Our largest hydraulic deck crane ever, an 8000 Pound Capacity Knuckle-Boom, Boom Extending Deck-Crane. Perhaps our most ambitious project to date, is this tender-handling system designed by Nautical Structures in cooperation with Kevin H. Calhoun, Naval Architect, and as part of a major vessel refit in the Rybovich-Spencer Shipyard, West Palm Beach, Florida.

The second image at right shows the Knuckle Boom Deck Crane during its Lloyds testing trials in the Rybovich-Spencer Shipyard, in West Palm Beach, Florida.

The challenge was to develop a crane system with the capability to launch and retrieve a 30 foot "Python" Tender from either side of the 180 foot CRN built Motor Yacht. To make the process just a bit more interesting the tender stores below the upper boat deck, adjacent to the ship's gymnasium in a specially constructed
Tender Store Room.

As part of this project Nautical Structures constructed a hydraulic deck hatch, 32 feet long by 11 feet wide, and weighing just over three tons. For security while at sea, nine hydraulic dogging cylinders engage the watertight frame around the hatch. When opening the hatch, sensors indicate when all hydraulic dogs are retracted and the large hatch-opening cylinders are enabled. The hatch, which doubles as the ceiling of the Tender Store Room, opens just over center to maximize the opening into the Tender Store Room and provides the access necessary to retrieve the tender.

The EZ-8000 Knuckle Boom, Boom Extending Deck Crane stores in 15 feet on deck. When fully deployed it boasts an outreach of 31 feet, six inches with full load capacity of 8000 pounds. With five axis range of motion this is one of the most versatile crane designs available. While its most daunting task is the launch and retrieval of the 8000 pound "Python" tender, its daily duty will be to service the two boat-deck tenders, launching and retrieving the tenders from either side of the yacht. The Crane is controlled with proportional joysticks, providing finger-tip precision and the ability to control up to three functions simultaneously. Two halogen flood lights are installed at the end of the knuckled boom for night launching operations.

The EZ-8000 Knuckle Boom, Boom Extending Deck Crane is a true "Yacht Crane", and not a marinized version of a truck crane. Constructed primarily from
aluminum alloy, all materials used in the construction of this equipment were carefully considered for the intended sea duty. The stainless steel axles are isolated from the aluminum structure with composite bushings.The structure is finished with a five-step painting process. The metal is etched, and a two-part epoxy primer is applied. Fairing compounds are laid on and blocked down, and a second coat of the epoxy primer sandwiches the fairing. Three coats of Sherwin Williams' Proline polyurethane paint is applied.

This is one of a series of knuckle boom deck cranes produced by Nautical Structures. A 4000 pound capacity crane was delivered to Lurssen Yachts, Bremen, Germany for a 96 meter yacht recently delivered. A 2500 pound capacity crane is currently under production for the 120 foot M/Y Lady Linda, built by Delta Marine, in Seattle, Washington.