Full-Length Battens

One of the most common discussions with potential sail customers regards full-length battens. The conversations fall into two broad categories: speed and sail handling.
The entire subject and all the related considerations are about a four-beer discussion, so for now I will focus on the “full-length battens are faster” theory and introduce the “handling” aspect in overview. There are typically two main factors contributing to the faster myth: shape retention, both in the immediate and over time, and increased sail area.

First, consider the retrofitting of full-length battens to an old sail. We all have a mate with an old sail that is degraded in shape. This means the point of maximum camber has moved aft of where it needs to be, usually well aft of 50%. The addition of full battens and the compression employed in tensioning them artificially pushes the sail’s shape back into place. So the customer comes in with a tired blown out sail and leaves with a sail that now has some semblance of a more usable and effective sail shape. Thus, is born the idea that “full-length battens are faster.”

The second way this usually plays out is when a customer buys a brand new sail with full-length battens. The fact that it is a new sail will by definition make it faster than an old sail…just ask any one-design racer. Secondly, the fabrics the sail is made of, even the lowly Dacron, are far superior to the materials available say 15 years ago.

battonsThen there is the current design trend towards larger roach mainsails. There are constraints on roach, however. With respect to the idea of additional roach, almost universally on “normal” production cruiser/racers or cruising boats, the roach (or more accurately the “girth”) of the sail is constrained by the proximity of the backstay to the leech. Girth is the sail’s width, luff to leech, at fixed points up the sail. So if one replaces the 15 year old blown out sail with a new one having these 2015 characteristics, it will certainly be faster, but not necessarily due to batten length.

Another constraint applies to those sailors who do any kind of racing requiring a rating assessment. In this case, the girth (and thus the roach) can be no longer than the length of the girth derived by applying a formula based on the boat’s E dimension. The E dimension is roughly the maximum length of the foot of the sail. There are standard formulas for the maximum amount of girth a sail may have and they are based on percentages of the E applied at 25%, 50% and 75% up the luff from the tack. Girths over the calculated lengths for the sail will incur a handicap penalty. The maximum girth permitted in this calculation is often such that the sail may just reach the backstay or a few inches past it. Such a modest roach can be supported with “regular” battens.

Finally, if full-length battens are faster, why do one-design classes such as the J-105, where competition is hot and the length of the battens is not restricted, not have full-length battens? If full-length battens were faster, then all boats would have them. Their absence indicates to me that the value of full-length battens to the J-105 fleet is insufficient to warrant the money spent. The only true way to determine if full-length battens are faster is to do a two-boat comparison test where everything else on the boats is identical.

The other aspect of full-length battens is in the area of “better” or “easier” sail handling. This suggests that when hoisting, lowering or reefing, a full-length batten sail is somehow easier to deal with. Well, maybe. The big issue with the ease of handling aspect of a full-length batten sail is the friction between the slide on the sail and the mast track. A full-length batten exerts a compression force which pushes the slide forward into the mast track. The longer the batten, the more compression there is, and so the greater the friction on the track.

Friction is an aspect of full-length battens that is little considered, but is a big factor on the ease of handling the sail. For instance, when sailing off the wind with the mainsail eased out and you wish to reef the main, it is very difficult (verging on impossible) to get the sail down. This is because the sail is laying across leeward rigging AND the compression force is acting on the track, jamming the slides into one side of the track. This situation is aggravated with modern rigs with swept-back spreaders, causing the sail to contact the rigging even sooner when the sail is eased.

Another consideration is the prevalence of using a simple batten box and webbing to attach the slide to the batten box. In this case, in addition to the “normal” friction, the batten end at the luff wants to over rotate, causing even more friction at the slide-track interface. Sailmakers use this method because it is cheaper and doesn’t need to be broken out as a line item in a quote. There is hardware that will alleviate this issue, but it is expensive (perhaps $50-$75 per batten, which I feel warrants its own separate line item), and it is only of partial help since the friction is largely a function of the slides on the mast track anyway.

It is possible to install a dedicated slippery luff track and car system, but this equipment is very expensive. It is also best done with a considerable amount of coordination between the sailmaker, the hardware supplier and the installer. For a 45 foot boat, it is not impossible that full-length battens will run 20-25% of the cost of the sail, or more if a dedicated track is used.

In summary, yes there are potential advantages to installing full-length battens and a low friction luff track system, but in general this is a better value in larger boats bound offshore with short-handed crews. It adds another level of complexity, expense, and it requires additional design and coordination among your suppliers. I will address this and other details in a future “Under the Hood.”

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