Boat davits or simply davits are a type of metal structure that is used on ships, big boats, and cruise ships. Davits are crane-like instruments that are used on aquatic vehicles to hold, lower, raise and support objects like smaller boats, dinghies, and anchors. Davits are also sometimes referred to other similar crane arms where they are used to support suspended load in other applications.
Boat davits particularly are used on bigger boats to hold lifeboats and lower them on embarkation level in an emergency situation. Also, boat davits are used to lowers lifeboats into the water to retrieve someone in case of man-overboard.
Since lifeboats are a requirement on bigger water vehicles, boat davits are also mandatory for their easy movement. That is why naval architects design these davits to fit effectively into limited deck spaces and provide easy access in an emergency situation. To accommodate different types of vehicles and requirements, there are different types of boat davits available.
1. Gravity Type
The most common type of boat davit is the gravity type. It usually consists of two main parts, the crane arm and the deck frame that acts as a runway for the arm. When a lifeboat is being lowered into the water, the arm of the davit travels down the runway until it reaches the fixed spot where the boat is disengaged from the davit hook and ready to be lowered into the water.
Then continuous veering of the hoist wire travels the boat into the surface of the water. During the hoisting phase, the hoist wire’s ball-weight engages a stopping point on the davit hook. When the boat reaches the hook, the hoist wire transfers the ball weight to the davit arm, where it moves back up the runway until it reaches the housing position.
2. Traversing Gantries
Traversing gantries are usually used in aircraft carriers where the lifeboats are housed at gallery deck level boat bays. These gantries allow the boats to be lifted easily clear of the crutches and traversed off to the carrier’s side. The winch on the gantries is fitted with a wire with a compensating mechanism attached to its lead which allows for the raising and hoisting of the boat. The gear in the mechanism is designed to automatically alter the length of the falls to aid the boat’s vertical movement onto the water surface. A man at the front and back end of the boat is positioned to retain the disengaging hook and the fall block.
3. Hinged Screw Type
The third type of boat davit is the hinged screw type that was used mainly by the majority of destroyer ships and frigates for general purposes. These davits have a worm-wheel attached to the davit that uses a threaded screw on the extending davit arm. The worm and worm-wheel can be rotated by a handle to turn the davit in or out. The davit arms use I-bar sections that are shaped to hold the boat in upright against the gripping pads when it is in the inboard stowed position. The weight of the boat is them transferred to the keel chocks installed on each davit.
4. Pivot Torque Type
Pivot torque type davits like gravity types have two main components, a deck frame, and a davit arm. Together the frame and the arm along with the boat hinges on the carrier’s deck pivot. A coil spring is installed between the deck frame and davit arm to help relieve some of the resistance the davit suffers while hinging outboard when the ship has an adverse heel. This coil spring has enough effort bring the center of gravity of the davit outboard of the pivot pin. Then the weight of the boat is transferred to the davit hook, where it engages or disengages during the hinging process.
If you are searching for a boat davit for your vehicle, or want to find out more about boat davits then visit the Euro Offshore BV website.