Sails 

One of the more obvious ways of distinguishing American merchant ships at sea during the 19th century, as against the British or European, was the colour of the sails. The Americans used heavy cotton duck, which stood out snowy white in the distance, whereas the British used flax canvas sometimes with a hemp mixture, which appeared as a greyish or pale fawn colour, which although likely to become bleached in time, never had the same snowy whiteness as cotton. American naval ships often carried flax canvas. Centuries before, the lowest sails of the old galleon types were made of a coarse heavy material known as kersey, and some contemporary references name these sails as kerses, which may possibly be the origin of the word course or coarse, although the word course in other contexts also means a layer or row, such as in bricks or slates. Ships usually carried a spare suit of sails, and the oldest worn canvas, well patched, would be used in fair weather regions, changing to the best canvas for heavy weather .

  The sail cloths were assembled by sewing overlapping seams, the best method known as double round seam. The perimeter of the sail was folded over (tabled) about 4 to 6 in. for the lower courses, 3 to 5 in. for topsails, and 3 in. for smaller sails, and to this hem was stitched a stout boltrope always on the after side of square sails and not the extreme edge.
Additional strength was given by sewing an extra cloth of canvas (lining) over the side edges (leeches) ; a folded cloth horizontally at the reef points ;
a narrower one at the foot (roach) and a short distance up; and one at the head, with vertical cloths part way up the sail in line with each buntline, all of these except at the head being on the fore side of the sail.

  The seams were an average of 1.5 in. wide, but on fore and aft sails varied somewhat. The spanker seams were wider at the foot, say 3 to 3.5 in. occasionally 5 in., and about 2.75 in. at the head, in the main body being 1.5 in. Each seam tapered gradually to these widths, which helped to make up the shape of the non-parallel sides and gave a slight convex curve (roach) at the foot and slight bag in the middle. Occasionally American spankers were made from extra wide duck of 42 in. width ofbolts, but a false seam was stitched in the middle to preserve the stiffness and flatness.
Large jibs had seams about 3 in. at the foot and 2.5 in. along the stay. Some sailmakers, carrying on with an old tradition, gave belly to the square sails also, but the most efficient sails were made as flat as possible, Americans excelling at this, with the cotton duck often looking like 'veneered boards covered with white beads'.

  The success of the famous yacht America in 1851 has been attributed to this. An interesting account is recorded by a steamship officer on seeing the America approaching off the Isle of Wight apparently without any mainsail set. 'So completely was the sail covered [hidden] by the mainmast that not a particle of it was visible; there was no belly to the sail and the gaff