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

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

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

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

Drawing of the GB/CL/1921a design

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

A fast escort

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

A 36-knot light cruiser

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

My 1921-style light cruiser

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

Picture of the "Super-Fast Battlecruiser Alternative 2"

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

More about the "Alternative Super Fast Battlecruiser" design

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

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

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

Volume analysis is difficult, due to lack of data

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

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

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

Six shafts on a narrow ship

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

Hitting the wall...

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

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

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

The 29,000 ton battleship design

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

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

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

Machinery volume and SHP/ton

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

I'm doing all this empirical work to calculate volumes

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

The next step is to add "volume" analysis

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

New features to my Warship General Design program

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

I want to add range calculations for specified cruising speed

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

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

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

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

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

Winston Churchill on Destroyers

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

The "Super Fast Battlecruiser": experiments

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

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

Metacentric height at legend displacement (GM)=5.25 ft

I have looked at Greg Locock's DreadCAD Excel spreadsheet

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

I've been doing some experiments with Cp and Cm

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

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

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

actual speed for 280000.0 SHP is 36.4983 knots

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

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

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

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

This is part of the result from my program:

Designed draft=29.4996 ft

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

Legend Displacement=31230.0

Legend Draft=26.8499

Submergence of 1390.61 of actual displacement per foot

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

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

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

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

Metacentric height at legend displacement (GM)=4.73343 ft

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

British weight groups

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

My latest attempt at specifying the "super fast battlecruiser"

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

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

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

At Displacement=28708.8 tons

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

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

actual speed for 410000.0 SHP  is 40.0295 knots

Metacentric height at legend displacement (GM)= 3.30897 ft

My 17in/45 gun design

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

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

     Relative ballistic performance: 0.80 

     Muzzle energy = 378.3 megajoules = 139421.9 foot-tons 

     Relative muzzle energy: 0.89 

     Typical barrel length: 46 calibers 


     Elevation          Range        Time      Velocity   Fall Angle 

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


          Armor Penetration - Vertical Belt Armor 

               (Relative armor quality, 0.83) 

               Maximum penetration: 41.00 inches 


     Elevation          Range            Belt       Deck 

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


     Maximum range = 38900 yards at 46.4 deg elevation 

Weight groups

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

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

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

Designed Displacement: 17,000 tons

Legend Displacement: 17,630.8 tons

Length: 521.5ft

Beam: 82ft

Draft: 28.8ft

Cp: 0.556

Cm: 0.90

Cb: 0.5004

Machinery: 54,000 SHP

Designed Speed: 24 knots

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

Secondary Battery: 12-3in/50 QF

Tertiary Battery: 6-47mm/50 QF

Main Battery Turret Armor: 9in

Main Battery Barbette Armor: 9in

Lower belt: 9in

Upper belt: 6in

Belt forward: 6in

Belt aft: 6in

Lower deck: 1in

Upper Deck: 1in

Deck forward: 1in

Deck aft: 1in

Anti-Torpedo Bulkhead: 1in

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

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

Designed draft=27.8055 ft

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

Legend Displacement=17630.8

Legend Draft=28.8372

Submergence of 768.321 of actual displacement per foot

At Displacement=17630.8

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

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

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

actual speed for 54000.0 SHP  is 24.5081



Deep Load Displacement=19299.4

Deep Load Draft=30.9476

Submergence of 778.621 of actual displacement per foot

At Displacement=19299.4

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

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

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

actual speed for 54000.0 SHP  is 24.152


At Legend Displacement:

Waterline Coeff=0.671089

Block Coefficient=0.5004

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

CG above keel = 30.23

Stability Coeff (nu)=0.559814

Height of CG as a fraction of the depth=0.559814

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

Metacentric height at legend displacement (GM)=5.20457 ft


At Deep Load Displacement:

Waterline Coeff=0.671089

Block Coefficient=0.5004

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

CG above keel = 28.6229

Stability Coeff (nu)=0.530053

Height of CG as a fraction of the depth=0.530053

Freeboard=23.0524
Draft=30.9476
Beam=82.0

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

I want to revisit Colonel Cuniberti's 1903 battleship design

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

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

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

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

Metacentric height at legend displacement (GM)=8.84576 ft

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

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

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

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

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

Metacentric height at legend displacement (GM)=9.36508

Waterline Coeff=0.661362

Block Coefficient=0.513

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

Metacentric height at deep load displacement (GM)=10.4897

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

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

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

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

The real ship figures were:

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

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

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

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

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

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

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

Designed draft=25.5564 ft

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

Legend Displacement=26139.6

Legend Draft=26.7214

Submergence of 1226.82 of actual displacement per foot

At Displacement=26139.6

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

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

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

actual speed for 152400.0 SHP  is 33.1235

Waterline Coeff=0.65521

Block Coefficient=0.5035

Stability Coeff (nu)=0.546438

Height of CG as a fraction of the depth=0.546438

Freeboard=25.2786

Draft=26.7214

Beam=85.0

Metacentric height at legend displacement (GM)=7.49797

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

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

Output from my program for the Queen Elizabeth class

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

Specification filename: GBBB1912ShipSpec.txt

Designed draft=27.0885 ft

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

Legend Displacement=27887.0

Legend Draft=27.9784

Submergence of 1177.65 of actual displacement per foot

At Displacement=27887.0

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

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

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

actual speed for 75000.0 SHP  is 25.1725

Deep Load Displacement=30458.8

Deep Load Draft=29.9594

Submergence of 1193.43 of actual displacement per foot

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

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

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

actual speed for 75000.0 SHP  is 24.411

Waterline Coeff=0.717182
Block Coefficient=0.60325

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

Metacentric height at legend displacement (GM)=4.09912

Waterline Coeff=0.717182
Block Coefficient=0.60325

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

Metacentric height at deep load displacement (GM)=5.5319

Warship General Design Program status

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

Armor on the "upper deck sides"

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

Some approximations from Edward L Attwood

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

For ships with a fine waterplane, the approximation is:

tons per inch = (Length x Beam)/600

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

tons per inch = (Length x Beam)/530

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

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

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

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

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

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

Issues for General Design of Warships

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

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

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

My warship general design program: status

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

Ship:  Ger/CB/1906

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

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

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

Hull Weight=12393.2

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

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

Main Battery armor thickness: 6.0

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

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

Waterline Coeff=0.65521

Block Coefficient=0.5035

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

Total Armor Wt=4483.48

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

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

Metacentric height (GM)=4.50924

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

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

Stability calculations

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

Experimenting with my Ger/CS/1905 design

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

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

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


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

More experimenting with the Hood-type ship

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

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

legend displacement: 36,300 tons

length: 890ft

beam: 104ft

draft: 26.5498

SHP: 144,000

Cp: 0.55

Cm: 0.94

Part of the power curve:

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

I was experimenting with a Hood-like ship

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

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

"an Oldie but a Goodie" book on Naval Architecture

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

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

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

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

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

Computer program status

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

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

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

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

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

Machinery Weight=1500.0

Hull strength

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

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

Capitani Romani class cruisers

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

Warship General Design program status

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

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

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

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

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

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

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

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

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

Armament:

1. specify gun characteristics
2. specify gun mounting

Armor:

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

Speed:

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

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