Differences

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--- drawingboard:components:propulsion:water [2024/06/28 13:05] – tailkinker
+++ drawingboard:components:propulsion:water [2024/07/08 13:38] (current) – [Sail Performance] tailkinker
@@ Line 3: / Line 3: @@
 There are a wide variety of ways and means to make a vehicle move through the water.  As with most other forms of propulsion, you will start by determining the amount of motive thrust you will want for a given speed.  Bear in mind that speeds over about 60 kilometers per hour will usually require a specialized hull, hydroplanes, or an abundance of horsepower.
-To determine the thrust that you will need, start by calculating the drag of your vehicle.  Multiply your vehicle's Area value by the Streamlining Factor from the table below.
+To determine the thrust that you will need, start by calculating the Drag of your vehicle.  Multiply your vehicle's Area value by the Streamlining Factor from the table below.
 ^Streamlining  ^  Factor  ^
-|None  |  10  |
+|None  |  100  |
-|Mild  |  2  |
+|Mild  |  20  |
-|Moderate  |  1  |
+|Moderate  |  10  |
-|Good  |  0.75  |
+|Good  |  8  |
-|Excellent  |  0.5  |
+|Excellent  |  5  |
 Now that you've got the drag, you can calculate your thrust based on your desired speed.  Start by finding the cube of your speed, in kilometers per hour.  (Multiply your speed by itself, then multiply that product by your speed again.)  Divide this value by 600, then multiply by your Drag.  The resulting value will be the Newtons of thrust you need to attain that speed.
+===== Oars =====
+Not the most powerful, nor the most reliable, of propulsion systems, a decent pair of arms on a paddle or two can be surprisingly powerful.  Each set of oars produces 50 Newtons of thrust.  However, that assumes that the paddles are on oarlocks, and the rower can use both arms to full potential.  If the rower is using a paddle, rather than a set of oars, they only generate 25 Newtons of thrust.  This includes those using a double-ended paddle, as they can only use one blade of the paddle at a time.
+Each rowing station occupies one cubic meter and weighs five kilograms, and will cost 20\[ce].  Of course, the person filling that space must be considered as well;  a human being is considered to weigh 100 kilograms and to occupy one cubic meter.
+===== Sails (TR -4) =====
+Low-cost, low-tech, powerful and efficient, sails were the principal means of propulsion for water vessels for most of human history, and are still used for recreational purposes.
+However, one cannot simply slap sails on a ship without limit!  First off, adding sails to a vessel has unfortunate effects on its streamlining.  A vessel's sails cannot have a Streamlining better than Mild.  Note that the vessel's hull can still have a better Streamlining, but if the vehicle is to be used anywhere except in the water, its Streamlining is considered to be Mild.
+Second, the sails must be attached to a mast.  The maximum size for a mast is four times the vessel's Linear value, or 50 meters, whichever is less.  A vessel may have one mast if TR -4, two if TR -3, four if TR -2 or six if TR -1 or better.  Your masts do //not// need to be the same length.
+To find the maximum area of sail any one mast can support, find its total length on the Linear column of the [[drawingboard:fundamentals:scale#Volume Table]], then read back to the Area column.  Choose any size of sail up to this limit.  But note that your masts will have some mass;  if you want less sail area than your masts support, you should probably reduce the size of your masts!
+Masts and sails don't take up any volume inside the vehicle.  To find the mass of your mast, find its volume on the [[drawingboard:fundamentals:scale#Volume Table]], and divide by eight to find its mass in tonnes, or multiply by 125 to find its mass in kilograms.
+Sails will weigh 5kg per square meter, and will cost 10\[ce] per square meter.  If your vessel is TR 0 or better, you can use synthetic sailcloth, with will weigh 3kg per square meter, but will cost 100\[ce] per square meter.
+==== Sail Performance ====
+Multiple masts will allow you to hang more sail on your vessel, but you will suffer a loss of efficiency due to turbulence within the sail system.  To find your total thrust from your sails:
+  - Add one to your total number of masts, then divide by two;
+  - Multiply this value by your sail area;
+  - Multiply the product by 25.  This is your sails' thrust in Newtons.
+This assumes a fresh breeze (about 10 meters per second wind speed), which is about the strongest wind that you really want to sail in.  If the wind is stronger than this, the excess thrust generated by the wind will be eaten up crashing through taller waves.  However, if the wind is less than a fresh breeze, your speed will drop.