Originally posted by BTAirsol
Based on the weight of water, 1gal = 8.33 pounds. Then if fuel weighs close to the mass of water, 75 gal drop weighs 624.75 pounds. 150 gal drop tank weighs 1,249.5 pounds. Area needs to be calculated for the drop tank, but I bet they are close to this size of the bombs. The casing on alum drops vs steel bombs will be different in mass weight.
For 100/130 avgas, calculate using 6 pounds per gallon (close enough for government work).
Thus:
75 gallons x 6 = 450 lb + 45 lb for tank and hardware, or 495 pounds per tank.
P-38 with 150 gallon tanks: 150 x 6 = 900 lb + 70 lb for tank and hardware, or 970 pound per tank.
But, for real drop tanks the capacities were usually different from their general classification. Here's some examples:
75 gallon steel tank (P-47 and P-51): Actual capacity was 84 gallons.
108 gallon steel or paper tank (P-47 and P-51): Actual capacity was really 108 gallons.
150 gallon steel tank (P-38 and P-47 in SWPA): Actual capacity was 160 gallons.
200 gallon steel tank (P-47): Actual capacity was 215 gallons.
200 gallon paper tank (P-47): Actual capacity was 205 gallons.
300 gallon steel tank (P-38): Actual capacity was 310 gallons.
My regards,
Widewing