48
Russ E. Davis
float data. Richardson, who was creative and loved boats, airplanes, and adventure,
set the audacious goal of using moorings to explore the circulation along a 1000-km
line between Massachusetts and Bermuda. This would require moorings (i.e., anchor,
mooring line, and flotation) strong enough to resist currents and instruments that
could provide accurate measurements from these moorings. This remarkable effort,
which lasted over a decade, was a fundamentally experimental war against Murphy’s
Law.
The Buoy Project began with the most difficult mooring type using a surface
buoy subject to high loads from strong surface currents and surface waves. The surface
float, a 2.9-m-diameter toroid with 3-ton displacement, had a rigid bridle connecting
to the mooring line and a tower holding anemometer, light, and radio beacon. It was
chosen for stability to overturn, simplicity of construction, strength, and ease of handling. The initial mooring line was polypropylene rope the buoyancy of which reduced
peak line tension and surface-buoy size. Because loading caused the polypropylene
to slowly creep and the conventional-lay rope to untwist (and in-line instruments to
rotate rapidly), the line was switched to plaited nylon line with increased stretchiness,
reducing wave loading and allowing the line’s scope to increase with loading. Fastenings corroded at unpredictable rates that were apparently related to stress. Fish bite
was identified as a cause of mooring failure so the upper mooring line was switched
to torque-balanced steel wire. Anchors were hybrids of weight to resist mooring-line
tension, chain to keep the mooring line off the bottom, and ground tackle to resist
sliding over the bottom. Deployment was as follows. The surface buoy is deployed
first, then the string of line and instruments is assembled as the mooring streamed
behind the ship, and finally the anchor is dropped overboard, causing the surface
buoy to race across the surface until it was over the anchor, sometimes moving 3
knots with a rooster tail behind it. Edward Brainard (1967) captured the challenge of
Richardson’s operations:
My first impressions . . . were highlighted by the awesome feeling of great depths,
15,000–18,000 ft., tremendous Gulf Stream currents 4.5 knots or more, and the
great loneliness of little 8 ft. diameter toroids sitting out in the vast cruel sea
hundreds of miles from home.
With this perspective, one sees that although the average mooring life was barely
3 weeks, the early WHOI buoy work was a remarkable success. Indeed many of
the components and techniques used in moorings today are evolutions from those
developed by the Buoy Program.
Richardson left WHOI in 1963 and Buoy Group leadership passed to Nick
Fofonoff and Ferris Webster. Fofonoff, who had already significantly advanced the
theory of nonlinear ocean circulation, was an inspired choice who led the Buoy
Project for more than a decade. During most of this time Bob Heinmiller managed the
group as it methodically converted moorings from engineering challenge to measurement system; Heinmiller and Fofonoff (1995) describe this evolution. Initial surface
mooring recovery involved a weak link that was broken by tensioning the mooring.
Russ E. Davis
float data. Richardson, who was creative and loved boats, airplanes, and adventure,
set the audacious goal of using moorings to explore the circulation along a 1000-km
line between Massachusetts and Bermuda. This would require moorings (i.e., anchor,
mooring line, and flotation) strong enough to resist currents and instruments that
could provide accurate measurements from these moorings. This remarkable effort,
which lasted over a decade, was a fundamentally experimental war against Murphy’s
Law.
The Buoy Project began with the most difficult mooring type using a surface
buoy subject to high loads from strong surface currents and surface waves. The surface
float, a 2.9-m-diameter toroid with 3-ton displacement, had a rigid bridle connecting
to the mooring line and a tower holding anemometer, light, and radio beacon. It was
chosen for stability to overturn, simplicity of construction, strength, and ease of handling. The initial mooring line was polypropylene rope the buoyancy of which reduced
peak line tension and surface-buoy size. Because loading caused the polypropylene
to slowly creep and the conventional-lay rope to untwist (and in-line instruments to
rotate rapidly), the line was switched to plaited nylon line with increased stretchiness,
reducing wave loading and allowing the line’s scope to increase with loading. Fastenings corroded at unpredictable rates that were apparently related to stress. Fish bite
was identified as a cause of mooring failure so the upper mooring line was switched
to torque-balanced steel wire. Anchors were hybrids of weight to resist mooring-line
tension, chain to keep the mooring line off the bottom, and ground tackle to resist
sliding over the bottom. Deployment was as follows. The surface buoy is deployed
first, then the string of line and instruments is assembled as the mooring streamed
behind the ship, and finally the anchor is dropped overboard, causing the surface
buoy to race across the surface until it was over the anchor, sometimes moving 3
knots with a rooster tail behind it. Edward Brainard (1967) captured the challenge of
Richardson’s operations:
My first impressions . . . were highlighted by the awesome feeling of great depths,
15,000–18,000 ft., tremendous Gulf Stream currents 4.5 knots or more, and the
great loneliness of little 8 ft. diameter toroids sitting out in the vast cruel sea
hundreds of miles from home.
With this perspective, one sees that although the average mooring life was barely
3 weeks, the early WHOI buoy work was a remarkable success. Indeed many of
the components and techniques used in moorings today are evolutions from those
developed by the Buoy Program.
Richardson left WHOI in 1963 and Buoy Group leadership passed to Nick
Fofonoff and Ferris Webster. Fofonoff, who had already significantly advanced the
theory of nonlinear ocean circulation, was an inspired choice who led the Buoy
Project for more than a decade. During most of this time Bob Heinmiller managed the
group as it methodically converted moorings from engineering challenge to measurement system; Heinmiller and Fofonoff (1995) describe this evolution. Initial surface
mooring recovery involved a weak link that was broken by tensioning the mooring.