Composite Hopper cars vs Regular or Coke Hoppers

Composite hoppers were built during the war. (WWII) They have a steel frame and wooden sides. This was done to save on materials for the war effort. 

From the internet:

The story of these 2-Bay Rebuilt War Emergency Hoppers begins in 1942 when the War Production Board directed car builders to substitute wood for steel wherever possible in car superstructures. The familiar 2-bay “war emergency” composite hopper was a result of this directive. Those cars had wooden side sheets and end slope sheets (although the middle slope sheets remained steel.) This saved a bit over two and a half tons of steel needed elsewhere for the war effort. Unfortunately, the wood boards were considerably thicker than steel sheet which effectively lowered the cubic capacity of the car. While you could build ten composite hoppers with the steel of nine all-steel hoppers, the lower capacity of the composite cars meant you needed more composite cars to carry the same load. During 1944, the directive was set aside and cars that were on order were delivered with the familiar diagonal bracing but with all steel construction. After the war, as composite cars came due for serious maintenance, the wood side and slope sheets were replaced with steel. A large majority of the composite cars were rebuilt in this manner sometime during the 1950s.

Thank You for answering my question I appreciate it.

Southern Mike -  I've long wondered what the back story was on composite hoppers.  Thanks for your detailed explanation!  Much appreciated! 

Wow I did not realize I was not by myself in wondering this. Again Thank You for the speedy answer.