Submitted on October 1, 2001 by Wesley Bachman

Question: What is the advantage or disadvantage of a loose footed main sail?

Answer: North Sails favors loose footed mainsails for most of our cruising customers. The loose foot allows the sailor to adjust the shape of the lower 20% of the mainsail by easing the outhaul to add depth to the sail or pulling the outhaul very hard to flatten out the lower section of the sail.

The alternative to a loose foot arrangement is to equip the sail with slides along the foot, which hold the fabric on the boom. The slides don't add to the strength or durability of the sail. On the contrary, the slide attachment points tend to add to the cost of maintaining the sail. The sail fabric is more highly loaded in the area of each attachment and as teh fabric degrades with use and UV exposure, the sail is more likely to rip at any attachment point that is slightly more loaded than it was designed for.

Race mainsails are often constructed with a lens shaped panel of lighter weight fabric connecting the straight foot of the sail with the boom. This arrangement is called a shelf-foot. It is meant to act as an endplate on the mainsail when the boat is on downwind angles. The shelf-foot is typically attached with a continuous rope in the groove on the top of the boom. When sailing upwind the outhaul is pulled tight and the shelf-foot collapses. The contribution to performance from the shelf is negligable.

There are some practical advantages to a loose foot. During installation of the sail, the sail battens can be loaded on the dock, the sail flaked and tied and then loaded directly onto the top of the boom. This works especially well if you have lazy jacks. When it is time to remove the sail, it can be flaked on the boom, bundled with sailties that are run around the sail but over the boom and then lifted off. Reefing lines can be deadended on the boom without concern for ripping a slide off the foot of the sail if the line is tied in the wrong place.

In short, with modern, low stretch sail fabrics, slides or other attachment points along the boom do not offer any advantages.

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