[PnP] Ship Project - Ship Movement

Scott Adams longshot at darktech.org
Sat Sep 2 06:03:46 CEST 2006

   *  Naval Navigation

         This document covers aspects of naval navigation for the
      Powers and Perils RPG system.  First a study of Wind is given
      followed by Earth based facts.  With this rules for navigation
      follow at the bottom.

   *  Wind Information 

         In order to know the rules and system for sailing on the high
      seas and extensive waterways one must have a basic understanding
      of the science of wind.  After an explanation of wind properties
      the document will discuss the rules on ship navigation.
         Wind is moving air. Warm air rises, and cool air comes in to
      take its place. This movement creates the winds around the globe.
      Winds move at different speeds and have different names based on
      their speed. Winds are also grouped by their direction. Easterly
      winds blow from east to west, while westerly winds blow from west
      to east.  Winds occur when the surface and atmosphere warms up
      by the rays of the sun.  
         The fastest recorded wind speed is 230 miles per hour and
      occurred in New Hampshire in 1934. Although, winds can get faster
      in tornadoes. The windiest place in the world is in Antarctica.
         Since the Earth spins, the winds try to move to the right in
      the northern hemisphere, and to the left in the southern hemisphere.
      This is called the Corollas Effect.
         Prevailing winds are a series of belts around the globe that
      produce steadily blowing winds near the surface. Trade winds are
      steady and flow towards the equator. Jet streams are narrow zones
      of very strong winds in the upper troposphere.
         Winds move at different speeds and have different names based on
      the Beaufort Scale. This scale is shown by numbers from 0 to 12 which
      goes from calm air to breezes to strong winds or gales .
         The jet stream is a fast flowing, river of air found in the
      atmosphere at around 12 km above the surface of the Earth just
      under the troposphere. They form at the boundaries of adjacent air
      masses with significant differences in temperature, such as of the
      polar region and the warmer air to the south. Because of the effect
      of the Earth's rotation the streams flow west to east, propagating
      in a serpentine or wave-like manner at lower speeds than that of
      the actual wind within the flow.
         The equator receives the Sun's direct rays. Here, air is heated
      and rises, leaving low pressure areas behind. Moving to about thirty
      degrees north and south of the equator, the warm air from the equator
      begins to cool and sink.
         The sea breeze is most common along tropical coasts, being felt
      on about 3 out of 4 days. The warmer temperatures, increased solar
      radiation and generally weaker prevailing winds in the low latitudes
      promote the development of the sea breeze. In general, the climatic
      significance of the sea breeze decreases with latitude. In temperate
      regions, it is generally a phenomenon of late spring and summer when
      atmospheric conditions (higher temperatures, weaker large-scale
      winds) are most favorable to the formation of the thermally
      induced, sea-land circulation system.
         Lakes may also develop a similar local wind circulation pattern.
      Here the inland moving wind is known as the lake breeze. Lake
      breezes are quite common in late spring and summer, for example,
      along the shorelines of the Great Lakes, providing local residents
      with a place of refuge during hot, humid summer days.
         Wind speeds for maritime purposes are expressed in knots (nautical
      miles per hour). In a discussion of wind direction, the compass point
      from which the wind is blowing is considered to be its direction.
      Therefore, a north wind is one that is blowing from the north
      towards the south.

         The Beaufort Scale:

            Wind Speed  International      Effect of Wind
      Scale (Km/hour)   Description          on the sea
        0      <1       Calm              Small wavelets
        1     1-5       Light Air         Small wavelets
        2     6-11      Light Breeze      Small wavelets
        3    12-19      Gentle Breeze     Large wavelets to small waves
        4    20-28      Moderate Breeze   Large wavelets to small waves
        5    29-38      Fresh Breeze      Moderate waves, many whitecaps
        6    39-49      Strong gale       Large waves, many whitecaps
        7    50-61      Fresh Breeze      Large waves, many whitecaps
        8    62-74      Fresh gale        High waves, foam streaks
        9    75-88      Strong gale       High waves, foam streaks
       10    89-102     Whole gale        Very high waves, rolling sea
       11   103-117     Storm             Very high waves, rolling sea
      12-17   >117      Hurricane         Sea white with spray and foam

      To Convert Km/hour into Knots the conversion is 0.54 km = 1 Knot. 

   *  Earth Based Facts

         The following are actual facts from Earth ancient history.

         1. Ships can typically sail in a 25 knot wind without suffering
      structural damage.  But beyond they suffer damage.

         2. A ship can typically turn 3 degrees a second or 2 minutes
      for a full turn.  This was typical of Triremes.  Based on Trireme
      tests a ship going 6.1 knots at 32 strokes had a turn diameter
      of 62 meters (1.9 ship lengths) with only a loss of 50% in speed.
      While a ship going at 7 knots speed or 34 strokes had a diameter
      of 110 meters and only a 20% speed loss.

         3. Typically a fleet could sail 60 sea miles or 110 km per
      day in the ancient world.  

         4. Power rowing was only in light knot winds and only efficient
      up to 5-6 knots.  

         5. Propulsion was done by sails or oars.  But with magic that
      can also add or supplement another method of travel.

         6. The type of sail used depended on purpose and the winds at
      the time. Square sails were used in medium winds up to a lot of
      wind.  Square rigged sails were common in the open sea.  The
      spritsail was a foremast used to sail with a beam wind.  Square
      sails gave stability on large ships and heavy seas.  Square
      sails were typically fore and aft sails.  Square sails were
      common in the smaller seas like the Mediterranean.  
            Triangular sails (lanteen sails) gave better maneuverability.
      These sails were typically tall and high peaked sails both fore and
      aft positioned.  Triangular sails were used typically during
      weaker winds and in large oceans like the Atlantic.  
            Warships were oared typically while Merchant ships used
      triangular sails typically.

         7. Winds tend to blow stronger at midnight and dawn in some
      areas of the globe.  

         8. Best sailing was at speeds of 5 knots generally.  A galley
      was known to get 7 knots at best speed.

         9. Wind speeds: Favorable Winds - 4-6 knots (2-9 range).
      Unfavorable winds - 2-2.5 knots against winds. In fleet operations
      favorable gave 2-3 knots and Unfavorable 1-1.5 knots.
      With wind 14 knots could be done for sailing

        10. Typically rowers could get 5 knots at 30 strokes per minute.
      With the ship moving 5 meters per stroke.  A ship could go 8.5
      knots at 46 strokes giving 6 meters per stroke.  More trials show
      33 strokes giving speed of 5.67 knots with best at 6.65 knots with
      a range of 38-49 strokes.    The best speed of 6.95 started from
      15 stroke burst at 30 seconds in 500 meters.  The first 5.67 speed
      was over 2,000 meters.  Twenty five strokes was the minimum run.
      Typically rowers could go 6 knots from standing to rowing in
      just 30 seconds.  The average was 6.65 knots at 38 strokes in
      a 2,000 meter space.  It took 32 seconds for 7 knots in trials
      and 7.7 knots in short bursts with 1 rudder down.  It was possible
      for 8 knots with 1 rudder down and one half up.  This was done
      during trireme trials over days.  Thus on average rowing gave
      an average of 5.4-5.77 knots or a 6.95 knots at best speed up
      to 8.9 knots in a 8 minute burst.   The max typical speed under
      oar was 9 knots.  
            It has also been shown with an average 8.6 knots for a 17-18
      hour day with 7-8.5 hours of just rowing the ship could make 129
      sea miles or 236 kilometers. But this was extreme circumstances.  

        11. Surface currents makes up only 10% of the water in the ocean
      while Deep currents make up the other 90%.  Surface currents cover
      the upper 400 meters of the water surface.  A wind blowing for 10
      hours over the water will move the surface water at 2% of the
      wind speed.  Thus a 10 knot wind improves speed by 0.2 knots.

        12. It is common to determine 1 knot of speed equal to 1 nautical
      mile per hour of speed.  Thus if a ship travels at 20 knots in one
      hour, it would have traveled 20 nautical miles.

        13. Air at the equator moves with the ground below, so its
      east-west motion matches that of the equator.

        14. In the age of sailing ships, sea-captains took advantage of
      the global air flow system.  Sailing from Spain to America, they
      would go closer to the equator, a more southern route that took
      advantage of the "trade winds." blowing from the east. Sailing
      back home they would go further north and use the westerlies.

        15. Merchants sailed with an average speed of 5 knots.  They
      tended to sail zigzag to go with winds.  This resulted in twice
      as long trip usually.

        16. The Trireme was used before penteconters.  They had 25 Rowers
      on each side with 3 tiers of oars (1 oar per man).  Some were known
      to travel 14 knots per hour but only in good weather.  They were
      so light they could be easily blown off course in high winds. They
      used broad bladed steering oars (2 of them) each handled by 1 man.

        27. Quinqueremes came after Triremes.  They were 3-4 tier oared
      boats with 1 oar having 2 men.  They were more heavy and less prone
      to being blown off course.

        28. Cargo ships typically had an average speed of 5 knots.  They
      had to sail zigzag courses to go with the best winds.  This
      typically made trips twice as long though.

   *  Sailing in the Perilous Lands

         The following information is on rules for navigation and sailing
      in the Perilous Lands.   Obviously there are two methods to navigation
      in the game - sailing and rowing.  Rowing may not require a full day
      of rowing but when the winds are short or when a constant speed is
      needed, rowing is used.  One can alternate between the sailing and
      rowing rules as needed.  Magic may improve both methods of travel.

         A Referee who wishes to create realistic weather systems for
      weather and navigation should decide where the equator is.  According
      to Richard Snider the equator runs through the Ro'babza hidden
      city.  This places the equator far to the south on the Perilous Lands
      map.  This would clearly make the northern continent far cooler than
      those lands in the south for sea heat patterns.  Based on earth
      global air flow patterns we can then associate certain patterns to
      certain areas of the Perilous Lands.  The northern edge of the Sea
      of Tears would tend to have strong winds going west to east while
      the southern edge would have moderate winds going east to west but
      may tend to stay non-constant.  The top northern edge of the Lands
      would have west to east winds.  The great islands like A'korchu,
      Fomoria and Lemasa may have their own patterns.  But tend to have
      west to east in the northern side and east to west in the southern

         But the Referee can assign his own wind and current systems for
      each area he is gaming in.  If you sail near Clima on the north
      side the winds would tend to be from west to east.  But if the
      Referee wishes them they could move north to side like many areas
      of the nortern areas may tend to do.

         For ships navigating the Perilous Lands waters the following
      rules can be applied:

         1. Design Global and Local Weather, Wind and Water currents.
      This would include direction, speed and general climatic conditions.
      This will setup the typical sailing patterns.  Referee should apply
      seasonal data to these local systems.  In summer winds may be stronger
      with more storms compared to winter when direction of wind may
      change randomly.  At the very least the Referee should determine
      local weather and water systems for his area of play.

         2. The Referee should also determine specific water navigationl
      sites and areas.  This would include reefs, sandbars, unusually
      fast water currents, seamounts, marsh and swamp areas and even
      underwater hazards like sunken ships.

         3. To add realism the Referee can also determine navigational
      aides that might be present.  This would include buoys, beacons,
      flags, lights and lighthouses.

         4. The Referee will then have to determine the type of ship
      that is being used for travel.  Some may only sail while others
      only row.  Others may do a combination of rowing and sailing.
      Once this is determined the following charts can be used.
   *  Movement Charts

          The following information is on rules for navigation and sailing

      A. Rowing

         A average NPC class rower will have a starting EL of 1 with a max
      EL of 4 typically.  A PC class character will average EL10 with
      a range of EL 10-20.  It is estimated 4.5 strokes is equal to 1
      knot of efficient speed roughly.  Use the first chart if you wish
      to have a simplified movement scheme.  Use the second if you wish
      to determine more exact methods of travel under good winds.  Use
      the Burst chart for quick start speeds like in combat.  Fast
      Triremes are known to have been 20-50% more agile.  

         1. Simple Rowing Speed [Per Strategic Turn if no replacement crew]
                Ship/Boat Type     Range
                  Barge           10 miles
                  Merchant        20 miles
                  Warship         80 miles

         2. Typical Rowing Movement for an average rowing ship
               Number of   Knots
                Strokes    Speed    Meters Per stroke (average)
                   *         *                *
                  25        4.88             3.5
                  30        5.00             3.55
                  33        5.67             4.025
                  35        5.89             4.18
                  38        6.65             4.72
                  39        7.92             5.62
                  40        8.50             6.00
                  44        9.00             6.39

                     * - Under 25 strokes was rare
               Average - 5.4-5.77 knots cruising, 6.95 knots in a burst
               Meters per Knot was determined at 0.71 per knot.
               Above table is based on historical data.

         3. Speed Bursts
               Given a area of 2,000 meters the following is based on
            trials for speed bursts:

                Number of    Number of   Burst
                 Strokes      Seconds    Speed (knots)
                   15           30       5.65      
                   20           32       7.00
                   21           33       7.70
                   22           35       8.00

         4. Speed Modifiers [Optional]
               The first speed modifier number is for cruising speed and
            the second is for speed bursts of quick speed.   All modifiers
            are additive.  Number of Rowers may influence a ship's speed
            as well as Tonnage but there is no hard data to reflect in
            this chart at this time.  

            A. Ship/Boat Type
                 Ship/Boat Type     Speed Modifier
                    Barge            x0.125 / x0.20
                    Merchant         x0.25  / x0.10
                    Warship              -  / -
                    Fast Trireme     x1.25  / x1.20 to x1.50

                 Wind Speed 
                                      [With Ship]       [Against Ship]
                    No Winds             -  / -             -  / -
                    Poor Winds       x0.25  / x0.125    x0.125 / x0.05
                    Average Winds    x1.00  / x1.00     x0.25  / x0.10
                    Good Winds       x1.25  / x0.25     x0.375 / x0.125
                    Superior Winds   x1.50  / x0.75     x0.50  / x0.25

                 Crew Skill
                    EL    Modifier          EL   Modifier
                     0    x0     / x0       11   x0.165 / x0.330
                     1    x0.015 / x0.030   12   x0.180 / x0.360
                     2    x0.030 / x0.060   13   x0.195 / x0.390
                     3    x0.045 / x0.090   14   x0.210 / x0.420
                     4    x0.060 / x0.120   15   x0.225 / x0.450
                     5    x0.075 / x0.150   16   x0.240 / x0.480
                     6    x0.090 / x0.180   17   x0.255 / x0.510
                     7    x0.105 / x0.210   18   x0.270 / x0.540
                     8    x0.120 / x0.240   19   x0.285 / x0.570
                     9    x0.135 / x0.270   20   x0.300 / x0.600
                    10    x0.150 / x0.300   21+  x0.015 / x0.030 per EL

                    Should use a Crew or Group Average EL.  

                 Magic - As stated by the Magic Item or Spells.

         Example: A Barge is being chased by a Warship.  The Barge
         has a typical cheap crew.  Barge captain orders ship to oar.
         The Rowing Officer beats 30 strokes giving a 5 knot speed.
         The Barge crew EL is only 1.  The Warship orders a 35 stroke
         beat giving it a 5.89 average knot speed.  Both ships only
         need to cruise to close in before doing any burst speeds.
         There are good winds with both ships.  The Warship crew is
         skilled with a EL3 on average.  With modifiers the final
         speeds are as follows:
            Barge - Speed - 5.00        Warship - Speed - 5.89
                    EL    - x0.015 [1]            EL    - x0.045 [3]
                    Winds - x1.25                 Winds - x1.25
                    Type  - x0.125                Type  - -
            Final Speeds  - 6.95                        - 7.63
         The Warship should be able to catch up in a short time.
      B. Sailing Navigation

         Use information in the first chart (1) for a quick and dirty
      system of sailing speeds.  But you'll still need to determine the
      type of winds that are in the area (see #2). Once the Wind Type
      is determined use #3 to determine the random wind speed. 

         1. Simple Sailing Speed 
            The Following figures are for one strategic turn of sailing.
         These figures are for ships that hug the coastline (90% of the
         ships tend to do so).  At night these ships lay anchor.
                                    Wind speed 
               Ship Type      Poor     Average     Strong
               Merchant     10 miles   20 miles     40 miles
               Warship      20 miles   60 miles    100 miles

         2. Wind Type

            Roll D100 for the Season of the year:

               Wind Type    Spring   Summer   Fall   Winter
            No Winds/Trace   01-05   01-03    01-02  01-02
            Low Winds        06-21   04-19    03-17  03-13
            Poor Winds       22-35   20-35    18-32  14-29
            Average Winds    36-55   36-76    33-68  30-50
            Good Winds       56-95   77-93    69-94  51-97
            Superior Winds   96-100  94-100   95-100 98-100

         3. Wind Speed

            The Wind Speed could be for one hour of time or serve as
         an average speed for the entire Strategic turn.  Roll D100
         on the following chart:

              Wind Type          Roll    Knots   Beaufort Scale
            No Winds/Trace       01-50     0           0
                                 51-100    1           0

            Low Winds            01-33     1           1
                                 34-66     2           1
                                 67-100    3           1

            Poor Winds           01-25     3           2
                                 26-50     4           2
                                 51-75     5           3
                                 76-100    6           2

            Average Winds        01-20     6           3
                                 21-40     7           3
                                 41-60     8           3
                                 61-80     9           3
                                 81-100   10           3

            Good Winds           01-17    10           4
                                 18-34    11           4
                                 35-51    12           4
                                 52-69    13           4
                                 70-87    14           4
                                 88-100   15           4
                                  Roll  Knots Scale  Roll  Knots Scale 
            Superior Winds       01-02    15    5   51-52   40*    8
                                 03-04    16    5   53-54   41*    9
                                 05-06    17    5   55-56   42*    9
                                 07-08    18    5   57-58   43*    9
                                 09-10    19    5   59-60   44*    9
                                 11-12    20    5   61-62   45*    9
                                 13-14    21    5   63-64   46*    9
                                 15-16    22    6   65-66   47*    9
                                 17-18    23    6   67-68   48*    9
                                 19-20    24    6   69-70   49*   10
                                 21-22    25    6   71-72   50*   10
                                 23-24    26*   6   73-74   51*   10
                                 25-26    27*   7   75-76   52*   10
                                 27-28    28*   7   77-78   53*   10
                                 29-30    29*   7   79-80   54*   10
                                 31-32    30*   7   81-82   55*   10
                                 33-34    31*   7   83-84   56*   11
                                 35-36    32*   7   85-86   57*   11
                                 37-38    33*   7   87-88   58*   11
                                 39-40    34*   8   89-90   59*   11
                                 41-42    35*   8   91-92   60*   11
                                 43-44    36*   8   93-94   61*   11
                                 45-46    37*   8   95-96   62*   11
                                 47-48    38*   8   97-98   63*   11
                                 49-50    39*   8   99-100  64+*  12-17

            * Over 25 Knots ships begin to take damage. 

            To determine distance traveled 1 knot = 1 nautical mile
         thus a ship sailing in a 5 knot wind for one hour sails 5
         nautical miles in that hour.  

         4. Drifting

            A ship can be carried away by currents causing the ship to
         drift off course.  To determine the Navigator should roll
         each day 2D10 + his Navigator Skill EL.  Then consult the
         following table:

             Final Result     Drift Situation
                01-11           High Drift
                12-17           Low Drift
                18+             No Drift

             Low Drift [Roll 1D6]
                1-3 Move North-West or South-West 1 Hex
                4-6 Move North-East or South-East 1 Hex

             High Drift [Roll 1D6]
                 1  Move North 1 Hex
                 2  Move North-East 1 Hex
                 3  Move South-East 1 Hex
                 4  Move South 1 Hex
                 5  Move South-West one Hex
                 6  Move North-West one Hex

             [For Low Drift the direction depends on the previous direction
         they were moving.  Example: If ship is sailing south and low
         drift occurs a 2 is rolled.  The ship moves south-west since the
         ship was going south.]

   *  Final Notes

         The above information is not meant to be all inclusive for every
      boat and ship type.  Given two boats a rowboat and a merchant
      ships the rules above may have to be slightly modified.  The Referee
      will have to play with the above rules to fit their needs.
         There are many other aspects of navigation not covered here like
      techniques and technology.  Some ancient techniques include
      latitude sailing and "dead reckoning".  In latitude sailing a
      boat would sail on the lines of latitude.  Sailors would use the
      sun's position using sun dials, hands or other sun devices at noon.
      This would yield a angle used in calculations.  They would then
      sail parallel to known points of existing lands.  This method
      was more accurate than dead reckning which used guesses of where
      a ship was at any one time when the sun was not handy.  Technology
      for sailing would include advanced instruments like the astrolabe,
      sextant, sun dials among many other items.  These items are
      beyond the scope of this article as I meant to cover only movement
      in navigational terms.

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