Prahl cruise array deployment/recovery Slide 1: Winches – in our past cruises we used the grey winch on the left, which was overkill for our operations.

Prahl cruise array deployment/recovery

Slide 1: Winches – in our past cruises we used the grey winch on the left, which was overkill for our operations. Chris DuPont brought along the blue winch on the right for trace metal work. This winch or something similar would be sufficient for our purposes.

Slide 2: Array and sediment trap deployment – The array uses a 180-m ½” 8-braid nylon line with a ~100 lb weight at the bottom. It would be great if SIO can supply the weight (please let me know by June if you cannot and I will purchase one to be put on the ship before it leaves MARFAC). It has been easiest to use the A-frame for array deployment and recovery. This slide shows deployment of a sediment trap cross with 12 VERTEX-style particle interceptor traps each filled with a saline solution.

Slide 3: Sample bottles – Our most challenging bottle deployments are 25-L polycarbonate carboys. Water is transferred from several Niskins to these polycarbonate carboys and the bottles placed in bags made from cargo net. The bags are attached to the line using carabiners (rated at minimum 500 lb breaking strength). Since a 25-L carboy filled with seawater weighs ~80 lbs, it is difficult to attach the bagged bottle to a taught line. During deployment/recovery, tension is taken off the array line by clipping into a line attached to a cleat on the deck. Once tension is off the line, the bottles can be lowered onto the deck and easily/safely clipped or unclipped from the line. The distance from deck to A-frame is critical – it must be enough for us to lift all bottles from a given depth range above the deck so we can clip into a quick-link in the line to remove tension. We typically deploy about a dozen 25-L carboys or 4 depth ranges with 3 carboys per depth interval. This slide shows us recovering the array – the person kneeling on deck is clipping the deck line into a quick-link threaded into the 8-braid nylon array line. We also deploy a variety of smaller bottles (2 and 8 L).

Slide 3: Bottles on the deck. This slide illustrates removal of the bottles from the line once the tension has been taken off the line. The reverse procedure applies when attaching the bottles to the line – remove tension by clipping quick-link into deck line, attach bottles to array line, lift in air to take tension on array line, unclip from deck line and deploy.

Array Deployment/Recovery pg1

Slide 4: This slide shows the block we have used in the past. It is small enough to maximize distance from deck to block but wide enough to allow our hardware to pass easily through it.

Slide 5: Bagged bottle on line. I include this photo to clarify how the bottles are attached to the line. A quick-link is threaded through the line and the bagged bottles attached to the quick-link using a carabiner that is additionally secured with a cable tie (strength rating 100 lbs). A pigtail at the bottom attaches using a carabiner attached to the array line, which simply keeps the bottle from flopping around.

Slide 6: Spar buoy, floats. We follow the in situ array using a spar buoy equipped with an RDF (please let me know if you need the frequency) and strobe. There is approximately 10-15 m of line with three small floats between the spar and 4 hard hat floats. The 10-15 m of line is sufficient to grapple for recovery. The hard hat floats are lightweight plastic long-line floats that are attached to the array line in a fashion similar to the bottles (carabiner additionally secured with a cable tie). There is usually a mechanical quick release mechanism that we have used to hold tension on the line while deploying the spar buoy and floats. It would be great if this were still on board. I think it is standard equipment because there was a similar one on the Revelle. Please note the cleat on the deck with the green line – this is the line used to clip into a quick-link to take stress off the line while attaching (and removing) the bottles to the line during deployment (and recovery) (e.g., see slide 3).

Array Deployment/Recovery pg2

Winches

Array/sediment trap deployment

Sample bottles

Bottles on the deck

Block on A-Frame

Bottle on line