page_title: Flexible barge
section_title: Zipper
hierarchical_section_title: Flexible barge / Technology / Zipper
caption_attribution_description: English: REFRESH fabric equipped with zipper
context_page_description: A flexible barge is a fabric barge for the transportation of bulk fresh water or other liquid bulk items such as chemicals or oil.
context_section_description: Zippers play an important part in extending the capacity of the waterbag beyond what is practically achievable by a single textile piece. The Spragg and REFRESH concepts both feature prominently zippers, albeit with a fundamental difference in its function.
  In the Spragg design, large waterbags are connected together like boxcars in a "train" fashion to increase the amount of liquids delivered at a time. It is estimated that the flexible barges could be as large as 14 meters in diameter and 150 meters in length, holding up to 17,000 cubic meters of fresh water or any other transportable liquid. Theoretically as many as 50 to 60 "waterbags" could be connected to one another and towed, although such a test has not been done to date. 
  Engineers suggest that the fabric barge can hold a "train" of 4,500,000 US gallons (17,000 m³) of liquids.
  A zipper coupler system is 10 times stronger than what is pulled by a 4,300 hp tug. Laborde Marine estimates a 4,300 horsepower tug with a bollard pull of 110,000 pounds can pull a "train" of fifty or so flexible barges weighing up to 1,300,000 tons. The "train" speed would be about 3 knots. This is over 700 acre feet (8,600,000 hl) of fresh water or other liquid per trip.
  In the REFRESH design, the container itself is assembled on shore starting from planar cuts of fabric. Zippers run all along the perimeter of the fabric and make it possible to join an indefinite number of modules. Since each module is not closed by itself, zippers need to be watertight in order to ensure that no seawater leaks in.
caption: REFRESH waterbag's fabric with embedded zipper
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