International Shipbuilding Progress

Using a linear theory the highest possible efficiency is considered for sculling propulsion by means of one wing or by two wings. The span of the wings is allowed to be finite and their interaction in case of two wings is taken into account. For a number of motions of the wings the quality number is calculated.

In a previous paper by Cardo et al. an analysis of the onset of subharmonic and superharmonic components in nonlinear rolling motion, leading to jump phenomena in the maximum amplitude, has been carried out.

Here, the probability of those phenomena as dependent on initial conditions for a set of frequencies of the exciting term around both 1/3-subharmonic and fundamental has been estimated. The onset of these phenomena is established by the numerical solution of the nonlinear rolling equation with initial conditions determined by a random simulation method.

New design techniques and components nowaday available were applied on the concept of controllable pitch propellers. Computational power is needed for detailed prediction of hydrodynamic load, for which purpose a discrete vortex model is applied. For controllable pitch propeller design a reliable calculation of blade spindle torques is very important.

Powerful computers and programs also enable detailed strength analysis of mechanical parts by means of the finite element method in order to obtain the most rational material use, resulting in the lowest weight and price. Model tests were performed in order to proof the validity of the calculated results.

The development in measuring techniques offers the possibility to select an accurate and reliable non-mechanical sensor for pitch measurement. The abolition of the mechanical pitch feed back and the application of standard hydraulic components result in a simpler design of the inboard oil transfer box on the shaft.

The fuel consumption of a ships propulsion unit with a controllable pitch propeller can be minimized by a microcomputer programmed in such a way that the most favourable combination of pitch and revolutions is found for a desired speed under all conditions.