Passive heave compensated davit

A passive heave compensation system for the at-sea loading and unloading of objects on a water vessel, the system comprising:

• a water vessel having a bow and a stem, and a vessel centerline extending in a bow-to-stem direction, the water vessel having an upper deck, and wherein the water vessel is afloat in a body of water;
• an object to be loaded and/or unloaded onto or from the water vessel, the object having an object centerline;
• a passive heave compensation arrangement comprising:
• a slewing gear attached to the upper deck of the water vessel;
• a stanchion extending axially in the vertical direction, wherein the stanchion has a deck-attachment end and a boom-attachment end, and wherein the deck-attachment end is attached to the upper deck via the slewing gear so as to be rotatable about a vertical axis;
• a boom extending axially and generally in the horizontal direction or at an angle to the horizontal direction, the boom having a stanchion-attachment end with an elbow thereat, and a head-attachment end;
• a first pin having an elongated first pin axis, wherein the boom is attached to the stanchion via the first pin, the boom pivotable with respect to the stanchion about the first pin axis;
• a capture head attached to the head-attachment end of the boom for capturing and cradling an object;
• a first winch on the stanchion, the first winch including a first winch cable connected to the elbow of the boom, whereat the first winch manipulates the pivoting motion of the boom about the first pin axis;
• a second winch on the boom, the second winch including a second winch cable that extends into the capture head and is connectable to the object, whereat the second winch manipulates capturing and cradling of the object from either the upper deck or the body of water, and wherein in the at-sea capturing and cradling of the object that is floating in the body of water, the vertical distance between the capture head and the object is a Reel Distance Rd, and wherein during a heave event a Heave Distance Hd is the vertical displacement distance, with respect to the water vessel, the object moves under a force of the water, and wherein the vertical displacement distance may be an upward displacement or a downward displacement;
• an elongatable and retractable gas spring extending from the stanchion to the elbow of the boom, wherein during a heave event the gas spring provides passive heave compensation by elongating if the Heave Distance Hd moved by the object is a downward displacement or retracting if the Heave Distance Hd moved by the object is an upward displacement, to negate the vertical displacement distance Hd applying a force to move the boom by the Heave Distance Hd, thereby keeping the Reel Distance Rd constant during the heave event.