Controllable pitch propellers,their suitability and economy for large seagoing ships propelled by conventional,directly-coupled engines 1

Models of a tanker of 32,000 t.dw., 16,000 BHP and a freighter of 12,300 t.dw., 7,800 BHP, each propelled alternatively by a fixed blade propeller and a controllable pitch propeller, were extensively tested in the towing tank.

In addition to the hydrodynamic results some thought is given to the possible consequences of an engine room arrangement in which the main engine is constantly turning in the same direction with only restricted variation in the number of rpm.

The economic aspects of controllable pitch propellers are also considered.