Are we overdesigning destroyers?

[Guinness]

A while back, I used the line drawings in Friedman's US Destroyers to calculate the US flush-decker's average freeboard and seakeeping using SpringSharp. IIRC the seakeeping number came out being something like 0.20.

At the time, we all sort of dismissed that. Rocky called them nothing more than surfaced submarines (paraphrasing).

Well, anyway, tonight I decided to take a hack at the same experiment using Friedman's new RN Destroyers book, in this case using HMS Matchless, an M-class DD from the 1913-14 program. Her seakeeping number works out to be 0.21 on an average freeboard of 8.92 feet, with trim set way to the right. (SS below).

Also note the BC: 0.503. Friedman doesn't list BCs in this volume, but I've derived that from all the other measurements given.

At any rate, I'm planning on doing a few more of these during the holidays. My suspicion is our expections of destroyer seakeeping and freeboard are way way off, at least compared to OTL.

Maori, Great Britain Destroyer laid down 1914

Displacement:
   829 t light; 855 t standard; 972 t normal; 1,066 t full load

Dimensions: Length overall / water x beam x draught
   273.33 ft / 271.95 ft x 26.67 ft x 9.33 ft (normal load)
   83.31 m / 82.89 m x 8.13 m  x 2.84 m

Armament:
     3 - 4.00" / 102 mm guns in single mounts, 31.00lbs / 14.06kg shells, 1914 Model
     Breech loading guns in deck mounts
     on centreline, evenly spread, 1 raised mount
     Aft Main mounts separated by engine room
     2 - 1.58" / 40.0 mm guns in single mounts, 1.95lbs / 0.89kg shells, 1914 Model
     Breech loading guns in deck mounts
     on side, all amidships
   Weight of broadside 97 lbs / 44 kg
   Shells per gun, main battery: 120
   4 - 21.0" / 533.4 mm above water torpedoes

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 2 shafts, 38,682 shp / 28,857 Kw = 34.00 kts
   Range 2,530nm at 15.00 kts
   Bunker at max displacement = 211 tons
     Caution: Delicate, lightweight machinery

Complement:
   86 - 113

Cost:
   £0.155 million / $0.620 million

Distribution of weights at normal displacement:
   Armament: 12 tons, 1.3 %
   Machinery: 587 tons, 60.4 %
   Hull, fittings & equipment: 221 tons, 22.7 %
   Fuel, ammunition & stores: 143 tons, 14.7 %
   Miscellaneous weights: 8 tons, 0.8 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     163 lbs / 74 Kg = 5.1 x 4.0 " / 102 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.35
   Metacentric height 1.2 ft / 0.4 m
   Roll period: 10.3 seconds
   Steadiness   - As gun platform (Average = 50 %): 27 %
         - Recoil effect (Restricted arc if above 1.00): 0.09
   Seaboat quality  (Average = 1.00): 0.17

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.503
   Length to Beam Ratio: 10.20 : 1
   'Natural speed' for length: 16.49 kts
   Power going to wave formation at top speed: 76 %
   Trim (Max stability = 0, Max steadiness = 100): 82
   Bow angle (Positive = bow angles forward): 5.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      15.75 ft / 4.80 m
      - Forecastle (12 %):   14.67 ft / 4.47 m
      - Mid (20 %):      14.00 ft / 4.27 m (7.50 ft / 2.29 m aft of break)
      - Quarterdeck (7 %):   7.50 ft / 2.29 m
      - Stern:      7.50 ft / 2.29 m
      - Average freeboard:   8.92 ft / 2.72 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 205.3 %
      - Above water (accommodation/working, high = better): 54.1 %
   Waterplane Area: 4,845 Square feet or 450 Square metres
   Displacement factor (Displacement / loading): 31 %
   Structure weight / hull surface area: 28 lbs/sq ft or 137 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.54
      - Longitudinal: 0.85
      - Overall: 0.56
   Hull space for machinery, storage, compartmentation is extremely poor
   Room for accommodation and workspaces is cramped
   Ship has quick, lively roll, not a steady gun platform
   Caution: Lacks seaworthiness - very limited seakeeping ability

Misc weights:

8t: two torpedoes

EDIT: Modified the sim using the speed run at trials for top speed, in stead of SHP number.

[Tanthalas]

oh im fairly sure we do, although thats part of the reason I use steped deck hulls (I can up the seakeaping, Stability, and Fireplatform)

[The Rock Doctor]

It's likely we are.  This has been a recurring issue with pretty much anybody I've seen using SS.  Question is - should we set a minimum acceptable seakeeping level that would be adequate?  Folks can design down to it then.

[Tanthalas]

It's likely we are.  This has been a recurring issue with pretty much anybody I've seen using SS.  Question is - should we set a minimum acceptable seakeeping level that would be adequate?  Folks can design down to it then.

I wouold be in favor of shothing like that honestly.

[Guinness]

Let me do a spreadsheet of a bunch of OTL RN and US DDs. I suspect that will give us a useful average. It'll take a couple of days. I think I may do the same for some Cruisers and Battleships for which I have decent line-drawings to capture freeboard from too, just to see.

[miketr]

I look forward to your data.

I have long disliked what we have for TB's.

Michael

[miketr]

While you are doing the research, can you check for gun numbers and sizes?  I have long felt that the DD's we have in navalism are over gunned.  There are multiple examples of 10 gun DD's on less than 2,500 tons in the game.

Michael

[Tanthalas]

While you are doing the research, can you check for gun numbers and sizes?  I have long felt that the DD's we have in navalism are over gunned.  There are multiple examples of 10 gun DD's on less than 2,500 tons in the game.

Michael

I doubt we have multiple DDs packing 10+ guns on less than 2500 tons, especialy since AFAIK my and the Dutck 1K toners are the most over guned DDs in the Nverse (both only pack 5 guns).

and compleatly outside that point Spring Sharp was intended to sim ACs and Pre Dreads, im amazed it preforms as well as it is with DDs and other truely fast ships.

[miketr]

http://www.navalism.org/index.php?topic=690.msg36060#msg36060

Sorry just the Dutch it looks like but I did find many 5 gun DD's, one 6 and one 7.

Michael

[Tanthalas]

http://www.navalism.org/index.php?topic=690.msg36060#msg36060

Sorry just the Dutch it looks like but I did find many 5 gun DD's, one 6 and one 7.

Michael

oh we have tons of 5 gun jobs, but most of them pack fewer torpedos than similar historic ships did.  For example the US 1K ton jobs only had 4 guns but they all packed 8-12 Torps, where in the Nverse our DDs are more likley to pack 6-9 torps and ship 5 guns.

as to the J class JFC, I thought I was out there when I started thinking about 8 guns on 1500 tons... Oh and realy the 1500 ton cans didnt start turning up till 1930 or so OTL if I remember corectly

[Guinness]

Well off the top of my head:

most pre WW1 RN FDA starting with the "30 knotters" shipped a twelve pounder, 4 3 or 6 pounders, and 2 18 or 21 inch TTs, sometimes with 2 reloads. They all displaced between 400 and 700 tons light, and had decent but not gigantic fuel loads (I'll get that figure later). Speed on trial ranged from 27 up to 34 knots (but trial loads varied). The later boats, like the beagles, L and M classes had pretty big margins, so they absorbed decent depth charge loads later as well. Pretty much all of these also shipped a wireless set eventually.

So taking that example, yeah we're overgunning. Right before the war the Germans began fitting their boats with 88s, so the Brits went to 3x4" guns on about 800ish light and 33 knots with 2 tubes.

[Desertfox]

Yes, we are...

The Dutch monsters could shred ANY WWII destroyer with ease, and theres a few other designs out there that would make a Fletcher think twice. When I left N-verse a while back, the Van Hakes where big ships (3x4" 700 tons) now they are barely 'destroyers'. My Kidd class was originally designed as destroyer leaders and now are undergunned and had to be redisigned to a decent size.

My destroyers do have extreme range and good seakeeping, but that's due to their operating theater and being more like mini-cruisers than overgrown torpedo boats.

[Guinness]

I'm only about 6 ships into this analysis, all RN destroyers of the pre-WW1 period. What I've found so far is that freeboard slowly increases with their size, but once raised forecastles were adopted, there's a nice steady curve there. However, the theoretical maximum speeds increase, so "seaboat quality" declines.

So on first impression, I wonder if we might not ditch seaboat quality largely as a way of evaluating DDs, but rather look at some straight avg freeboard vs. speed  vs. length concept.... Something to discuss while I work I guess.

Also, incidentally, Friedman has a great discussion of what conditions RN destroyers were "trialed" under. The RN made great pains to try to find a "realistic" trialing regime, running ships starting with full fuel loads, etc. etc. Especially with their oil fired boats, SS is actually doing a pretty good job of simming their speed right up to the 34 odd knot L and M class. I find this interesting. In almost all cases, I'm just using engine year = lay down year for simplicity here.

When I'm done, I'll post a bunch of the SS's too, so others can compare.

[Walter]

So on first impression, I wonder if we might not ditch seaboat quality largely as a way of evaluating DDs, but rather look at some straight avg freeboard vs. speed  vs. length concept.... Something to discuss while I work I guess.

Actually with the simming of the historical DDs and TBs of Japan, I pretty much ignored the seaboat ratings I was getting, especially with the TBs.

[P3D]

There issues with simming destroyers can be originated to three main problem:
1. Seakeeping as noticed above
2. N2/3verse Wesworld-based rules give too much extra strength for decreased speed. I still think that some of my suggestions would have solved it adequately.
3. Torpedo mounts are too light. When I wanted to make torpedo tubes weight twice as much, I was shouted down that how I dared to think about it.