Tony DeGiulian at NavWeaps had some suggestions for sources

Tony DeGiulian, from NavWeaps.com, had a suggestion for the source that would have weights for gun directors and included some example weights. He says that the source for director weights is John Campbell's book Naval Weapons of World War II. I never had any interest in this book until I found that I needed weights for fire control directors so that I could better calculate metacentric heights for WWII ships. I may need to consider that for WWI ships, as well, but hadn't seemed to need that information.

Fire Control Directors

In analyzing American cruiser designs from the 1930's, I find that to correctly model them, I need to allow for Fire Control Directors, their weight and their position, so that they affect stability correctly. For the Radar era, that needs to be included, as well. My approach would be to have a Fire Control Director database and a Radar database. A ship specification would have room to list directors, by type and height to their base from the keel. The stability calculations would need to factor them in, when appropriate.

Cruiser guns

In the Southwest Pacific in 1942 and 1943, the Americans found that he 8in/55 gun had too slow a rate of fire while the 6in/47 gun was outranged by the "Long Lance" torpedo. The 6in/47 gun could fire 10 rounds per minute, and the Brooklyn class had 15 of them. They could fire so rapidly that you could see a stream of shells heading for the target.The US might well have benefitted from a 175mm gun with a 176 lb. shot. The US was building 175mm guns for the Army, so it was a known caliber, although not in the Navy. Concievably, they could have built a new gun with a 16cm or 16.5cm caliber.

The Atlanta class cruisers (CL-51)

I have been experimenting with testing designs based on real ships to see how they compare with what is computed. Earlier today, I tried the Atlanta class cruiser, and found the phenomenon that Frank Fox had told me about. For the Atlanta class to reach their measured speed at a given SHP, their propulsion efficiency would need to be adjusted. Thanks to Friedman's book about American cruisers, I have the real coefficients (Cp and Cm), as well as accurate dimensions. There are also figures about speeds, displacements, and power. I found that to reach the correct speed, that the propulsion efficiency needed to be adjusted to 0.53. For those who are interested, the coefficients are: Cp=0.603 and Cm=0.832. Those are destroyer-like figures, from my experience.

Motor ships

The Admiral Graf Spee had machinery that generated 54,000 HP with a weight of 1,648 tons. That is a HP/weight of machinery ratio of about 32.77 HP/ton. The machinery space volume seems to have been something like 171,000 cubic feet. That would mean 3.167 cubic feet per HP. I've tried an example ship based on this type ship. The gun I will use is a 11in/50 gun firing a 718 lbs. shot. The muzzle velocity is 2,764 ft/sec. I'm having some trouble getting the metacentric height low enough. For better or worse, this is a typical problem. The good thing about this design is that the ship with this gun would be much stronger than any conventional cruiser. The standard displacement is 11,460.9 tons. The maximum range is 14n438.1 nm. That is with an armament of 6-11in/50, 8-6in/50, and 6-4in/50 guns. The belt is 3.3in. That is thicker than a real panzerschiffe, but not by much. The speed is 27.6 knots at normal load and 26.9 knots at deep load.

Battleship-Cruisers

After William Hovgaard described the "Battleship-Cruiser" as a type in the early 20th Century, that prompted people to think in new ways about ship types. The Italians and Japanese were actually early adopters. At the time of the Russo-Japanese War, the Japanese designed armored cruisers with 4-12in guns. The Japanese had also hoped to build a ship like Colonel Cuniberti's "Ideal Battleship for the British Navy" (1903), but they didn't have enough 12in guns. They had to settle for a "semi-Dreadnought" with a mix of 12in and 10in guns. The Colonel Cuniberti designed the Roma class fast battleships that had 2-12in guns and a fairly high speed (21.5 knots). The 1921-type British battlecruisers could have been classed as fast battleships, as the Hood almost was. The late 1930's fast battleships were exactly what William Hovgaard envisioned.

The reality is that ship sizes were limited by a number of factors

Often, the size of ships was limited by budgetary factors. There was also a strong British navy prejudice, at least in some quarters, against really large ships. In the "1921" design process, for example, they had to back off from 18in-armed battlecruisers and accept 16in guns. The battleships were still to be armed with 9-18in guns, but the battlecruisers had to have smaller. The battlecruisers were really fast battleships, but were only limited in armament, not armor or speed. They were really much better ships than the so-called fast battleships built in the late 1930's and early 1940's. The American ships were especially underwhelming. The worst were the North Carolina class. Their problems were partially corrected in the South Dakota class. At least, the South Dakota's were structually sounder and better protected.

The DreadnoughtProject.org website

Tony Lovell pointed out this website to me, recently. The site is called The Dreadnought Project, and has some really impressive 3D models, as well as scans of German plans from the 1890's up until 1918 or so. He is using a 3D modeling tool called Rhino 3D (or Rhinocerous) that does NURB modeling. It gives really impressive results. I just downloaded an evaluation copy.

A Question: how much should ship characteristics be constrained by date?

I ask the question about whether a high-level ship design program should restrict characteristics by date. I think that political considerations could reasonably be waived, if in an alternate world situation where you were designing your own ships and building program, you could possibly specify a ship in 1905 that had 8-20in guns and 15in armor. Reasonably, the guns could be 20in/35 or 40 caliber, and the size would be less. The look would be transitional between pre-dreadnought and dreadnought. The size would still be large, but there could be restrictions against using triple turrets. I'm choosing an extreme case. More normally, you might restrict ships to being under 20,000 tons and to 12in/45 guns at the upper end. You could also restrict SHP/ton of machinery to 10.0, as was the case for British battleships up until 1912. Battlecruisers had better powerplants than that, but only marginally. So, that is the question: by year, what should be premitted with respect to ship characteristics?

Japanese Cruisers: SHP/ton of machinery weight

Since I am interested in ship design, I thought that computing the SHP/ton of machinery for some representative Japanese cruisers. For better or worse, I am generally using trial data for SHP.

• Tenryu 59,844 SHP 1042.9 tons 57.38 SHP/ton 1919
• Kuma 91,229 SHP 1588.1 tons 57.445 SHP/ton 1920
• Nagara 92,670 SHP 1630.3 tons 56.84 SHP/ton 1922
• Yubari 61,336 SHP 1056.5 tons 58.056 SHP/ton 1923
• Aoba 103,003 SHP 2173.7 tons 47.386 SHP/ton 1927
• Haguro 132,568 SHP 2689.5 tons 49.29 SHP/ton 1929
• Mogami 154,266 SHP 2477.3 tons 62.27 SHP/ton 1935
• Kumano 153,698 SHP 2358.1 tons 65.18 SHP/ton 1937

Now, let's design the cruiser analog to the "moderate dimensions" battleship

I have been experimenting with a battlecruiser analog to my "moderate dimensions" (for 1921) battleship. The battlecruiser has the same armament (9-15in/45 and 16-5.5in/50 guns) and can make 31 knots at normal load. The normal displacement is 30,237 tons (at the present), and has dimensions of 814ft x 95ft x 29.8ft. The coefficients are: Cp=0.53 and Cm=0.90. The armor basis is 9in. This is only a preliminary cut, as I haven't made a drawing, yet. Without a drawing, you can't be sure that everything will work.

The "Moderate Dimensions" trap

Lord Brassey, and many others got caught up by the "Moderate Dimensions" trap. The argument stems from the knowledge that in sailing naval warfare, you didn't build a fleet of 100 gun ships, you built a fleet with a few 100 gun ships and many 74 gun and 64 gun ships. Logically, they thought the same idea should hold true in navies of ships built of steel and powered by steam. The counter argument is that you will end up with small ships, simply by the passage of time, as your latest ships will dwarf those built 5 years earlier. The biggest ships are the best armed and best protected, and nothing else can stand up to them. So don't build small, more lightly armed ships, as they are a waste, and will be defeated.

I've fallen into the moderate dimensions trap, myself, in that I'm interested in a smaller battleship, built to 1921 standards, with 9-15in/45 guns and 16-5.5in/50 guns. The speed would be 24 or 25 knots with a 32,500 ton displacement. The ship would be suitable for convoy escort and operations in secondary theaters. They could still put up a credible fight against stronger ships, although they would be unable to fight the really big ships with 18in or larger guns.

The obvious thing to do now would be to try and make a Capitani Romani-style ship

What would a "Capitani Romani" style ultra-fast cruiser look like? It would be small. With a standard displacement of about 3750 tons, the normal displacement should be about 425o tons. The design would be moderately larger than my GB/CL/1921e ship. I think that dimensions should be 462ft x 45ft x 16ft with coefficients of Cp=0.66 and Cm=0.86. The power plant should be very lightweight but high power. I need to experiment to see what can be done. For my design, I would have 6-5.5in/50 guns (510 lbs broadside). It probably should have 8 guns, or should have 8-5.1in/50 guns. I'll have to see how this works in my program. The answer is that I was able to make the design work, but with a very high power-weight ratio. The revised dimensions are 462ft x 43ft x 13.6ft. The hull depth is 30.5ft and the normal displacement is 4,184 tons. The ship can reach 41 knots at normal displacement and only 36.8 knots at a deep load displacement of 5569 tons. The stability is adequate, as the metacentric height at normal load is 2.2ft and 3.96ft at deep load.

I'm working on a small cruiser design

Given that I have a 5.1in/50 gun design, the next idea was to create a small cruiser design for use as a convoy escort and cruising ship. I want to have 8-5.1in/50, as that has a broadside weight in excess of 500 lbs (568 lbs). I correctly guessed that 29 knots was possible at normal load. That is with a designed power of 40,000 SHP. The challenge is stability. My current compromise is to reduce the range, and raise the metacentric height, slightly, to get the normal displacement down under 3,800 tons. That still gives a metacentric height of 2.014ft at normal load. That is sufficient for such a small ship. The range of stability would still be great enough to be safe. The crusing range at normal load would be 2,780 nm and at deep load would be 7,078 nm. The dimensions are 439ft x 43ft x 13ft with coefficients of Cp=0.61 and Cm=0.88. The secondary battery is 8-3in/50 in twin mounts for AA use. The 5.1in/50 gun is also capable of 45 degrees elevation and AA fire. The ship has a 1in deck and 2in side armor.

The 5.1in/50 gun

The British came very close to adopting a 5.1in gun similar to that used by the Germans and French. The actual caliber was 13cm, but the gun was typically referred to as a 5.1in gun. With a heavy shot, this gun is also quite potent for its size. The piece would weigh 5 tons and has a 71 lbs shot. The muzzle velocity is 2774 ft/sec. The gun performance looks like this:

               Maximum penetration: 13.33 inches


     Elevation          Range            Belt       Deck

       1.9 deg        4100 yards          8 in
       3.6 deg        6400 yards          6 in
       7.1 deg        9800 yards          4 in
      12.8 deg       13300 yards          ...        1 in
      18.6 deg       15600 yards          2 in
      27.1 deg       17900 yards          ...        2 in
      47.7 deg       19300 yards          ...        3 in


     Maximum range = 19500 yards at 42.5 deg elevation

The 7.5in/50 gun performance

There is a striking difference between the 7.5in/50 gun firing a light projectile at high velocity and a heavy projectile at a lower velocity. This is what the performance looks like for the 200 lbs AP Shot at 2948 ft/sec:

     Elevation          Range            Belt       Deck

       1.3 deg        3500 yards         14 in
       2.1 deg        5100 yards         12 in
       3.2 deg        7100 yards         10 in
       4.9 deg        9400 yards          8 in
       6.6 deg       11300 yards          ...        1 in
       8.0 deg       12600 yards          6 in
      14.5 deg       17200 yards          4 in
      16.7 deg       18400 yards          ...        2 in
      25.9 deg       22100 yards          ...        3 in
      35.4 deg       24400 yards          2 in
      36.6 deg       24600 yards          ...        4 in


     Maximum range = 25200 yards at 44.5 deg elevation

This is the gun with a velocity of 2691 ft/sec and a shot weight of 240 lbs:

     Elevation          Range            Belt       Deck

       1.1 deg        2500 yards         16 in
       1.9 deg        4200 yards         14 in
       3.0 deg        6200 yards         12 in
       4.7 deg        8500 yards         10 in
       6.0 deg       10100 yards          ...        1 in
       7.2 deg       11400 yards          8 in
      11.6 deg       15200 yards          6 in
      15.0 deg       17400 yards          ...        2 in
      21.2 deg       20700 yards          4 in
      22.4 deg       21200 yards          ...        3 in
      30.7 deg       24000 yards          ...        4 in
      40.1 deg       25700 yards          ...        5 in
      48.1 deg       25800 yards          2 in


     Maximum range = 26000 yards at 44.7 deg elevation

I find it pretty amazing how more potent the gun is with the heavier shot.

The 7.5in/50 gun

The 7.5in gun seems like a very "pre-Dreadnought" caliber. I just designed a gun that is a 7.5in/50 gun weighing 18.75 tons. That would be the weight without the breech. I've gone ahead and used the standard shot weight of 200 lbs. The muzzle velocity is 2,948 ft/sec. That is sufficient to do a good bit of damage at relatively close range. The shot would rapidly lose velocity, as the shot is only 0.474 of the cube of the shot diameter in inches (a useful empirical relationship). A better shot weight would be at least 210 lbs or greater. 210 lbs is about 0.5 of the cube of the gun caliber. A really heavy shot would be 240 lbs (similar to the 15in/42 shot).

A moderate-sized heavy cruiser design with 9-7.5in/50 guns

I don't know how viable the design is, but I thought last night that I would like to try an Exeter-type heavy cruiser (moderate dimensions) with 9-7.5in/50 guns. That gives a heavier broadside than 6-8in/50 guns and probably is superior from a gunnery perspective. I know that the British didn't like the 9-gun layout, but the ship would be able to fire alternate 4 and 5 gun salvos. That should be superior to 3-gun salvos from an Exeter. The normal displacement is 9,070 tons with dimensions of 590ft x 60ft x 16.7ft. The designed speed at the normal displacement is 32 knots and not quite 31 knots at deep load. The maximum range, at 15 knots, is 10,090 nm. The belt is 3in and 16ft wide and the decks are 1.5in + 1in. The range at the normal load is only 4,030 nm at 15 knots. The normal fuel carried is 685 tons and the additional fuel carried at deep load is another 1,030 tons. I've designated the design as the GB/CA/1921d.

Details about the GB/CL/1921d type

Tonight, I fleshed out the British 1921-style commerce protection light cruiser. It came out with a Washington Naval Treaty Standard Displacement of 7,160 tons. The dimensions are 555ft x 57ft x 16.6ft, with a normal displacement of 8,060 tons. The belt is 3in and is 16ft wide and 350ft long. The barbettes and turrets are also 3in. The decks are 1in + 1in, amidships. The metacentric height at normal displacement is 5.27ft. The normal range at 15 knots is 4,451 nm. The maximum range is 10,175 nm. The speed at normal displacement is 32 knots and at deep load is 30.75 knots. The armament is 9-6in/50 and 6-4.7in/50 guns. The machinery is arranged using the unit system and is 48 SHP/ton of machinery.

A light cruiser for trade protection (1921-style)

Major navies had a definite need for a light cruiser for trade protection (in the period from 1903-1945). For 1912, an 8,000 ton ship is a very reasonable size. My initial estimate for dimensions would be 555ft x 57ft x 18ft, with coefficients Cp=0.56 and Cm=0.88. This is only very slightly more than 8,000 tons. I would like to see a speed of 32 knots, as that seems to be the minimum acceptable speed at normal displacement. I would go with a 9-6in/50 gun armament with a secondary armament of 4.7in/50 guns.

The GB/CA/1921c1 armored cruiser design

It turns out that the GB/CA/1921c1 design can reach 32 knots after all. This is my compact armored cruiser design with 9-9.2in/50 and 6-4.7in/50 guns. The belt is 6in and 16ft wide. The citadel is 372ft long. The deck armor isn't even too bad. I reduced the upper deck to 2in while lower deck and slopes stayed at 2in as well. While the designed displacement is 14,700 tons, the Washington Naval Treaty standard displacement is just 13,426 tons. The speed at deep load is 31 knots. The range at normal fuel load of 950 tons is 4,142 nm. The maximum range is 12,209 nm. Both are at a cruising speed of 15 knots. The design has a 6in CT and a 4in comm tube. There are two stacks with funnel caps.

My revised 9.2in gunned armored cruiser

I did some more work towards revising my 1921-style armored cruiser with 9-9.2in/50 guns. I rolled back to a much smaller ship: 14,700 tons, dimensions of 635ft x 70ft x 23ft, Cp=0.56, and Cm=0.90. I need to run the revised design through my program to see how the design is fleshed out by my program. I am looking at a 6in belt, hopefully 16ft wide. I am into the "all or nothing" philosophy, so the citadel will be fairly short on a 635ft ship.

This is too big a ship for the armament

My impression is that this design is too large for the armament. I've started an inboard profile drawing, and the turrets look very small in relation to the ship size for a 721ft long ship.

A triple 9.2in/50 turret

I am probably the only person in the world interested in this, but I calculate the barbette diameter give the caliber of the gun and the number of barrels per turret. For the triple 9.2in/50 turret, the barbette diameter would be 26.6ft (rounded). I always figure that 60% of the barrel protrudes from the turret face, so in this case, the guns would protrude 23ft.

A 1921 "armored cruiser"

I've started the design process for a 1921-style "armored cruiser". I am experimenting with an armament of 9-9.2in/50 and 6-4.7in/50 guns. The side armor, initially is 6in. I'm not sure what power or anything else would be appropriate. I still like 32 knots but could live with 31 knots. I must not have a 9.2in/50 gun defined, as I got the usual "not-a-number" result for metacentric height. That is a sure sign of an undefined gun. I ran the gun program to calculate the muzzle velocity for a 50 caliber 9.2in gun (I'm going with 2,900 ft/sec). The preliminary dimensions are 721ft x 84ft x 48ft depth. The draft at normal load is 26.4ft. Design is an iterative process, and I don't have an inboard profile, yet, so this is very preliminary. My belt, amidships, is 7.5in KC, 16ft wide (two decks high). My designed speed is 32 knots at normal load and 31 knots at deep load. I'm hoping for a maximum cruising range of 10,000 nm.

The slower heavy cruiser design

The rationale for a slower heavy cruiser design would be to have greater protection. Even if slower, the minimum speed should be 32 knots. My designs are generally low, so they tend to have too much stability, before I take measures to raise the center of gravity. By shortening the hull and lowering the power, a 16-foot wide belt, 3 inches thick can be carried. There is almost excessive deck armor: 3in + 2in amidships. That's with my favorite armament for a heavy cruiser: 9-8in guns. I like the 9.2in/50 gun, as well, but it takes a larger ship.

A fast, 1921-style heavy cruiser

After having finished my first cut at a faster 1921-style light cruiser (37 knots), I decided to do a fast heavy cruiser design with 9-8in/50 guns. I used Rick Robinson's "Big Gun" program to aid my gun design effort. It would have been nice if his program would estimate the weight of the piece, but it doesn't. I use a formula: D^3 x Length in Calibers / Constant to determine the weight in tons. The only reasonable thing to do is to look at example guns to determine the constant. I used 1365.33 as the constant. I derived that from the 7.5in/50 gun (for better or worse). The idea is to have a heavy cruiser that is capable of more than 35 knots at normal load, carries 9-8in/50 guns, and has a 10,000 mile maximum cruising range at 15 knots. The speed at deep load is about 34.4 knots (at 15, 337 tons).

Tweaking the GB/CL/1921 Design

I am interested in further modifying the GB/CL/1921 design. One thing I want to experiment with is to move the forward guns further towards the bow. I also want to do away with the semi-superfiring 4.7in/50 guns, at the forward and after parts of the superstructure. I would put all the 4.7in/50 guns on the broadside (3 per side). I want to move the funnels forward, as well. I might even try to increase the machinery power, if there is volume to expand further.

My rationale for high-speed ships is for strategic mobility

I'm all but convinced that the Italian Captani Romani class scout cruisers would not be able to reach 43 knots in service. If they had, they would be the ideal ships for operations in the Mediterranean Sea. Their range-speed combination gave them ability to stage mining operations at night at a considerable distance. The British Abdiel class were an attempt to perform a similar mission, but with a less-capable ship. I have to agree with the American view that speed for tactical purposes is less important, once we got past the point of fighting Jutland-style battles. The ability to move ships a considerable distance in a short time is still a needed capability, even in modern times. In WWII that ability was needed even more than now.

Warship Speed in the early 20th Century

I have mixed feelings about the utility of speed in warships during the period from 1903 to 1945. For one thing, the period is not uniform. From the 1920's on, airpower had become a major factor. Prior to 1914, airpower was essentially a non-factor in operations.

During that time, the tactical value of speed was clear. The more speed, the greater the tactical advantage. After 1918, not all navies agreed on the importance of speed. In Britain, they were about ready to only build fast battleships (called battlecruisers, but heavily armored and gunned). In the U.S., the authorities dismissed the value of speed and were ready to build 32 knot cruisers rather than emulate the Japanese. The Japanese retained their mania for speed. The Nagara class were intended to be 36-knot ships. The original intent for the "10,000 ton cruisers" was for them to be 35-knot ships. They retained that desire right up until 1941. Having fast cruisers gave them ideal companions for fast aircraft carriers.

Specs for my 1921 super destroyer

Continuing my obsession with radical ship designs is my GB/DL/1921 super destroyer. The idea is that construction would have commenced in 1921.

• Year: 1921
• Length: 376.0 ft
• beam: 40.0 ft
• Hull depth: 26.0 ft
• Design displacement: 2840.0 tons
• Cp: 0.66
• Cm: 0.82
• Machinery Wt. Basis: 66.0 SHP/ton
• Hull Wt. Basis: 3.00 x 10^-3
• FreeboardForward: 25.0 ft
• FreeboardAmid: 13.0 ft
• FreeboardAft: 15.0 ft
• Designed SHP: 75000.0
• Designed Speed: 36.0 knots
• Board Margin: 50.0 tons
• Electrical Power KW: 300.0
• Main Batt Gun Type: 4.7in/50
• Main Batt guns: 5.0
• Main Batt Mount Type: shield
• Normal Fuel: 200 tons
• Extra Fuel for Deep Load: 250 tons

This is the drawing of my "fast escort" (GB/DD/1921)

I decided that I needed a "fast escort" for the high-speed battlecruisers. This is the drawing of my first attempt at such a design (GB/DD/1921).

This is my GB/CL/1921b light cruiser design

I revised my design for the GB/CL/1921 light cruiser, today, to implement several improvements, including higher speed. This is my drawing of the ship.

Drawing of the GB/CL/1921a design

This is my drawing of the GB/CL/1921a design which I originally designed in May 2002.

A fast escort

I have the design for a fast escort, a large destroyer-type. I wanted to have a suitable screening vessel for fast battlecruisers. Even a 2800 ton ship will lose speed in a seaway, but a 2800 ton destroyer leader behaves better than a 1400 ton destroyer. I have settled for a ship that can easily reach 37 knots at normal load. I had experimented with a version that could exceed 38 knots, but backed off because of the size (over 3200 tons). With only 5-4.7in/50 guns and 3-21in torpedo tubes, the ship is underarmed, but I didn't want twin mounts or larger guns. The dimensions are 376ft x 40ft x 12ft with coefficients of Cp=0.66 and Cm=0.82. The metacentric height (GM) is 3.72ft at normal load and 4.48ft at deep load. The normal range is 2,212nm at 15 knots and the maximum range is 4,977nm at 15 knots. The Washington Naval Treaty Standard Displacement is 2,435 tons.

A 36-knot light cruiser

I was curious whether a light cruiser of the size and technology of my 1921 design might be able to reach 36 knots. I had an idea that the answer would be yes, as the Japanese Nagara was a small, 36-knot design. I just did some calculations at a greater power and found that the boiler room and engine room size needed could be accomodated in a 572 ft 7750 ton ship. The boiler and engine rooms would only need to be expanded to 166ft x 42ft x 20ft (boilers) and 117ft x 42ft x 20ft (engines).

My 1921-style light cruiser

I had done a 1921-style light cruiser with 9-6in/50 guns and 6-4.7in/50 AA guns, and when I did weight, stability, and volume analysis, the design worked. I had to resized engine rooms and boiler rooms, but I had allocated adequate space, at least when using a contemporary SHP/ton measure. I had allocated too much space to boilers and not enough to engines. The dimensions are 572ft x 54ft x 15.7ft at normal displacement. The coefficients are Cp=0.61 and Cm=0.90.

Picture of the "Super-Fast Battlecruiser Alternative 2"

I just finished a drawing of the Super-Fast Battlecruiser, Design Alternative 2. This is the first time that I have actually done the volumes analysis for the boiler and engine rooms, so that the drawing accurately reflects what is needed for the design "to work".

More about the "Alternative Super Fast Battlecruiser" design

By moving the turrets closer to the ends (although the fore turret is 175ft from the forward perpendicular and the after turret is about 140ft from the transom), I was able to fit in enough volume for a 400,000 SHP machinery, albeit at 48 SHP/ton. That lightened the normal displacement to 32,544 tons, and with a length of 821ft, that was sufficient to achieve a very wild 39 knots. At a deep load displacement of about 37,126 tons, the ship can still make 37.6 knots. I chose a cruising speed of 18 knots, so the cruising range at normal fuel load is only 1,609 nm. At deep load with extra fuel the range is 5112 nm at 18 knots. That would be sufficient for a quick deployment to the Western Hemisphere.

I'm working on an "alternative" 1921-style "Super Fast Battlecruiser"

My modified design is flush decked with a transom stern. The bow is flared and rises to about 36ft above the waterline. To accommodate very highpower machinery, I have had to lengthen the citadel. That pushes the forward 17in/45 twin turret at least 50ft further forward. The bridge structure is reminiscent of what Edward Attwood and Stanley Goodall were using on the "1921" ships that were being designed prior to the Washington Naval Treaty. The machinery follows the "unit system", and pushing the forward turret further towards the bow gives more of a cruiser look than the design previously had.

Volume analysis is difficult, due to lack of data

I have temporarily been hung up on doing volume analysis in my program. I have the engine and boiler room volumes handled, but everything else is problemmatic. I SHOULD be able to do analysis on armament, but equipment and things like that seem out of reach, for now. The best I could do right now is to pull numbers out of the air. I'm not totally opposed to that, but I would rather do better.

I'm surprised (but maybe shouldn't be) that the shorter ship could be faster

A variant of my "super-fast battlecruiser" can reach 39 knots, and since the maximum waterline length is just 814ft, as opposed to the so-called "29,000 ton battlecruiser", which a variant was 865ft, I would have thought it might be slower. I suppose the issue is that the "super-fast battlecruiser" variant is lighter, being only 32,832.1 tons, while the longer ship is much heavier, being 39,025.2 tons. The heavier ship can reach 38 knots, which I suppose is an achievement for such a large ship. Both ships are odd types. They are like nothing ever contemplated. The closes thing to them were the British light battlecruisers such as the Glorious and Courageous and the German design studies from 1917 and 1918. The GK 3022 was designed for 34 knots and had four large guns in two turrets.

Six shafts on a narrow ship

Certainly this is a pretty outrageous thing to contemplate, but I find a compelling desire to find a way to have six shafts and engines. My approach is to use very light, high power per weight machinery, which implies smaller machinery, and to have a destroyer-like shafting, where the shafts angle down from the horizontal. It may be a bad idea, but I would also angle them out, very slightly. That would certainly reduce their efficiency, in that the main thrust would not be on the centerline of the ship, which is the most desirable arrangement. I would also crowd the shafts together so that there might be some undesirable turbulence between propellors and adjacent shafting. I would either have a round, destroyer-like stern or else would actually go to a wide transom. A wide transom would have some beneficial effects at high speed, although it would also increase drag at lower speeds.

Hitting the wall...

An interesting feature of powering ships fast is that you can reach a point where the cost in increased SHP to increase speed by a knot is prohibited. I just experimented with this fast battlecruiser type to see if with the maximum SHP, with six shafts, if 39 knots would be possible. The answer is no. The best that can be done is about 38.5 knots. As it is, the ship is designed to be a "hotrod". At least, the ship is pretty well protected for being a very fast battlecruiser (16ft-wide 8in belt, with heavy deck armor).

The "so-called" 29,000 ton battlecruiser has the usual issue

The 29,000 ton battlecruiser has this issue, in that the silhouette is so low, that I have been having great difficulty in raising the center of gravity. Part of the issue is that I wanted at least 36 knots speed, if not 37 knots. To do that, the displacement shot up to 34,222 tons. The original intent was to achieve 38 knots, which would take 6 engines and shafts, due to the "70,000 SHP limit". I may yet try an "alternative design" that would test what it would take to reach 38 knots. I have done all the obvious things to raise the CG, and it is still too high. I'm not prepared to modify the "basic look" of the ship. The ship was intended to carry 4-13.5in/45 guns at 38 knots on 29,000 tons. That seems way beyond reach, just as Colonel Cuniberti's "Ideal Battleship" couldn't be achieved on the 17,000 ton displacement. To stay at that size, I chose to reduce the armor, until it became a "battleship-cruiser". In this case, the basic looks of the "29,000 ton battlecruiser" was similar to a light cruiser. Given the dimensions, that creates a great difficulty with metacentric height. It also demands light cruiser-style machinery, to achieve an reasonable weight and volume on the boiler rooms and engine rooms.

The 29,000 ton battleship design

Thanks to Blogger, I just lost what I had written about testing my Warship General Design computer program. The 29,000 ton battleship design seemed like a good test case for the program. There was the drawback that I did not have as much information that I would have liked from 30 years ago. I just had the basics, and would have to augment that in the ship specification. This is the basic specifications as originally conceived:

• 29,000 tons displacement at normal load
• dimensions: 620ft x 95ft x 30.2ft
• Cp=0.59
• Cm=0.97
• Armament: 6-13.5in/45 and 10-6in/50
• Machinery: 40,000 SHP

I found out quickly that I needed to decrease the Cp. I decided to go with 0.54, although lower would have given a higher speed. That alone raised the maximum speed to over 23 knots. I also found out that I needed to raise weights to decrease the metacentric height (GM). The ship is basically short and wide, so that inherently implies a high GM. I decreased the lower belt to 13in and increased the upper deck to 5in. I also included "upper deck side" armor. That lowered the GM at normal load to 4.92ft and at deep load to 6.77ft. The latter is still almost too large, but that is what seems reasonable.

Machinery volume and SHP/ton

I had not really been aware of the volume issue, although I knew that some of my designs might have problems with insufficient volume for the machinery. Boiler room volume per SHP looks like a hyperbolic function where the volume per SHP is a function of the SHP/ton of machinery. I have plotted this over the range of 10 SHP/ton up to 75 SHP/ton, so I have a reasonable coverage. I have some fast battlecruisers designs that work strictly from a weight analysis, but would fail on volume, if the SHP/ton were not increased. I also have realized that I need to be able to specify the "vitals" height, as a destroyer "vitals" would occupy the full depth, minus a double bottom, if there was one. A battleship would have the "vitals" below the armor deck.

I'm doing all this empirical work to calculate volumes

I finally have my calculations for engine room size working, on a "per engine basis". I have been studying WWI ship engine room volumes. I have thought that you necessarily have to base the size on the "SHP/ton of machinery". It is not linear, as you might expect, although I am using a piecewise linear solution for part of the equation. I am using the equation for a line (y=mx+b), but I am computing the m and b using the SHP/ton weight basis. That seems to be working. Last night, I was really concerned that the engine room sizes were going to be so large as to be not workable. The next step will be to estimate boiler room sizes.

The next step is to add "volume" analysis

I am now contemplating adding "volume analysis" as the next feature of my Warship General Design program. Everything takes up space: boilers, turbines, turbogenerators, steering gear, fuel, crew (about 22 cubic feet per man is average), armament, stores, and equipment (and more).

New features to my Warship General Design program

You now specify normal fuel and the additional maximum fuel weights in tons and the cruising speed in whole knots. I calculate the normal range and the maximum range in nautical miles. The power consumed for the electrical power generation is a factor in the range calculations.

I want to add range calculations for specified cruising speed

It would be tempting as a next step to add the range calculation at a specified cruising speed, as Frank Fox showed me two years ago. For now, I will not automatically calculate the optimal Cp, but do the calculation and let the program's user rerun with the calculated Cp, if they want.

There is a different optimal Cp at legend and deep load displacements

At least for the "Super Fast Battlecruiser-Alternative Design", there are different optimal Cp's. At legend displacement of 34,339.9 tons, the optimal Cp is 0.61 with a Cm of 0.91. This produces a maximum speed of 37.8853 knots. At deep load displacement of 39,697.6 tons, the best Cp is 0.56, which produces a maximum speed of 36.7051 knots. The actual best speed with the designed Cp of 0.61 is 36.6468 knots, which is not significantly different. I need to decide if I am going to let the program design the Cp. My power curve calculation computes the draft at the displacement and form coefficients, so that is not a problem. I would need to use the resulting draft in stability calculations, as well.

I've tryed opimizing and found that the smaller the Cm as possible, the better

I need to change my attempt at optimizing hull form, and only optimize for Cp (prismatic coefficient). There is the issue that the best Cm is at 0.8, the lower end of what I tried. My take is that I just need to use the designed Cm and optimize Cp, only. It actually turned out that all I had to do was provide a flag to determine where to write the output to the log file, or not. That allowed me to repeatedly run the function for determining the actual speed for a given SHP, and use that in the optimization process.

Winston Churchill on Destroyers

Winston Churchill likened building slow destroyers to breeding slow racehorses. He had wanted to build 35-knot destroyers in the 1912-13 estimates, but ended up building the L-class ships which were designed to be 29-knot ships. The problem wasn't corrected until the M-class in 1913-14 estimates, which were nominally 34-knot ships. That was a huge improvement over what they had been building: small, conservative destroyers. They were handicapped by a school of thought that believe that destroyers were only to protect the fleet against enemy torpedo attacks, rather than for use in offensive action.

The "Super Fast Battlecruiser": experiments

I have tried a 6-shaft plant for the battlecruiser and found that it is hardly worth the effort. Increasing the power to an outrageous 380,000 SHP only gets 37.885 knots at 34,339.9 tons. The dimensions were 812ft x 87.5ft x 30.47ft with a Cp of 0.61 and a Cm of 0.91. I was able to increase the protection:

• main battery turrets: 11in basis (greatest thickness)
• main battery barbettes: 9in basis
• lower belt: 9in
• upper belt: 6in
• deck forward: 2in
• deck aft: 3in
• a/t bulkhead: 1.5in
• shields on 4in guns: 1in

Metacentric height at legend displacement (GM)=5.25 ft

I have looked at Greg Locock's DreadCAD Excel spreadsheet

I had seen Greg Locock's DreadCAD spreadsheet about 3-1/2 weeks ago, but only looked at it more seriously, yesterday. My "response" to seeing it is to consider writing a program to generate lines for ships using Taylor's Standard Series. Basically, there is a family of curves of cross-sectional areas, there are cross sections of known area, and we could programmatically interpolate new, evenly spaced cross sections and generate a spreadsheet, which we could use to draw the lines for printing. I will need to assess the best was to viewable lines, but having the lines described as points will allow us to apply Simpson's Rule to the lines to do various calculations. I like Greg's approach, because he got me to rethinking what could be done programmatically.

I've been doing some experiments with Cp and Cm

I have been tweaking the specs for my Ger/CS/1905 scout cruiser and the "Super-fast" battlecruiser to maximum speed. For the battlecruiser, there is the 70,000SHP/shaft limitation that has an effect. I thought it odd, but the lowest Cp doesn't give the highest speed. This is close to the best that can be done:

At Displacement=30949.2 tons
Length=804.0 ft
Beam=87.0 ft
Draft=28.2078 ft
Cp=0.61
Cm=0.9
Cb=0.549
DLR=59.5498
Wetted Surface=79812.8 sq. ft.
B/H=3.08425

At speed of 35knots power is 223938.0 SHP
At speed of 36knots power is 258375.0 SHP
At speed of 37knots power is 301770.0 SHP

actual speed for 280000.0 SHP is 36.4983 knots

I've wondered if optimizing Cp and Cm would be a worthwhile exercise. I would iterate over two ranges, looking for the highest speed for the maximum SHP.

The modified "Super-fast" battlecruiser design (circa 1920)

ook the basic design for the really fast battlecruiser and modified them to try and get the Spring Style program to "work". I've used a variant of those specs to see what my program would produce with them:

• year: 1920
• length: 804.0 ft
• beam: 87.0 ft
• depth: 55.5 ft
• displacement: 34,312.0 tons
• cp: 0.60
• cm: 0.97
• machineryWtBasis: 28.6 SHP/ton of machinery
• hullWtBasis: 3.0x10^-3
• freeboardForward: 35.0 ft
• freeboardAmid: 26.0 ft
• freeboardAft: 26.0 ft
• forecastleLength: 270.0 ft
• designedShp: 275,000.0
• designedSpeed: 35.0
• boardMargin: 100.0 tons
• electricalPowerKW: 800.0KW
• mainBattType: 17in/45
• mainBattNum: 4.0
• mainBattMount: turret
• mainBattNumMounts: 2.0
• secBattType: 4in/50
• secBattNum: 16.0
• secBattMount: shield
• secBattNumMounts: 6.0
• forecastleDeck: 0.0 in
• upperDeck: 2.0 in
• lowerDeckSlopes:0.0 in
• lowerDeckFlat:0.0 in
• mainBattBarbette: 9.0 in
• mainBattTurret: 11.0 in
• upperDeckSide: 0.0 in
• upperBelt: 6.0 in
• lowerBelt: 6.0 in
• beltLength: 430.0 ft
• beltForward: 0.0 in
• beltAft: 0.0 in
• deckForward: 0.0 in
• deckAft: 3.0 in
• antiTorpBh: 1.5 in
• secBattArmor: 1.0 in
• uptakeArmor: 1.5 in

This is part of the result from my program:

Designed draft=29.4996 ft

Hull Weight=11646.3 tons
Secondary Battery Weight=80.96
Armament Weight= 2474.16
Total Armor Weight=4199.17
Machinery Weight=9615.38
General Equipment Weight=1029.36
Normal Fuel Weight=1029.36
Maximum Fuel added Weight=2573.4
Reserve Feedwater Weight=2004.75

Legend Displacement=31230.0

Legend Draft=26.8499

Submergence of 1390.61 of actual displacement per foot

At Displacement=31230.0
Length=804.0
Beam=87.0
Draft=26.8499
Cp=0.6
Cm=0.97
Cb=0.582
DLR=60.0903
Wetted Surface=80174.1
B/H=3.24024

At speed of 35 knots power  is 225983.0 SHP
At speed of 36 knots power  is 260739.0 SHP
At speed of 37 knots power  is 303780.0 SHP
actual speed for 275000.0 SHP is 36.3313 knots

Deep Load Displacement=35808.2
Deep Load Draft=30.1823
Submergence of 1409.25 of actual displacement per foot

At speed of 34 knots power  is 232583.0 SHP
At speed of 35 knots power  is 261412.0 SHP
At speed of 36 knots power  is 305432.0 SHP
actual speed for 275000.0 SHP  is 35.3087 knots

Metacentric height at legend displacement (GM)=4.73343 ft

Metacentric height at deep load displacement (GM)=6.97987 ft

British weight groups

I was just rereading the weight group discussion in William Hovgaard's book General Design of Warships, and saw that one error that I have been making is including barbettes in the armament group, not the armor group. The rule is that turrets fall into the armament weight group but barbettes are in the armor weight group. That might account for my difficulties in accounting for the armor weight group in the Queen Elizabeth class. It would not affect the stability calculations, as I attempt to account for all the weights and their position.

My latest attempt at specifying the "super fast battlecruiser"

I was successful at specifying and doing the calculations for my "Super Fast Battlecruiser" design, using the current state of my warship general design program. This was the picture of what it looked like: . This ship has an armament of 4-17in/45 and 16-4in/50 guns. This is some of what my program produced:

At Displacement=28708.8
Length=800.0 ft
Beam=85.0 ft
Draft=25.3893 ft
Cp=0.6
Cm=0.97
Cb=0.582

Total Armor Weight=4166.51 tons
Designed SHP=410000.0 
Mach Wt Basis=40.0 SHP/Ton of machinery
Machinery Weight=10250.0 tons
General Equipment Weight=960.0 tons
Normal Fuel Weight=960.0 tons
Maximum Fuel added Weight=2400.0 tons
Reserve Feedwater Weight=2988.9 tons
Legend Displacement=28708.8 tons
Legend Draft=25.3893 ft
Submergence of 1351.88 of actual displacement per foot

At Displacement=28708.8 tons

DLR=56.0719
Wetted Surface=76678.3
B/H=3.34786

At speed of 10knots power  is 2873.4 SHP
At speed of 11knots power  is 3774.54 SHP
At speed of 12knots power  is 4835.44 SHP
At speed of 13knots power  is 6072.19 SHP
At speed of 14knots power  is 7502.44 SHP
At speed of 15knots power  is 9324.9 SHP
At speed of 16knots power  is 11431.4 SHP
At speed of 17knots power  is 13784.6 SHP
At speed of 18knots power  is 16407.0 SHP
At speed of 19knots power  is 19312.1 SHP
At speed of 20knots power  is 22514.5 SHP
At speed of 21knots power  is 26004.9 SHP
At speed of 22knots power  is 31165.9 SHP
At speed of 23knots power  is 37151.1 SHP
At speed of 24knots power  is 43607.0 SHP
At speed of 25knots power  is 50598.1 SHP
At speed of 26knots power  is 58102.8 SHP
At speed of 27knots power  is 66131.4 SHP
At speed of 28knots power  is 74693.9 SHP
At speed of 29knots power  is 88418.3 SHP
At speed of 30knots power  is 104903.0 SHP
At speed of 31knots power  is 123016.0 SHP
At speed of 32knots power  is 142806.0 SHP
At speed of 33knots power  is 163796.0 SHP
At speed of 34knots power  is 185916.0 SHP
At speed of 35knots power  is 209122.0 SHP
At speed of 36knots power  is 240865.0 SHP
At speed of 37knots power  is 278425.0 SHP
At speed of 38knots power  is 318175.0 SHP
At speed of 39knots power  is 362385.0 SHP
At speed of 40knots power  is 408577.0 SHP
At speed of 41knots power  is 456762.0 SHP

actual speed for 410000.0 SHP  is 40.0295 knots

Metacentric height at legend displacement (GM)= 3.30897 ft

My 17in/45 gun design

I ran my 17in/45 gun design through Rick Robinson's gun calculation program with the following results. This is the sort of gun that would have been built after 1920, if there had not been a Washington Naval Treaty:

     Caliber = 17.0 inch (43.2 cm) 
     Shell weight = 2555 lbs (1159 kg) 
     Muzzle velocity = 2650 fps (808 m/s) 

     Relative ballistic performance: 0.80 

     Muzzle energy = 378.3 megajoules = 139421.9 foot-tons 

     Relative muzzle energy: 0.89 

     Typical barrel length: 46 calibers 


     Elevation          Range        Time      Velocity   Fall Angle 

       2.5 deg        5700 yards     7.0 sec   2254 fps     2.8 deg 
       5.0 deg       10300 yards    13.7 sec   1980 fps     6.1 deg 
       7.5 deg       14200 yards    20.0 sec   1790 fps     9.8 deg 
      10.0 deg       17600 yards    26.0 sec   1656 fps    13.7 deg 
      12.5 deg       20500 yards    31.8 sec   1560 fps    17.7 deg 
      15.0 deg       23100 yards    37.4 sec   1493 fps    21.7 deg 
      20.0 deg       27600 yards    48.1 sec   1421 fps    29.5 deg 
      25.0 deg       31300 yards    58.2 sec   1404 fps    36.5 deg 
      30.0 deg       34300 yards    67.9 sec   1418 fps    42.8 deg 
      35.0 deg       36600 yards    77.1 sec   1451 fps    48.1 deg 
      40.0 deg       38100 yards    85.8 sec   1493 fps    52.6 deg 
      45.0 deg       38800 yards    94.1 sec   1539 fps    56.8 deg 
      50.0 deg       38600 yards   101.8 sec   1584 fps    60.5 deg 


          Armor Penetration - Vertical Belt Armor 

               (Relative armor quality, 0.83) 

               Maximum penetration: 41.00 inches 


     Elevation          Range            Belt       Deck 

       1.4 deg        3400 yards         36 in
       2.1 deg        4900 yards         34 in
       2.7 deg        6100 yards          ...        1 in 
       2.9 deg        6400 yards         32 in
       3.8 deg        8200 yards         30 in
       4.8 deg       10000 yards         28 in
       5.0 deg       10400 yards          ...        2 in 
       6.0 deg       11900 yards         26 in
       7.4 deg       14100 yards         24 in
       7.4 deg       14100 yards          ...        3 in 
       9.1 deg       16400 yards         22 in
      10.1 deg       17700 yards          ...        4 in 
      11.2 deg       19000 yards         20 in
      13.6 deg       21600 yards          ...        5 in 
      13.9 deg       22000 yards         18 in
      17.4 deg       25400 yards         16 in
      17.5 deg       25500 yards          ...        6 in 
      20.2 deg       27700 yards          ...        7 in 
      22.3 deg       29400 yards         14 in
      22.8 deg       29800 yards          ...        8 in 
      25.6 deg       31600 yards          ...        9 in 
      28.3 deg       33300 yards          ...       10 in 
      29.2 deg       33800 yards         12 in
      31.1 deg       34800 yards          ...       11 in 
      34.0 deg       36100 yards          ...       12 in 
      37.0 deg       37300 yards          ...       13 in 
      39.0 deg       37900 yards         10 in
      39.9 deg       38100 yards          ...       14 in 
      43.0 deg       38700 yards          ...       15 in 
      46.2 deg       38900 yards          ...       16 in 
      49.5 deg       38700 yards          ...       17 in 


     Maximum range = 38900 yards at 46.4 deg elevation 

Weight groups

Yesterday, I ran into the issue of weight groups and how they are defined. I have data for an American battleship design and started to enter that into my program. I quickly found that I couldn't make the design work as specified, and then realized that to make it work, I would need to transform the data into the British weight groups, not the American. In Chapter III of General Design of Warships, William Hovgaard has a comparison of the British, American, and French weight groups. My program is hard-wired to use the British weight group scheme, and could not easily be modified to use the American (at least not without many code changes).

Specs for a version of "The Ideal Battleship for the British Navy"

The following is what I used for the version of Colonel Cuniberti's "Ideal Battleship for the British Navy". I had to reduce the armor to be able to keep the size under 18,000 tons with the specified length and beam:

Designed Displacement: 17,000 tons

Legend Displacement: 17,630.8 tons

Length: 521.5ft

Beam: 82ft

Draft: 28.8ft

Cp: 0.556

Cm: 0.90

Cb: 0.5004

Machinery: 54,000 SHP

Designed Speed: 24 knots

Main Battery: 12-12in/45 (4x2, 4x1)

Secondary Battery: 12-3in/50 QF

Tertiary Battery: 6-47mm/50 QF

Main Battery Turret Armor: 9in

Main Battery Barbette Armor: 9in

Lower belt: 9in

Upper belt: 6in

Belt forward: 6in

Belt aft: 6in

Lower deck: 1in

Upper Deck: 1in

Deck forward: 1in

Deck aft: 1in

Anti-Torpedo Bulkhead: 1in

The first run from my program for Colonel Cuniberti's battleship

I found that if I severely cut back the armor protection, I could get a reasonable result for Colonel Cuniberti's "Ideal Battleship for the British Navy" from 1903. Instead of a 12in armor basis, I found that a 9in basis was more workable. I also had to give pretty powerful machinery to achieve the desired speed, and to use a lighter-weight machinery to do it:

Designed draft=27.8055 ft

Hull Weight=6511.95 tons
Tertiary Battery Weight=3.8916
Armament Weight= 3013.89
Total Armor Weight=3261.92
Machinery Weight=3375.0
General Equipment Weight=510.0
Normal Fuel Weight=510.0
Maximum Fuel added Weight=1275.0
Reserve Feedwater Weight=393.66

Legend Displacement=17630.8

Legend Draft=28.8372

Submergence of 768.321 of actual displacement per foot

At Displacement=17630.8

Length=521.5 ft
Beam=82.0 ft
Draft=28.8372 ft
Cp=0.556
Cm=0.9
Cb=0.5004

DLR=124.311
Wetted Surface=48515.7
B/H=2.84355

At speed of 10knots power  is 1983.53 SHP
At speed of 11knots power  is 2596.19 SHP
At speed of 12knots power  is 3404.1 SHP
At speed of 13knots power  is 4408.89 SHP
At speed of 14knots power  is 5567.12 SHP
At speed of 15knots power  is 6881.56 SHP
At speed of 16knots power  is 8365.81 SHP
At speed of 17knots power  is 10018.2 SHP
At speed of 18knots power  is 12518.6 SHP
At speed of 19knots power  is 15375.7 SHP
At speed of 20knots power  is 18522.1 SHP
At speed of 21knots power  is 21955.0 SHP
At speed of 22knots power  is 25689.7 SHP
At speed of 23knots power  is 31378.4 SHP
At speed of 24knots power  is 46152.3 SHP
At speed of 25knots power  is 61598.7 SHP

actual speed for 54000.0 SHP  is 24.5081



Deep Load Displacement=19299.4

Deep Load Draft=30.9476

Submergence of 778.621 of actual displacement per foot

At Displacement=19299.4

Length=521.5
Beam=82.0
Draft=30.9453
Cp=0.56434
Cm=0.9045
Cb=0.510445

DLR=136.076
Wetted Surface=50759.7
B/H=2.64984

At speed of 10knots power  is 2093.98 SHP
At speed of 11knots power  is 2740.18 SHP
At speed of 12knots power  is 3593.29 SHP
At speed of 13knots power  is 4654.88 SHP
At speed of 14knots power  is 5878.19 SHP
At speed of 15knots power  is 7266.12 SHP
At speed of 16knots power  is 8832.88 SHP
At speed of 17knots power  is 10576.8 SHP
At speed of 18knots power  is 13371.3 SHP
At speed of 19knots power  is 16583.1 SHP
At speed of 20knots power  is 20119.5 SHP
At speed of 21knots power  is 23977.4 SHP
At speed of 22knots power  is 28173.0 SHP
At speed of 23knots power  is 34664.5 SHP
At speed of 24knots power  is 51432.0 SHP
At speed of 25knots power  is 68328.5 SHP

actual speed for 54000.0 SHP  is 24.152


At Legend Displacement:

Waterline Coeff=0.671089

Block Coefficient=0.5004

CG of hull=21.7742 Hull Wt=6511.95
CG of machinery=11.3933 Mach Wt=3375.0
Armor Center of gravity=43.6179
CG of armor=43.6179 Armor Wt=5324.78
CG of normal fuel=12.1954 Normal Fuel Wt=765.0
CG of max fuel= n/a  Additional Max Fuel Wt=0.0
CG of upper works=69.12 Upper Works Wt=71.3698
CG of general equipment=28.08 General Equip Wt=510.0
Main Armament CG=50.0 Main armament wt=3013.89
Secondary Batt CG=0.0 Secondary Batt wt: 0.0
Tertiary Batt CG=0.0 Tertiary Batt wt: 3.8916

CG above keel = 30.23

Stability Coeff (nu)=0.559814

Height of CG as a fraction of the depth=0.559814

Freeboard=25.1628 ft
Draft=28.8372 ft
Beam=82.0 ft

Metacentric height at legend displacement (GM)=5.20457 ft


At Deep Load Displacement:

Waterline Coeff=0.671089

Block Coefficient=0.5004

CG of hull=21.7742 Hull Wt=6511.95
CG of machinery=11.3933 Mach Wt=3375.0
Armor Center of gravity=44.4982
CG of armor=44.4982 Armor Wt=5324.78
CG of normal fuel=12.6479 Normal Fuel Wt=765.0
CG of max fuel=12.6479 Additional Max Fuel Wt=1275.0
CG of upper works=69.12 Upper Works Wt=71.3698
CG of general equipment=28.08 General Equip Wt=510.0
Main Armament CG=50.0 Main armament wt=3013.89
Secondary Batt CG=0.0 Secondary Batt wt: 0.0
Tertiary Batt CG=0.0 Tertiary Batt wt: 3.8916

CG above keel = 28.6229

Stability Coeff (nu)=0.530053

Height of CG as a fraction of the depth=0.530053

Freeboard=23.0524
Draft=30.9476
Beam=82.0

Metacentric height at deep load displacement (GM)=6.77938 ft

I want to revisit Colonel Cuniberti's 1903 battleship design

I will be reanalyzing Colonel Cunibert's 1903 all-big gun battleship design with my program in its current form. I expect that I will find, as before, that he was extravagantly over-optimistic about how small the ship could be (17,000 tons). What he described was clearly a battleship-cruiser, similar to William Hovgaard's original conception.

Now, the Ger/CB/1906 with the latest version of my program

Trying out the Ger/CB/1906 design is not as traumatic, as it naturally has a higher center of gravity and lower GM (although still really high). This is another low-silhouette, fast battlecruiser design. The main difference is that the main armament is 8-12in/45 guns with a secondary armament of 12-4in/50 guns. The side armor is still only 4in and the upper deck is 3in. The main battery turrets and barbettes are 6in. Here is what the output from my program is like for this design:

Designed draft=25.5564 ft
Hull Weight=11016.0 tons
Secondary Battery Weight=60.72 tons
Armament Weight= 2155.72 tons
Total Armor Weight=2675.07 tons
Machinery Weight=8428.57 tons
General Equipment Weight=750.0 tons
Normal Fuel Weight=750.0 tons
Maximum Fuel added Weight=1875.0 tons
Reserve Feedwater Weight=1075.28 tons
Legend Displacement=26570.4 tons
Legend Draft=27.1617
Submergence of 1226.82 of actual displacement per foot
At Displacement=26570.4
Length=800.0 ft
Beam=85.0 ft
Draft=27.1617 ft
Cp=0.53
Cm=0.95
Cb=0.5035
At Displacement=26570.4 tons
DLR=51.8952
Wetted Surface=73767.3
B/H=3.12941
At speed of 10knots power  is 2705.44 SHP
At speed of 11knots power  is 3546.97 SHP
At speed of 12knots power  is 4538.67 SHP
At speed of 13knots power  is 5695.98 SHP
At speed of 14knots power  is 7035.9 SHP
At speed of 15knots power  is 8695.54 SHP
At speed of 16knots power  is 10608.1 SHP
At speed of 17knots power  is 12746.2 SHP
At speed of 18knots power  is 15131.1 SHP
At speed of 19knots power  is 17776.2 SHP
At speed of 20knots power  is 20695.3 SHP
At speed of 21knots power  is 23879.4 SHP
At speed of 22knots power  is 27982.3 SHP
At speed of 23knots power  is 32612.8 SHP
At speed of 24knots power  is 37606.0 SHP
At speed of 25knots power  is 43023.9 SHP
At speed of 26knots power  is 48845.8 SHP
At speed of 27knots power  is 55081.6 SHP
At speed of 28knots power  is 61741.0 SHP
At speed of 29knots power  is 75542.8 SHP
At speed of 30knots power  is 92998.3 SHP
At speed of 31knots power  is 111556.0 SHP
At speed of 32knots power  is 131184.0 SHP
At speed of 33knots power  is 152017.0 SHP
actual speed for 147500.0 SHP  is 32.7832 knots
Deep Load Displacement=29520.6 tons
Deep Load Draft=29.5859
Submergence of 1243.27 of actual displacement per foot

Metacentric height at legend displacement (GM)=8.84576 ft

Metacentric height at deep load displacement (GM)=10.0769 ft

I'm doing some outrageous things to try and lower the GM

After calibrating my program for the Queen Elizabeth class, I am now wrestling with the ship specification for my GB/CB/1905 design to try and lower the metacentric height (GM). I have had only moderate success at this, but I do have the GM at the legend displacement below 10ft (!). I must admit that the ship has a low silhouette, given that it doesn't have superfiring turrets. There are just the forward and aft 12in/45 twin turrets with 9 single 6in/50 guns in armored shields. As things stand right now, this is what I have:

Designed draft=26.0604 ft
Hull Weight=10995.6 tons
Secondary Battery Weight=165.6 tons (includes protection)
Armament Weight= 1576.08 tons (includes protection)
Total Armor Weight=4097.17 tons
Machinery Weight=8428.57 tons
General Equipment Weight=750.0 tons
Normal Fuel Weight=750.0 tons
Maximum Fuel added Weight=1875.0 tons
Reserve Feedwater Weight=1075.28 tons
Legend Displacement=27392.4 tons
Legend Draft=28.5543 ft
Submergence of 1195.69 of actual displacement per foot
At Displacement=27392.4
Length=770.0 ft
Beam=85.0 ft
Draft=28.5543 ft
Cp=0.54
Cm=0.95
Cb=0.513
At Displacement=27392.4 tons
DLR=60.001
Wetted Surface=73481.9
B/H=2.97679

At speed of 30knots power  is 104406.0 SHP
At speed of 31knots power  is 125104.0 SHP
At speed of 32knots power  is 147027.0 SHP
At speed of 33knots power  is 170186.0 SHP
actual speed for 147500.0 SHP  is 32.0204

Metacentric height at legend displacement (GM)=9.36508

Waterline Coeff=0.661362

Block Coefficient=0.513

Stability Coeff (nu)=0.445718
Freeboard=24.9905
Draft=31.0095
Beam=85.0

Metacentric height at deep load displacement (GM)=10.4897

I'm still "wrestling" with the Queen Elizabeth class

Something about the Queen Elizabeth class battleships is challenging. It didn't work at all in Rick Robinson's "Spring Style" program (at least the way I specified it). In my program, I'm having trouble getting a large enough metacentric height (GM) at the legend displacement. The deep load is better, but still lower than the real ships. One good thing is that I have a more complete weight and stability model than I did, even earlier today. I have yet to deal with volumes and seakeeping ability, but that is coming soon. As it stands right now, I am getting the following results:

Legend displacement of 29,625.5 tons with a GM of 4.54955 ft

Deep load displacement of 32,234.7 tons with a GM of 5.66306 ft

The real ship figures were:

Normal displacement of 30,030 tons with a GM of 5ft

Deep load displacement of 33,260 tons with a GM of 6.5ft

This is actually not so bad, although the question will be how it affects my light battlecruiser design that has a low center of gravity. I may need to see how I can raise weights in it to raise the center of gravity, so that the GM is not so outrageously high.

It seems like the Queen Elizabeth class metacentric height issue is related to the correct CG for the hull

I found that if I used a "hack" to reduce the hull depth so that it is from the keel to the main deck, rather than the forecastle deck, the center of gravity is at the correct level, and the computed metacentric height (GM) is at 4.13811 ft for the legend displacement and at 5.56843 ft for the deep load displacement. Considering what I am doing, that is pretty good. With the "Spring Style" program, the GM is too low and the Queen Elizabeth class would be unstable (among many other problems).

My Ger/CB/1906 design was intended to be able to make 33 knots

My ship was intended to be able to make 33 knots at 120,000 SHP. The dimensions were 800ft x 85ft x 25.6ft at 25,000 tons displacement. The coefficients were Cp=0.53 and Cm=0.95. To actually make 25 knots, the design is required to be pressed by about 25%. This is part of the generated output from my program:

Designed draft=25.5564 ft

Hull Weight=10608.0 tons
Armament Weight= 2167.84
Total Armor Weight=2477.87
Machinery Weight=8581.08
General Equipment Weight=750.0
Normal Fuel Weight=750.0
Maximum Fuel added Weight=1875.0
Reserve Feedwater Weight=1111.0

Legend Displacement=26139.6

Legend Draft=26.7214

Submergence of 1226.82 of actual displacement per foot

At Displacement=26139.6

Length=800.0
Beam=85.0
Draft=26.7214
Cp=0.53
Cm=0.95
Cb=0.5035

At Displacement=26139.6
DLR=51.0539
Wetted Surface=73166.9
B/H=3.18098

At speed of 10knots power  is 2681.28 SHP
At speed of 11knots power  is 3515.47 SHP
At speed of 12knots power  is 4498.56 SHP
At speed of 13knots power  is 5645.86 SHP
At speed of 14knots power  is 6974.24 SHP
At speed of 15knots power  is 8617.25 SHP
At speed of 16knots power  is 10510.3 SHP
At speed of 17knots power  is 12626.6 SHP
At speed of 18knots power  is 14987.3 SHP
At speed of 19knots power  is 17605.7 SHP
At speed of 20knots power  is 20495.4 SHP
At speed of 21knots power  is 23647.6 SHP
At speed of 22knots power  is 27712.4 SHP
At speed of 23knots power  is 32301.0 SHP
At speed of 24knots power  is 37249.1 SHP
At speed of 25knots power  is 42618.2 SHP
At speed of 26knots power  is 48387.9 SHP
At speed of 27knots power  is 54567.8 SHP
At speed of 28knots power  is 61167.7 SHP
At speed of 29knots power  is 74726.2 SHP
At speed of 30knots power  is 91848.3 SHP
At speed of 31knots power  is 110051.0 SHP
At speed of 32knots power  is 129304.0 SHP
At speed of 33knots power  is 149739.0 SHP
At speed of 34knots power  is 171291.0 SHP

actual speed for 152400.0 SHP  is 33.1235

Waterline Coeff=0.65521

Block Coefficient=0.5035

Stability Coeff (nu)=0.546438

Height of CG as a fraction of the depth=0.546438

Freeboard=25.2786

Draft=26.7214

Beam=85.0

Metacentric height at legend displacement (GM)=7.49797

My original Ger/CB/1906 design was intended to be radical

As another test case, I wanted to run my Ger/CB/1906 design through my Warship General Design program. This design was intended to be radical, and incorporated some features that were inappropriate to the date. The biggest departure was the 25 degree inclined armor. The belt was thin. Oddly enough, over the magazines, it was 3 inches of KC (Krupp Cemented) armor while over the machinery spaces it was 4in of KC armor. There was a 3in upper armored deck, and this was the only horizontal armor. The turrets and barbettes for the main armament were 6in thick at the maximum. There was no anti-torpedo bulkhead, although there was subdivision as if there were. The citadel was extremely short, being 425ft long. This was a weight-saving device to keep the armor weight as low as possible, while securing some protection. The silhouette was low, with the turrets and barbettes, a small bridework and light tripod forward, and 12-4in/50 QF guns in shields with splinter protection only. The main armament was 8-12in/45 guns. The designed power plant was 120,000 SHP at 14 SHP/ton of machinery. However, the plant was intended to be able to forced by about 25%, to something like 152,400 SHP. I took the same numbers as the battlecruiser Tiger, which was designed for 85,000 SHP but was completed as being capable of being forced to 108,000 SHP. That was a 27% increase over the designed power.

Output from my program for the Queen Elizabeth class

This is still incomplete (due to the secondary battery), but is getting better. I have been extending and tweaking the program to get the weights correct, and then to adjust the metacentric height calculations. The armor and armament center of gravity calculations are really quite good, as you can compute something close to actual weights, and can estimate the CG of pieces quite well. This is an excerpt from the output. The metacentric height is still on the low side, compared to the real ship:

Specification filename: GBBB1912ShipSpec.txt

Designed draft=27.0885 ft

Hull Weight=8896.92 tons
Armament Weight= 4173.59
Total Armor Weight=8559.14
Machinery Weight=3947.37
General Equipment Weight=810.0
Normal Fuel Weight=810.0
Reserve Feedwater Weight=546.75

Legend Displacement=27887.0

Legend Draft=27.9784

Submergence of 1177.65 of actual displacement per foot

At Displacement=27887.0

Length=639.0
Beam=90.5
Draft=27.9784
Cp=0.635
Cm=0.95
Cb=0.60325

At Displacement=27887.0
DLR=106.881
Wetted Surface=67541.6
B/H=3.23463

At speed of 10knots power  is 2755.54 SHP
At speed of 11knots power  is 3617.84 SHP
At speed of 12knots power  is 4631.78 SHP
At speed of 13knots power  is 5913.31 SHP
At speed of 14knots power  is 7577.03 SHP
At speed of 15knots power  is 9462.83 SHP
At speed of 16knots power  is 11596.3 SHP
At speed of 17knots power  is 13971.9 SHP
At speed of 18knots power  is 16622.4 SHP
At speed of 19knots power  is 19692.1 SHP
At speed of 20knots power  is 26705.0 SHP
At speed of 21knots power  is 34398.0 SHP
At speed of 22knots power  is 42760.0 SHP
At speed of 23knots power  is 51837.1 SHP
At speed of 24knots power  is 61601.3 SHP
At speed of 25knots power  is 72109.5 SHP
At speed of 26knots power  is 88870.7 SHP

actual speed for 75000.0 SHP  is 25.1725

Deep Load Displacement=30458.8

Deep Load Draft=29.9594

Submergence of 1193.43 of actual displacement per foot

At Displacement=30458.8
Length=639.0
Beam=90.5
Draft=29.9572
Cp=0.644525
Cm=0.95475
Cb=0.61536
Hull Weight=8896.92 tons

At Displacement=30458.8
DLR=116.737
Wetted Surface=70587.3
B/H=3.02097

At speed of 10knots power  is 2912.55 SHP
At speed of 11knots power  is 3824.2 SHP
At speed of 12knots power  is 4895.63 SHP
At speed of 13knots power  is 6245.72 SHP
At speed of 14knots power  is 7991.76 SHP
At speed of 15knots power  is 9970.22 SHP
At speed of 16knots power  is 12207.9 SHP
At speed of 17knots power  is 14698.8 SHP
At speed of 18knots power  is 17477.5 SHP
At speed of 19knots power  is 20729.4 SHP
At speed of 20knots power  is 28960.3 SHP
At speed of 21knots power  is 37991.4 SHP
At speed of 22knots power  is 47811.2 SHP
At speed of 23knots power  is 58467.6 SHP
At speed of 24knots power  is 69931.5 SHP
At speed of 25knots power  is 82262.5 SHP

actual speed for 75000.0 SHP  is 24.411

Waterline Coeff=0.717182
Block Coefficient=0.60325

Stability Coeff (nu)=0.606506
Height of CG as a fraction of the depth=0.606506
Freeboard=26.7716
Draft=27.9784
Beam=90.5

Metacentric height at legend displacement (GM)=4.09912

Waterline Coeff=0.717182
Block Coefficient=0.60325

Stability Coeff (nu)=0.573974
Height of CG as a fraction of the depth=0.573974
Freeboard=24.7906
Draft=29.9594
Beam=90.5

Metacentric height at deep load displacement (GM)=5.5319

Warship General Design Program status

My work on this program has progressed so that for the Queen Elizabeth class battleships. I still haven't been able to account for all the armor weights that were supposed to make up the total weight (about 8600 tons). I still have to add coverage to the stability calculations for some new armor weights, as well. I still hope to have this completed by the end of the day tomorrow, depending on the impacts of other responsibilities (which are impeding progress today).

Armor on the "upper deck sides"

One feature that I need to add to my program is to include the possibility of armor on the "upper deck sides". I've long been aware of this feature in some ships, but I have generally avoided armoring that place in my own designs. What I am seeing is that to account for all the armor weight in the Queen Elizabeth class and similar ships, I need to include the possibility to armor places that I have not previously allowed, including the upper deck side, the forecastle, and an upper armor strake at the ends, above that at the waterline.

Some approximations from Edward L Attwood

Rick Robinson's "Spring Style" program produces a "tons-per-inch immersion" figure for a ship design. He must be using some approximation such as that shown on page 200 of Edward L. Attwood's book, War-Ships: A Text-Book on the Construction, Portection, Stability, Turning, Etc., of War Vessels. I am looking at a copy of the 6th Edition from 1917.

For ships with a fine waterplane, the approximation is:

tons per inch = (Length x Beam)/600

For fuller ships, such as a battleship, the approximation is:

tons per inch = (Length x Beam)/530

There is a table that compares the approximation with the real figure for four ship types, and they all are within 3% (usually better) of the correct figure. For wargame-oriented ship design, this is perfectly acceptable.

I'm calibrating my program against the Queen Elizabeth class (1912)

I realized that to get weights and stability as close to being correct as possible, considering that I am just doing "back of the envelope calculations" anyway, I needed to calibrate my program against a real ship design. I chose the Queen Elizabeth class, as that seems like a good example, and the "Spring Style" program seemed to fail with it (perhaps I was using the wrong inputs). One thing I noticed is that I need to include the protection for the armament, as well as ammunition, into the armament weight group, and remove it from the armor weight group. I don't think that I need to alter my stability calculations, but I do need to alter the weights.

An important difference between what I am doing and what Rick Robinson's "Spring Style" program does

Rick Robinson's "Spring Style" program for warship design takes the approach that the designed displacement is sacrosanct, and that if you load the design up with large machinery, guns, and armor, that you will keep the displacement constant and start reducing the hull weight, even if it goes below what is feasible. Stability is another likely casualty, along with seakeeping and roominess.

My approach is to increase the displacement as you add weights. That will still affect the stability, and will increase the draft, and slow the speed. My plan is to calculate power curves for at the legend displacement and the deep load displacement, and not for the designed displacement that was desired. I do calculate a "designed draft" based on the "designed displacement", as that figure is required to do the weights analysis.

Issues for General Design of Warships

The following are issues to be considered when doing the general design for a warship:

• dimensions
• form coefficients (prismatic and midships coefficients)
• displacement
• armament
• armor
• power and speed
• weights analysis
• volume analysis
• freeboard, stability, and seakeeping
• structural strength and hull weight

My warship general design program currently addresses eight of these issues. I am in the process of going through each issue, doing verification and fixing problems. When this list is complete, the next step is a warship design expert system that will choose characteristics which would be processed and fleshed out by this component.

My warship general design program: status

I made quite a bit of progress this weekend. I now have my code to compute metacentric height "working", in the sense that it runs and generates plausible numbers using equations from William Hovgaard's book, General Design of Warships. This is some of what the program generates (some of it just for debugging purposes):

Ship:  Ger/CB/1906

Submergence of 1277.66 of actual displacement per foot
Displacement=30800.0 tons
Length=814.0ft
Beam=87.0ft
Draft=30.2326ft
Cp=0.53
Cm=0.95
Cb=0.5035

Displacement=30800.0
DLR=57.1055
Wetted Surface=80113.8
B/H=2.87769

At speed of 10knots power is 2949.25 SHP
At speed of 11knots power is 3867.17 SHP
At speed of 12knots power is 4946.95 SHP
At speed of 13knots power is 6206.73 SHP
At speed of 14knots power is 7661.17 SHP
At speed of 15knots power is 9468.02 SHP
At speed of 16knots power is 11564.1 SHP
At speed of 17knots power is 13912.3 SHP
At speed of 18knots power is 16531.2 SHP
At speed of 19knots power is 19444.7 SHP
At speed of 20knots power is 22639.6 SHP
At speed of 21knots power is 26134.2 SHP
At speed of 22knots power is 30474.6 SHP
At speed of 23knots power is 35539.3 SHP
At speed of 24knots power is 41019.4 SHP
At speed of 25knots power is 46925.4 SHP
At speed of 26knots power is 53291.7 SHP
At speed of 27knots power is 60110.0 SHP
At speed of 28knots power is 67420.9 SHP
At speed of 29knots power is 80560.5 SHP
At speed of 30knots power is 100888.0 SHP
At speed of 31knots power is 122507.0 SHP
At speed of 32knots power is 145428.0 SHP
At speed of 33knots power is 169711.0 SHP
actual speed for 146000.0 SHP is 32.0236

Hull Weight=12393.2

Main battery type=12in/45
found main battery gun: 12in/45
Main battery gun weight=57.67
found secondary battery gun
Secondary Battery gun weight: 2.2

Lower Belt Weight: 480.0
Upper Belt Weight: 480.0
Upper deck weight: 1566.0
Lower deck weight: 848.25

Main Battery armor thickness: 6.0

Machinery Weight=8111.11
General Equipment Weight=924.0
Normal Fuel Weight=924.0

Legend Displacement=28540.5
Deep Load Displacement=30850.5
Deep Load Draft=29.6884

Waterline Coeff=0.65521

Block Coefficient=0.5035

CG of hull=29.4118
CG of machinery=29.2
CG Lower Armor Belt=30.2326
CG Lower Armor Belt M=14511.7
CG Upper Armor Belt=40.2326
CG Armor deck slopes=30.2326
CG lower armor deck=34.2326
CG upper armor deck=42.2326

Total Armor Wt=4483.48

CG of armor=36.3691
CG of normal fuel=24.1861
CG of upper works=82.5
CG of general equipment=42.5

Main battery type=12in/45
found main battery gun: 12in/45
Main battery gun weight=57.67 tons
Armament Weight: 1088.73 tons
Armament CG=52.7326ft
CG above keel = 31.9127ft
Stability Coeff (nu)=0.638254
Height of CG as a fraction of the depth=0.638254
Freeboard=19.7674ft
Draft=30.2326ft
Beam=87.0ft

Metacentric height (GM)=4.50924

I'm working on estimating the center of gravity of armor for ships

Within the framework of my program for warship general design, I'm presently working on estimating the center of gravity for my "generic" ship. For specific ship, some of the factors drop out, as they have a zero coefficient. I will factor in the armor CG to my metacentric height (GM)calculation based on what is William Hovgaard's book, The General Design of Warships (pages 80 to 100). There is an equation for estimating GM that I have mechanized in my program (equation 20, the Stability Equation).

Stability calculations

Circa 1971, we had an even more naive view of warship design than we have today (my friend and I). I am somewhat more sophisticated now, in the sense that I have a better system for computing power curves (actually based on a real system, not some empirical hack). The next issue that I will be tackling is stability. What I want to have is a "back of the envelope" system that is still based on the correct theory. With what I am doing, I am just not going to have the detail to do an exact computation. I would like to do better than what I have been doing (nothing). I would also like to do better than the "Spring Style" program. The "Spring Style" program is a noble effort, and I was really excited when I originally found it and started experimenting. I lost some of my enthusiasm as I found "issues" with it (power calculations, stability, and strength calculations). I felt obligated, since I had criticized it, to do better.

Experimenting with my Ger/CS/1905 design

I had not run my evolving general design of warships program against a relatively small ship, yet. I started with my scout cruiser design that was inspired by the "Super Swift" concept. I had not been sure as to what an appropriate hull weight factor might be, but from looking at March's British Destroyer book, it seems that something like 3.0 x 10^-3 or somewhat larger is about right. This is what my preliminary run looks like:

Submergence of 244.002 of actual displacement per foot
Displacement=2480.0
Length=370.0
Beam=38.0
Draft=12.9928
Cp=0.559
Cm=0.85
Cb=0.47515
Hull Weight=1254.85 tons
Displacement=2480.0
DLR=48.9606
Wetted Surface=15326.6
B/H=2.92469
lowCpIndex=1
highCpIndex=2
lowCpFraction=0.55
highCpFraction=0.6
cp Interpolation Factor=0.18
At speed of 10knots power  is 591.491 SHP
At speed of 11knots power  is 791.208 SHP
At speed of 12knots power  is 1026.65 SHP
At speed of 13knots power  is 1302.82 SHP
At speed of 14knots power  is 1620.28 SHP
At speed of 15knots power  is 2035.83 SHP
At speed of 16knots power  is 2548.21 SHP
At speed of 17knots power  is 3122.88 SHP
At speed of 18knots power  is 3764.19 SHP
At speed of 19knots power  is 4470.45 SHP
At speed of 20knots power  is 5788.18 SHP
At speed of 21knots power  is 7396.0 SHP
At speed of 22knots power  is 9142.03 SHP
At speed of 23knots power  is 11036.3 SHP
At speed of 24knots power  is 13078.6 SHP
At speed of 25knots power  is 16390.0 SHP
At speed of 26knots power  is 19953.2 SHP
At speed of 27knots power  is 23741.2 SHP
At speed of 28knots power  is 27780.7 SHP
At speed of 29knots power  is 32079.5 SHP
At speed of 30knots power  is 36735.5 SHP
At speed of 31knots power  is 41606.5 SHP
At speed of 32knots power  is 46645.3 SHP
At speed of 33knots power  is 51959.3 SHP
At speed of 34knots power  is 56880.4 SHP
At speed of 35knots power  is 60905.8 SHP
actual speed for 60000.0 SHP  is 34.775
Hull Weight=1254.85

Main battery type=4in/50
found main battery gun: 4in/50
Main battery gun weight=2.2


Machinery Weight=1000.0
General Equipment Weight=74.4
Normal Fuel Weight=74.4
Maximum Fuel added Weight=0.0
Reserve Feedwater Weight=0.0
Legend Displacement=2478.55
Deep Load Displacement=2664.55
Deep Load Draft=13.686

More experimenting with the Hood-type ship

I was running through more experiments with the original design for the Hood this morning. I was adjusting the prismatic and midship coefficients to see what effect they had on speed. Leaving the displacement constant, lowering either coefficient has the effect of increasing the draft. When I reduced the Cp to 0.53, the speed actually fell off. I just tried a "light cruiser" Cp and Cm (a high Cp and a low Cm). That had the effect of lowering the speed.

The sure-fire way to increase speed without increasing power was to increase the waterline length. When I increased the length to 890ft, the speed calculated by my program goes up over 32 knots. The specs for the ship in this case were:

legend displacement: 36,300 tons

length: 890ft

beam: 104ft

draft: 26.5498

SHP: 144,000

Cp: 0.55

Cm: 0.94

Part of the power curve:

At speed of 20knots power  is 25410.8 SHP
At speed of 21knots power  is 29361.2 SHP
At speed of 22knots power  is 33665.3 SHP
At speed of 23knots power  is 39244.9 SHP
At speed of 24knots power  is 45789.9 SHP
At speed of 25knots power  is 52893.0 SHP
At speed of 26knots power  is 60556.0 SHP
At speed of 27knots power  is 68739.5 SHP
At speed of 28knots power  is 77479.4 SHP
At speed of 29knots power  is 86787.5 SHP
At speed of 30knots power  is 98317.3 SHP
At speed of 31knots power  is 118491.0 SHP
At speed of 32knots power  is 141457.0 SHP
At speed of 33knots power  is 167021.0 SHP
actual speed for 144000.0 SHP  is 32.0995 knots

I was experimenting with a Hood-like ship

I wondered how my power calculation program would do with a ship like the Hood. I don't know the coefficients for the Hood, so I had to guess. These are my results:

Displacement=42200.0 tons
Length=850.0ft
Beam=104.0ft
Draft=30.0641ft
Cp=0.585
Cm=0.95
Cb=0.55575
Hull Weight=13392.6 tons
Displacement=42200.0 tons
DLR=68.7156
Wetted Surface=95826.5
B/H=3.45927
At speed of 10knots power  is 3633.33 SHP
At speed of 11knots power  is 4773.53 SHP
At speed of 12knots power  is 6117.54 SHP
At speed of 13knots power  is 7684.03 SHP
At speed of 14knots power  is 9486.35 SHP
At speed of 15knots power  is 11681.5 SHP
At speed of 16knots power  is 14369.1 SHP
At speed of 17knots power  is 17377.4 SHP
At speed of 18knots power  is 20738.2 SHP
At speed of 19knots power  is 24451.1 SHP
At speed of 20knots power  is 28529.1 SHP
At speed of 21knots power  is 32999.6 SHP
At speed of 22knots power  is 38195.1 SHP
At speed of 23knots power  is 45949.4 SHP
At speed of 24knots power  is 54340.8 SHP
At speed of 25knots power  is 63381.5 SHP
At speed of 26knots power  is 73112.8 SHP
At speed of 27knots power  is 83556.7 SHP
At speed of 28knots power  is 94665.1 SHP
At speed of 29knots power  is 106519.0 SHP
At speed of 30knots power  is 129111.0 SHP
At speed of 31knots power  is 155055.0 SHP
actual speed for 151280.0 SHP  is 30.8545

"an Oldie but a Goodie" book on Naval Architecture

Edward L. Atwood was the head of the Battleship Section, working for Sir Eustace Tennyson d'Eyncourt, the Director of Naval Construction from 1912 to 1923. Edward L. Atwood lead the design of the battlecruiser Hood and the cancelled 1921 ships. He was also a prolific writer. I have a copy of four of his books (including multiple editions of one).

Theoretical Naval Architecture is a fine little book. I have an edition printed in March 1943. It is readily available at a moderate cost.

Another is War-Ships: A Text-Book. I am have a copy of the Sixth Edition from 1917 open, looking at a photograph of the battleship Orion.

Then, there is the book The Modern Warship from 1913. The picture opposite the cover page is a photograph of a large model of the battlecruiser Queen Mary (lost at Jutland). This book is odd, in that it is very small, but it has many small gems, such as the breakdown of the costs for the battleships Neptune, Hercules, and Colossus.

The fourth book is A Textbook of Laying Off. I have a copy printed in February 1943.

Computer program status

The power calculation program is working well. I may have a standalone version of that as it is a natural thing to want, if you are interested in ship design and analyzing ships. I am currently working on the warship general design program which takes a specification file and produces a detailed list of weights, as well as the power curve. I expect to include range calculations, as well, based on Frank Fox's system that takes electrical generation power usage. This is another good candidate for a standalone program. The ultimate intended user of this program is a warship general design expert system, which would take very high level specs and produce some alternative ship designs, for use in gaming.

A German light cruiser design for 1916Submergence of 410.25 of actual displacement per foot

I conceived of this light cruiser design in 1971. The idea was a German-looking ship with three funnels (with casings halfway up the stacks), three twin 6-inch gun mounts, with one forward and two aft, with one superfiring over the other (with blast shields). I will be expanding what is printed, as I add to the weight calculations.

Submergence of 410.25 of actual displacement per foot
Displacement=5400.0 tons
Length=475.0 ft
Beam=48.0 ft
Draft=16.5294 ft
Cp=0.59
Cm=0.85
Cb=0.5015
Hull Weight=1778.4 tons
DLR=50.3864
Wetted Surface=25625.0
B/H=2.90392

Power curve:
At speed of 10knots power is 975.323 SHP
At speed of 11knots power is 1283.41 SHP
At speed of 12knots power is 1678.73 SHP
At speed of 13knots power is 2141.78 SHP
At speed of 14knots power is 2675.14 SHP
At speed of 15knots power is 3281.73 SHP
At speed of 16knots power is 3968.67 SHP
At speed of 17knots power is 4921.3 SHP
At speed of 18knots power is 6085.65 SHP
At speed of 19knots power is 7373.01 SHP
At speed of 20knots power is 8786.94 SHP
At speed of 21knots power is 10334.9 SHP
At speed of 22knots power is 12295.8 SHP
At speed of 23knots power is 15526.8 SHP
At speed of 24knots power is 18998.9 SHP
At speed of 25knots power is 22713.3 SHP
At speed of 26knots power is 26703.4 SHP
At speed of 27knots power is 30958.2 SHP
At speed of 28knots power is 37983.1 SHP
At speed of 29knots power is 46159.3 SHP
At speed of 30knots power is 54769.2 SHP
At speed of 31knots power is 63886.6 SHP
actual speed for 60000.0 SHP is 30.5737

Machinery Weight=1500.0

Hull strength

Frank Fox told me that he believed that a ship that has a length-to-depth ratio of 16 or under will have a normal weight structure. I noticed that the Renown, as built, had a length-to-depth ratio of about 16.2. My estimate of the weight basis for the hull is 3.084357 x 10^-3. Compare that with the Lion which had a length-to-depth ratio of about 13.2. I estimate that the weight basis for the Lion's hull was about 2.957 x 10^-3. Perhaps we could use the curve fitting tool to generate a function for computing hull weight basis. I doubt that it is that simple, as I suspect that light cruisers and destroyers might have a smaller weight basis (my term).

The Acasta (K-class) had a length-to-depth ratio of about 15.9. The weight basis was about 3.02x10^-3. I was amazed that this metric would be so consistent. I had trouble finding a destroyer for which I had a hull weight to do this calculation.

Capitani Romani class cruisers

I just spoke with Frank Fox, and he expressed scepticism that the Attilio Regolo or Scipione Africano could have maintained 43 knots in service. Frank suggested that I run some calculations with my program. Apparently, the 43 knots claim is of the same value as the 40 knots claim for the Renown and Repulse when new, or 39 knots for the destroyer leader Swift, or 40 knots for the Atlanta. Namely, the claims were not any good at all. IF the Scipione Africano were extremely light and was pressed to extreme overload, it would be capable of 43 knots. At a more normal load of 5,035 tons and at the designed SHP of 110,000, the speed would only be 36 knots. If pressed hard, the maximum speed would be on the order of 39 knots. There are many uncertainties, as I don't know the correct hull form coefficients. It seems very likely that at normal loaded condition, these ships would have had trouble reaching 40 knots, despite what has been published. IF they were very light, then that is another matter. If they could be run at a displacement of 4,035 tons and pressed to 137,000 SHP, then 43 knots is possible.

Warship General Design program status

The power calculations component now seems to be working quite well. I can do interpolation to give the fractional speed for a whole number designed power in SHP. I should be able to do the reverse, as well, to compute the exact power for a whole number speed in knots. I am now working on the weight calculations. I am computing a legend displacement and deep load displacement. I expect to do the Washington Naval Treaty "Standard Displacement as well. As of now, I am intending to do some stability calculations as well as dealing with volumes. I believe that I have strength covered, in the sense that I know what I call a "weight basis" is for real ships. If you build a battleship hull and the hull weight is 0.003 x length x beam x depth, you will have a pretty satisfactory result. That is actually more than is needed for shorter, deeper ships. Here are some example weight bases:

• Invincible: 0.002902 girder: 11.8
• Courageous: 0.00265 girder: 15.4
• Repulse: 0.00308 girder: 16.2
• Lion: 0.002975 girder: 13.2
• Queen Elizabeth: 0.00285 girder: 11.8

I should have realized that Rick Robinson's "Spring Style" program has a lot of "hacks"

I have been studying Rick Robinson's "Spring Style" program, and so far, I have been disappointed to see that it is filled with "hacks" that only "sort of" give the right numbers. Partly, the scope of what he is doing is larger than I intend to do. He is trying to cover 1860 to 1945, while I am concentrating on 1905 to 1927 (although it will pertain to the 1900 to 1945 range). I am going to adapt my Excel spreadsheet calculations rather than doing "hacks", as much as possible.

I tried designing a Queen Elizabeth class battleship, and found it didn't work in Rick Robinson's program

I thought it would be instructive to try out a real ship in Rick Robinson's "Spring Style" program. I immediately thought of the Queen Elizabeth class. I was disappointed that it didn't work, when entered in a straight-forward way. The program claimed about strength and stability, plus the calculated speed was too high: 26 knots. The real speed should be more like 24 knots. My program is more accurate than what he is doing. He also doesn't use prismatic coefficient, which is an essential factor (he is using block coefficient, instead, which isn't something that you use directly for speed calculations).

I've started my program for doing general design of warships

I have started work on a program to do general design of warships. I have a list of things that I would like to have in my program: Hull weights (don't limit weights to what is available):

1. be able to calculate the weight of a hull that is strong enough, but lightly built
2. be able to calculate a hull weight that is of typical strength and weight
3. be able to calculate a hull weight that is stronger than needed
4. be able to deal with destroyer and scout cruiser hulls

Armament:

1. specify gun characteristics
2. specify gun mounting

Armor:

1. allow for two armor decks
2. allow for funnel base armor
3. allow for guns to be in turrets, casemates, batteries, open mounts, "en barbette", single mountings with shields

Speed:

1. use my power curve calculations based on The Speed and Power of Ships
2. use electrical load in calculating cruising range

This is a start on the specifications. I will be augmenting and modifying this list, as I proceed on my implementation

Rick Robinson's program is useless for designing small ships

Well, Rick Robinson said as much: his program is intended for designing larger ships, not destroyers. I was trying to design my 1905 scout cruiser, and finally had to give it up as a lost cause.

I struggled to get a stable version of the "Super-Fast Light Battlecruiser"

One of the ships that I kepted working and reworking (with Rick Robinson's "Spring Style" ship design program) was the "Super-Fast Light Battlecruiser". What I finally ended up with was not so "Super-Fast", although 35 knots is pretty fast. This is what was produced, although it is not pretty:

fastcbl, laid down 1920

     Length, 804 ft x Beam, 87.0 ft x Depth, 29.5 ft
          34312 tons normal displacement (31571 tons standard)

     Main battery:       4 x 17.0-inch (2 x 2)
     Secondary battery: 16 x  4.0-inch

          Weight of broadside: 10338 lbs

     Main belt, 4.0 inches; ends unarmored
     Upper belt, 4.0 inches
     Torpedo bulkhead, 1.0 inches
     Armor deck, average 2.0 inches
     C.T., 4.0 inches

     Battery armor:
          Main, 4.0"
          

     Maximum speed for 225027 shp = 34.43 knots
          Approximate cruising radius, 14500 nm / 12 kts

     Typical complement: 1261-1639


                    Estimated cost, $30.612 million (£7.653 million)

          Remarks:

     Relative extent of belt armor, 55 percent of 'typical' coverage.

     Main belt does not fully protect magazines and
     engineering spaces.

     Magazines and engineering spaces are cramped, with poor
     watertight subdivision.

     Roomy upper decks; superior accommodation and working space.


          Distribution of weights:
                                                       Percent
                                                       normal
                                                    displacement:

          Armament .........................   1292 tons =   4 pct
          Armor, total .....................   4014 tons =  12 pct

               Belt                             912 tons =   3 pct
               Torpedo bulkhead                 570 tons =   2 pct
               Deck                            1801 tons =   5 pct
               C.T.                              91 tons =   0 pct
               Armament                         640 tons =   2 pct

          Machinery ........................   7868 tons =  23 pct
          Hull and fittings; equipment .....  14289 tons =  42 pct
          Fuel, ammunition, stores .........   4289 tons =  13 pct
          Miscellaneous weights ............   2560 tons =   7 pct
                                              -----
                                              34312 tons = 100 pct

          Estimated metacentric height, 5.6 ft

     Displacement summary:

          Light ship:             30023 tons
          Standard displacement:  31571 tons
          Normal service:         34312 tons
          Full load:              36368 tons

          Loading submergence 1391 tons/foot

     +++++++++++++++++++++++++


     Estimated overall survivability and seakeeping ability:

          Relative margin of stability: 1.19

          Shellfire needed to sink: 18353 lbs = 7.5 x 17.0-inch shells
               (Approximates weight of penetrating
               shell hits needed to sink ship,
               not counting critical hits)

          Torpedoes needed to sink: 2.1
               (Approximates number of 'typical'
               torpedo hits needed to sink ship)

          Relative steadiness as gun platform, 48 percent
               (50 percent is 'average')

          Relative rocking effect from firing to beam, 0.65

          Relative quality as a seaboat: 1.02

     +++++++++++++++++++++++++


     Hull form characteristics:

          Block coefficient: 0.58
          Sharpness coefficient: 0.37
          Hull speed coefficient 'M' = 7.57
          'Natural speed' for length = 28.4 knots
          Power going to wave formation
               at top speed: 56 percent


     Estimated hull characteristics and strength:

          Relative underwater volume absorbed by
               magazines and engineering spaces: 145 percent

          Relative accommodation and working space: 191 percent


          Displacement factor: 106 percent
               (Displacement relative to loading factors)


          Relative cross-sectional hull strength: 1.08
               (Structure weight per square
               foot of hull surface: 187 lbs)

          Relative longitudinal hull strength: 1.45
               (for 26.0 ft average freeboard;
               freeboard adjustment +6.6 ft)

          Relative composite hull strength: 1.11

I find that the "Spring Style" program is addictive

I have been experimenting with the "Spring Style" program, and find it hard to stop. I have been trying some "over-the-top" designs that we did in the early 1970's. I find that I have had to modify the designs so that they "work" in many cases. I just did the GB/BB/1914 design conceived by my friend Cliff for the British navy. It was intended to 'bust loose" from the usual constraints. Here are the specs:

• laid down 1914
• length: 800 ft
• beam: 120ft
• draft: 33.1ft
• normal displacement: 48,489 tons
• "standard" displacement: 45,446 tons
• main battery: 9-18in/45 (3x3)
• secondary battery: 20-5in (10x2)
• broadside weight: 24578 lbs
• main belt: 15in, ends unarmored
• upper belt: 10in
• torpedo bulkhead: 2in
• armor deck average 5.0 inches
• conning tower: 12in
• battery armor: main 15in, secondary 2in
• maximum speed for 97,017 SHP 26.16 knots
• approximate cruising radius: 15,200 nm at 10 knots
• typical complement: 1634 to 2124 men
• estimated cost; $23.361 million (£ 5.840 million)

There are more details generated by the program, but this is a start. I would like to try generating a power curve with my own program to see how it compares. Anyway, I like Rick Robinson's program. I want to study it to see what he is doing.

Another interesting piece of software from Rick Robinson: "Spring Style" (warship design)

Rick Robinson has another DOS program written in C that you can download. It is doing general design of warships. You can download the source in C, so that you can actually see what he is doing (just like the Big Gun program). I experimented with it, and he is doing "quite a bit" (in some ways). He is going "easy" on armor weight calculations, but he is doing strength and stability calculations, so this is not some lightweight thing.

Gun performance: 9.2in/45

I have been looking around at what software exists for guns and ships. I have been experimenting with Rick Robinson's "Big Gun" program. I just ran the simulator to generate data for a 9.2in/45 guns with a 380 pound AP shot. Here is an example. The data is the gun elevation, the range that the shot would travel, and the belt and armor penetration. You get two tables. One has output that shows the gun elevation, the range, the time of travel, the terminal velocity, and the fall angle in degrees. The other has the gun elevation, the range, the belt and deck penetration, based on parameters that you supply to the program. Rick includes his C source code with the download.

• 1.1 deg 2600 yards 18in belt
• 1.8 deg 4200 yards 16in belt
• 2.8 deg 5900 yards 14in belt
• 4.2 deg 8000 yards 12in belt
• 5.3 deg 9500 yards 1in deck
• 6.1 deg 10500 yards 10in belt
• 9.1 deg 13500 yards 8in belt
• 12.6 deg 16400 yards 2in deck
• 14.4 deg 17600 yards 6in belt
• 19.8 deg 20700 yards 3in deck
• 25.9 deg 23400 yards 4in belt
• 26.7 deg 23600 yards 4in deck
• 34.2 deg 25800 yards 5in deck
• 42.9 deg 27000 yards 6in deck

I'm tweaking my residual resistance tables and testing

I've been testing my program with real ships from different countries in the WWI timeframe. The main ships that aren't good enough are the Queen Elizabeth class and the Bayern class battleships. They both show too little SHP required to meet their designed speeds. I have been tweaking values in the tables to correct the results. I probably need to go back and reanalyze the tables to clean them up, as they are probably pretty rough, as they stand now.

Sanity checking power calculations: Lion class battlecruisers

As an experiment, I estimated values for the Lion class battlecruisers to see what sort of power that would be calculated for 27 knots. The answer is that my program came up with the following results for the parameters that I used:

• displacement: 26,779 tons
• dimensions: 700ft x 88.5ft x 28.6ft
• Cp: 0.575
• Cm: 0.92
• propulsive efficiency: 0.49
• speed: 27 knots
• SHP: 69,184.4
• residual EHP: 12,831.7
• frictional EHP: 21,068.7
• speed-length ratio: 1.0205

I thought that this was reasonable result, given the inherent sloppiness of the program vis-a-vis hand calculations where I looked up exact Cr values from The Speed and Power of Ships.