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Wet Navy Design Rules

by Terry McInnes

Most colony worlds will have substantial oceans as well as lakes and rivers. These bodies of water can become means of transportation between a colony town and its farms, or among several colony sites. Water may also be an avenue of exploration beyond the settled area. All you need to take advantage of water transportation are wet ships. Here are design sequences that enable the Traveller New Era referee to design muscle, wind, and steam-powered vessels that can be built using the resources of a colony world. Note that part of this design sequence uses some system and subsystem design sequences published in GDW's publication Fire, Fusion, and Steel. You should have a copy of Fire, Fusion, and Steel available as you will need some of the tables and other information contained in that publication. For convenience, Fire, Fusion, and Steel is often refered to as 'FF&S' in this chapter.

The Law of Buoyancy

All vessels that float on the oceans of a world observe a basic natural law that affect every aspect of their design, be they hollow logs or fusion powered submersibles. This basic law is the law of buoyancy. Buoyancy works like this: if an object weighs less than the weight of fluid it displaces, it will float in the fluid. If it weighs more than the displaced fluid, the object will sink. This law applies to any fluid be it a gas or a liquid. Buoyancy enables steel ships to float on oceans and balloons filled with light gases to float in atmospheres.

Wet Vessels

With buoyancy as a starting point, virtually any wet vessel may be designed using these basic design sequences. These include:

Non-Powered Vessels: These include muscle and wind-driven craft ranging from simple rafts propelled by polling or rowing to large sail-powered merchant vessels and warships.

Powered Vessels: These include surface craft beginning with TL 4 steam-powered paddle driven riverboats and steam/sail vessels, and eventually continuing to submarines and hydrofoils at higher TLs.

Ship Design Factors

Units Used in Ship Design

Displacement Tons-- This is the standard Traveller hull volume measurement. One displacement ton is equal to 14 cubic meters of volume (the volume occupied by one ton of hydrogen). In Wet Navy ship design, the hull's resistance through the water and the vessel's resulting power requirement to reach a desired speed is calculated using displacement tons. This unit is also used to calculate the speed that can be reached with a given amount of power.

Metric Tonnes-- One metric tonne of displacement is equal to 1 cubic meter of volume (the volume occupied by one ton of water). It is also equal to one ton of mass. The vessel's weight, the weight of the water it displaces, and the available free buoyancy is calculated in metric tonnes.

Cubic Meter-- The cubic meter is the standard unit of volume. One cubic meter equals one kiloliter in volume. One cubic meter of water weighs one metric tonne. 14 cubic meters of hydrogen weighs one metric tonne, and equals one Displacement Ton in volume.

Kilowatts-- One kilowatt equals 1,000 watts. This is the standard unit of power for small water craft.

Megawatts-- One megawatt equals 1,000 kilowatts. This is the standard unit of power for large water craft.

Kilometers per hour-- This is the standard unit of speed in Traveller. Two kilometers per hour are roughly equal to the ancient Terran "knot" unit of speed.

Step 1: Design Hull

Displacement is the weight of the fluid moved aside by a vessel's hull when it is floating or submerged in the fluid. If the displacement of the vessel is greater than the weight of the vessel, the vessel floats. If the displacement is less than the weight of the vessel, the vessel sinks.

Displacement is the starting point for all ship or boat designs. It is a fraction of the total hull volume expressed in displacement tons converted to the weight of the fluid it displaces (usually water) expressed in metric tonnes. The percentage of total hull volume varies with hull type. A submerged submarine, as an example, displaces 100 percent of its hull volume. On the other hand, a planing hull displaces only 30 percent of its total volume.

Displacement is calculated at one standard gravity as is the weight of the craft being designed. If the vessel is built on a world with a greater or lesser gravity, the gravity affects the weight of the fluid and the weight of the vessel equally. Therefore, the ratio of displacement to weight is independent of local gravity. However, the absolute weights of the displaced fluid and the vessel are not. A vessel that weighs more than the fluid it displaces on a .7 G world will sink just as surely as one on a 1.2 G planet. Displacement is listed in tonnes for vessels of one tonne or greater, in kilograms for smaller vessels.
To calculate the displacement vs. the weight of standard hulls listed on the Hull Size table in Fire, Fusion, and Steel:

1. Select a hull size from the Rate column in the FF&S Hull Size Table, and the material from which it is to be built from the Wet Ships Hull Materials Table.

2. Decide upon the thickness of the hull in centimeters. A thicker hull will have a greater armor value but it will weigh more. The minimum permitted thickness, regardless of the hull material selected, should be 0.40 centimeters.

3. Calculate the volume of the hull material using the procedure found in the 'Hulls'section of Chapter 1 of Fire, Fusion, and Steel. Then, multiply this figure with the appropriate weight modifier from the Hull Materials Table. Finally, multiply this number by the hull's actual thickness in centimeters. The resulting numbers is the hull's true weight in metric tons. The equation appears below:

    (Hull Volume) x (Wgt Modifier) x (thickness in cm)3D True Wgt

Hull Materials Table

TL  Hull Material        Toughness      Tonnes per     Price (MCr)
                         Modifier       Cubic Meter

0   Cured Hides (Z)      0.02           0.1             -
0   Bone/Lgt. Wood (Y)   0.1            0.4             -
1   Wood (W)             0.2            0.7             0.0005
3   Iron (I)             1.5            8               0.0016
4   Soft Steel (A)       1.7            8               0.0016
5   Hard Steel (B)       2              8               0.002
6   Light Alloy (L)      1.7            6               0.004
6   Fiberglass (Cf)      0.25           1               0.001
6   Titanium Alloy (Ct)  3              8               0.010
6   Aluminum  (Ca)       1              3               0.0015
7   Light Composite (Cl) 4              7               0.007
8   Compos. Lam. (C)     6              8               0.008
10  Crystaliron (CI)     8              10              0.009
12  Superdense  (SD)     14             15              0.014
14  Bonded SD (BSD)      28             15              0.028
17  Coherent SD (CSD)    40             15              0.035

4. Determine the hull's armor value. To do this, multiply the hull material's Toughness Modifier by the hull's thickness in centimeters. The resulting number is the hull's equivalent Armor Value.

5. Note the hull's volume in cubic meters from the Fire, Fusion & Steel Hull Size table.

6. Determine the hull type.20

7. Multiply the hull's displacement tonnage by the "% of Hull Displacing Fluid" figure for the selected hull type. This yields the volume in displacement tonnage of the portion of the hull that displaces fluid and the volume in displacement tonnage of fluid displaced.

Figure 1.

The volume of the fluid displaced is a percentage of the hull's displacement. This diagram shows a curved displacement hull vessel that displaces 50% of its hull displacement. The superstructure is separate from the hull and either of its displacements. The superstructure's volume and weight are calculated separately from the hull and added to those of the hull. Superstructures are discussed later in this chapter.

Hull Type Table

Hull Type            Resistance     % of Hull     Price
                                    Displacing    Modifier

Deep Displacement         0.9       90%           0.75
Parallel Displacement     0.7       75%           0.85
Curved Displacement       0.5       50%           1.00
Planing	                  0.3	    30%	          1.10=09
Hydrofoil (at speed)	  0.1	    10%	          1.50=09
Submerged submersible	  0.9	   100%	          1.50=09
Surfaced submersible	  0.5	    80%	          1.50=09
Submerged submarine	  0.3	   100%	          2.00=09
Surface submarine	  1.0	    90%	          2.00=09

*For basic hull only.  Thrust based-transmission must be added.

8. Multiply the tonnage of the displaced fluid by 14, then multiply the result by the appropriate modifier from the Fluid Density Table. This yields the weight of the fluid the vessel displaces. If the displaced fluid's weight is greater than the vessel's weight, the vessel floats; if less, the vessel sinks.

Fluid Density Table

Fluid                   Density Multiplier

Fresh Water             1.00
Sea Water               1.01
Ammonia                 0.75
Methane                 0.7
The result is the weight of the fluid displaced by the hull.20

9. Compare the weight of the hull with the weight of the displaced fluid. If the fluid weighs more, the vessel will float, if the vessel weighs more, it will sink. In that case, build a larger hull or choose a lighter hull material.

Length, Beam and Depth

Wet ship hulls are equivalent to a needle shaped spacecraft hull in terms of determining length from the FF&S Hull Size table. The maximum beam (width) of a hull is the length divided by 3. Finally, determine the depth of the hull (from the keel at the bottom of the hull to the main deck at the top) The result of multiplying these three figures together should equal the hull volume in cubic meters. As an example, a 1000 displacement ton hull with a volume of 14,000 cubic meters will be 90 meters long, 30 meters wide, and 15.5 meters deep.

Free Buoyancy

Free Buoyancy is the figure expressed in tons or kilograms calculated by subtracting the total weight of a vessel from the weight of the fluid it displaces. This is the weight of all additional elements you may add to the design until the vessel sinks. Calculate free buoyancy at each step during the design process when the weight of new elements such as weapons, cargo space, superstructure, fuel tankage, and crew accommodations are added to the design.


Weight is the total weight of the vessel listed in tons for large craft and kilograms for small craft of less than one ton. This figure includes the weight of the hull, superstructure if any, propulsion machinery, fuel, cargo, weapons, crew, passengers, and in the case of wind-driven craft, sails and masts. Hull weight varies widely and depends on the size of the vessel and the weight per ton of displacement of the material from which the hull is made.

Hull Form

After you have determined your displacement and the weight of the hull, select the hull form from the hull table. This determines the resistance of the vessel through the water, and each hull form's resistance figure affects the power needed to reach a powered vessel's design speed. These hull forms include:

Deep Displacement-- These are high capacity hulls are suitable for large merchant ships such as tankers and bulk carriers. However, they require more power to reach and sustain a given speed than other displacement hull types. Some 80 to 90 percent of a fully loaded deep displacement vessel's hull is below the water line.

Parallel Displacement-- Both sides of a parallel displacement hull run parallel to each other except at the bow and stern. Although easier and cheaper to build, this hull form has higher drag than a curved displacement hull. Most medium-sized merchant ships including freighters and passenger liners have parallel displacement hulls.

Curved Displacement-- This is the hull form used for most surface warships. The hull begins with a sharp bow and gently curves around the widest part of the hull, then tapers into the stern. The displaced fluid flows more efficiently with less drag around a curved hull. A vessel with a curved displacement hull will travel at a higher speed than a parallel displacement hull using the same amount of power.

Submersible-- This is a sealed variant of the curved displacement hull. It's designed for surface cruising and short submerged periods, and is relatively inefficient and noisy underwater.

Submarine-- This hull is optimized for submerged cruising. It's extremely efficient submerged, but when surfaced it generates a huge bow wave with tremendous resistance.

Hydrofoils-- A hydrofoil hull sits in the water like normal hulls when at rest or moving slowly, but rides on underwater wings at speeds over about 55km/hr. However, since the lift increases as square of wing dimensions, while weight increases as cube, hydrofoils are effectively limited to under about 300 tons mass.

Planing Hulls-- This hull is shallow and wide. At rest or at low speeds, it acts as a curved-displacement hull. As the speed rises, the hull begins to rise out of the water, and resistance drops off remarkably. Supported by the lift generated by its bottom, it will have a much higher top speed for the same power than any hydrostatically supported hull. At speed equal to 1.8 sqrt(Length) in km/hr, begins rising out of water.

Step 2A: Power

Power is needed to drive the vessel through the water. This can come from several sources including muscular power (from humans, other sentients or animals), wind power, or mechanical power.

The Types Available

Power interacts with the vessel's displacement and its hull form to produce velocity through the water. Mechanical power can be constant and drive a vessel at a constant maximum speed. Wind power is variable and is applied through a different set of principles than mechanical power, and requires its own design sequence. Muscle power may be constant for a period of time then decline.

After determining the hull's displacement, its material, configuration, and weight, the ship designer must choose the vessel's source of power. If the designer chooses to design an wind-powered vessel, he or she would skip to the wind-powered design sequence found later in this chapter. Otherwise, the designer should continue with the powered ship design sequence beginning in the next paragraph.

Powered Ships

A powered ship may range from a paddle-powered canoe to a steam boat. The design sequence is basically the same for each of these vessels and any other vessel that has a relatively constant source of power. To design a powered vessel:

Determine top design speed-- This is the maximum speed at which your vessel can travel. Note that power requirements increase by a factor of eight for each doubling of the top design speed.

Calculate hull resistance-- Use the formula R=3D(=C3WD) x rf where =C3WD is the square root of the hull's displacement multiplied by the percentage of the hull actually in the water and rf is the hull resistance factor found with each hull type in the Hull Types table. The result is R: hull resistance.

Calculate power needed to reach design speed with fully loaded hull-- Do this with the formula P=3D(RV^2/2)where P is power in kilowatts, R is the hull's resistance calculated in the previous step, and V is the top design speed. If you wish to calculate the power in megawatts divide the result by 1000 or calculate the power needed with the formula P=3DRV^2/2000.

Determine power plant-- Power plants that can be easily built on a colony world range from primitive steam engines available at TL 3 through TL 5 steam turbines. Power plants available at TL's 3 through 5 are listed in the power plant table included with this article. These include steam reciprocating, steam turbine, and internal combustion. As with other vehicle designs, install as many cubic of power plant as you need to produce the output needed to reach the top design speed as well as to provide for the vessel's other power needs. Note the weight of the power plant and subtract it from the available free buoyancy. Also, note the total fuel consumption of the power plant.

                     Power Plant Table
       (unless stated otherwise, values are per cubic meter)

TL  Type           PowOP   Price   Wgt.  Min.   Fuel   Fuel Type
                   MW/KL                 Vol.   KL/Hr

3  Early Steam
    Reciprocating  0.10     0.0005  2    0.25   0.15    Hydcrb (S)
4  Internal Comb.  0.30     0.001   1    0.05   0.2     Hydrocrb
4  Steam Reciproc  0.20     0.0005  2    0.15   0.15    Hydrocrb
5  Steam Turbine   0.35     0.002   2    1      0.15    Hydrocrb
5  Imp. Int. Comb. 0.40     0.002   1    0.01   0.25    Hydrocrb
7  Gas Turbine     0.50     0.005   1    0.5    0.3     Hydrocrb
8  MHD Turbine     0.60     0.01    1    1      0.2     Hydrocrb

* Hydrocarbon (S) indicates that this engine can only be built to
accept Wood or Coal.

Fuel Options: Steam engines of all types can be designed to use Wood or coal instead of Hydrocarbon distillates. Steam engines of TL 3 and 4 can ONLY use Wood or Coal. Also, any power plant from TL 7 and higher can be designed to burn LHyd instead of Hydrocarbon distillates at no energy penalty.
If wood is used, multiply energy output by 0.5 and fuel consumption by 3.
If coal is used, energy output remains the same but fuel consumption is multiplied by 1.5.

                    Nuclear Power Plant Table
       (unless stated otherwise, values are per cubic meter)
TL  Type           PowOP   Price   Wgt.  Min.   Fuel   Fuel Type
                   MW/KL                 Vol.   KL/Yr

6   Fission        0.30    0.1     10    30     0.75    Radioactives
7   Fission        0.60    0.1      8    20     0.25    Radioactives
8   Fission        1.00    0.1      6    10     0.1     Radioactives
9   Fusion         2.00    0.2      4    100    0.15    LHyd
10  Fusion         2.00    0.2      4    50     0.15    LHyd
11  Fusion         2.00    0.2      4    20     0.15    LHyd
12  Fusion         2.00    0.2      4    10     0.15    LHyd
13  Fusion         3.00    0.2      3    1      0.1     LHyd
14  Fusion         3.00    0.2      3    0.25   0.1     LHyd
15  Fusion         6.00    0.2      2    0.1    0.1     LHyd
16  Fusion         7.00    0.2      1    0.075  0.1     LHyd

Cold-Starting and Accelerating with Steam Engines All steam engines require 5 minutes to be cold-started. For every 50 kilowatts of power output (or fraction thereof), they require one additional minute. Therefore, a steam engine with a maximum output of 100 kilowatts would require 7 minutes to start.

In the event that a steam engine is not being run at maximum output, it requires 1 minute to generate every additional 50 kilowatts of power that it wishes to add. Therefore, if a 200 kilowatt steam engine was running at only 50 kilowatts output, it would take three minutes (of full fuel consumption) to increase its output level all the way to the maximum of 200 kilowatts.

Step 3A: Power Transmission

Determine Power Transmission-- Choose one from the Marine Power Transmission Table. These may be paddle wheels, screw propellers, hydrojets, or gravitic drive units. Note the efficiency multiplier of each unit. Multiply the power needed to reach the design speed with this multiplier and adjust the power or speed as needed. Note the weight and volume of each transmission unit and subtract the weight from the available free buoyancy. Where applicable, subtract the volume from the available hull volume.

Marine Power Transmission Table

TLTypeEfficiencyDiameter Ratio Weight Volume Cost
3 Side Wheel .75 1/10 1 ton/meter 1KL/meter 100/meter
4 Stern Wheel .80 1/10 3 ton/meter 3KL/meter 300/meter
4 Screw .95 1/1000 7 ton/meter 1KL/meter 1000/meter
6 Water jet .98 1/10000 5 ton/meter 5KL/meter 5000/meter
8 MHD tunnel .25 1/5000 10 ton/meter10KL/meter 50000/meter
10 MHD tunnel .50 1/10000 5 ton/meter 5KL/meter 100000/meter
Diameter Ratio meters in diameter of wheel, screw, or jet per metric tons of vessel being propelled. Note that where propeller diameter becomes excessive, the total diameter may be divided among two or more propellers. Propeller diameters may not exceed 10 meters. Weight3D ton per meter in diameter of wheel, screw, jet, or tunnel. Volume3D KL/meter in diameter of wheel or screw. KL/ton3D internal hull volume used for power transmission. Cost3D Credits per meter in diameter of wheel, screw, jet, or tunnel.

Available power transmission types, their advantages and disadvantages include:

Side Paddle Wheel-- This is the least efficient and most primitive marine power transmission. These have been used aboard inland and deep sea vessels, mostly powered by primitive steam engines. Side wheels are best suited for calm waters, and may be better suited to extremely shallow waters than screw propellers. Also, they greatly aid steering a vessel in tight quarters. An experienced ship's captain can spin a vessel around its vertical axis by going forward with one side wheel and reversing the other.

Side wheels are susceptible to damage. A collision, debris in the water, or a well placed shot could destroy a side wheel. They also cause problems in docking. And, in rough seas, they may be intermittently thrown clear of the water and race, causing damage to the engine by the rapidly varying load.

Stern Paddle Wheel-- As the name suggests, stern wheels are located at the stern of the vessel. Because they are located in the vessel's wake, they are more efficient than side wheels. They are also less susceptible to damage.

Stern wheels are best suited to calm inland waters and may experience racing and cause engine damage in rough ocean waters. They can also become quite large and bulky, and would not be suited for propelling large vessels.

Screw Propellers-- Screw propellers are the most common transmission devices and are the most efficient marine power transmissions for speeds up to 65 kph at mid-technology levels. They share the advantage of paddle wheels of not occupying volume within the vessel's hull. And they are relatively small and light compared with other transmissions for the size of vessels they propel.

Water Jets-- Using high-speed pumps to suck in and then eject water, these are best used on fast surface vessels. At higher tech levels, combined with the abundant power of fusion plants, these are the drive of choice for high-speed submarines because of their efficiency and relative silens.

MHD Tunnel Drive: Since seawater is conductive, an electrical current applied across a tunnel filled with water will cause a magnetic current, forcing the water through the tunnel. Early models require extremely bulky, cryogenically cooled superconducting magnets, while the advanced models are somewhat more efficient.

Step 2B: Sail Power

Wind pressure against the sails as well as aerodynamic forces, particularly with fore and aft rigged sailing vessels, generate the power that drive a vessel forward. Because wind is variable, the force that powers the vessel is variable. However, since it is possible to determine the maximum number (and area) of sails a ship can carry without being driven under, and its possible to determine the force generated by the wind blowing against these sails, the maximum speed for a sailing vessel can be pre-determined.

Sail Configurations-- There are two basic sail configurations:

1. Square rigged

2. Fore and aft

These configurations may be and often are combined on sailing vessels with more than one mast.

Square rigged-- Square rigged sails are large rectangles of cloth rigged perpendicular to the hull's main axis. They are designed to catch winds coming from the stern and from within 45 degrees from either side of the stern and take maximum advantage of these winds. To enable the vessel to sail courses closer into the wind and to help in tacking, a square rigged water craft often has a number of fore and aft sails mounted both on its after most mast and as jibs close to the bow. Square riggers are well suited for worlds with steady winds blowing from predictable directions where trade routes can take advantage of wind directions. Large merchant and men of war sailing vessels are square rigged.

Fore and Aft rigged-- These sailing craft have their sails mounted parallel to the main axis of the ship. They are exceptionally well suited for sailing with the wind coming from the beam and for sailing high up into the wind, where aerodynamic forces can pull the vessel along rather than push it. Fore and aft rigged craft are much less efficient than square riggers in taking advantage of a following wind because the after-most sail often blocks the wind from driving other sails to forward. Choose this type of rig if your craft is sailing in confined waters where frequent tacking and turning take place, or where you can't count on a steady wind from the same direction.

Sail Area-- The total sail area determines the maximum amount of force available to power a sailing vessel, and consequently the vessel's top speed. This area depends on the height and number of the vessel's masts, and the length of the yards-- wooden or metal beams that run at right angles to the mast.

Masts may be added at a rate of one per 15 meters of the ship's length. Large sailing ships are known to have three to five masts, while seven or eight masts are not unknown on the largest ships. Maximum mast height in meters equals the square root of a hull's volume in cubic meters. Maximum mast height for any vessel is fifty meters. Yards on square-rigged ships may be 130% the length of the beam. Yards on fore and aft-rigged vessels equal 50% the mast height in length.

With a square rig, calculate the sail area based on the rectangular area of the total number of sails rigged on the masts, plus 20 percent of the total to allow for jibs and stay sails rigged at the bow or between the masts. Fore and aft rigged vessels have basically triangular sails; one per mast, plus an additional 10 percent for jibs rigged at the bow.

Sail Power-- The power generated by wind on sails is determined in a standard atmosphere by this procedure:
1. Multiply the wind velocity in kilometers per hour by 0.28 to convert the wind velocity to meters per second.
2. Calculate the power available in watts with this formula. P3D {[(1286)S]V} 0.1
Where P3D power in watts
Where S3D sail area
Where V3D wind velocity in meters per second

On a world with a dense atmosphere, multiply the resulting force in watts by 1.5.; on a world with a thin atmosphere multiply by .75. Sails are impractical on worlds with very thin or trace atmospheres. Note: One kiloliter of standard atmosphere air weighs 1286 kilograms. This determines the constant in the formula used above.

Here are two examples of how ten kilometers per hour of wind can produce a vastly different amount power, depending on the sail area. The power output in both cases would increase as the wind velocity increases.

sail area    wind in km/hr   wind in m/s    watts       kilowatts
200            10             2.8         72016.00         72.016
1              10             2.8           360.08          0.36008

Note: When the power output (in kilowatts) of wind on the vessel's sails exceeds its hull volume (in cubic meters), the vessel's sails begin to take damage equal to 1 point per kilowatt of excess power. If the power output exceeds its hull volume (in cubic meters) plus its free Buoyancy, the vessel is either capsized (if it has a beam wind) or is driven under (if it has a following wind). If the vessel has wooden masts rather than iron or steel, the masts break when the wind load exceeds 75 percent of the vessel's displacement.

Sails should be shortened to reduce their area in heavy weather to prevent these disasters, and the ship should be headed into the wind in extreme cases.

When the total sail area is determined, calculate the potential speed expected at several wind velocities. Do this by calculating the power generated by the wind at various wind speeds, then calculate the potential speed with the formula: V^2=3DP^2/R where P is force in kilowatts and R is hull resistance.

This formula is based on kilowatts of power modified by the resistance of vessel's hull. Use the formula R=3D(sqrt(WD)) x rf where WD is the hull's20 displacement multiplied by the percentage of the hull actually in the water and rf is the hull resistance factor found with each hull type in the Hull Types table. The result is R: hull resistance.
Note that in some cases this calculation may result in vessel speeds exceeding wind speeds. If this occurs, reduce vessel speed to wind speed.
Sail Damage-- Determine sail damage levels: Divide the total sail area by 15 to calculate the level to destroy half the sail area; divide by 6 to calculate the level to destroy the sails and demast the vessel. Double these damage values for extra-strength synthetic sails.

Sail Costs-- Sails cost CR100 per square meter.

Sail Weight-- Dry canvas sails weigh approximately 1 kilogram per square meter. When wet, increase their weight to 2 kilograms per square meter. Synthetic sails (TL7) weigh 0.9 kilograms per square meter. However, they do not soak up water and weigh approximately the same wet or dry. Extra-strength synthetics (TL8) weigh 0.3 kilograms per square meter wet or dry. Sail Stowage Volume-- Canvas sails require 1 cubic meter of volume for every 25 square meters of sail area when stowed below decks (they may alternatively be furled on their yard arms.) Synthetic sails require .5 cubic meter of volume per 25 square meters, and extra-strength synthetics .3 cubic meter per 25 square meters.

Mast Weight and Cost-- Wooden masts weight 10 kilograms and cost CR 10 per meter of height. Iron masts become available at TL 4: they weigh .125 tons and cost CR 100 per meter of height.
Steel masts become available at TL 5: they weigh .1 ton and cost CR 100 per meter. Titanium masts become available at TL 7: they weigh 60 kilograms and cost CR 200 per meter. These values include the weight and cost of the yardarms.

Auxiliary Power-- Beginning at TL-4, auxiliary power sources may be added. These can include steam engines, internal combustion engines, batteries, fuel cells, or solar cells. Calculate the amount of auxiliary power needed for the desired speed while using the "iron breeze" and determine the weight and volume of the auxiliary power plant. Finally, calculate the auxiliary's endurance, fuel requirements, and range. Be sure to include sufficient fuel tankage for the required endurance and range. Remember, auxiliary power is needed to power any on-board electronics such as radios or sensors. This may be included in the form of wind generators, batteries, fuel cells, or solar cells if power is not desired for propulsion.

Step 2C: Muscle Power

Water craft may be powered by muscles as well as wind or machinery. Devices used to transfer muscle power to thrust include paddles, oars, and lever- powered screws.

Oars-- Oar locks allow oars to be used as mechanical levers that provide the most efficient way to transfer muscle power to propulsive thrust. Determining the amount of power generated by rowers is based on the species and skill of the rowers.

The basic value for any given species that is capable of rowing is 1/2 the species' average weight in kilograms. The average human weighs 70 kilograms. Therefore, the basic human rowing value is 35-- measured in watts of power produced by an individual human.

This basic wattage value is modified by ability. A rower's ability is determined by the total die modifier received for:

Strength Constitution Small Watercraft skill level

For each point of rowing ability, the rower is able to increase power output by 40% of the basic wattage value. As an example, an individual with Strength 7 (DM+1) and Constitution 7 (DM+1) has two points of rowing ability. Accordingly, the individual's basic wattage value is increased by 2 x 40% or 80%. This means that:

35 basic wattage x 1.83D 63 watts of total power.

Note that well-trained, highly fit individuals can easily double this level of output. On the average, professional rowing crews can be assumed to produce two times the wattage of average individuals of a given species.

For reference, average for Vargr and Aslan rowers are given below:

Species Avg Mass Basic Wattage Avg Individual

Vargr 55 27.5 50 Aslan 100 50 90

Oar-powered water craft require allocating 100 kilograms weight for each human and each rower's oar. Allocate 150 kilograms for each rower and oar if the rowers are Aslan, or 75 kilograms if the rowers are Vargr. Alocate 2 cubic meters of volume for each human rower stationed below decks within the hull, 3 cubic meters for each Aslan, and 1.5 cubic meters for each Vargr. Calculate the total power output by multiplying the individual rower's output by the number of rowers on board. Potential top speed may be calculated from the total power output.

Oars can have more than one rower to increase power. Each additional rower (after the first) adds 75% of his power to the oar. Each rower requires one meter of beam.

There is a limit to the number of oars that can be placed in a hull. Subtract twice the beam from the length of the hull in meters to calculate usable rowing space. Each oar in a bank of oars requires one meter within this space. Oars can be stacked to form more than one bank. Each bank requires one meter of height.

Oars weigh 10kg each and cost CR10 each.20

Paddles-- Light water craft may be propelled with paddles. Though this is similar to rowing a vessel with oars, less power is transfered because paddles have no leverage. A paddle will transmit 60% of the power generated by a rower using an oar.20

Paddles weigh 2 kg and cost CR10 each.

Muscle Engines: Mechanisms That Convert Muscle-Power to Useable Wattage

The following `engines' use muscle-produced wattage to power Marine Transmission systems .

Levers and Cranks: These devices are available at TL 3. They can only be used by sophonts, or creatures which can be trained to perform a repetitive, noninstinctual task. All workers re- quire at least Adequate crew positions. Species that are much larger or smaller than humans may have greater or lesser requirements.

Turnstiles/Treadmills: These devices are available at TL 1 and can be powered by any type of creature that has a movement rate of greater than `0'. All workers require 1 cubic meter per 10 kilograms of weight. So a human (average weight of 70 kg) would require 7 cubic meters of space.

Step 4: Pumps

All vessels leak at one or more points in their lives. Leaks may occur through damage, or through joints that gradually loosen, or through seepage. Water may also come aboard during heavy weather. Because of this, all vessels need pumps. Pumps aboard primitive vessels are muscle-powered. Pumps are mechanically or electrically powered on modern vessels . Be sure to install pumps with enough capacity to handle flooding in at least one large sealed compartment in case of damage.

Pumps are rated by the number of cubic meters they can pump per hour.

The Pump Table below gives the power required and the flow rate generated per cubic meter of pump volume at various tech levels. Pumps weigh one tonne per cubic meter. Power for TL2 and earlier pumps must come from muscle power at 35 watts per person.


TL	Power (MW)	Volume rate m3/hour
2-	0.005		4
3	0.005		5
4	0.01		10
5	0.01		15
6	0.01		20
7	0.01		25
8	0.01		30
9	0.03		80
10	0.04		90
11	0.04		100

Step 5: Superstructures

All surface vessels may have superstructures built on top of their hulls. Superstructures increase the total weight and volume of a vessel but do not add to its fluid displacement. Superstructures may range from small deck houses built aboard sailing vessels to massive structures almost the length of the vessel built to accommodate passengers aboard liners. Cargo vessels and warships generally have smaller superstructures-- generally not more than 20 to 30 percent of the hull's volume. To build a superstructure:

1. Determine the volume of the superstructure(s) in cubic meters.

2. Detemine the material volume (MV) of the superstructure by the following equation:
MV3D (2x(superstructure height) x (superstructure length + superstructure width) + (superstructure length x superstructure width))/100
The minimum superstructure thickness should be 0.25 cm.

2. Convert these to tons in hull equivalent tonnage.

3. Determine the weight of the superstructure(s) by multiplying the tonnage with the weight modifier from the hull materials table.

4. Determine the price of the superstructure by multiplying the tonnage by the price modifier for the selected material from the hull materials table.

Note that the hull and the superstructure may be (and often are) built of different materials such as a wooden deck house on a steel hull.

Superstructures may be used for the ship's bridge, for passenger and crew accommodations, or to house additional cargo. Deck cargo, stowed in sealed containers and stacked on deck become a type of temporary superstructure on many cargo ships. More than one superstructure may be built. A common cargo ship design is the "three-islander" with a superstructure housing the deck crew above the bow, a mid-ship's superstructure housing the bridge and officers quarters as well as messing facilities, and an aft superstructure over the fantail housing the engine room crew.

Step 6: Controls & Electronics

Unpowered primitive mechanical or basic mechanical (at TL5) controls are required for wet ships built in the context of World Tamers. Primitive mechanical controls cost MCr.0001 per displacement ton and basic mechanical controls cost MCr.0002 per displacement ton. All controls displace 0.014 cubic meters per displacement ton and mass 0.0014 tonnes per displacement ton. Any ship that employs sensors/fire directors requires controls of a tech level equal to or greater than the tech level of the sensors/directors. Also, nav aids cannot be installed at a higher tech level than the controls. Additional controls are listed on pg 47 of FF&S. Also, if any sensor has greater range than 30km, or if any MFDs are installed, a full computer must be installed. Otherwise, ships with electronic equipment that doesn't fit the above requirement only need a Model Flt computer.


Sonar is the sea equivalence of Radar. It is replaced by EMS sensors at TL-10+.

Table 7: Passive Sonar
 	Weight in tons by Tech Level	Price=09
Range	5	6	7	8	9	(Cr)=09
3	0.1	0.05	0.03	0.01	0.005	200=09
30	-	1	0.5	0.3	0.01	2,000=09
300	-	-	10	5	0.5	20,000=09
3,000	-	-	-	10	1	200,000=09
Power (MW): Weight/5
Volume (m3): Weight=D72
Table 8: Active Sonar
 	Weight in tons by Tech Level	        Price=09
Range	5	6	7	8	9	(Cr)=09
3	2	1	0.5	0.01	-	5,000=09
30	-	20	10	5	0.5	50,000=09

Power (MW): Weight/5
Volume (m3): Weight=D72
Variable-depth sonar is available beginning at TL7, costs 150%
as much as normal sonar, and has a volume equal to Weight=D73.=09

Step 7: Armament & Defenses

Turrets-- Turrets count as superstructures, and in all other ways are similar to the turrets on normal vehicles (ie if they are more than 10% of the volume they are main turrets). The turrets can be retractable if an internal volume equal to 110% of the turret is alocated (mass is equal to 1tonne/m3 of the turret, and price is Cr33/m3 of the turret).

Torpedoes-- Torpedoes are designed like submarines, at TLs below 5, they are unguided, at TL5-7 they are typically wire guided, and at TL7 and up they are typically target memory or seeker guided. Torpedo tubes are designed like Space Missles, except with the correct type of control system.20

Missles-- Designed as normal

Meson Guns-- Designed as normal

Particle Accelerators-- Usable underwater, either designed as normal, or turret mounted.

Lasers-- Large DEI lasers mounted in turrets can have their HPG in the hull. Also, standard starship laser turrets can be installed in the ship.

Defenses-- Ships can mount ESA, ERA, Nuclear dampers, Meson Screens, Tractor Beams, and Sandcasters. All but ERA and ESA are usually turret or partially turret mounted.

Step 8: Crew

Weapons and Defenses
As per weapon.

Powered Vessels

Calculate the number of crew members you need aboard your vessel. You will need crew members to stand watch on the bridge, as lookouts, and in engineering spaces.

At least one crew member must be provided for each five kiloliters of power plant aboard a TL6+ powered vessel with a power plant of one kiloliter or greater. If the vessel is fueled with coal or wood, at least two crew members must be provided for each 5 kiloliters of power plant. If the vessel is to be underway for more than eight hours, enough engineering crew members must be provided to stand two four-hour engineering watches every 24 hours. The engineering department is supervised by a Chief Engineer. If more than one crew member is on watch, the senior watch stander is an Assistant Engineer.

On merchant vessels, two senior officers, the Master and First Officer, plus an officer and crew member for each watch. Bridge crews (except for the Master and First Officer) typically stand two four-hour watches every 24 hours. A normal merchant bridge crew includes a crew member at the helm and a watch officer. The bridge crew is equivalent to the Command Crew in FF&S starship designs.

Deck Department
Minimum of three crewmembers to serve as lookouts on watch and handle maintenance plus one additional crew member per 1000 tons fluid displacement. A boatswain supervises the deck crew and their maintenance work. The Deck Department is equivalent to the Maintenance Crew in FF&S starship designs.

As detailed in Fire, Fusion, and Steel. Minimum of one if carrying passengers or if voyage is expected to last longer than 5 days.

As detailed in Fire, Fusion, and Steel. Minimum of one if carrying passengers or if voyage is expected to last longer than 5 days.

Primitive Vessel Crews

Oar-powered craft must have at least one crew member for each oar. Up to four crew members may pull on one oar. If the craft will be rowed for more than eight continuous hours, a relief rower must be available for each oar. Sail-powered craft must have one crew member per 100 square meters of sail in addition to the command crew, gunners, or ship's troops. Primitive gun crews must include one member per every 2 kilos of each gun's weight of shot; e.g., a gun firing an eight-kilo shot must have four crew members.

Step 9: Accommodations

Vessels which will house passengers and crew for more than 24 hours require extended acccommodations. Passengers require one small stateroom or may double up in a large stateroom. Crew aboard steam-powered vessels (TL4+) are accommodated two to a large stateroom while officers each have a small stateroom. In truly cramped vessels of TL 1-3 , a more basic type of extended accommodation is available: the half bunk. The half bunk is either a light frame double bunk, or hammock, with just enough space for the individual's gear and provisions.

               Pwr   Vol    Mass    MCr
Half Bunk      --     6     .25     .0025

All other accomodation ratings are the same as listed in FF&S.
Aboard primitive craft (TL-3 or lower) provide 200 kilos of weight per person. This provides for his hammock, personal possessions, and food and water for 30 days. Each person should have at least 1 kilo of food and 2 kilos of water per day, more if the weather is hot or the work is hard.

Step 10: Maintenance Points

Calculate Maintenance Points using the rule in FF&S.

Step 11:Special Considerations-- Submarines

Ballast Tanks-- Submarines have to be able to alter their buoyancy at will. In order to surface, it needs to be positive, to dive, it needs to be negative, and to maintain a steady depth buoyancy has to be neutral. The design should include ballast tanks with enough volume that, empty, the submarine's final mass is less than its displacement, and filled with fluid, its final mass is greater than its displacement.

Pumps-- A submarine requires sufficient pumps to clear its ballast tanks fairly quickly. How quickly is the designer's choice, but it will affect how long it takes the submarine to dive and surface.

Pressure Hull and Maximum Depth-- A sub's max depth is 15=D7armor value.

Minimal Superstructure-- The smoother the sub's hull, the quieter it will be while submerged. Hence, the smaller the superstructure the better, usually limited to a small, fin-shaped conning tower for use while surfaced. Advanced designs may even have retractable conning towers, which require space within the hull equal to 110% of their volume (they mass in tonnes equal to 10% of the volume of the superstructure, and costs Cr33/m3 of the superstructure). Note that submarine superstructures do count towards the craft's displacement, unlike others.

Periscopes: Two types of periscope are available to allow subs to see above the surface, a night periscope and an attack periscope.

Night Periscope-- Equipped with large optics for maximum light-gathering, a night periscope requires 15m3, masses 15tonnes and costs Cr1,500.

Attack Periscope: Smaller in diameter than the night periscope to reduce chances of detection, the attack periscope requires 12m3, masses 12tonnes and costs Cr1,250.

Sensor/Radio Masts: Retractable masts may also be fitted to allow the submarine to use its radios or make sensor sweeps while submerged. Radio masts occupy 10m3, sensor masts 15m3. They each mass 1tonne/m3, and the maximum area of the sensors is 1m3.

Snorkels: Submarines with combination airbreathing/battery power plants may have a snorkel to allow them to use their airbreathing engines and recharge their batteries while submerged. Snorkels require 30m3, mass and cost Cr1,000. Every 10 MW worth of power plant requires an additional snorkel.

Step 12: Special Considerations-- Aircraft Carriers

Helicopters, VTOL aircraft and grav vehicles can operate off any vessel with a clear deck area big enough for wingspan or rotor diameter=D71.5, or length=D71.5 for grav vehicles. Fixed-wing aircraft with a mass less than 30 tons, and equipped with arresting gear can fly from dedicated aircraft carriers. Floatplanes can be launched from ships or subs by catapult, or lowered over the side by crane for water takeoff.

Flight Decks-- Design the flight deck as a superstructure one meter thick, 1.1 times as wide as the hull, and as long as the hull. Increase the final area by 20% if the flight deck is angled to allow for both takeoffs and landings at the same time.

Catapults-- Most aircraft require catapults to take off from carriers. Non-aircraft carriers may have catapults to launch seaplanes.

Table 10: Aircraft Catapults

TL	Type	                Mass  Length    Cost Capacity
                               (tons)   (m)     (MCr) (tons)
5	Gunpowder turntable	5	20	0.05	3=09
6	Hydraulic turntable	10	30	0.1	8=09
6	Hydraulic fixed	        10	30	0.1	8=09
6	Large hydraulic fixed	15	50	0.3	13=09
7	Steam fixed	        40	100	0.8	35=09

Islands-- The small superstructure located to one side of the flight deck is called an island, and provides additional command and control space, electronics space, etc. It may be retractable, in which case it requires space within the hull equal to 110% of its volume (mass in tonnes is equal to 10% of superstructure's volume in m3, and cost is equal to Cr 33/m3 of the island). Or it can be lowered down the side of the hull on tracks. The elevating mechanism then requires hull volume equal to 10% of the volume of the superstructure, and masses 1 tonne per m3 and costs Cr100 per m3.

Helicopter/VTOL/Grav Vehicle Platforms: Non-carriers may have flat, open, reinforced deck space set aside for Helicopter/VTOL/Grav Vehicle operations. Each pad costs Cr10,000, and requires a circular superstructure 1 meter thick with a diameter equal to 1.5xwingspan, rotor diameter, or grav vehicle length. It can be retractable mounted by supplying 110% of the volume of the aircraft plus platform. It masses 1 tonne per every 10m3 of platform plus aircraft. And it cost Cr30 per cubic meter.

Sample Wet Ship Designs

Here are four wet ship designs created using these rules. They are designed to be simply and easily constructed on a frontier world using local materials. They are made mostly of local wood. Their sails are fabricated from canvas that can be woven from plant fibers using TL3 textile processing equipment.
One powered vessel (the trawler) uses an internal combustion engine imported from off world, while the other (the riverboat) uses a simple reciprocating steam engine that can be fabricated in any TL4 foundry.
These profiles are similar to other TNE starship and vehicle profiles with one addtion: the bouyancy of the vessel expressed in tonnes of displaced water. If the loaded weight of the vessel exceeds the bouyancy value, the vessel sinks.


General Data
Displacement:  20 tons	Hull Armor: 0
Length:  20	Volume: 280
Bouyancy: 140 tonnes
Cost: MCr0.34	Target Size: VS
Configuration:  Curved Hull	Tech Level: 5
Superstructure: 70m3
Mass (Loaded/Empty): 140/18.4

Engineering Data
Power Plant: 200 kilowatt internal combustion, 30 day duration
Power Transmission: 0.5 meter screw propeller
Maximum Speed: 15 kph, 11.25 kph cruising.
Maintenance: 69

Commo: 300 km Radio

Crew: 4 (1 x Engineering, 1 x Maintenance, 1 x Steward, 1 x Command)
Crew Accommodations:  4 x Small Staterooms
Cargo: 100 m3
Notes:  In trawler role, nets are carried as deck cargo and hold
ice and caught marine life.  This design may also be used as a small


General Data
Displacement:  50 tons	Hull Armor 0
Length: 28	Volume: 700
Bouyancy: 490
Cost: MCr1.88	Target Size: VS
Configuration: Parallel Displacement Hull	Tech Level: 3
Superstructure: 1400 m3
Mass (Loaded/Empty): 299/68

Engineering Data
Power Plant: 500 kilowatt early steam reciprocating, wood fueled.
5 days duration with carried fuel supply of 72 m3  of wood.
Power Transmission: 5 meter diameter stern wheel.
Maximum Speed, 15 kph; Cruising Speed 11.25 kph
Maintenance: 296

Crew: 34 (20 x Engineering, 4 x Maintenance, 8 x Command, 2 x Stewards,)
Crew Accommodations: 5 x Small Staterooms, 29 x bunks.
Passenger Accommodations: 30 x Small Staterooms
Cargo: 190 m3
Note:  In this design, the hull functions as a bouyancy platform
a large deckhouse, although some cargo and wood fuel is stored
A large wooden deckhouse provides space for the crew and passenger
accommodations as well as the pilot house. The boiler and steam engine
are located directly on top of the hull within the first deck of the
superstructure.  This vessel is designed for service on calm waters such
as rivers and lakes.


General Data
Displacement: 10 tons	Hull Armor: 0
Length: 21	Volume: 140
Bouyancy: 70
Cost:MCr0.43	Target Size: VS
Configuration: Curved Displacement Hull	Tech Level: 3
Mass (Loaded/Empty): 13.9/4.9

Engineering Data
Rigging:  2-masted fore and aft rigged sailing ship with 79m3 of sail
on0B12-meter high masts..
Speed:  The following chart shows the ketch's speed at various
wind velocities.

Maintenance: 10

Crew: 6 (3 x Maintenance, 3 x Command)
Crew Accommodations: 1 x  Small Stateroom, 5 x bunks.
Passenger Accommodations: 1 x Small Stateroom
Cargo: 9 tonnes
Notes:  This is a small sailing vessel suitable for cargo hauling
and exploration, particularly among the islands of an archipelago
and in coastal waters.


General Data
Displacement: 600 tons	Hull Armor: 0
Length: 75	Volume: 8400
Bouyancy: 4200
Cost:MCr2.88	Target Size: Small
Configuration: Parallel Displacement Hull	Tech Level: 3
Mass (Loaded/Empty): 4164/64.35

Engineering Data
Rigging:  3-masted full rigged ship with main mast height of 50 meters.
Total sail area3D 2925 m3
Speed:  The following chart shows the clipper's speed at various wind

Maintenance: 4164

Crew: 36 (29 x Maintenance, 2 x Stewards, 5x Command)
Crew Accommodations:  1 x Large Stateroom, 4 x  Small Stateroom,0B31 x
Passenger Accommodations: 4 x Small Stateroom
Cargo: 4100 tonnes
Notes:  This is a large cargo carrying sailing vessel suitable for
voyages between continents.  It has a limited passenger capacity.

®1997 by Terry McInnes. Traveller is a registered trademark of Far Future Enterprises. Portions of this material are © 1977-2001 Far Future Enterprises
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