I have no idea what’s happening to this particular roach. It could be flopping off to leeward, or it might be curling back to windward, which is just as bad. I don’t know whether it’s a mainsail that tucks itself away inside the mast, or whether it rolls up on a free-standing stay running down outside the aft side of the mast.
But, despite my profound ignorance, I know of three ways in which sailmakers tackle the problem of making the mainsail roach follow the natural curve of the sail without collapsing to leeward or curling to windward.
The most usual way is to cut the mainsail with a hollow leech and thus do away with the roach altogether. That’s how jibs are cut. On a normal mainsail with a modest roach, horizontal battens are used to stiffen the sail in the area of the roach; but you’ll notice that foresails don’t usually have battens because their leeches are hollow-cut and there is no roach to worry about. The only drawback of a mainsail with a hollow leech is that you lose some sail area, but if the boat is designed to have a hollow leech in the first place, you can compensate with a slightly taller mast that accommodates all the desired sail area.
If you insist on having a regular roach on a furling mainsail, your sailmaker will probably resort to stiffening the roach with battens. You can have short battens or long battens, but both run up and down, parallel to the mast, and both bring their own problems. They have to be parallel to the mast so that they can roll up inside the sailcloth when the sail is furled, but they add bulk to the sail and can jamb in the mainsail slot if it isn’t wide enough.
I like best the idea of a roachless mainsail because it has few drawbacks and many benefits, not the least of which is freedom from the wear and tear on batten pockets, a constant and very comforting source of income for sailmakers.
I guess there will be some of you who are still wondering what a roach is, apart from an obnoxious tropical insect. Well, a roach is the curve in the side or foot of a sail. Square sails have a hollow roach in their foot to keep them clear of the mast stays when the yards on which they are set are braced up, and this is known as the foot roach. When sails are roached on their sides, as in the leech of a gaff mainsail, they are known as leech roaches.
On a Bermuda-rigged mainsail we often refer to the roach as being the area outboard of a straight line drawn from the head of the sail to the clew. And just in case you haven’t had enough of roaches by now, Baytripper, here are a couple of links to the sites of sailmakers who know what they’re talking about:
One ship drives east and another drives west by the same winds that blow.
It’s the set of the sails and not the gales that determines the way they go.
— Ella Wheeler Wilcox
“What’s Angela’s last name again?”