Davit arms are an indispensable component of modern naval architecture. A davit is a mechanical arm that can pivot out from its position folded against the side of a ship or boat's superstructure to raise or lower a heavy weight. One of the most common application of davits is to raise and lower lifeboats, but they are also used to help handle heavy fuel hoses as well as cargo items and spare parts.
Quadrantal davits are one of the oldest types still commonly in service. Usually used for smaller loads, such as the lifeboats carried by yachts and other private vessels, these are purely mechanical in their functioning, being deployed and operated by means of a hand-cranked winch.
Gravity Roller Track Davits
Gravity roller track davits use the force of gravity to deploy the arms from which the load (universally a lifeboat in the case of this system) will be deployed. They are known for a lighter weight than some other gravity-operated davit systems as well as the ease with which their relatively small footprint and overhead volume can be squeezed alongside the superstructure of vessels. When released, the "goose-neck" arms from which the lifeboat is suspended collapse along roller-lined tracks until the deck of the lifeboat is even with that of the ship from which it is being boarded.
Single Pivot Gravity Davit
More mechanically simple than the roller track davit, the single pivot davit rocks out over the side of the mother vessel on a joint (the eponymous single pivot) until the lifeboat deck is even with that of the ship.
Freefall davits take into account the development of the freefall lifeboat, which is designed to be deployed by simply dropping it from the side of the ship rather than slowly lowering it via a mechanical or electric winch, which have proven unreliable. The freefall davit is characterized by a pair of arms which rapidly swing the boat out over the water and away from the hull of the mother vessel before dropping it into the water below.
Crane davit is a catch-all term for a variety of davits used for deploying lifeboats as well as transferring heavy cargo, such as spare engine-parts or munitions, from shore to ship. Crane davits usually have a pivot point at their base from which they can be angled or slewed from side to side, a straight boom arm, and a mechanical or electrical winch that allows them to raise and lower objects attached to the end.
- Photo Credit lifeboat image by green308 from Fotolia.com