Model tests and full scale operation with surface piercing propellers

Surface piercing propellers have had several successful applications in field of high-speed vessels; rarely, however, have been used for conventional displacing vessels, where they are also known as partially submerged propellers (PSPs).This paper deals with the application of a PSP on a new livestock carrier, displacing about 5000t, which has been successfully trading since 1998. After a brief introduction, where the state-of-the-art is described, a few theoretical issues are discussed, and short description of the research and design work is presented. The results of various other tests performed with PSPs both with models and in full scale are also illustrated and briefly discussed; these have then been compared with results obtainable from conventional propeller installations. Risks of possible undesired phenomena and benefits related to the application of large scale PSPs on displacing ships of different types and sizes are also dealt with, and an overview of investigations recently carried out on a particular application of a PSP is illustrated.