weights: 80 tons, 9.4 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,699 lbs / 771 Kg = 41.8 x 4.3 " / 110 mm shells or 0.9 torpedoes
Stability (Unstable if below 1.00): 1.16
Metacentric height 1.0 ft / 0.3 m
Roll period: 12.0 seconds
Steadiness - As gun platform (Average = 50 %): 100 %
- Recoil effect (Restricted arc if above 1.00): 0.31
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has rise forward of midbreak
and transom stern
Block coefficient: 0.450
Length to Beam Ratio: 8.72 : 1
'Natural speed' for length: 18.47 kts
Power going to wave formation at top speed: 52 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 10.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 20.00 ft / 6.10 m
- Forecastle (40 %): 15.00 ft / 4.57 m
- Mid (40 %): 15.00 ft / 4.57 m (10.00 ft / 3.05 m aft of break)
- Quarterdeck (15 %): 10.00 ft / 3.05 m
- Stern: 10.00 ft / 3.05 m
- Average freeboard: 12.80 ft / 3.90 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 70.9 %
- Above water (accommodation/working, high = better): 118.7 %
Waterplane Area: 4,861 Square feet or 452 Square metres
Displacement factor (Displacement / loading): 174 %
Structure weight / hull surface area: 39 lbs/sq ft or 192 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.86
- Longitudinal: 3.80
- 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

F30 30 1to14 built

Misc weight is 30tons for mines, 30tons for ASW, and 20tons stores

Nordmark has 6 of these, and plans more. 630tons std seems adequate for this class and it's 1932 follow on's, though the 1935 class may be larger.

Quoted

Beware of hindsight! This probably is a lesson that still needs to be learned....

Its fairly obvious if you already have 600ton ships. Look at Italy. Previous escorts being 600tons then up to 1000tons or so. Might even grow a bit more.

Ack,
I think HoOmAn, Earl 822 and RA all posted while I was still typing my last response. The Nordmark ship is quite what I'm looking for and similar to what I put out, a bit heavier guns due to the transom.

I just wanted to add a note on weapons. These are overarmed compared to the classic RN escorts, they are meant for the different threat regime that I outlined, more as slow destroyers. Consider the 1,460 ton River class- the follow up to the Castle class, they have the 4" suggested to hole conning towers, 2 HA as RA suggested. Those were minimal outfits.

I'm looking at something at a weaponry fit more like a modified W class, at 1120 tons with 4x4.7". Except the W's had torps and the machinery for 31 knts. A 21 knot ship needs substantially less machinery. This would leave more room for weapons... or allow the same weapons fit on a smaller ship?

Thanks for bearing with me.

Quoted

I'm looking at something at a weaponry fit more like a modified W class, at 1120 tons with 4x4.7". Except the W's had torps and the machinery for 31 knts. A 21 knot ship needs substantially less machinery. This would leave more room for weapons... or allow the same weapons fit on a smaller ship?

Trade it for increased hull strength and seakeeping rather than weapons or decreasing size.

I think we're talking past each other. I know you know more than I on such things, but I'm not interested in making the classic British escort. I do take seriously the charge the vessel is to small to do the job. I have tried to address that by posting above the point about the Castles being lengthened specifically to address the wave period issue the 'to small' Flowers had, and I have tried to explain where on a Castle this armament would fit. Now, if I'm told that the beam is to narrow for a twin 100mm, or that SS is wrong and the hull form just doesn't work, great I'll buy that because I'm not the knowledgeable one here . In that case I would find it helpful to know what the minimums are.

Quoted

Originally posted by Red Admiral

Trade it for increased hull strength and seakeeping rather than weapons or decreasing size.

Well let's take the 629 ton standard vessel I earlier posted. The sloop had the length of the Castle class to avoid the wave-period problem cited for the 'to small' Flower class. The vessel also had 4x100mm- a little less than the "W"s 4x4.7". As indicated, the mounts are where the 4" and Squid were on the Castles- so they should fit.

Quoted

Originally posted by Kaiser Kirk
Hull strength (Relative):
- Cross-sectional: 0.90
- Longitudinal: 3.19
- Overall: 1.02
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

So, just what seakeeping and hull strength should I be shooting for? I know SS has issues with small vessels, but in my experience it's mainly in deckspace and when you try to sim real destroyer speeds.
Looking at a SIM of “Whitehall”- the last W, based on Jane’s of WW2 stats, default freeboard, no misc weight :

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 185.3 %
- Above water (accommodation/working, high = better): 95.5 %
Waterplane Area: 5,886 Square feet or 547 Square metres
Displacement factor (Displacement / loading): 56 %
Structure weight / hull surface area: 30 lbs/sq ft or 148 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.53
- Longitudinal: 1.74
- Overall: 0.60
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is adequate
Poor seaboat, wet and uncomfortable, reduced performance in heavy weather

Scaling the ships deck plan yields about 7.8’ per 1/16” inch, with the TTs being 3/16 or 23.5’.
Shortening the hull by that amount yields an 276.5’ (84m) vessel. Combining that with the new default freeboard and a speed reduction to 21 knots yields :

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 74.2 %
- Above water (accommodation/working, high = better): 121.6 %
Waterplane Area: 5,425 Square feet or 504 Square metres
Displacement factor (Displacement / loading): 187 %
Structure weight / hull surface area: 70 lbs/sq ft or 343 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 1.41
- Longitudinal: 4.80
- Overall: 1.59
Hull space for machinery, storage, compartmentation is excellent
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

The ship’s hull is 2.65x stronger and the amount of interior space now taken up is 40% of the original. I think that’s overbuilt with room to change, hence my seeking ways to either add weapons or get smaller. Where are the reasonable minimums?

I had a fiddle around with simming the Flowers, Castles and other frigates. These are not highly stressed vessels and tend to have a hull strength of around 1.5-2.0

SS definitely overestimates small, slow vessels.

Basically you want something as small as possible with 4x100mm guns and depth charges. Speed of 20knts or so.

Freeboard should be at least 6m forwards where you mount your guns, preferably more.

70m length so you can fit in a Type 0 dock.

About 10tons for sonar eventually. Another 20tons for depth charges in racks. An ahead throwing weapon eventually, about another 30tons.

Easily possible on about 1000tons, maybe can go a bit less if you increase fuel load - but where do you put the fuel?

Enter ship name, Enter country Enter ship type laid down 1930

Displacement:
939 t light; 985 t standard; 1,208 t normal; 1,386 t full load

Dimensions: Length overall / water x beam x draught
236.99 ft / 229.66 ft x 32.81 ft x 9.84 ft (normal load)
72.23 m / 70.00 m x 10.00 m x 3.00 m

Armament:
4 - 3.94" / 100 mm guns (2x2 guns), 30.51lbs / 13.84kg shells, 1930 Model
Anti-aircraft guns in deck mounts
on centreline ends, evenly spread
12 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1930 Model
Anti-aircraft guns in deck mounts
on side, all amidships
Weight of broadside 125 lbs / 57 kg
Shells per gun, main battery: 300

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

- Conning tower: 0.39" / 10 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 6,015 shp / 4,487 Kw = 20.40 kts
Range 10,000nm at 12.00 kts
Bunker at max displacement = 402 tons

Complement:
102 - 133

Cost:
£0.299 million / $1.196 million

Distribution of weights at normal displacement:
Armament: 16 tons, 1.3 %
Armour: 3 tons, 0.2 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 2 tons, 0.2 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 1 tons, 0.1 %
Machinery: 182 tons, 15.1 %
Hull, fittings & equipment: 688 tons, 57.0 %
Fuel, ammunition & stores: 269 tons, 22.3 %
Miscellaneous weights: 50 tons, 4.1 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
3,256 lbs / 1,477 Kg = 106.7 x 3.9 " / 100 mm shells or 1.2 torpedoes
Stability (Unstable if below 1.00): 1.17
Metacentric height 1.3 ft / 0.4 m
Roll period: 12.2 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.16
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has rise forward of midbreak
Block coefficient: 0.570
Length to Beam Ratio: 7.00 : 1
'Natural speed' for length: 15.15 kts
Power going to wave formation at top speed: 63 %
Trim (Max stability = 0, Max steadiness = 100): 25
Bow angle (Positive = bow angles forward): 10.00 degrees
Stern overhang: 3.28 ft / 1.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 22.97 ft / 7.00 m
- Forecastle (20 %): 19.69 ft / 6.00 m
- Mid (70 %): 19.69 ft / 6.00 m (11.48 ft / 3.50 m aft of break)
- Quarterdeck (15 %): 11.48 ft / 3.50 m
- Stern: 11.48 ft / 3.50 m
- Average freeboard: 17.49 ft / 5.33 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 65.4 %
- Above water (accommodation/working, high = better): 178.0 %
Waterplane Area: 5,358 Square feet or 498 Square metres
Displacement factor (Displacement / loading): 223 %
Structure weight / hull surface area: 59 lbs/sq ft or 286 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 1.06
- Longitudinal: 13.13
- Overall: 1.36
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is excellent
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

Thank you for the effort, and the example. I now have a baseline to work from, though she's quite close to what I was looking for as it is.

Edit: I've asked Hooman if we could have something added to the design rules for gentlemen regarding higher comp. hulls for these. That way other newbs won't wander the same path