Bar armor was a way of providing protection from RPGs (Rocket Propelled
Grenades) without making the vessel too heavy to float. Made from concrete
reinforcing bars or "re-bars", their purpose was to explode the rocket
before it hit the hull or the superstructure, thereby reducing the
thickess of plating needed to stop the schrapnel. The bars were welded
a few inches apart in a grillwork and were spaced about 18" away from the
hull. The space between the bars and the hull was filled with styrafoam
for a little extra flotation. Above the waterline, the space was often
used for boxes of C-rations and other storage.
In actuality, the bars did work most of the time, but not always. A
lucky shot could get through to impact the plating below and blow a hole
the size of your fist through it, spraying hot metal around inside. I'm
grateful for the times that the bars saved my butt.