Traditionally, the "sheer" is the fore-and-aft line of the hull at the main deck. It is a physical element in the construction of the vessel. Until the recent monstrosities of cruise liners it had a sweet upward curve toward both the bow and stern. Typically, the rise was 2 to 4 percent of the length of a merchant vessel, or about 0.6 to 0.7 percent of a passenger ship or large yacht. In a seaway, this upward curve maintained the freeboard as the hull pitched (bow up and down). It also gave strength of shape to the hull.
The "sheer line" is the fore-and-aft curve of the rail or decks which follow the sheer of the deck.
The "sheer stripe" or on yachts "cove stripe" is a decorative line which echoes the sheer but at a slightly lower level. It serves two purposes. One, it makes the sweet line of the sheer more obvious. And, two, it breaks up the expanse of the topside making the vessel appear longer and more sleek. The term "cove" comes from inscribing the line of the stripe into the hull. Typically, a rounded gouge would be used to cut what wood butchers called a "cove" in the sheer plank. Painters used this longitudinal cove to guide the painting of the line.
The "boot stripe" is a decorative stripe covering the area where the topside paint meets the bottom paint. In former years it covered the area between the light and load waterlines. It also has multiple purposes. One is to cover the "joint" where the topside and bottom paints meet to prevent bare skin which could cause corrosion. Older bottom paints lost their anti-fouling properties if they dried out, so boot topping was applied over the bottom paint to keep it active even when the ship was unloaded. The boot topping also allowed painters to cover up any mistakes or wanderings in the meeting of the two main paints with a smooth line. Another purpose is to work in tandem with the sheer stripe and make the hull appear longer. Curiously, a boot stripe appears of even width to the eye even though it is considerably wider in the bow and stern where the topsides curve outward instead of being vertical.
"Flare" is the outward curve of the topsides usually seen in the bows. It helps deflect spray from the decks and also increases the reserve buoyancy against pitching into head seas. Flare seldom extends aft more than a quarter of the ship's length.
In the stern, the flare is usually quite pronounced and so deserves a name of its own. Titanic had a "counter stern" which was also known a "schooner stern." This type of stern provided lots of reserve buoyancy necessary in sailing ships running before the sea on passages like rounding "Cape Stiff" (Cape Horn). Overtaking waves would lift the stern rather than simply was over the ship. Some waves were too large and ships did get "pooped." That was the term for a wave washing over the poop deck. Often as not it would take sailors with it, usually the men at the wheel of an old square rigger.
Many vessels had topsides that curved inward toward the sheer. This was most often called "tumblehome," although shipbuilders also used the term "flam."
In addition to the curve of the sheer, decks on ships traditionally have "camber." This is a slight tathwartships curve with the high point along the vessel's centerline. It helped water run off the decks and also gave strength of shape to the hull.
Next time we'll talk about catharpins and baggywrinkle.
-- David G. Brown
