I must confess that I had trouble fitting the machinery into the available space

It turns out that I needed to increase the depth and width of the machinery spaces to reduce the length of the boiler rooms and engine rooms. I might well still have to increase the power output of the plant to decrease the size further. The ship is overweight, still, from what I really wanted and the powerplant is busting out at the seems. The only thing left to do is to increase the power output above 66 SHP/ton of machinery.

OK, so I have been experimenting with a small CL

I have opted for a small CL rather than a large DL type. I have removed the torpedo tubes and added a small amount of side and deck armor. I have been struggling with the correct dimensions, as I would have liked a lower displacement. The dimensions that I have settled on for now are 439ft x 44ft x 13.8ft. The coefficients are the same: Cp=0.66 and Cm=0.82. The power is 72,000 SHP. That is good for 34 knots at the normal displacement of 4,116 tons. The speed at deep load is 31.2 knots. The range at 15 knots at normal load is 4308nm and the range at 15 knots and a deep load displacement of 5,261 tons. The deep draft is 17.3ft. The metacentric height at normal displacement is 2.76ft and at deep load is 4.57ft.

A larger DL or small CL

I want to design a large DL or small CL to act as a leader for my 2400 ton destroyers. I have been toying with a design that has 10-5.1in/50 guns in five twin turrets (three forward, two aft). I started with dimensions of 405ft x 41ft x 13ft, but all that will carry, reasonably, is 8-5.1in/50 guns. I could probably make it 9-5.1in/50 guns, but I suspect that triple turrets would be problematic for DP guns on a small vessel. My current thinking is something like 439ft x 43ft x 13.5ft.

I highly recommend 1/600 scale for doing ship drawing

I drew my last destroyer drawing at 1/600 scale (50ft/in) and I remembered why I like the scale. That is large enough that drawing accuracy is greatly improved. 1/12oo scale is too small. Small errors have a large effect on the drawing. I have done 770ft battlecruisers at 1/600 scale and it really helps for that size as well. The only problem with it is that scans must be pieced together graphically, and there are always small alignment errors.

I ran my big US destroyer design

I entered the initial values into a spec for my 2400 ton destroyer. I ran the program, and then drew a drawing. I tweaked the values based on my drawing and then reran the program. The normal range is 5110 nm at 15 knots and the maximum range is 10586nm, also at 15 knots. The metacentric height is very acceptable. At normal load, it is 3.3ft and and deep load is 5ft. The normal fuel load is 420 tons with an additional 450 tons at deep load. My design is flush decked with two funnels. There are two twin 5.1in/50 turrets forward and one twin turret aft. There are two quintuple torpedo tube mountings astern, but on top of the superstructure. My stability figures really do not account for those weights, but the stability situation is good enough that it should not be a problem.

Destroyers for War in the Pacific

If a 2100 ton destroyer is good for Pacific War fighting, why not a 2200 ton destroyer? The Gearing class dimensions also seem to be pretty reasonable. I would have thought that I would at least go with a 390ft ship. I would probably use coefficients of Cp=0.66 and Cm=0.82. For my liking, I am seeing 390ft as too long for a ship whose NORMAL displacement is 2200 tons. The draft is too shallow to be reasonable. The problem is that a Standard Displacement is quite different from a normal displacement. The normal displacement needs to be at least 2400 tons. Given that, then the dimensions would be 370ft x 38ft x 11ft. The guns would still be 6-5.1in/50 with 10-21in TT. The speed need only be 34 knots.

Super-Destroyers

Frank Fox told me that he had designed an American-style large destroyer for the WWII period. I have an interest in such a thing, myself. I have thought that a 5.1in gun (13cm) would be the thing to use. The gun is considerably more potent than a 5in/38 or a British 4.7in gun. The 5.1in shell is about the upper limit of what is easily manhandled. The British almost adopted such a gun in the 1930's, and then decided that the shell was too heavy. They stayed with the 4.7in gun until they finally adopted a more modern 4.5in DP gun during WWII. I would want a ship about 2750 tons with 6-5.1in/50 guns, and a torpedo armament of 10-21in TT. We all would wish for a 24in torpedo with capabilities equal to the Long Lance, but no one but the Japanese had done the work required to develop such a weapon. That gave the Japanese destroyers and cruisers a great advantage into 1943, until American night tactics and radar fire control finally gave them an edge.

Cruiser design patterns

I think that high-freeboard, flush-decked cruisers are a good design pattern. I have typically included at least a small transom stern, as well. The bow should have some flare and should be 5-10 ft above the amidships freeboard. The stern should be at least 2-3 ft above the amidships freeboard. I would only follow that pattern for larger cruisers. For smaller cruisers, I would either have a raised forecastle or at least a low stern and a fairly high, flared bow, even if the ship were flush-decked. An example would be the Atlanta class ships. For the larger ships, I would use triple turrets, usually 9 guns in three turrets. For ships with guns smaller than 8in, I would have at least 12, if not 15 guns in triple turrets, similar to the Brooklyn class and the original Mogami class design.

President Roosevelt was interested in having a ship like the French super-destroyers

In 1940, President Roosevelt expressed an interest in having a super-destroyer like those used by the French (such as the Fantasque or Volta). Given how the American designers gold-plated everything, the design turned out over4,000 tons, at which point all interest died. American design standards were quite different from those of the French, and there were some things you just couldn't due (regrettably). President Roosevelt had influence. The only reason that the Iowa class ships were built was due to his interest. The navy establishment had no interest. They wanted to build worse ships. They had no interest in a really fast battleship, despite the fact that they turned out to be the best American battleships ever built.

The 12-7.5in gun cruiser design works

I just did a preliminary run of my program with the design that I proposed. The dimensions are 665ft x 66ft x 23ft with a normal displacement of 13,620 tons. The coefficients are Cp=0.56 and Cm=0.84. The power plant is 90,000 SHP for a speed of 32 knots at normal load. I was able to have a 4in belt, barbettes and turrets, with 3in + 2in decks. The metacentric height at normal load is 3.86 ft. The range at a normal load, with 1,000 tons of fuel is 4,709 nm at 15 knots. The range with 2,700 tons of fuel, at 15 knots, is 12,715 nm. The full load displacement is 15,976 tons. The speed at full load displacement is 30.8 knots. The armament is 12-7.5in/50 and 8-4.7in/50 guns. The 4.7in/50 guns are DP. The design includes a catapult and hanger.

A cruiser with 12-7.5in/50 guns would make sense

The 7.5in/50 gun still has merit for a 1921 ship. The gun needs to be mounted in a turret. I would prefer a triple turret, rather than twin. The 7.5in/50 Mk.III weighed 15 tons 9 cwt and 3 qrs. The AP shot was 200 lbs. The rate of fire was 5 rounds per minute. I would put the gun on a 13,500 ton ship with a speed of 32 knots. The primary role would be commerce protection, although I could see a role in fleet actions, or at least in detached task forces (as they came to be known in WW II). I would retain a secondary armament of 8-4.7in/50 guns. I would have a 4in belt. If I didn't say, the ship would be built for the British navy.

Calculating the rudder post position

I have a factor that I use to determine the postion of the rudder post. I take the waterline length and divide by 1.045. That seems to give a good rudder post position. I have been using this for the last 3-1/2 years. Not actually having built and run a ship, it is somewhat hard to know if this is a reasonable thing, but it is based on some example ships that were sufficiently maneuverable.

I just ran my program for my 9.2in/50 gunned cruiser

It is a little problemmatic to try and build a spec for a ship without a drawing, but I did it anyway. The Washington Naval Treaty Standard displacement was 16,036 tons. I was able to give the ship 9-9.2in/50 and 8-4.7in/50 guns, a 6in belt, a 3in deck, and 32 knots of speed. The normal displacement ended up as 17,861 tons. The dimensions are 670ft x 75ft x 23.6ft. The coefficients are Cp=0.585 and Cm=0.9. The ship is flush-decked with a 120,000 SHP machinery plant.

I still believe that there is room for a 9.2in gun ship for the 1921 building program

The British 9.2in/50 gun was a pretty effective gun, with a good range and rate of fire (4 rounds per minute). The AP shot weight was 380 lbs. The piece weighed 28 tons. My preference would be for a 17,000 ton ship with 9-9.2in/50 guns and a 4.7in/50 secondary armament. I would like to see a 6in belt and a 3in deck on such a ship, and a maximum speed, at normal displacement, of 32 knots.

In the early 1900's William Hovgaard suggested that the best battleship would be large and fast, with good armor and guns

William Hovgaard's crystal ball was pretty accurate. About 30 0r 35 years early, he predicted the fast battleship (or at least recommended it as the best bargain). Don't build battlecruisers, but build "battleship-cruisers", which would be fast, have the biggest guns and the heaviest armor. New developments and larger ships would make the older ships less capable, and they would then be used as ordinary battleships. Why build inferior ships when time would produce them, anyway.

Battleships and Battlecruisers

In effect, the fast battleships built in the 1930's and 1940's were battlecruisers with a new name. The North Carolina class ships definitely sacrificed protection to achieve speed and a heavy armament. They also sacrificed structural strength and ridigidy in the process. Except for their armament layout, the 1921 British battlecruisers (the G3 design) were better than most of the ships built as fast battleships. They sacrificed gunpower to achieve speed and protection. While the corresponding battleships would have carried 9-18in guns, the G3's had 9-16in guns. Due to the frenzy to achieve the most on a given displacement that was rampant in Britain in 1921, the armament layout was strange. They would have not given up that much by having a more conventional layout (two turrets forward, one aft), and they would have been superior ships.

SpringSharp

A business associate pointed out a website and warship general design program: SpringSharp.com. They started with the SpringStyle code and greatly improved the program (according to all accounts). The new program is a .NET Windows program. By all indications, this will be interesting to try. I can understand that they are keeping the source code to themselves, as there always might be a commercial value to this sort of work. I will evaluate the program to see if I might learn anything I could use.

WWII-era cruisers were largely "belted cruisers"

From the 1920's on, most cruisers had such a narrow swatch of armor that they had become "belted cruisers", along the lines of the Orlando class ships. The belt was covered by a deck, and the belt was almost submerged, being essentially one deck high. The British cruisers tended to have more coverage, in that they had armor that rose above the machinery spaces on the side, for a shorter distance than was covered at the waterline. As ships were increasingly overweight, much as in the 1880's, the belt was almost totally submerged. In the British case, the only part that had much above-water coverage was that above the machinery spaces. You can see it on the Edinburgh, Southampton, and Dido class ships, as well as others.

An amusing exercise: "modernizing ironclads"

I have been looking through my journal for 1999, which contains many ship drawings. One feature of early 1999 were my drawings of "modernized ironclads". "Modernized" almost doesn't do justice to what I did. For example, there is a ship with a tower foremast, a single funnel, flush deck, anti-aircraft guns, and a modern-looking flush decked hull. The bow is flared, and there are two stockless anchors. There is a ship labeled: "Inflexible", as if this were a ship with 4-16in guns (now BL, not MLR), 6-secondary guns, and 40mm and 20mm AA guns. On an earlier page are shps named "Shannon" (like the original belted cruiser) and "Narcissus", another cruiser. Then, there is a ship that looks rather WWII-like, but labelled "Southampton", and obviously a light cruiser built to something like the dimensions of the British pre-WWI light cruiser. The armament is 9-6in/50 guns, with two triple turrets forward and one aft.

I am pushing the upper limits on ship size

When I just tried to see what the top end for the very large battleship with 21in guns was, I ended up with a Reynolds number above 5.99x10^9! I need to add some more data for Schoenherr frictional resistance coefficients. I tried increasing the power to 350,000 SHP. To actually do that requires 6 shafts, as there is the approximate limit of 70,000 SHP per shaft. Above that loading, the shaft will fail. So to increase power to 350,000 SHP requires 6 shafts with 58,333-1/3 SHP per shaft.

The very large battleship design

I found out that the very large battleship, at higher speeds had a Reynolds number on the order of 5.6x10^9. My Schoenherr table, before this morning, only had values up to 4.999x10^9. I extended the table, and that solved the problem I was seeing last night. I had to turn on some printing so that I could see what was happening and what I needed to do to fix the problem. For Reynolds numbers above 5.0x10^9, the frictional resistance ended up as zero.

I can see now how I can improve the modeling of superstructure, so that I can get better stability calculation results. I also need to account for the heavy rangefinder and main battery fire control director mounted very high on a tower mast.

The optimal super-large battleship

I spent much of 1999 drawing very large battleships and battlecruisers. I just opened a record book to a page that has a large battleship drawing with some specifications. The ship carries 9-21in/45, 12-6in/50, 8-4inAA, and 44-40mm AA guns. The displacement is given as 115,000 tons. The speed given is 31 knots. The armor mentioned was 17in belt and 7in + 4in decks. I did a few calculations with the BigGun program and designed the 21in/45 gun. The muzzle velocity is 2,575 ft/sec, and the AP shot is 5,000 lbs. The piece weighs 311 tons. That is using my design coefficients, and may be heavier than someone else's design. The question is: how well does this design stand up with the preliminary design program? I had some sort of problem on my first run, but one goodie is that the triple 21in gun barbette is 45 ft in diameter. I suspect that some table lookup in the power calculations was out of range for a ship of this size! If I give a power of 190,000 SHP, the expected speed is 29.6 knots. The normal displacement is 108,008 tons. I should probably be able to tell what the issue is, with a little debugging, sometime tomorrow.

Cruisers and torpedoes

As long ago as the Spanish American War, naval officers realized that carrying torpedo tubes above water on cruisers was extremely hazardous. The conventional response was to carry below-water torpedo tubes on the larger cruisers. The smaller scouts carried torpedo tubes almost like they were destroyers. The modern light cruisers, such as the Arethusa, carried substantial above-water torpedo armaments during World War One. They were frequently used in action, with some success. By the 1930's, the US Navy had removed torpedo tubes from their cruisers. The only exceptions were the Omaha's and the Atlanta class. The British never removed their torpedo tubes, while the Japanese carried highly effective and sophisticated torpedo armaments on their cruisers, especially the heavy cruisers. They proved their effectiveness at Savo Island and other battles. The Allies, especially the Americans, were shocked by the range and effectiveness of the Japanese 24in Long Lance torpedoes. At one point, the Americans actually were considering remounting torpedoes on 6in and 8in cruisers. It only happened post war, however, and only as ASW weapons.

Is there any benefit to speed in large ships?

Admiral Fisher would say, "Speed is armor". Without thinking about it, the natural reaction would be to say that the more speed the better. John Paul Jones didn't say "Give me a slow ship for I intend to go in harm's way". The lessons of World War II in the Pacific showed that there was still a need for ships that could make 34 to 35 knots. The requirement was caused by the need for escorts to "run" with the fast carriers. The Japanese had retained the requirement for 35 knots through the 1920's and 1930's. Their first examples were the 5,500 ton light cruisers. All of the 8in gun cruisers also aspired to 35 knots, although as the ships became heavier, they lost the ability to make that sort of speed. The United States had made a conscious decision in the 1920's to abandon high speed, after heading that direction in the 1916 to 1921 time frame. The only ships from that period to complete were the Omaha class light cruisers and the Lexington and Saratoga. They ultimately were not as fast as originally planned. They originally were all 35 knot ships. The change in direction was because of the idea that aviation obviated the need for fast ships. If anything, in the modern era, the situation has gotten even "worse" in the sense that the new ships we building and planning are slow by early 20th Century standards.

More about the light cruiser design

One merit of the light cruiser design I just described is that it has substantial freeboard. The bow has a substantial rake with the bow suitably flared. A more balanced design might scale the speed back to 35 knots and add a fourth twin turret. I actually happen to prefer triple turrets, although from a purely gunnery perspective, four twin turrets is preferable. With the barrels in separate sleeves, you can alternatively fire four gun salvos. This can produce much smaller spread at long range than triple turrets, especially of the guns are in a single sleeve.

My second Italian-looking light cruiser

I had glanced at the drawing, last night, and though that this design must be like the Muzio Attendolo, or Raimondo di Monteccucoli, but I was wrong. The dimensions are: 575ft x 52ft x 17.4ft (designed). The normal designed displacement was intended to be 6,000 tons with a 7,500 ton full load displacement. The armament surprised me, as it was only 6-6in/50 guns. There are some small patches of 1in armor, with a 1/2in deck. There was room to give the design more power, so I did. The original intent was to make 37 knots. The only thing was, is that it takes more like 104,000 SHP to reach that, rather than the original 67,400 SHP.

I can report my light cruiser could reach 39 knots

I just did a quick data entry job and ran my program for my fast light cruiser (5,000 tons). The displacement was a good estimate. At 5,093 tons the ship could reach 39 knots. The deep load speed is 36 knots. The actual Washington Naval treaty Standard Displacement was 4,452 tons. The deep load displacement was 6,680 tons. The normal range was 3,351 nm. The maximum cruising range at 15 knots was 10,054 nm. The max fuel capacity was 1,200 tons. The normal fuel load was just 400 tons.

My attempt at a Bartolomeo Colleoni-style light cruiser

My attempt at an Italian-style light cruiser caught my eye, tonight. I am guessing that my design dates from about 1973. The standard displacement was to be 5,000 tons with a 6,500 ton full load displacement. The dimensions were 555ft x 50ft x 16.3ft, with a 30ft hull depth. The coefficients were Cp=0.56 and Cm=0.90. The hull structure is rather light, the factor being 2.85 x 10^-3. That produced a hull weight of 2,370 tons. The power was 90,000 SHP normal and 108,000 SHP on overload. The machinery weight was 1,800 tons. That means that the overload SHP was 60 SHP/ton of machinery. The armament was 8-6in/50 and 4-4in/50 QF. There was only 55 tons of protection, so that ship was essentially unarmored. The design speed was 42 knots. I suspect that the actual speed would be much less than that.

My friend's GB/DL/1905 design

My friend Cliff conceived of a family of destroyer-type ships that would fill the role of both light cruisers and destroyers. The 1905 DL type was 1,200 tons with a speed of 35 knots. The armament was strange, in that the guns he specified were 4-88mm/50 QF. He also specified 2-21in torpedo tubes, although I don't believe that anyone had a 21in torpedo in service at that date. The coefficients were Cp=0.56 and Cm=0.85. The dimensions were 326ft x 30ft x 9ft. The design incorporated superfiring guns, fore and aft. There were three funnels, with two low and the first funnel raised. There was the usual raised forecastle. When I try to run my program, I am having a problem with the design being overweight. I will need to look at what could be done to solve the problem.

Narrower beam producing a better ship seems counterintuitive to me

When I narrow the beam for the Ger/BB/1907 down to 90ft, I seem to produce a better ship. The speed is somewhat higher and the metacentric height is reasonable: 3.27ft at normal load and 4.68ft at deep load. The displacement comes down to 24,948 tons for the normal displacement. The design goal was 25,000 tons, so this works very nicely. The thing is, why shouldn't a 105ft beam work? Isn't more, better, even for beam?

The problem seems to be "excessive beam"

I experimented with a 95ft beam for the Ger/BB/1907 design, and the metacentric height dropped to something closer to an acceptable number. That tells me that the problem is related to a beam being greater than needed, given the other design parameters.

My Ger/BB/1907 design

I'm experimenting with my Ger/BB/1907 design. The basic concept was a 25,000 ton ship with 8-12in/50 guns and 12-4in QF. The lower belt was 13in as was the turret face thickness. The barbettes were 10in. The decks are 3in + 1in. The designed speed was 24 knots. The dimensions were: 620ft x 105ft x 26ft, with coefficients of Cp=0.56 and Cm=0.95. The main problem I am seeing is a metacentric height that is too high. The ship would be excessively stiff, which I would think would mean that it would have a tendency to roll. The speed isn't a problem. Because of the combination of length and displacement, 46,591 SHP is sufficient to reach 24 knots. What seems to have been my originally designed power, 54,000 SHP, would actually give a speed of 25 knots. I can't tell if the stability issue is a "bug" in the specification or the actual design.

There is not as much weight information for WWI destroyers as I would like to see

The definitive book on British Destroyers (March) is sorely lacking in the sort of data that we need to be able to design WWI-era destroyers. That is not to say that there is none, for there is a bit. There is just not the breadth of data that would need to design a range of destroyers (large and small, from 1905 to 1921). D. K. Brown generally doesn't have that sort of data, either. He is more concerned with what I would call "structures".

An 870 ton 1905 destroyer

My German 1905 destroyer (admittedly, a "super ship") was 870 tons designed displacement. I seem not to be able to make that work with my program. The "Standard Displacement" is 865 tons, but the "normal displacement" is 1,103 tons. The machinery produces 27,000 SHP and a speed of 32 knots at the normal displacement. The dimensions are 270ft x 28ft x 10.46ft, with coefficients of Cp=0.66 and Cm=0.74. The armament is 2-4in/50 QF and 2-18in TT (actually 17.7in). All 18in torpedoes of this era were actually 45cm in diameter, even the British "18in".

Nathan Okun on the Bismarck, compared to contemporaries

Nathan Okun is the foremost expert on armor and penetration of our time. He has an instructive article about the Bismarck's protection system compared to contemporary ships. By the time he wrote this article, the wreck of the Bismarch had been found and explored.

D. K. Brown's book A Century of Naval Construction

The book is dated, but has a good deal of information about what happened with British warship design and shipbuilding from 1919 to 1945 (he covers the earlier periods as well). D. K. Brown writes that Stanley Goodall was the greatest naval architect of all time. He certainly was a giant in his field. His first ship design was for the Arethusa class light cruisers of 1912. They set the pattern for modern cruiser design. He had his hand in submarines, destroyers, and aircraft carriers, as well. His best ships were never built: the 1921 battlecruisers cancelled because of the Washington Naval Treaty.

You couldn't build a balanced cruiser within the 10,000 ton limit

Norman Friedman's reflection of considered opinion up until WWII was that you couldn't really build an 8-in gun cruiser that would be a balanced design within a standard displacement of 10,000 tons. The Japanese approach was to try to build 10,000 ton ships but do whatever was needed to build a successful ship. That mean that their ships exceeded 10,000 tons by a good amount. That was true for the Italians, as well. I have written previously about the Trento and Trieste. The Americans, who wanted the treaty regime to "work" tried hard to stay within the 10,000 ton limit. The result was that they produced ships that were seriously compromised. Some of their best ships were "taken apart" at Savo Island. Those were ships that they sorely needed, as well, such as the Astoria, Quincy, and Vincennes. Of the 18 pre-war heavy cruisers, they lost the Chicago, Houston, Northampton, Indianapolis, Astoria, Quincy, and Vincennes. The Indianapolis had almost survived the war, before being torpedoed.

The North Carolina Class Battleships

I was amazed at how Garzke and Dulin blow off any criticism of the North Carolina and Washington. Norman Friedman makes clear how close they came to failing. My estimate as to the cause of the disease was the extreme measures taken to keep the design within the 35,000 tons standard displacement. They failed, but in doing so, they severely compromised the design. The worst feature was the severe longitudinal vibration. That problem was "bandaided" by trying various combinations of propellors, which partially helped. Almost as bad was the lack of hull strength. The symptoms showed up when the North Carolina was torpedoed, and flooding was much more extensive than should have been for a new ship. Another example was the collapse of the Washington's bow after a collision with the Indiana. A battleship should have been able to shrug off such a collision, but that was not the case with the Washington. The ships were also too wet, as the hull depth had been drastically reduced as another weight-saving measure. There is a picture showing whitewater breaking over the bow, almost continuously, and a huge wake, while escorting a carrier in wartime. The basic concept for the class was sound. They just had a poor implementation.

The Japanese heavy cruiser Takao

Janusz Skulski's book about the Takao gives some of the coefficients and other numbers, which I found very instructive. Left to my own devices, I have typically thought that cruisers would have a prismatic coefficient (Cp) less than 0.6 and the midship coefficient around 0.9. I seem to be pretty much wrong, at least for fast cruisers. The coefficients for the Takao were Cp=0.627, Cm=0.822, waterplane coefficient=0.721, B/H=2.776. The weight basis for machinery seems to have been 51.42 SHP/ton of machinery.

American triple turrets with guns all in the same sleave

I consider that the American practice of having triple turrets with three guns in the same sleeve was a bad practice. The opposite extreme was the British triple 4in gun mounts on the Renown and Repulse, as originally built, which added unneeded complexity for rapid fire guns. The American triple 14in gun turrets on battleships were the first appearance of three guns in a single sleeve, as far as I can tell. I suppose that it was an attempt to simplify the design. Apparently, saving weight was also a factor. The real reason that the single sleeve happened is that the Americans lacked experience with long range firing with triple turrets. To get smaller spreads, individual sleeves were critical. There needed to be a way to make small corrections in elevation for individual guns. Apparently, the American system didn't allow for this feature. If the guns got out of alignment from firing, there was no way to realign them. The same bad practice was continued for the "Treaty Cruisers", apparently up through the New Orleans class.

DL-1 Norfolk: another Atlanta class variant

The DL-1 Norfolk was based on the Atlanta class light cruiser hull. The post-war goofiness had set in by the time she was designed. She was armed with only 8-3in/70 rapid fire guns and 4-twin 20mm AA mounts. She also had 8-ASW torpedoes in single mounts and 4 of the "Weapon Alpha" devices. He speed was 33 knots, showing how the navy had backed off from higher speeds after the end of the war. Since 1949, armaments and speeds have decreased. Much of the weight and volume now goes to electronics. The navy decided that the Norfolk type was too little capability for the cost: a self-inflicted wound, typical of the Cold War era.

The fast AA cruiser devolved to the Mitscher class DL design

When the fast anti-aircraft cruiser armed with twin 5in/54 guns seemed to grow too large, the navy ended up building a very large destroyer in place of that design. The ships were originally classified as destroyers (DD), but ended up as destroyer leaders (DL). These were the Mitscher class ships. They had several of the twin 5in/54 gun mounts. They had a very similar look, as they had the twin cruiser funnels, similar to the Atlanta class ships.

US Navy thinking about speed in cruisers

Before 1921, the US Navy still believed in fast cruisers. In the 1920's, that thinking changed. The idea was that aviation made speed in cruisers irrelevant. Given that, 32 knots was more than adequate. What they didn't realize was the impact that aircraft carriers would have on tactics. By 1944-1945, American thinking had changed. Now, they wanted 35 knot cruisers, if they could get them, to run with the aircraft carriers. There was a replacement for the Atlanta class cruisers that would have been armed with with twin 5in/54 guns in power mounts. The Atlanta class turned out to be too slow, although they had a good anti-aircraft armament. The idea was to build a faster ship that would still be a good anti-aircraft platform. Again, this was needed for the fast carrier task forces. A good source on the subject is Norman Friedman's book U. S. Cruisers.

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.

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.