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====== Hull Shape ======

The shape of the vehicle will impact a lot of variables in the future.  Right away, it will have a significant effect on your Area value.

===== Legs =====

If your vehicle is a walker of some sort, it will need legs.  You can install as many legs as you want, but there's a big price to be paid for that.

Half of your vehicle's volume will be given over to its legs.  Divide your volume by two, go back to the [[drawingboard:fundamentals:scale|Volume table]], and look up the new Area and Linear values.  That's for the part of your vehicle that //isn't// legs.

Then take that volume, and divide it among the number of legs your walker has.  This should be done evenly, as you're going to install the walker drivetrain evenly.  Go to the Volume table, and look up the Area and Linear values for your leg.  

Total the Area volumes for both the body and the legs.

<WRAP 80% box round center>
Intending to build a 40-tonne medium walker, Gary starts with a Volume of 120.  Half of this becomes his walker's body, giving him an Area of 16 and a Linear of 4.  He decides to give his walker four legs, and divides 60 by 4, getting a Volume of 16 for each leg.  That's an Area of 6.76 and a Linear of 2.6 for each leg.  6.76 × 4 = 27.04, + 16 = 43.04 square meters total, a lot more than the 25 square meters he would have needed for a tank!
</WRAP>

===== Multiple Hulls =====

This is seen on catamaran and trimeran ships, on multi-engine airplanes (especially of World War II vintage), and in many of the more fanciful science-fiction spacecraft.  It imparts an increase in stability and maneuverability, but at the cost of increased surface area.  This will result in a greater percentage of the vehicle's mass being given over to its hull and armour.

If your vehicle falls in this category, multiply its Area value by 1.2.

===== Pressure Hull =====

If your vehicle is a submarine, it will need a pressure hull.  Multiply its Area by 1.16 to account for that hull.  Also, be prepared to spend some mass on that hull in the next step.

===== Streamlining =====

Streamlining will improve the speed of many sorts of vehicles, but at the cost of increased Area.

**No** Streamlining is the base;  there is no change in Area.

**Mild** Streamlining is typical of sports cars, most ships (anything more streamlined than a raft or barge), or propellor-driven airplanes.

**Moderate** Streamlining is commonly found on supercars, submarines, or sub-sonic jet aircraft.

**Good** Streamlining is common on supersonic jet aircraft.

**Excellent** Streamlining is normally only found on missiles, rockets or the fastest of airplanes.

^Streamlining  ^  Factor  ^  Cost  ^
|None          |    ×1    |   ×1   |
|Mild          |  ×1.07   |   ×1   |
|Moderate      |  ×1.13   |  ×1.3  |
|Good          |  ×1.2    |  ×1.7  |
|Excellent     |  ×1.25   |   ×4   |

===== Wings =====

A certain amount of wing is needed just to get in the air!  Multiply your vehicle's mass, in tonnes, by 3.6, then multiply by the Streamlining Factor from above.  That's the Minimum Wing Area you need to install.  Your main body provides a small amount of lift;  subtract one-tenth your main body's Area from the minimum Wing Area.

Then just add that Minimum Wing Area into your vehicle's total Area.  You can, if you wish, add more wing area.  It will affect certain fiddly details such as your stall speed, aerial handling and runway takeoff distance.

==== Wing In Ground Effect ====

If the wing is intended only to operate within the ground effect, you can halve the Minimum Wing Area.  However, your aircraft cannot fly higher than your vehicle's Linear value, expressed in meters.