Boats on large men-of-war usually are handled by powerful cranes that hook on to slings attached to hoisting eyes built into strong parts of the boat's frames. A set of davits is nothing more than a double crane, and performs the same duty in a different manner.
The function performed by the davits is the swinging out of the boat from the deck to a point from which it may be lowered; the reverse of this occurs when the boat is hoisted. Hoisting operations are done by means of wire or line tackles, which are attached to the boat's bow and stern and which lead from the davit heads to some source of power.
Radial Or Round Bar
To swing out a boat with the radial or round bar type of davit, the boat first must be hoisted clear of the deck. It must be moved aft by rotating the davits until the stem clears the forward davit. The davit then is rotated outboard to draw the boat's bow out and forward, and the after davit is rotated so that the stern will follow through. The radial type of davit provides a speedy method for swinging out a light boat.
Quadrantal
The quadrantal davit has the advantage of unnecessary hoisting of the boat prior to swinging out. The arms are fitted to a traveling gear that moves outboard on a wormshaft when a crank is turned. The davit head moves outboard in an arc of a circle, and as it rises from deck position, with the boat falls (tackles) taut, the boat is lifted out of the chocks. Heavy metal lifeboats on transport and passenger craft are handled by quadrantal davits. They can lift nested boats by swinging the top boat out, cranking in after releasing, and picking up the next one.
Gravity
The gravity type of davit is entirely mechanical, and can handle the heaviest boats. The davit arms are spanned together permanently to form a cradle, which travels up and down a track on rollers. Upon releasing a brake, the cradle carries the boat down the track; one man can put the boat over the side. The wires that slack the cradle are also the boat falls, so that further releasing of the brake will continue the boat on down to the water. Hoisting in is done by means of power winches.
Heavy assault landing craft (LCVPs) are carried in gravity davits. This type has the advantage of providing a ship with a speedy means for getting all her boats out at once with a min;mum of manpower.
Many gravity davits have wire falls that serve both to hoist and lower the davit arms and to hoist and lower the boat. Most hoisting in davits, is done by a pair of boat tackles called falls. The upper block of the tackle, containing the hauling part of the falls, is shackled to an eye in the davit head; the lower block is hooked to the boat's hoisting eye. The hauling part of the tackle is belayed (secured) to a cleat on the davit arm, and the long slack, necessary to lower the boat to the water, is coiled down for running on deck. When the boat is to be hoisted, the hauling part is led through a block at the foot of the davit to a suitable source of power.
Automatic releasing To prevent the hook from tumbling and coming out of the hoisting eye, a short lanyard on the pea of the counterbalance is figure-eighted around the shank and tip. When lowering, there must be a man in the boat tending each fall. Just before reaching the water, the line tenders throw off all but the last of the figure eights, keeping the lanyard taut at all times. After the boat is waterborne, the man in charge gives the order: "Cast off the after fall." The man tending this fall then throws off the last turn, grabs the block by the cheeks, and pushes it clear of the boat. The men on deck take it from there, pull it up, or pull it to the side of the ship. The forward fall is handled in the same manner on the order: "Cast off the forward fall." Remember: In casting off, it is always the after fall first; in hooking on, it is always the forward fall first.
Never let your fingers get tangled up in the releasing hook when letting go or hooking on. The sea may drop out from under the boat and leave its weight on the hook, which may have closed again accidentally. If your finger is in the hook, you could very well lose it. In hooking on, always lead the lanyard through the hoisting eye, and use it to pull the hook through. Haul upward to close the hook, and bend the lanyard around its shank to hold it closed.
The bottom boat rests in blocks, called chocks, fitted to the hull forward and aft. She
is secured to the deck by gripes, which usually are turnbuckles hooked to a clamp over the gunwale and attached to a padeye in the deck by means of a pelican hook. A pelican hook is a device that can be opened instantly by knocking away a ring holding it closed. Upper boats rest in chocks fitted into the boats below them, and griped down similarly.
Boats under radial and quadrantal davits are also secured on deck in the same way. Quadrantal davits, lift the boat out of the chocks, but do not lift it clear over them. The outboard half of the chock is hinged in way that it may be dropped flat, so that the boat can clear it. Dropping the chock must be done before you start to crank the davits out.
