In the last few years the ship building industry has seen a variety of new technologies entering the market. If observed carefully, it can be seen that all the advanced technologies are more inclined towards environmentally friendly traits and improved efficiency. In this article we will learn about a new technique for designing ship hull which is known as M-hull technology, and is different from the conventional ship hull design that we studied in a previous article.
M-hull technology is an innovative development that uses a specifically M shaped hull to create an air cushion below the vessel in order to reduce the air drag. The M shaped hull captures the bow wave energy to form an air cushion, which thus reduces the drag. The reduction in drag provides exceptional speed to the vessel, a trait that conventional vessels are devoid of.
Understanding What Happens Beneath the Vessel
A conventional vessel when moves through the water, it generates a bow wave which is followed by a trough and stem wave. The formation of bow wave depends on the speed of the vessel, its draft, water depth and shape of the bow. This means that if the shape of the bow is blunt and the draft of the vessel is more, then the bow waves produced will be large; whereas if the bow is blunt and the bottom is straight, the bow waves generated will be smaller.
The bow waves have a peculiar trait. They move forward at a faster speed initially and then gradually lose speed. The waves move at an angle to the hull and generate an energy that can be harmful to the nearby boats or structures. The M hull technology utilizes this energy for a better use by increasing the efficiency of the vessel and preventing wastage of the bow wave energy.
Construction and Working
The design of M hull consists of three main features as follows:
- the central displacement section
- the planing tunnels
- rigid skirts
The central displacement section is what supports the vertical skirts that are attached through out the structure. The design is made in such a way that the skirts are able to capture the hull waves inside the planing tunnel. The incoming bow waves spirals along the planing tunnels and trap the incoming air, forcing it towards the aft.
The planing tunnels also have a slope moving downwards to compress the aerated water for forming the air cushion and reducing the drag. This air cushion increases with the speed of the boat, thus providing additional thrust to the vessel and also reducing the fuel intake.
The first vessel to be made by using M Hull technology is Stiletto, a craft entirely made of carbon fiber. Stiletto is capable of speed up to 50 knots. As the vessel moves forward the stern wake energy that is flowing aft is captured by millions of bubbles under the ship. This characteristic not only helps in making an air cushion underneath the ship but also to absorb the noise made by ship’s machinery. The technology is presently being used by U.S Navy; however it will soon be seen in large transport and commercial vessels.