Submitted on March 13, 2002 by Rudy Ludeke

Question: I own a Baba 30 and am considering new sails. I have read everywhere that a full-roach main is a good idea. I’m cool with that, but I would like to know, scientifically (in laymen’s terms no less) why this is so? I’ve heard of the light air advantages, but that doesn’t seem like enough. Would it really make a difference on my heavy cruiser?

Cheers,
Rick Beddoe
1979 Baba 30, Soñadora

Answer: Hi Rick, There are three reasons why a large roach mainsail will result in better performance for your Baba 30:

1) More sail area. This one is pretty self explanatory.

2) Less aerodynamic drag as a percent of the sail area. The more narrow the tip of the airfoil, the more turbulence and drag will be associated with the air flow around the foil. A wider head on the mainsail helps to keep the airflow traveling from the luff to the leech, further up the sail. This is why Americas Cup boats and Volvo 60s have such wide head sections on otherwise very narrow mainsails. It is the same priciple that leads to endplates on wings and keels.

3) A sail with more roach area tends to be more self tending in puffy wind conditions. In stronger winds the leech of the sail will twist open, effectively flattening the sail in cross section. When the wind subsides the fabric recovers and the sail is deeper again. With less roach the leverage of the batten ends is reduced so the flattening effect is not apparent.

There are some handling issues that need to be considered before you decide on a large roach mainsail. Some boat owners object to having the batten ends overlapping the backstay. There is really no structural or sail fatigue problems related to the battens hitting the backstay. In very light winds the battens may not blow past the backstay on tacks or gybes. Motorsailing directly into the wind with the mainsail up can be annoying as the battens will be constantly whapping against the backstay. For these reasons many of North Sails customers elect to build their cruising mainsails so that the upper battens extend all the way to the backstay, but not beyond it.

Regards, Dan Neri

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