Lake Freighter - Design

Design

Because these vessels must traverse the locks of the Great Lakes Waterway, they all have features in common, and their appearance differs from similarly sized ocean-going freighters. For instance, they are narrower and generally longer. An early variation of the type (designed by Alexander McDougall and built from 1887 through 1898) was the "whaleback" design, which featured significant tumblehome in the sides of the hull and a rounded bow, looking rather like the back of a whale. Where the superstructure of an ordinary freighter used to have the bridge in the center of the vessel, lake freighters typically have the bridge and associated superstructure on the bow. Traditionally they had a second island, over the engine room in the stern. These dual cabined boats were constructed between 1869 and 1974. The R. J. Hackett premiered the style and the second Algosoo was the final vessel designed this way. More recently built lakers, like the CSL Niagara, have a single large superstructure island right astern.

Vessel speeds are not as important on the Lakes as on the ocean. Ports are often closer together than in ocean trade, so cargo capacity is more important than speed. Lake vessels are designed with the greatest box coefficient to maximize the vessel's size in the many locks within the Great Lakes/St Lawrence Seaway system. Therefore, ship designers have favored bluff bows over streamlined bows. After World War II, several ocean freighters and tankers were transported to the Great Lakes and converted to bulk carriers as a way to acquire ships cheaply. Several of them served well in the role and continue to sail today (American Victory (fmr. Middletown), Lee A. Tregurtha, and a few others).

Another distinguishing feature of Lake vessels versus Ocean vessels is the cargo hatch configuration. On the Lake vessels, the hatches are traditionally spaced 24 feet (7.8m) apart. This configuration was needed to match the hatches to the loading facilities. At the turn of the 19th century, most ore loading facilities had loading chutes spaced every 12 feet (3.8m). The ship designers used this pattern for their hatch configuration. This pattern continues today, even with modern Lake vessels. A lake vessel has many more hatches than an ocean vessel of equal length.

The largest deep lock at the Soo is the Poe Lock which is 1,200 feet (370 m) long and 110 feet (34 m) wide. Because of size restrictions, thirty vessels on the lakes can only pass between Lake Superior and Lake Huron using the Poe lock although none approaches the lock's size. Many lakers are restricted to the Lakes, being unable to navigate the St Lawrence Seaway whose locks allow a maximum vessel size of 740 feet (226 m) in length or 78 feet (24 m) in breadth. The shallow draft imposed by the rivers (typically dredged to about 28 feet (8.5m) by the United States Army Corps of Engineers) restricts the cargo capacity of Lakers, but that is partially recovered by their extra length and box design. Since Great Lakes waves never achieve the great length or period of ocean waves, particularly compared to the waves' height, ships are in less danger of being suspended between two waves and breaking, so the ratio between the ship's length, beam and its depth can be a bit larger than that of an ocean-going ship. The Lake vessels generally have a 10:1 length to beam ratio, whereas ocean vessels are typically 7:1. The dimension of locks is the determining factor in Lake vessel construction.