The concept of sailing ships has evolved significantly. In ancient times, sailing ships were characterized by large, fluttering sails that used wind power for propulsion. These sails were supported by wooden supports called masts. These masts were as tall as the sails and were sturdy in structure to withstand wind loads, ship motion, and adverse weather conditions.
Gradually, these sailing ships came down from the sea into the pages of history and masts began to acquire a completely different meaning. Due to the development of technology and communications, these masts have acquired a different importance on most modern naval vessels.
Ship Masts
These ship masts now serve different purposes:
- They act as carriers of light signals and audio signals, such as beacons and horns.
- Wireless transmission and communication systems capture radio signals, acting as communication towers for ships.
- Radar is an integral part of navigational devices as it provides the precise position of a ship in real time, along with the geographical coordinates of nearby land or traffic within hundreds of nautical miles.
- It also assists defending ships with highly advanced defense detection and search.
- Masts have evolved from simple mechanical supports to complex electrical, electronic, and communication devices to ensure the safety and navigation of the ship while it is underway.
A detailed description of a modern ship’s mast is beyond the scope of this article, but its design essence and basic components can be briefly explained.
A mast generally consists of the following parts:
Truss structure: This is the main steel structure where various types of equipment are placed. It is larger and heavier in defense ships. Depending on its size and complexity, it usually has a central structure of tubular, cylindrical, or conical shape. It is mounted and fixed on the upper deck above the superstructure/deckhouse of the ship, such as the bridge deck or the top of the bridge.
It also contains the main power and transportation lines. Secondary substructures emerge from the main steel structure. Depending on the complexity of the system, these branches may exist in one or more levels. Antennas, lighting, and sound systems are usually installed on these branches.
Antenna: The antenna is the most important part of any wireless transmission system. It sends signals or waves from the field and receives signals from external sources. For practical purposes, this antenna is usually placed on these outer branches of the truss structure.
Radar: After the days of the compass, radar has now been the primary source of navigation for any ship. Radar electronically transmits signals to the bridge regarding the position of the ship. The radar system is usually located at the highest point on the ship. Advanced types of radar, such as very high frequency (VHF), are used on military ships and have extremely high detection capabilities.
On most modern ships, radar is either X-band or S-band. Technically, the radar system is electronically integrated with the ship’s navigation and detection system, which consists of radio, maps, sonar, other specialized underwater systems, emergency systems such as SART, satellite communications, and Global Positioning System (GPS) devices.
Cables and Power Lines: The mast consists of a complex network of cables and power lines inside. These lines power the various systems on it and transmit electronic signals back and forth. Most of these lines are connected to the navigation bridge.
Having briefly discussed the various parts of the rudder, let us now look at the main aspects of its design from a structural point of view.
The design philosophy of the radar system usually considers the following aspects:
Strength and Durability: Since the ship is constantly exposed to various weather elements and its movement, its structure must be durable. Truss structures are usually built with high-quality steel. High-quality aluminum and composite materials are also used in many designs. Finite element analysis of the structure is mostly carried out before the structure is manufactured and installed on board.
Vibration: This is also a very important aspect, as the structural frequency of the expected loads and the electrical frequency generated by the high-voltage power supply must be evaluated against the natural frequency of the ship structure to avoid resonance. Nowadays, vibrations caused by eddy currents are also taken into account.
Fatigue: Since the mast structure is expected to remain unchanged throughout the vessel’s life, fatigue resistance is also critical and must be tested for durability under incoming loads.
Connections and Fasteners: This is an essential part of the design process as the overall structure is heavy, contains many systems and equipment, and is bolted or welded directly to the surface. Therefore, connections are checked at each mounting point to ensure that they can withstand all types of severe loads and that there will be no failure at the end.
Local stresses at hot spots in joints, welds, and connections are checked.
Corrosion due to continuous exposure to the elements.
These radars are also equipped with high-quality insulation systems to protect against lightning strikes, which are very common on the open sea, especially during stormy weather. These isolation systems protect all critical systems within the radar mast and are connected to the ship’s grounding system.
The wires are also properly designed and insulated to prevent burns and short circuits that can cause major fires on board, especially during rainy seasons.
Radars are usually installed after the ship is completed and the electrical installation is mostly complete. From a design perspective, radar equipment contains hardware elements. Most equipment, systems, and devices on masts are rated for reliability as per COLREG or LSS (Lights, Sounds and Signalling) guidelines required by classification societies and the International Maritime Organisation.
