4.0 Deployment Work on Monday and Tuesday, August 21 and 22, 2000
4.1 Fish Cage Assembly at the Portsmouth Naval Ship Yard Dry Dock No. 3
A team of UNH and Net Systems personnel worked at Dry Dock No. 3 on Monday from Gary Normandeau’s barge (Pickering Marine) and the RV Galen J. to assemble the cage system. The net was lowered by crane and attached to the top of the cage with eight quick connectors, the perimeter lines were stretched (by a rope come-along) and attached to the rim, and lines were attached to the tensioning/harvest ring at the bottom of the cage with 1 inch shackles. The harvest ring was then lowered to the bottom of the spar spreading and tightening the net. The harvest ring was maintained in place by four bolts and wing nuts that are periodically adjusted. The newly painted nylon net with a 4 cm stretch gave off a Caribbean blue glow in the water.
Figure 7. A to scale drawing of the top of the anchor line, the grid corner rig and float and the lower bridle line. The lower bridle line is shown in its two positions (1) cage on the surface with line up, and (2) counter weight on bottom and cage in lower position.
Figure 8. A top view of the Northeast grid corner rope ring with four load cells attached. The strongback to the lower left (in the lower riser line side of ring) carries the electronics pressure case with batteries and recorder for the four load cells. The telemetry wire runs from the electronics to the transmitter on the fish cage. The load cell cables to the electronics pressure case and the telemetry cable from the pressure case to the fish cage are not shown.
Figure 9. In running the electrical cables from the electronics to the four load cells, enough slack had to be in the cables, and they had to be protected from abrasion by all possible movement of the load cells, anchor line, lower bridle line, and cage bridle line.
On Tuesday, while the Nobska was working on the first two anchors, another crew was working at the Portsmouth Naval Shipyard completing the Northern net cage for deployment. Two load cells were attached to the cage rim, and electrical cables run from the load cells up to the cage platform. The electrical cables were attached to the net rope with tie wraps. Slack was left in the cables to allow for movement of the load cells. The electrical cables were tied to the net after the tensioning ring had been fully extended to pull the net tight. In addition, the cage bridle lines were attached to the load cells, one of which contained the electrical telemetry cable from the northeast corner. This wire was also run up the net and tie wrapped into position. The environmental sensors (pressure, temperature, optical backscattering and acoustic currents) were mounted on a frame that bolted to the fish cage spar. This was lowered into position with the barge crane and held by a rope while bolted. The cables from the environmental sensors were run through a hole in the spar deck, and the telemetry and load cell cables were protected from chafing by garden hose and also run through the hole in the spar deck. This hole leads into the electronics mounting tubes that will be installed by divers later.
When the cage was assembled, Dave Fredriksson tied an InterOcean S4 current meter inside the net to measure the water velocity in the net during the cage tow out to the site on the next day. Jim Irish also prepared a Sea Bird pressure instrument that Dave attached to the bottom of the fish cage. Then the barge crane was used to lift the cage as high as safe (about 1 meter), and a pelican quick-release was used to drop the cage. The response as the cage moved back to equilibrium position will give parameters important to understanding the cage's behavior as a damped harmonic oscillator. Four separate observations were made. The Sea Bird pressure sensor was set to sample at 4 Hz for 14.5 minutes every 15 minutes. Good data was collected and is being analyzed to assist the cage and mooring modeling effort. The cage overshot about 10% of the displacement, and reached a maximum negative displacement about 25 seconds after release.
Return to the Top4.2 Nobska Loading and Departing WHOI.
The ropes with electrical cables, a 1,100 lb anchor for possible offshore fish cage "normal mode" tests, chain, hardware, temporary fish cage mooring and shipboard support equipment was loaded on the FV Nobska on Friday and Monday. It departed the WHOI dock at 1400 EDT on Monday 21 August for the Port Authority Pier in Portsmouth, New Hampshire. On board the Nobska were its crew and Will Ostrom from WHOI. Jim Irish drove up on Monday with the load cells and environmental sensors, and Walter Paul followed on Tuesday with the four-load cell corner ring assembly.
Back to 3.0 Fish Cage Moorings.
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Continue to 5.0 Tuesday, August 22 2000