Mack (naval architecture)

In naval architecture, a mack is a structure which combines the radar masts and the exhaust stack of a surface ship, thereby saving the upper deck space used for separate funnels and the increasingly large tripod masts used to carry heavy radar aerials.

It is a common design feature on post-World War II warships (e.g. the rebuilt Baltimore-class cruisers) and on some cruise ships.

The French Navy (Marine Nationale) used a combined exhaust stack and rear director mast on the Richelieu-class battleships in the late 1930s.

It provided unbalanced and unattractive designs, which led to a reversion to separate masts and funnels in subsequent RN vessels.

The close proximity of exhaust fumes to delicate radio and radar equipment led to corrosion problems, making macks unpopular for later designs.