Mainsail Choice

Mainsails are divided into two types: those with battens and those without. 

What do battens do?

Battens function similarly to the framework of a tent in that they keep the material taut and smooth. The roach would flap uncontrollably if there were no battens. They act as I-beams on the sail, resisting forces that try to compress the leech in towards the luff when the sail is sheeted in. The open-leeched airfoil shape is preserved, and the sail does not become fuller and more semicircular as the breeze increases. Battens also provide much-needed structure and support, which aid in the maintenance of the shape and durability of your sail.

The compression loads are transported to the mast by full-length battens. The more full-length battens you use, the more durable your sail will be and the better it will hold its shape in a breeze. Furthermore, the more structure you give your sail, the less it will flog.

What makes a good batten?

Battens must be stiff enough to withstand compression loads. Solid, pultruded glass battens are inexpensive, tough, and virtually indestructible, but they frequently lack the stiffness required. They are also not tapered. Because they mimic the sail shape when compressed and better preserve the airfoil shape, tapered battens have an advantage.

There are several flat, foam-cored, laminated tapered battens that work well on smaller boats.  They are not as tough as solid glass, but they are typically lighter. Round battens perform best on larger boats because their shape provides stiffness without adding to their size. Furthermore, they are extremely difficult to break. And always keep a spare on board.

Potential problems with battens

The disadvantage of full-length battens is the compression they impart on the luff hardware. The luff is forced into the back of the mast by the battens. This causes friction and causes the sail slides to twist and toggle in the groove. Slides occasionally lock up, making it impossible to raise or lower the sail. Batten compression, at the very least, causes chafe and wear at the inboard end of the batten where it presses against the mast.

Another issue with full-length battens is that they tend to protrude past the mast, resulting in a V-shaped wrinkle. The wrinkle at the inboard end of the batten prevents the sail from being smooth and clean.

To avoid these issues, use shorter battens, but this creates another issue: the compression loads are transferred to the sail cloth rather than the mast. That can wear down the fabric and cause hinging over time. Each of these issues becomes more defined as the sail grows larger.

Though battens can cause additional wear to your slides or sail fabric, the benefits outweigh the disadvantages. When it comes to mainsails, you have three options: conventional, in-mast furling, and in-boom furling.

Full-length battens have become standard issue in the top sections of conventional mainsails. It is entirely up to you whether or not to use battens for the remainder of the sail, as well as how long those battens should be.

Battens are not an option if you have an in-mast furling system. Removing them may have an adverse effect on the sail's shape and size, as well as its performance. Vertical battens can be used, but they are more difficult to maintain and may compromise functionality for a relatively small gain in area and leech support.

Furling systems built into the boom provide the best of both worlds. They do require more attention, especially when it comes to protecting the luff tape while furling, but they also offer uncompromised size and structure with the convenience of roller furling.

Whether you go with traditional sails or a furling system, full-length or shorter battens, make sure you understand your options so you can make the best choice for your boat.