November 3, 2011

Dump that roach

ONE OF THE PEOPLE I taught to sail once asked: "Why do mainsails have battens when foresails don't?"
   I replied with the shocking truth. "To make more money for sailmakers," I said.
   The fact is, you don't need battens in a mainsail. You only need battens if the sail has a roach. So what's a roach? Well, if you draw an imaginary straight line from the masthead to the outer end of the boom, any sail area that protrudes aft of that line is a roach. And the problem with a roach is that it's floppy. It has to be kept in line with the rest of the mainsail by stiff battens of wood or plastic, otherwise it will do no work, flap in a breeze, and generally drive you crazy.
   But it's not necessary to have a roach. Your jib or genoa works perfectly well without a roach. It has a slight scoop in the opposite direction, as a matter of fact.  It's what's known as a hollow leech. So why don't mainsails have hollow leeches?  Well, some do, actually, and they're usually found on cruising boats. Racing boats have roaches because they want that extra sail area up high where the wind blows harder, and they benefit mostly from the roach when they're sailing off the wind.
   But there are good reasons why you shouldn't have a roach. It's not needed when you're beating because the great majority of the sail's lift then is generated at its leading edge, the strip next to the mast. And boats that generate weather helm on the beat will positively benefit from losing some sail area so far aft. They will not suffer at all from having no roach and no battens.
   But most sailmakers are driven by racing boats and racing rules, which also affect the design of cruising hulls, of course. So the great majority of coastal and deep-sea cruisers end up with battens in their mainsails simply because it's de rigeur for racers.
   Sailmakers confirm that battens add considerably to the maintenance costs of any sail. Short battens crease and bend the cloth just forward of the pocket, where persistent chafe and flexing wear out the sailcloth. Full-length battens, besides adding considerably to the cost of a mainsail, put considerable stress on the leech and luff ends of their pockets.
    It's easier to handle, stow, and bag a hollow-cut mainsail, and you don't have to worry about the roach clearing the backstay when you jibe.  Next time you're considering a new mainsail, give some serious thought to dumping the roach. Your sailmaker might have more difficulty making his Mercedes payment, but you won't be sorry.

Today's Thought
Cut your cloth, sir, according to your calling.
— Beaumont and Fletcher, The Beggar's Bush

“Waiter, do you serve crabs here?”
“Sit down buddy, we serve anyone.”

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)


Chuck said...

Good essay. What do you think about the foot of a sail that is boomless? Should it be full, hollow, or straight?

John Vigor said...

Well, Chuck, I'm not a sailmaker, but I reckon it should be either full or straight. Most headsails are boomless and fairly straight on the foot, but racing decksweeper genoas have a full, rounded foot.
I can't see much point in a hollow foot. Some sails for square-riggers were hollow on the foot, of course, but that was to avoid chafe on standing rigging.

John V.

Brion Toss said...

I am not a sailmaker either, but I do know that your essay on roaches is deeply flawed, and needlessly insulting to sailmakers. But let's start with square-riggers. The foot of a squares'l is hollow, not to avoid chafe on the standing rigging, but because a hollow inevitably forms between the clews. It's a straightforward vector result. Otherwise sails with no stays to hit (upper tops'ls, for instance, would have flat or full feet.
Similarly, mains'ls have roach, not due to greed on the part of sailmakers, or racing rule influence, but because a roach makes a more efficient aerodynamic shape. There are reasons to create hollow-leach mains'ls, but always at a performance (efficiency) price. But the point here is that mains'ls can have roach, because of the support provided by the mast and boom. And they can have a full foot because the vectors are utterly different than on a squares'l.
Finally, I'm not a racer, but I'm grateful to them for all the things that they've tested, at great expense, for my clients. Because of racers, cruisers can sail more comfortably, reef less often, clear lee shores better, etc., and much of that comes from improvements in mains'l design. Perform a roach-ectomy if you have an in-mast furler, or if easy furling trumps all other mains'l considerations (but watch out for leach curl, the bane of roachless mains.

Chris Harris said...

Hey Brion. Thank you for stopping on your way through Portland earlier this year to give us a seminar. I hope you decide to come back and do something like that again. But please, easy on Mr. Vigor.
John, I love this forum and I love your style. Thank you.

Baytripper said...

Ok, all the above comments are very interesting. However, are there any suggestions as to how to stabilize an unstable roach in a roller furling mainsail especially in high winds?

John Vigor said...


I suggest you contact Mr. Brian Toss. He seems very sure he knows all about roaches.


John V.