Boatnerd Discussion Forum

Tug 589 is correct--mid summer drafts are in effect from 1 May thru 15 September. I was taught that the varying load lines are assigned by the classification society based upon the need for additional reserve buoyancy relative to the historical weather conditions for the different time frames.

Actually I beleive the dates for Mid Summer are May 1 thru Sept 30. The dates you have are known as the Intermediate Drafts.

[quote="Manitoba Mariner"]Mid summer draft is the maximum allowed draft a ship may be loaded at at the mid ship load line. The Mid summer draft on the Great lakes are effective in the following dates: from April 1 to April 30 and October 1 to October 31.

In essence the load lines (or Plimsoll Marks) allowes the ship to attain a safe freeboard according to historical weather in a given region.[/quote]

Also, warm fresh water provides less buoyancy than warm salt water, so a ship coming in from the Atlantic in the summer will need to either offload cargo, fuel, or ballast prior to entering the Great Lakes if loaded to maximum summer salt water draft.

Actually the temperature of the water has no effect on how much water a ship will draw. The water density ie. fresh, brackish, salt water is what determines that factor.

Warm water provides less buoyancy, being less dense than cold water. A ship will sit lower in warm water than cold water.

Old boat owners used to overload their ships which led to sinkings and the loss of life. Today, boat hulls have Plimsoll marks for the legal limit a ship can be safely loaded. The Plimsoll mark adjusts for the difference in bouyancy for fresh water, salt water, and mid-summer.

Mid summer draft is the maximum allowed draft a ship may be loaded at at the mid ship load line. The Mid summer draft on the Great lakes are effective in the following dates: from April 1 to April 30 and October 1 to October 31.

In essence the load lines (or Plimsoll Marks) allowes the ship to attain a safe freeboard according to historical weather in a given region.

What does the term mid summer draft mean?