Sunday, January 15, 2012

Making the sails, part I

Sailmaking (and mending) is traditionally a winter activity, and so it is for me.  The only carpentry-related thing I did since the new year was to laminate together two layers of 1X2 lumber for each yard.  The main yard will be 8 feet (2438 mm) and the mizzen 7 foot 4 inches (2235 mm).  I need to round the edges, sand and finish, but that can wait.  Which brings us to the sails.

I ordered my materials from Sailmakers' Supply, including 16 yards of sailcloth, thread, seamstick (2-sided tape to hold seams together while sewing), sailmakers' tape, a grommet kit (including cutter, punch and die) and a couple of other things.  I ordered 36-inch-wide cloth, with plenty of extra for screw-ups.  The supplier sent me 56-inch wide cloth by mistake (I think) so rather than sending it back I used it.  It took fewer seams and I have even more left over, but the wider expanses of cloth were a little harder to handle.  All in all a good outcome.

Sails are actually airfoils, similar to wings.  They work better if their shape is optimized, and that involves curvature in three dimensions and things such as flare and camber.  Last time I made sails I knew nothing about this and I cut and sewed them dead flat.  They work OK (they stretch and bend with the wind) but I wanted to do better this time.

Before I go on let me spell out the terms.  A trapezoidal sail has four sides and four corners.  Not surprisingly, each has a unique name, obscure to all but sailors.  The four sides are foot (bottom), head (top), luff (leading edge, forward), and leech (trailing edge, aft).  The four corners are tack (forward bottom), clew (aft bottom), throat (forward top) and peak (aft top).

To put some 3-D curvature into the sails, I did the following to each:

1.  I put a curve in the foot (about 3 inches maximum).
2.  I put a curve in the head (2 inches max), partly to accommodate the bending of the yard.
3.  I sewed a dart starting at the tack (3/4 inch maximum fold width, or double that in total overlap) and moving up and in diagonally.
3.  I used broadseaming, that is seams of variable width, with maximum at the luff and minimum about 40% aft.  I used a rule of thumb of about 1/2 inch extra seam width per 30 inches on the luff end, less at the leech.

Working with sailcloth is tough.  It's slippery, crinkly and stiff.  Plus I had to remember after several years how to wind bobbins and thread the sewing machine and all that.  Plus one of our cats went nuts with all the thread, tape, scraps and crinkly cloth, so I had to lock her away many times.  But I am happy to say that the basic cutting and sewing of the sail shapes is done. 

The next steps are:
1. Sew on reinforcing patches for the four corners.  Ditto for the extra tack and clew corresponding to each reef.  I intended to have two reefs in each sail but may keep it to one.
2. Finish the foot and leech by sewing the edges under.
3. Finish the luff and head with tape.
4. Put in grommets in the four corners (and reef corners) and along the head (to lash it to the yard).

I will post photos once the sails are nicely finished.  After that there is also sewing the reef points and batten pockets.  I'll explain then.

Until then, keep checking 176 inches.

boatbuilder

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