I would be willing to run ship designs through my program

If anyone besides me would be interested, I would be willing to supply a specification template and run your warship design through my program. The output file is not neat or pretty, but is packed with information. You will find that you cannot specify your ship as closely as you would like, as the input to my program is a compromise. Admittedly, I have made the specification increasingly exact, as I became dissatisfied with the results. You can email me with your request, and I will respond with a specification attachment that is an example. You will probably need me to answer questions.

Danger Spaces and Immune Zones

I first saw a danger space mentioned in old Jane's Fighting Ships. The 1914 Jane's mentions the danger space. This is the space where the trajectory of the shell carries below the height of the ship, while not striking the water. This ignores the issue of whether a shell can penetrate the ship's armor. An immune zone is the distance from the firing gun where the target ship's armor defeats the arriving shot. The shot may hit either deck or side armor, depending on the range. The immune zone concept is what drove the "all or nothing" armor design philosophy. There had been a recognition, from testing, that thin armor could still detonate a shot. The thin armor will allow an armor-piercing shot to easily penetrate and activate the fuse, so that after a delay, a charge will explode. If a shot hits an unarmored area, the fuse will likely not be activated, and the shot will not explode. Therefore, only protect the most important parts of a ship, and do that with the thickest possible belt armor. The belt needs to be backed by a splinter deck, below the belt, and for protection against plunging fire, there needs to be an upper deck, placed at the top of the belt. The upper deck will activate the fuse, causing the shot to explode, hopefully above the splinter deck.

B/H as a factor in propulsion

I believe that the smaller the B/H ratio the lower the residual resistance. That means that a ship like the Trento, with a B/H of about 3.0, could be faster if she had a narrower beam. I experimented with decreasing the beam to 65.6ft and then to 62.6ft, and the speed increased for the same power.

More about the Trento

I really am interested in why the Trento design is so fast. My estimate for the standard displacement is 11,213 tons. The real normal displacement is 12,328.9 tons. The nominal normal displacement is more: 13,114 tons. That may be part of the answer: what I am using is lighter than the real ship. If I use my "optimal Cp" of 0.61, the Trento can make 36.1 knots. That is with 150,000 SHP. I may be giving the Italians more credit than they deserve, as I am using a machinery weight of 54 SHP/ton. Another explanation is that the B/H is pretty high. The designed B/H is about 3.0.

The Italian Trento class works like it should

Since I have long been interested in fast ships, I naturally took an interest in the Italian cruisers from 1925 to 1943. I just ran the Trento class heavy cruiser design through my program, and "it works". It works in the sense that for 150,000 SHP, the speed is 35 knots. That's at the normal displacement of 13,114 tons given on the Italian navy website. My deep load speed is 33.6 knots. I was never that sure that the nominal speed (35 knots) was actually a good number, but I can see that it is feasible. Admittedly, that is with a propulsion efficiency of 0.53. The coefficients that I used are Cp=0.536 and Cm=0.88. If the Cp were 0.61, it could make 36 knots. That is actually the speed they were said to have in the Conway's book, All the World's Fighting Ships 1922-1946.

I find myself very gullible with respect to ship speeds

I find that I can be very enthusiastic about the prospect of high speeds, especially as reported in Jane's Fighting Ships and the Warship periodical. A long time ago, and not being very knowledgable about the issues, I had believed that the Atlanta could have reached 40 knots no trials. I now know that she was lucky to reach 32 knots. Other high speeds that we shouldn't have believed were for the destroyer leader Swift (1905) and the Renown and Repulse in 1918. The Renown and Repulse, when light could reach 32 knots, but something like 40 knots was a ridiculous claim. As I have written in the past, I was taken in by the 43 knots claim for a Capitani Romani-class light cruiser in 1943. Frank Fox had warned me against the idea, but I had to actually do the calculations for myself. Quite quickly, I saw that at a normal displacement, in service, even 41 knots would probably have been beyond reach.

Some in the British navy were ready to adopt superfiring guns in 1905

You wouldn't realize that there were progressive influences in the British navy in the period from 1905-1914, but they were there. For example, Admiral Fisher wanted to be a progressive, although he often didn't actually know what would be the best thing to do. He was someone who "could make things happen", and he would embrace anything which held some promise to be an improvement. He like big guns ("Hit first, hit hard, and keep hitting"), many of them, and speed ("Speed is armour"). He accepted the need to fit adequate armor ("Armour is vision"). His armored cruiser design still had a mixed caliber armament. It was Captain Bacon who suggested that the new fast armored cruiser carry 12in guns. At one point, Fisher was in favor of a 12-12in gun armament with two levels of superfiring guns, all on the centerline. That was quashed due to the size limitations imposed.

Retrograde influences on British warship design from 1903 to 1927

The period specified is non-intuitive, but the retrograde influences on British warship design were present at least as early as 1903. The first casualty was the semi-Dreadnought design (4-12in/45 and 12-9.2in/50) that was proposed. Building was delayed until 1904 and then the size was reduced to produce the extremely cramped and reduced Lord Nelson and Agamemnon. There were many culprits. Budgetary pressures were a constant issue, early in this period. There was also the issue of Liberal governments not liking building armaments. The greatest individual negative influence was John Jellicoe. He seems to have had a misplaced sense of proportion. For him, being able to conveniently handle boats was more important than providing a smoke-free foretop (for example, the Orion class). Successive, conservative chief engineers also contributed. The British navy could have adopted small tube boilers much earlier, but instead, their designs were saddled with machinery that weighed too much and took too much volume than their German counterparts. After 1914, resources were an issue. I suspect that the top priority was providing armaments to the army in France. The navy's priority received a boost only from the need to deal with German submarine warfare. That allowed the navy build more destroyers and smaller ships. They were also forced to deal with German mine warfare, and to build suitable minesweepers (better than the the torpedo gunboats in use in 1914). Some light cruisers could be built, but larger ship construction languished. The only thing that kept the construction of the Hood going was the fear of what the Germans might be doing. As it was, she was only finished postwar and her sisters cancelled. The planned "1921" battleships and battlecruisers were kept smaller and less capable due to a combination of budgetary and docking issues. They were stillborne, due to the Washington naval treaty, but desire to build the best ships in the available displacement had lead to the extreme armament layouts. Like Captains Hiraga and Fujimori, in Japan, Stanley Goodall seemed to relish squeezing everything that he could from the available displacement, even if the result was extremely odd. Of course, his chiefs, Sir Eustace Tennyson-d'Eyncourt (DNC) and Edward L. Attwood were complicit in the atrocity. That influence lead to the unfortunate Nelson and Rodney, completed ini 1927.

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.