The slipway is generally an economic system for dry docking small vessel up to say 1000 tons displacement and even up to say 5000 tons displacement.
The definitive characteristic of the slipway is the use of the inclined plane to bring vessels out of the water and dry dock them. This takes the form of ways beams to carry the load with anti-friction, usually rails, on which to move the cradle that carries the vessel out of the water. There seems to be little uniformity in the design and detailing of these systems and in the methods of constructing them. In general, these components seem to be undertaken on an ad hoc basis with little input of lessons from prior projects or of in-depth design. Commonly projects are undertaken by a process of “copy what was done last time and don’t ask any questions”!
In approaching the design and construction of a slipway it is essential to understand the limitations of the construction process and the conflicting requirement of the finished structure. Marine construction tends to be the roughest of all fields of civil engineering while to be effective, the ways demand very high quality of construction comparable to the ways for container cranes. Successful slipway projects are only achieved by the happy marriage of these two and that requires a lot of ingenuity. It is the lack of knowledge of ways and means of designing and constructing these systems that has held back the more general use of the slipway system.
This paper reviews the general issues involved in the ways for slipway systems and, where relevant, the interaction with the other two main components, the cradle and the winch. It then explores the various elements of the ways and the methods for designing and/or constructing them. The problems of meeting the requirements for the construction of the underwater portions are particularly onerous. Specialized and sophisticated equipment and temporary works are a feature of construction today. This is even truer in the construction of slipway ways but notably lacking in application: the field being treated as something of a “Cinderella”.
Specific topics treated in order to understand the field cover ship loads, ways geometry, ways structure, anti-friction, methods of construction, specialized equipment needed and methods of dimensional control and allowable tolerances.