A davit is a crane-like device used to support, raise and lower equipment such as boats and cannons on a ship.
The most popular application of davit systems is to lower an emergency lifeboat to the embarkation stage, where it can be boarded. The lifeboat davit has fallen (now made of wire, traditionally made of manila rope) to lower the lifeboat into the water. Davits may also be used to rescue staff from the water if they have fallen overboard.
The International Maritime Organization is responsible for the upkeep and service of davits. The country’s own Coast Guard is in charge of enforcing the rules.
Development
When A.P. Schat invented a series of systems in 1926 that enabled the lifeboat to skate over blockages on a ship’s hull, recognized as the “Schat Skate,” the davit tremendously increased from its initial “gooseneck shape” to the current devices.
The lifeboat was then lowered uniformly with the aid of a self-braking winch device. That type of davit crane, available from various sources, is now required by shipyard requirements. Similar Schat-developed systems are used offshore oil and gas rigs, where they are mounted around the frame.
Material development has also been a part of the davit’s development. Davits have historically been made of aluminum or steel. Recent developments in composite materials have led to the production of carbon fiber davits with a high power-to-weight ratio.
This allows davits to be stowed while not in use and the same davit to be used in several deck sockets permanently installed on deck.
Lifeboat types
Davits are made to fit into deck spaces deemed appropriate by naval architects:
- Hand-powered davit, radial (obsolete). This style was used on the RMS Lusitania’s lifeboats. Each arm must be manually rotated out; manila rope falls are used. The swung-out arm has a goose-neck shape.
- Mechanical (obsolete) – Like the radial davit, both arms are moved out simultaneously by a screw system; manila rope falls are used. The Welin Quadrant davit, which was used on the RMS Titanic, is an example.
- Gravity (industry standard) – There are many types; one person can operate; wire falls are used.
- Davit is transported to the embarkation deck via a roller that slides down a track.
- The lifeboat is pushed over the side of the craft using a single pivot point.
- Multi pivot – A common feature on cruise ship promenade decks. When the room is at a premium, this is a great option.
- The lifeboat slips off the ship in a free fall. The lifeboat must be sealed. Davits are now the most common form of davit on merchant ships. This form does not employ the use of falls.
- Fixed – This is a standard feature on oil rigs. The lifeboat is lowered into the water after being hung above the water (at embarkation level).
Components
Liferaft
These can be fully sealed, partially enclosed, or completely open. (Because there are already pictures of these on the website.)
Frapping Lines
Except for the fixed and freefall davits, these lines are used on all davits. The frapping line moves the lifeboat and the tricing pendant over to the embarkation deck to be filled.
Complaints
The Lifeboat was kept in the stored position by ropes when on the move.
Tricing pendants
Lines used to move the lifeboat over to the embarkation deck so the Frapping strings could be attached.
