12 June, 2000
12 June 2000
Mooring - Part II.
We awoke today to a much calmer ride - we were in the ice. We headed back out of it early to find suitable water for the open ocean, anchor-last deployment for the test mooring discussed yesterday. Seabeam was used to locate a suitable target location (see Janice’s or Susan’s journal about Baby Knoll for a discussion of Seabeam). Then the Healy sailed three nautical miles past the target point so that it could lay out the mooring on its way to the target.
If you were like me, you probably envisioned them putting one end in the water and letting the rest just play out until the whole mooring was off the ship. Well, it is a bit more complicated than that! Because of the size, weight and tension involved, each piece of the mooring is attached while the mooring is held fast to the ship by ropes, then raised off the deck using an A-frame hoist and a powered capstan. Once attached, each section is then lowered into the sea off the stern of the ship. This is repeated until each piece of the mooring has been attached to the ever-lengthening line in the water. Picture it this way - to make this chain out of a bunch of friends you would tie a 20m rope to one friend and they would jump in the water (not here, they would die of hypothermia!) Then another friend holding on to the end of that 20m piece of rope and tied to a second 20m piece of rope would wait until the first piece is near its end before they jump in. This continues until all the friends have jumped in, or in the mooring’s case, until the pieces have been attached. For this 200m test mooring, this took about an hour and a half. According to John Kemp, the 4000m moorings he has done have taken as much as 23 hours!
After the mooring had been underwater for three hours, we went to recover it. After deployment, John and Jeff had used a system of triangulating the anchor’s position based on signals sent from the transponder. A signal is sent and returned from the transponder telling how far away it is from the ship. This is repeated at three other points and if you then draw a circle around each of the points representing their distances from the transponder, the circles will intersect showing you the transponder/mooring’s location. This gives researchers and exact point to return to when they wish to retrieve their mooring, which may be as much as a year after it was deployed. When John triggered the transponder to release the mooring it popped up about 100m off the starboard side of the ship. Perfection! You want it close to the ship, but not banging underneath it. Then, because it would be difficult to reach the floats from the deck of the ship, a small boat was lowered from the HEALY to attach a line with a hook to the top float cage.
Once the float assembly is hooked up, bringing the mooring back on board is like sending it off. Each section is pulled on board and each part is taken off and secured. It is important to secure (attach) things to the deck or they can roll around causing serious injury. This is the same whether you are in a 420’ icebreaker or a pleasure boat out on the lake. Once everything was secured, we were back underway headed for the ice. This test appeared to be a success.
Tomorrow we will do the anchor first deployment of the test mooring, but this time we will be operating in the ice. How do you think this will differ from today’s mooring exercise? Check in tomorrow to see!
p.s. Good luck to all my students on their final exams!!!!!
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