Quote:
Originally Posted by aerohead
1) I presented examples of 'shapes' which were optimal.
2) 'Large' was not a given constraint.
3) 'Shortening' will do exactly as you say, and lengthening will do exactly as you say with respect to interior volume.
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(1) A certain level of practicality is needed, therefore a certain level of interior space for cargo and passengers.
(2) There are four general ways of increasing or decreasing interior volume, roof height, floor height, width, and length, as well as door and wall, roof, floorboard and engine bay thicknesses (related to, but not exclusively, crumple zones)
(3) Taking any shape and making it wider or taller in order to increase interior space to an acceptable amount increases cross-sectional area and therefore increases drag.
(4) Increased length does induce a small amount of surface friction against the fluid (air) but usually makes up for it by allowing more gradual curves.
(5) Once you reach a Cd of 0.04 then increasing the length will induce greater drag but not near as much as increasing the height or width to the same interior volume mainly due to increased cross-sectional area.