by hausen » February 15, 2012, 1:06 pm
Ore carriers certainly can carry grain - in fact the ore/grain trade is the bread and butter for Canadian bulkers like the Algocape, Montrealais, or Pineglen. The carriage of ore on one trip and then a consumable like grain on the next is not an issue - a ship's cargo holds can readily be well cleaned and dried out between cargoes if needed.
The issue with many American lakers like the Humphrey or Sherwin is cubic capacity. Iron ore is one of the densest cargoes a freighter carries while grains are some of the least dense. A ton of wheat or especially barley or corn takes up much more space in a ship's cargo hold than a ton of iron ore. American lakers like the Humphrey were designed with the carriage of iron ore, not grain, in mind. Their cargo holds didn't have as much cubic capacity as they could have for a vessel that size. That means that if one were to try to put a load of grain aboard, say, the Humphrey, her holds would've been filled completely to the brim with grain long before she reached her maximum cargo capacity measured in weight. She would've likely maxed out at something like 18,000 tons of wheat even though on the same day in the same port she could've been loaded with 23,000 or 24,000 tons of iron ore.
Similarly sized Canadian bulkers, on the other hand, were designed and built specifically to carry grain down the Seaway from the lakes to Canadian transshipment ports (Montreal, Quebec, Sorel, Trois-Rivieres, Baie Comeau, and Port Cartier), and then iron ore from Canadian ports on the Gulf of St. Lawrence (Pointe Noire, Sept-Isles) back into the lakes. Even though their outer dimensions were very similar to ships like the Humphrey, their cargo holds had much more space in them, allowing them to simultaneously be filled up with a cargo of grain but also weighed down 'to their marks'. The difference between the Humphrey at 710' x 75' carrying 18,000 tons of wheat per trip and, say, the Menihek Lake at 715' x 75' and able to carry 23,000 or 24,000 tons of wheat per trip might not seem like much but over 16 - 20 grain loads per year that difference starts to add up. A mothballed Humphrey would not likely have been much of an ideal candidate to replace an aging early '60s-vintage Canadian bulker being retired in the late '80s or early '90s.
Ore carriers certainly can carry grain - in fact the ore/grain trade is the bread and butter for Canadian bulkers like the [i]Algocape[/i], [i]Montrealais[/i], or [i]Pineglen[/i]. The carriage of ore on one trip and then a consumable like grain on the next is not an issue - a ship's cargo holds can readily be well cleaned and dried out between cargoes if needed.
The issue with many American lakers like the [i]Humphrey[/i] or [i]Sherwin[/i] is cubic capacity. Iron ore is one of the densest cargoes a freighter carries while grains are some of the least dense. A ton of wheat or especially barley or corn takes up much more space in a ship's cargo hold than a ton of iron ore. American lakers like the [i]Humphrey[/i] were designed with the carriage of iron ore, not grain, in mind. Their cargo holds didn't have as much cubic capacity as they could have for a vessel that size. That means that if one were to try to put a load of grain aboard, say, the [i]Humphrey[/i], her holds would've been filled completely to the brim with grain long before she reached her maximum cargo capacity measured in weight. She would've likely maxed out at something like 18,000 tons of wheat even though on the same day in the same port she could've been loaded with 23,000 or 24,000 tons of iron ore.
Similarly sized Canadian bulkers, on the other hand, were designed and built specifically to carry grain down the Seaway from the lakes to Canadian transshipment ports (Montreal, Quebec, Sorel, Trois-Rivieres, Baie Comeau, and Port Cartier), and then iron ore from Canadian ports on the Gulf of St. Lawrence (Pointe Noire, Sept-Isles) back into the lakes. Even though their outer dimensions were very similar to ships like the [i]Humphrey[/i], their cargo holds had much more space in them, allowing them to simultaneously be filled up with a cargo of grain but also weighed down 'to their marks'. The difference between the [i]Humphrey[/i] at 710' x 75' carrying 18,000 tons of wheat per trip and, say, the [i]Menihek Lake[/i] at 715' x 75' and able to carry 23,000 or 24,000 tons of wheat per trip might not seem like much but over 16 - 20 grain loads per year that difference starts to add up. A mothballed [i]Humphrey[/i] would not likely have been much of an ideal candidate to replace an aging early '60s-vintage Canadian bulker being retired in the late '80s or early '90s.