Investigation into the load lines on the Great Lakes came about in the early 1960s when it was realized that the existing load line regulations didn't adequately cover the longer vessels coming into service and the planned 800 to 1,000 foot lakers.
A committee was formed by the Society of Naval Architects and Marine Engineers and included the American Burea of Shipping (ABS), the US Coast Guard, and the Department of Transport in Canada.
Several vessels were instrumented with hull stress gauges, and the Edward L. Ryerson even had wave buoys that were deployed from her deck to measure wave heights, lengths and other wave spectra data. It was discovered during the Daniel J. Morrell storm in late November 1966, when the Ryerson was on Lake Michigan, that wave lengths could reach over 700 feet in length and not the previously assumed 250-350 feet in length.
The ships that were built in the 1950s didn't receive strapping when they were granted increased load lines, but they did require stronger doors on the spar decks, increased heights of the ballast and tunnel vents and various other modifications. The Supers and Maritimers received deck strapping to increase their hull section modulus along with the other changes noted for the 1950s built ships.
After the Fitzgerald sank, the NTSB and Marine Safety Board recommended that the load line changes be rescinded, but this never came about. Instead existing load lines stayed in place as vessel owners increased the strength of ships from the 1950s by doing conversions to self-unloaders - in those so done. An excellent write-up on the load line changes and hull springing of the Great Lakes ships was presented by David Groh at the Ship Structures Symposium in early Fall 1975. http://www.shipstructure.org/pdf/75symp09.pdf
Load Line Increases 1960s to 1970s
-
Guest
Load Line Increases 1960s to 1970s
During the late 1960s and early 1970s, several existing steamers operating in the US flagged lake fleet received load line increases. If I recall correctly, this involved the installation of deck strapping to several (if not all) of these vessels. I believe the ships granted these load line increases included the Supers, Maritimers, and nearly all of the 1950s built steamers. I know that there was some consideration given to the unintended effects of increasing the load lines and the concurrent decrease of the vessel freeboard in heavy weather following the loss of the Edmund Fitzgerald in 1975 which was then operating with an increased load line in comparison to when it was designed and built. I'm not really trying to start a discussion as to what impact this may have had in the Fitzgerald sinking but please feel free to comment in this regard if so desired. I'm actually more interested in what, if any, impact the sinking had on those ships already given the increased load line certifications. Was there a review of how the characteristics of each individual ship or class in heavy weather were affected in comparison to before the increased load lines were granted? Was there any regulatory action taken to rescind the increased drafts?