Sail Trim:
Tips & Techniques

Mainsail Battens

The best battens for boat speed

Battens have a significant impact on your mainsail's shape and your boat speed. Here's how to select, install, and adjust your mainsail's battens to gain a speed edge.

  • Select Main Battens
  • Full Main Battens
  • Leach Battens
  • Batten Shapes and Tuning

Ullman fibre path genoa - Genoa trim techniquesTypes of main sail battens

Battens come in all shapes, sizes and kinds. They are installed in batten pockets of all types on the leech of the mainsail or they are full-length battens which span the sail from the leech to the luff. The battens support the roach of the sail and they maintain the designed sail shape. (The roach is the sail area that extends past a straight line from the head to the clew of the mainsail). Some battens have an even thickness and others are tapered with one end thinner. If you are using tapered battens, always use the tapered end towards the luff edge of the sail and the thicker end on the leech of the sail. This way the bend of the batten matches the designed sail shape.

Batten design

Sailmakers specify the battens to fit the designed draft position of the sail. The battens should maintain the sail shape rather than alter the designed shape. You can change the batten stiffness and tension to help maintain the design as the sail shape changes in the different wind conditions..

Full Main Battens

Full battens are classified by their draft position and bend characteristics. The draft position is the fore and aft location of the maximum amount of bend at a given bend pressure. This measurement is given in a percentage of the batten's overall length, starting at the inboard end. The poundage it takes to reach this maximum draft position is the weight of the batten. For example, a batten would be classified as 56 inches long x 5/8 inches wide x 40% draft x 6.5 lbs.

Sailmakers specify the battens to fit the designed draft position of the sail. The battens should maintain the sail shape rather than alter the designed shape. You can change the batten stiffness and tension to help maintain the design as the sail shape changes in the different wind conditions.

Leach Battens

Leech battens are simply classified as soft, medium soft, medium, medium hard and hard. Leech battens have a tapered flex tip to smooth out the intersection between the batten and the sail. This flex tip helps transfer the batten shape into the designed sail shape. The sailor and sailmaker can choose which type of leech battens to use depending on what wind condition the mainsail is designed for and what wind condition the sailor sails in. The soft battens are good in light air and waves and the hard battens are good in heavy air. The medium battens are used for the wind and wave conditions in between light and heavy air

Battens are attached to the mainsail leech by two types of batten pockets: pockets that allow batten tension adjustment or leech pockets that do not allow adjustment. Usually the nonadjustable pockets are on the lower two or three batten pockets. These pockets have elastic on the inboard end to press the batten against the leech and prevent the batten from coming out. Install these battens tapered end first and make sure the batten is long enough to fill the pocket so that the batten maintains pressure against the leech. The batten should be difficult to install and remove. On heavy air days, put a piece of sail repair tape over the pocket opening to further insure the batten will not fly out. Some sails have adjustable Velcro flaps on leech batten pockets. If you have this type of pocket, use just enough batten tension to remove the sail wrinkles for each different wind condition.

Batten Shapes and Tuning

In regards to batten shape, use the battens that are provided with the sail from the sailmaker for the middle two battens. These battens are tapered with a very flexible inboard end so there is not a hard spot on the sail where the batten and the soft sail material intersect. It is a nice speed edge to use two different battens for the bottom batten. One of these battens has a softer bend for light air and chop, a characteristic that provides lower leech return to improve power and pointing, and the other batten has a stiffer bend to keep the leech exit straight in heavy air.

Some 'modern' racing boats and dinghies are now using mainsails with several full battens, a system which is similar to what catamarans have been using for years. These full battens provide sail shape control, prolong the life of the sail and help support a larger roach. The only problem with all of these advantages is learning how to utilize them to sail faster. The type of batten and the tension with which it is inserted in the pocket are the two variables that you can control.

Tuning a Full Batten Main Sail

In a mainsail with two or three full battens, the lower one or two full battens should be a slightly tapered with an all-purpose weight to span a variety of wind ranges. These battens should be installed tight enough to just remove the vertical wrinkles or puckers around the batten pockets that appear while sailing. This tension will keep the sail smooth and not alter the designed sail shape. One note here is that the sail can stretch and the batten pocket adjuster can loosen while sailing. It is a good idea to tighten the battens each day before sailing in a multi-day regatta. You may even need to tighten the battens in between races on heavy air days. You can usually tell if a batten is too tight by several clues. The clues for full battens are as follows: a sail shape that is too full, battens that will not invert in jibes and tacks for the wind strength, and for a draft that is pushed too far forward in the sail. The clue for a tapered leech batten is a hard spot in the sail at the inboard end of the pocket and/or the batten forcing too much shape in the leech of the sail.

The top batten is the critical batten because the sail is narrower near the head and the upper sail shape is important to pointing and speed. Because of the smaller area in the head of the sail, the batten type and tension have a greater effect on the sail shape than farther down in the sail. To keep things as simple as possible, carry two top battens. One batten should be a light to medium air batten and the other one should be a heavy air batten. The light batten should be fairly light and soft and have the draft position around 45% to 50%. The batten should be fitted in the pocket with medium tension in light air so the batten will flop from side to side easily. In medium conditions, put the batten in the pocket firmly so the batten will remain inverted when you are trying to flop the batten from side to side by hand. The light air batten powers up the top of the mainsail by making it fuller, leading to a firmer leech with more leech return. The end result is more speed and higher pointing in these maximum power conditions.

Heavy Air Batten Tuning Tips

The other top batten is a heavy-air batten. This batten is stiffer and has the draft farther forward, around 40% to 42%. The advantage of a heavy air batten is that it pushes the draft forward in the sail, flattens the top of the sail and opens the upper leech. All of these things are depowering mechanisms that make the boat easier and faster to sail. The heavy air top batten is installed in the pocket very tightly because it is a stiff batten and creates the tension the batten needs to take advantage of its designed shape. A batten under a great deal of tension, the batten has a hard time inverting during tacks and jibes. One solution to aid in flopping the batten from side to side is to spray the batten with a dry lubricant such as McLube. The lubricant reduces the friction between the pocket and the batten to allow the batten to move inside the pocket.

Carrying extra battens and changing battens for different conditions may sound like a lot of work, but making a sailboat go fast is the sum of a lot of little things. If you take the time to understand how battens work and how they affect the sail shape, battens are no different than any other sail control. They can be used as a tool to make your mainsail span the entire range of wind and sea conditions. Putting the right batten in before each race is just one more item to mark off of your pre-race checklist.

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