The first ship to use EDO Western's new Model 482 NAVTRAK docking system will be one of the six 312,000-dwt tankers being built in Japan for National Bulk Carriers for long-term charter to Gulf Oil Corporation. This ship is scheduled for delivery in February. Another installation will be made on Nomikos (London) Ltd. new 250,000-dwt tanker, Alexander the Great, building in Japan and scheduled for delivery in 1970.
With the advent of the giant supertankers, berthing and mooring has become a problem. The gentlest of bumps by a 300,000-ton ship, for example, can cause considerable damage.
The EDO Western Corporation, Salt Lake City, Utah, a subsidiary of the EDO Corporation of College Point, N.Y., has developed a computerized sonar docking system for use on large vessels. The digital-computation and sonar equipment serves as an instantaneous four-direction recorder of absolute over-the-bottom velocities. It measures the fore or aft speed, and also the bow and stern lateral movement of the ship either to port or starboard, displaying the results in feet per minute and at one-second intervals.
EDO Western's Model 482 NAVTRAK employs the so-called Doppler effect. The digital computation system of the NAVTRAK docking sonar translates the Doppler-effect information into bow and stern lateral velocities, either to port or starboard, and fore or aft velocity. It automatically adjusts for error that could occur because of variations in water temperature and salinity. The electronic equipment also compensates for ship motion (pitch, roll, yaw and heave), providing real over-the-bottom velocities with accuracy estimated at 99 percent.
The computer transmits the figures on fore or aft and bow and stern movement second by second to a primary display panel on the bridge and to optional remote panels in either or both wings of the ship.
Two transducers, which send and receive the sonar signals, are hull-mounted, one fore and the other aft. They can be installed in sea-chest assemblies to permit removal without the need for drydocking.
Operating conditions for the NAVTRAK docking equipment range from a minimum of one foot clearance beneath the hull of the ship to water depths in excess of 150 feet.