Ship Design Guidelines

[The Rock Doctor]

Ship Design Guidelines:  In Alphabetical Order

Where in doubt, rely on common sense and historical practice. 

This is a "living" document; entries may be added as events or discussions warrant them.

Block-coefficients

0.38 is the absolute minimum.  Coefficients should be reflective of the size and speed of the vessel.

Hoists

Protected cruisers should have hoists with the gun mounts, if the appropriate technology has been researched. Destroyers of WWI had no hoists for individual guns.  A cruiser without hoists has a lower sustained rate of fire, and is more vulnerable due to the ammo exposed on the deck.

Hull Strength

Minimum 0.50 cross-sectional hull strength for ships built to Destroyer/TB tech; otherwise, composite hull strength of 1.00 is recommended.  Ships not meeting this criteria are at risk of moderator-inflicted incidents.

Length to Beam Ratio

Ratios should be reflective of the size and speed of the vessel.

Length to Beam Ratios of 12:1 (smaller, faster ships) or 10:1 (larger or slower ships) or less are reasonable and do not risk moderator-inflicted incidents.  Ships approaching circular shape risk moderator-inflicted performance issues.

Miscellaneous Weights

This will be added to as new items are suggested or become available.

Boats:  Typical ship's boats are part of fittings.  Extra boats, landing craft, or attack craft require 2 t of miscellaneous weight per tonne of boat weight:  the difference accounts for cranes and hull reinforcements.

Coalling/Oiling Gear:  Considered part of ship's fittings.

Depth-charges:  1 t per three depth charges, including rails.  1 t per thrower, once available.

Fire Control:  250 t for ships built to BB/AC Architecture; 100 t for any other ship above the nation's maximum DD/TB size; 25 t for DD/TB and ships of similar size.  Monitors may use the next-smallest system, but will suffer in engagements against moving targets.

Fluff:  Flag facilities, medical facilties, climatization, extra pumps, and so forth are assigned weight as the player sees fit.  Moderators may assign performance bonuses to the ship under specific circumstances if the facilities warrant it.

Mines:  1 t per mine, including associated laying and storage equipment.

Radar and Remote-Hearing Devices:  25 t per installation is recommended, though the effectiveness of these devices is questionable.

Torpedoes: 

16" (1890 Tech):  0.5 t each
18" (1899 and 1905 techs):  1 t each
21" (1908 tech):  1 t each
21" (1913 tech):  2 t each
24" (1918 tech):  3 t each

Troops:  1 t per four troops for short-ranged landing craft.  2 t per troop for long-term (> 1 day) embarkment.

Wireless:  10 t for a short-range (100 mile) set, 25 t for a long range (250+ miles) set.  Redundant installations are allowed.  New construction laid down 1/1/13 or later does not require weight to be set aside for short-ranged sets.

Shafts

Four shafts are the most that may be installed aboard a ship.

Speed

For ships not constructed to Destroyer/TB tech, the SS2 reported top speed is just that. For ships constructed to Destroyer/TB tech, the SS2 reported top speed should be considered that ship's top in-service speed in a seaway. To calculate the speed attained by that ship on trials in smooth water, you can use the following equation:

To calculate the trial speed, first find the base bonus derived from it's light displacement, starting with what "band" the ship is in:
<=210: 6 knots
<=250: 5 knots
<=500: 2.75 knots
<=750: 1.5 knots
<=1000: 1.125 knot
<=1500: 0.75 knots
<=1750: 0.6 knots
<=2000: 0.5 knots
over 2000 tons: 0 knots

In each band, then divide the bonus for that band by the value of the light displacement divided by the upper limit of that band..

So for instance, for a 450t (light) dd, do this: 2.75 / (400/500) = the "base" bonus of 3.44 knots.

Then mix in the machinery modifier, which is simply the normal displacement percentage of machinery/0.6 (so that a machinery weight of 60% = 1), then multiply the base bonus above by that figure.

For one example ship:
Displacement: 250t
Mach %: 51.7 (or after divided by 100, 0.517)
Speed: 28.08

Base bonus: 5 / (250/250) = 5
Mach modifier: .517/.6 * = .861667

So the bonus = 5 * .861667 = 4.31 (rounded to 2 decimal places), or 4.5 (rounded to the nearest half knot), giving a new clean water optimal condition trial speed of 32.5 knots (using the half-knot rounded figure).

Or for ease of use, use this calculator:



Springsharp

SS2 is the program we use.  We do not use SS3.  If the ship can not be designed from scratch in SS2 using our design guidelines and naval technology trees, the design is invalid.

Transom Sterns

The utility of this hull form is not yet recognized and is not to be used in designs.

[The Rock Doctor]

EDIT TRACKER

15/9/2008:

Edited Wireless Weights - not required for short-range sets on new construction

Edited Fire Control weight description - to clarify requirement for small warships

Edited Transom Sterns - more clearly disallowed

Added Springsharp - clarifying what program we use

4/2/2009:

Added Speed - detailing difference between expected service speeds vs. trial speed in small fast ships, and providing means of calculating trial speed

10/3/2009:

Updated Speed - updated method for calculating trial speed in small fast ships to a new method based largely on displacement.

9/6/2009:

Updated the location of the trial speed box to a page hosted on navalism.org.

[The Rock Doctor]

Based on SS Guidelines, and my years of watching CV design at Wesworld.  Try it out, and see how you do replicating historical designs.  Report back for discussion...


1.  Sim your hull.

2.  Use the waterline dimensions to determine the theoretical maximum number of aircraft embarked:  L (metres) * B (metres) / 70. 

3.  Determine your airgroup, subject to the limit of #2. 

If the total number of aircraft is less than 25, assign as miscellaneous weight 25 t per aircraft. 

If the total number of aircraft is 25 or higher, assign as miscellaneous weight the square of the number of aircraft (900 t for 30 A/C, 1600 t for 40).

This figure includes all aspects of the aviation component - aircraft, fuel, ordnance, catapults, aircrew facilities.   

If the carrier is a conversion, multiply the required miscellaneous weight by 1.5 to represent inefficiencies of hull form, etc.

4. If you chose an airgroup greater than 70% of your theoretical maximum, you will require two hangars.  This will determine your freeboard later on.

5.  For an open bow (Yorktown)or taking-off ramp (early Furious), raise or lower the stem as necessary.  For an enclosed or hurricane bow (Ark Royal, sim a raised forecastle extending 15% of the ship's length.  The carrier may have a modest lowered quarterdeck aft Courageous).

6.  For carriers in which the hanger floor is the strength deck and the hanger is a light-weight structure atop it (most Japanese and American carriers), your freeboard represents the hanger floor.  If the ship has two hangars, the freeboard corresponds to the floor of the upper hangar.  Bear in mind that there is probably an average cruiser-like freeboard between the waterline and the lower hangar floor.

There is no need to simulate the hangar sides or flight deck - the weight is assumed to be relatively insignificant.

Make a note directly under the SS report's "Armour deck" line that the ship has one (or 2) lightweight hangar(s)

7.  For armored box carriers, the freeboard represents the height of the armored flight deck.  Bear in mind that this will be atop one or two hangars and a typical cruiser-like freeboard.

The thickness of the armor deck should be 150% of your intended average flight deck thickness (i.e., 4.5" if you want 3").  The extra 50% represents the weight of the armored hangar floor with the same thickness.

Use upper belt armor to represent armored hangar sides.  Length will correspond to hangar length, and height to your hangar height (4-6 metres, depending on preference)

Make a note directly under the SS report's "Armour deck" line that the ship is an armored box carrier, and note the actual average thickness of the flight deck and hangar floor.  Note also the number of hangars.