A Compliant Surface Mooring System for Real-Time Data Acquisition

U.S. GLOBEC Georges Bank long-term moored program : part 1 - mooring configuration

“…In GLOBEC, we adopted the use of the elastic tethers that keeps the mooring cable taut and off the bottom, and allows the use of lighter weight hardware, mooring cable and buoy. This approach has worked well in the Gulf of Maine (Wood and Irish, 1987), in Massachusetts Bay (Irish, et al 1992) and in GLOBEC on Georges Bank , Irish, 1997and 2000, and Paul, et al, 1999. The compliant tethers keep the mooring watch circle small, so there is reduced chance of fishing gear entanglement as the anchor is nearly under the buoy.…”

“…The buoy (Fig. 9) was a reworked steel float as used in the Gulf of Maine , Irish et al, 1992and Wood and Irish, 1987. For the first six-month deployment, only surface sensors were put on the buoy because we were unsure of the survivability of the system in the harsh environmental conditions found on the Crest of Georges Bank.…”

The determination of the elastic modulus of rubber mooring tethers and their use in coastal moorings

“…Figure 7 shows the elastic tethers in the middle of the mooring with sensor packages above it and the release and bottom flotation below (Irish and Kery, 1996, Irish, 1997, Paul, et al, 1999. Figure 8 shows the elastics at the bottom of the mooring (Wood and Irish, 1987, Geyer et al, 1992, Irish and Kery, 1996, Irish, 1997and 2000. The location at the bottom was selected because sensors spaced along the mooring cable received power down the cable and sent signals back up the cable to the buoy for storage and telemetry.…”

“…As the tethers normally don't have the capability of supporting electrical conductors, they must be located below the electromechanical cable. In bottom located tether applications, both four (Wood and Irish, 1987) and six tethers have been successfully used in an assembly (Irish and Kery, 1996, Irish 1997and 2000. Figure 6 shows the four-tether assembly used in the mooring configuration in Figure 10, and Figure 7 shows a six-tether assembly after recovery used in the mooring configuration shown in Figure 9.…”

“…The elastic tethers deployed in GLOBEC were used until they were damaged by fishing activities or recovery operations, or were stretched so the splices slipped by unknown reasons (Irish, 1997 and2000) -none lasted more than 18 months. In the Gulf of Maine (Wood and Irish, 1987) and in Massachusetts Bay (Geyer et al, 1992) the tethers were deployed for one year or more. In the Gulf of Maine, the depth was incorrectly read from the Precision Depth Recorder (improperly corrected for transducer depth), and the moorings were deployed with tethers stretched at slack water to about 200%.…”