[aerohead]

Hello all.As we move into the colder weather,and later as we move back into warmer times,the density of the air will be affecting our air drag.--------- For those who'd like to contemplate the implications of changing air density,the following is offered.------------------ Air density,designated by the Greek letter rho,and used in aerodynamic drag calculations is defined as the ratio of the air's specific weight,divided by the local acceleration due to gravity (g).-------------------- A sling-psychrometer can be used to measure accurate dry and wet-bulb temperatures,and using a Psychrometric chart (available from air conditioning contractors) one can determine current specific weight of air.------------ Standard air is measured around 59-degrees F and has a specific weight of 0.07651 pounds per cubic foot.------------------- (g) as measured at sea-level,is 32.2 ft/second/second.------------------ running the numbers,for standard air, 0.07651/ 32.2 = 0.002376.------------ Rho is commonly stated at 0.00238 at standard conditions.------------ Anyone with a psychrometer,or access to local weather conditions,a chart,and a calculator can calculate current air density to determine what cold winter /or hot summer air means to there drag.