Headsail Reefing Basics - SailNet Community
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Headsail Reefing Basics

A little attention to detail can go a long way toward improving the performance and longevity of your headsails.
During the Fourth of July weekend when many Americans were enjoying warm, sunny weather and backyard parties, I was slugging to windward en route to Newfoundland. This is not a complaint, mind you—it was my choice to be there—but helming the boat in some particularly unpleasant seas made me think about this series of articles I have been writing for SailNet, and how important some of the information is for sailors heading offshore. It's easy to write about sails and sailmaking when distance gives you an objective perspective, but when it's all actually happening to you, the words you have written take on a new, and somewhat more urgent meaning. 

The part that really struck me was how badly most boats sail to windward with roller-reefed headsails. I was part of a crew sailing a Swan 59, a class of yacht known for its superb windward performance, among other attributes. On this occasion, however, we were not doing so great. One of the problems encountered when roller reefing a sail is that the moment the first turn is taken to reduce sail area, the airfoil shape of the sail is ruined. You reduce sail area and stop the heeling and leeway, but any power and performance you might have had from the headsail is severely lessened. 

This overhead cross section of a headsail shows that most headsails are designed to have their maximum draft at 33 percent aft.
Most headsails are designed to have their maximum draft (depth) at about 33 percent aft from the headstay, or luff. This is optimal, and important for your headsail to work properly with your mainsail. As soon as a sail is reefed, the draft moves to a position where it isn't of much use, despite such features as foam luff pads and double swivels. I'll discuss some of these features in a moment, but for now, back to my sailing trip.

Having noticed our lack of windward performance for a while, I gave some thought to the other option for reducing sail—changing headsails like in the old days. But watching cold, green water sweep the foredeck, I became prepared to trade performance for convenience and realized that I was glad we had the furling unit on board. Two lessons quickly became clear. The first is knowing and recognizing the limitations of roller-reefed headsails and planning trips accordingly (which often means avoiding lee shores). The second lesson is just how important fabric, features, and sail engineering are to a good sail.

Keep in mind that when you reef a headsail, the result is a higher-aspect ratio form, which will require distinctly different trim.
In previous articles I wrote of the benefits of tri-radial construction versus cross-cut. These benefits become more apparent on a reefing headsail that is required to cover a broad wind range. The hope is that the fabric will accomplish the impossible—that it will shrink and flatten the sail when the wind increases instead of stretching and making the sail bag out. This isn't entirely possible, but with good engineering, sailmakers can still make it so the sail will retain its shape while reefed. Under normal circumstances, the load from the clew travels across the sail toward a point at the middle of the luff, and then it diverges toward the head and tack. On large, low-aspect, overlapping sails, the loads are less intense along the leech, but on a reefed, high-aspect sail, almost all the loading runs up the leech. So you can see how difficult it is to engineer a headsail that does a good job in all wind conditions.

To be sure you get the headsail you want, consider the following features that any reefing headsail should have:

Having a foam luff on your roller-furling headsail can make all the difference in the shape of the sail once it becomes partially rollled up.
Foam Luffs Having a foam-filled luff goes a long way toward creating a decent sail shape once the sail is reefed. The luff pad is usually a sewn-in piece of closed-cell foam that runs the length of the luff of the sail, tapering toward the head and tack, with its widest portion halfway up the luff. As you take the first turn on the roller furler, the foam pad rolls up and bulks in the middle of the forestay. With each successive turn, the added bulk removes shape from the sail, thereby flattening it, or at least stopping it from getting full. 

UV Sunshields    Sailmakers learned long ago to add an acrylic or UV-treated polyester fabric to the leech and foot of the sail to protect the genoa when it is rolled up on the headstay. The fabric does not add to the strength of the sail, however, but does add to the life of the sail by protecting it from harmful UV rays.

Overhead leech lines, UV protection, and large, reinforced panels are three headsail features cruising sailors should look for in addition to foam-filled luffs.
Leechlines    If your sails are high-clewed, or if your boat is so big that you can't reach the clew to adjust the leechline, you might consider an overhead leechline. Any leechline adjusts the tension of the leech, but this arrangement is adjustable from both the tack and the clew. With this system, the leech line runs over a small block at the head of the sail and down through a pocket along the luff. Bear in mind that you can't adjust the leech line when a roller-furling sail is wrapped around the headfoil, so make sure it is tensioned sufficiently before roller reefing. 

Head and Clew Patches    With roller-furling sails, the first parts of the sail to get rolled up are the head and tack patches. They need to be extended (larger) so that the structural integrity of the corner is preserved when the sail is partially reefed. Have your sailmaker mark the foot of the sail so that you have a reference point when reefing. This will allow you to pre-mark the correct location for the genoa lead.

Reinforced Hanks    If you have hanked-on sails, you need a reinforcement patch behind each hank. The point-loading on hanks is fairly significant and can rip the luff of the sail if each hank is not properly reinforced.

Telltales    Headsail trim is important to the cruising sailor. Have your sailmaker add telltales to the luff of each headsail. Using those as a reference, you can adjust your sheet-lead position so that all the telltales along the luff of the sail lift at the same time. If the top telltales lift first, move the sheet lead forward. Conversely, if the lower telltales lift first, move the lead aft.

Sailmakers lay out panels and engineer sails differently depending upon their aspect ratio. The loads on low-aspect sails travel out into the body of the sail The loads on high-aspect sails run right up the leech. 
Trim Lines    For a quick reference on the proper sheet lead, line up your headsail sheet with the trim line that extends from the clew of the sail. If your sheet and the trim line are lined up, you can be sure that you've got the genoa lead in roughly the right place. 

In my next article on headsails I will look at ways to get the most performance from your sails, and discuss various sail options for going offshore. After reading that, you should be well equipped to make the right headsail choices for your boat. Remember, these products are an important part of your overall inventory and by extension, your safety. 

By the way, we made Newfoundland in good time aboard the Swan, and spent some enjoyable days cruising the island's rugged south coast. It's a remarkable part of the world, made more interesting because the small towns that dot the coast have no access by road. Weekly ferry service is their only link to the outside world. The high-sided fjords and windswept bluffs of this region make for some compelling scenery, but you only want to be out here if your sail inventory is in good order. 

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