Trawls_SOW_20230217_revised20230412_0002.docx

Scope of Work – 70-ft. wing trawls and 39-ft Yankee trawls for fisheries research Construction and delivery of four (4) 70-ft wing trawls and four (4) 39-ft Yankee bottom trawls with roller footgear per specifications below. Both trawl types are used to quantify the abundance and species composition of demersal (bottom-dwelling) fish in the Laurentian Great Lakes. Recent unexpected losses of existing trawls have depleted the Great Lakes Science Center’s net inventory. Additional back-up trawls must be acquired to ensure the center can complete its science mission and fulfill its obligations to key partners, such as the Great Lakes Fishery Commission. Sample nets can be provided to the awardee as a template for net construction; however, for purposes of estimating material and labor costs, net specifications are described below and in the attached cut sheets. Final specifications and cut-sheets for the new nets also must be provided by the awardee.

Net specifications: 70- ft. (2- seam) wing Trawl with 70-ft. headrope and 90-ft footrope Net made of twisted (black) nylon netting of the following size mesh and thread (see Figure 1):

· 4-in. stretch mesh No. 18 thread dogears

· bosom and square 5-in. stretch mesh No. 15 thread upper body

· 4-in. stretch mesh No. 15 thread lower body

· 3-in. stretch mesh No. 18 thread funnel

· 2-in. stretch mesh No. 36 thread codend (140 mesh around × 120 mesh deep); inner liner of ½-in. stretch mesh No. 147 knotless nylon netting (300 mesh around × 300 mesh deep)

· Codend rigged with 2-in. I.D. galvanized net rings for lazyline and purse rope

· Head and footropes of 5/8-in. diameter Poly-Dac net rope with legs extended 20 feet and wire rope thimbles spliced in at each end

· Wing ropes of ½-in. diameter braided nylon rope rigged down each seam, beginning at wing tips and extending downward through codend

· Floats: Plastic, 5- to 8-in. diameter; floats spaced at center of bosom of headrope (number of floats determined by net manufacturer)

· Footrope chain: 3/8-in. galvanized steel

· Upon completion, net treated with preservative

· Replacement of twine mesh with Dyneema (combination of high-density polyethylene and ultra high-density polyethylene) is acceptable. Nets constructed from Dyneema would not require floats. Figure 2 shows a possible design for a 70-ft wing trawl constructed from Dyneema.

Shipping Address (70-ft wing trawls): U.S. Geological Survey-Cheboygan Vessel Base, 606 Water St., Cheboygan, MI 49721

Figure 1. Original design/specifications for 70-ft. wing trawl constructed from twine.

Figure 2. Modified 70-ft. wing trawl design constructed from Dyneema.

Net specifications: 39- ft. (2- seam) Yankee Trawl with 39-ft. headrope and 51-ft footrope with with roller footgear (see Figure 3 below).

Net made of twisted (black) nylon netting of the following size mesh and thread:

- Top and bottom wings 3 ½” stretch mesh No. 24 (.073”) thread

- Square 3 ½“ stretch mesh No. 24 thread upper body

- Body/Belly 2 ½“ stretch mesh No. 24 thread upper and lower body

- 2 ½” stretch mesh No. 36 thread polyethylene outer cod end (140 mesh around × 14’ deep); inner cod end liner of 3/16“ 35 lb. Delta knotless nylon netting (600 mesh around × 16’ deep)

- No rings on cod end

- Head and footropes of 9/16-in. diameter galvanized combination wire with legs extended 4 feet and wire rope thimbles spliced in at each end

- Wing ropes of ½-in. diameter braided nylon rope rigged down each seam, beginning at wing tips and extending downward through cod end

- Floats: 7 - 8” Deepwater aluminum or 8” Hi-impact Plastic floats spaced evenly at center of headrope

- No footrope chain. Instead, a 9/16” galvanized combination wire hung below the 39’ footrope by 7 links of 3/16” drop chain on each end of a pair of 6” rubber disks (rollers) spaced 6” apart evenly along wire. Chains tied to footrope and roller wire. Rollers and wire extended to and attached to thimbles. LSBS to supply 6” rubber disks.

- Upon completion, net treated with preservative Shipping Address (39-ft yankee trawls): U.S. Geological Survey-Lake Superior Biological Station (LSBS), 2800 Lake Shore Dr. East, Ashland, WI 54806-2427

Figure 3a. Desired top cutting plan for 39-ft Yankee trawl.

Figure 3b. Desired bottom cutting plan for 39-ft Yankee trawl.

Figure 3c. Desired wing design (wing top) for 39-ft Yankee trawl.

Figure 3d. Desired wing design (wing bottom) for 39-ft Yankee trawl.

Figure 3e. Desired wing design (wing ends) for 39-ft Yankee trawl.

Figure 3f. Desired cod end specifications for 39-ft Yankee trawl.

Figure 3g. Float and chain hanging plan for 39-ft Yankee trawl.

Figure 3h. Design and hanging of roller foot gear for 39-ft Yankee trawl.

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