78 foot beam US lakers

[guest at sea]

In the 1970s there were several US lakers built with a 78 foot beam: Roger M. Kyes, Charles E. Wilson, H. Lee White, Joseph L. Block and American Mariner. 78 feet seems like an arbitrarily selected number given that the maximum breadth permitted by the Seaway did not increase to 78 feet until 1994, and Canadian ships of that era were being constructed with only a 75 or 76 foot beam. ...was there another reason they were built to those dimensions?

I remember reading on an older version of the boatnerd message boards years ago that at least one of the reasons a 78' beam was chosen for these ships was because that was the maximum width that could still be easily loaded at gravity-fed / chute-style ore docks. Any beam wider than that would have to flip around end-to-end or shift sideways from one adjacent dock to another to allow chute loading to be done from both the port and starboard sides of the ship, to ensure even loading / side-to-side trim. That end-to-end or side-shift method was how 105' wide ships like Roger Blough and Presque Isle were loaded during the 1970s before the gravity chute style ore docks at Duluth and Two Harbors were retrofitted with wider-reaching conveyor shuttle loading booms.

[Guest]

U.S. vessels with a 78-foot beam built between 1973 and 1980 were designed to use the Poe Lock, as the USACE don't allow vessels with that width to use the MacArthur Lock. The St. Lawrence Seaway Authority didn't allow vessels with a 78-foot beam to transit the Welland Canal and St. LAwrence Seway locks until 1994.

The downside of a vessel with a 78-foot beam using an 80-foot wide lock chamber was seen a few years back when an ocean vessel with such a beam became trapped in one of the U.S. Seaway Locks during a late December transit. Ice buildup on the lock walls caused the development of an ice collar which firmly wedged the vessel in the lock chamber and it took several days to extricate the vessel from the lock.

[algowest]

Interesting question.
St. Lawrence Seaway officially changed the maximum length (to 740') and beam (to 78') in two stages in 1994, according to my research. One year earlier, American Mariner departed with a grain cargo from Toledo on July 6, 1993, and headed down the Seaway. I believe this was the first transit of a 78' wide vessel, after fender modifications were performed at Lock 7 WSC and also at the U.S. Seaway locks. Curious what information others may have on how the 78' beam was arrived at for those ships you named...

[Guest]

In the 1970s there were several US lakers built with a 78 foot beam: Roger M. Kyes, Charles E. Wilson, H. Lee White, Joseph L. Block and American Mariner. 78 feet seems like an arbitrarily selected number given that the maximum breadth permitted by the Seaway did not increase to 78 feet until 1994, and Canadian ships of that era were being constructed with only a 75 or 76 foot beam. Was the Welland Canal allowing ships of a 78 foot beam in that era? Or was there another reason they were built to those dimensions? Since none of those vessels exceeded 730 feet in length it seems they must have had some lock or locks in mind.