A Comparative Lengthening Study of a Shallow-draft Purse Seiner

Lengthening has been a common refit in the shallow-draft salmon-seining fleet of the Pacific Northwest and Alaska since the early 1990s. Generally these small vessels are modified without any formal engineering support. Although the 2010 USCG Authorization Act promises to improve the amount of engineering dedicated to small fishing vessels, 88 percent of shallow-draft seiners are too small to be affected by the new rules. This paper is offered as a starting point for owners, builders, and naval architects to seek voluntary and collaborative engineering solutions for future lengthening projects. To this end, this paper describes two prevalent methods of lengthening, quantitatively compares the resulting changes in vessel characteristics with the original craft, and identifies potential problems and solutions. Background information is provided to familiarize the naval architect with the owner’s requirements. It is the author’s hope that this paper could help naval architects deliver an efficient engineering package with a tight scope to budget-conscious owners who are considering lengthening their shallow-draft purse seiners.