Choosing the Right Headsail for your Sailboat - Sail Magazine

Choosing the Right Headsail for your Sailboat

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Less is more, but having the right headsail is vital offshore

Less is more, but having the right headsail is vital offshore

As with many things, change comes slowly in the marine world, sometimes imperceptibly slowly, and we only notice how much things have changed when we look at an old photograph. That’s what happened to me. I was trolling through my photo archives when I noticed a photo of a cruising boat, rail down, lugging a low-clewed overlapping genoa sailing upwind in a seaway. It reminded me of sailing in the days of the IOR rule, when 150 percent genoas were the name of the game, and we were bound and determined to use them no matter the conditions. How things have changed! The IOR Rule has been relegated to the history books (thankfully), and the need to lug oversized sails around is also slowly becoming a thing of the past, especially for those sailors cruising blue water.

This drawing shows the difference between 150 and 130 percent genoas

The drawing at left shows the difference between a 150 and 130 percent genoa; note how the bigger sail sheets much lower than the smaller one. The drawing at right shows how overlap is calculated by dividing the luff perpendicular, or LP (drawn at a right angle from the luff to the clew), by the J dimension, or length of the foretriangle. `

If you are thinking of going offshore and wondering what sails are right for you, let’s start by getting rid of some of the old ideas. Most modern boats don’t need big overlapping headsails to perform well sailing upwind. There was a time when you needed as much square footage as you could get just to get your boat moving. Boats were heavy, keels long, and the only thing that could get a boat going was sail area. “It all started to change with the advent of light masts and even lighter rigging,” says Tyler Doyle, head of Doyle CFD, which specializes in computational fluid dynamics. “With lighter masts yacht designers have been able to increase mast height without too much effect on righting moment, and a high-aspect sailplan with a jib that overlaps no more than 105 to 110 percent is a very efficient rig. Adding more overlap to this kind of boat is not going to improve performance, it’s just going to cost you more for the sail.”

A means of easily adjusting sheet leads is essential for good sail trim

A means of easily adjusting sheet leads is essential for good sail trim

Of course, there is more to it than that–there always is. Specifically, most older cruising boats do not have a lot of stability because they have shallow keels, old fashioned heavy sails and aluminum masts. In addition, while the center of effort (CE) of the overall sailplan is low, which is good, the boats still need sail area to give them some horsepower, and that goes back to large, overlapping headsails. The real debate then comes down to trying to decide how large and how much overlap.

“The problem with a 130-percent headsail when compared against a 150-percent headsail or a non-overlapping headsail is that the 130-percent sail has the worst sheeting angle of the lot,” says North Sails’s JB Braun. Braun is also one of Team Oracle’s lead sail designers, so he knows a bit about sails. “For the sheeting angle, you need to take the angle from the tack to the clew and see how much it’s offset from the centerline of the boat. Non-overlapping headsails are great, you can have a narrow sheeting angle, but often when sailing offshore you don’t want to sail that close to the wind because of the sea conditions. When trying to determine what size sail is right for your boat there are a lot of variables, and much of it comes down to the kind of boat you are sailing and the kind of offshore passage you are planning. If there is a lot of reaching the sheeting angle does not matter. If it’s an upwind trip then you need to consider the trade-offs. With sailing you always have to consider the trade-offs.”

The combination of small overlap and high clew is ideal for cruising

The combination of a small overlap and high clew is ideal for cruising

Still, in general a 130- to 135-percent headsail is the most versatile size for cruising boats, largely because the sail shape is flat enough that it can be reefed with some efficiency. Larger sails, on the other hand, are typically also light-air sails, and in order for them to work in light winds the sail has to be designed with a deep camber. As a consequence, when you roll them up and use them reefed there is no way to take in enough of the camber to make the sail work efficiently to windward. To combat this problem, many roller-furling cruising headsails include a strip of dense foam (or lengths of rope) that runs along the luff of the sail from the head to the tack. As you take a turn on the furler this strip of foam then bulks up around the headstay so that with each successive turn it removes some additional camber from the sail. However, while this approach works well, it can’t perform miracles.

The combination of small overlap and high clew is ideal for cruising

The cutter rig is ideal for offshore cruising. 

Beyond that, any boat going offshore will also need something smaller than a 130 percent headsail to help it contend with severe weather. You can perhaps get away with a single working sail if you are sailing along the coast, but it’s not good seamanship to cross an ocean with only one headsail. Most people don’t like changing sails, but to be prudent and to sail efficiently a second, smaller headsail with an LP (luff perpendicular—the distance from the clew of the sail to the closest point on the luff) of around 105 percent, with the ability to reef the sail to 85 percent and still have an efficient sail shape, is a good idea. Preserve your 130-percent sail and change to the smaller headsail as the breeze increases. And if you are heading off on a passage where there is a good chance of sustained strong winds, you won’t regret changing to the smaller headsail before you set off.

The most efficient rig for long-haul passagemaking is a cutter rig with a staysail hanked on to an inner forestay. Yes, hanked, so you can get rid of it when you need to hank on a storm jib. As part of an efficient sailplan, the staysail allows you to balance the boat and easily change gears as the wind fluctuates by reefing and unreefing the headsail. Bearing in mind that very few cruisers attempt to sail close-hauled, a double-headsail rig with the staysail set under the headsail is a good way to go upwind.

Beyond that, the other big problem with the boat in that old photo was the height of the clew, a racing relic passed along to cruisers, who without too much thought, have continued to sail with the clew lower than the lifelines.

 A large overlap on a small cruiser

A large overlap on a small cruiser

“Besides some added performance, a lower clew offers a boat slightly more stability in the sail,” says David Hodges, owner of Ullman Sails in San Francisco. “With a lower clew the headsail is pinned down close to the block, while a higher clew will sometimes have as much as 6ft or more of line between the block and the clew, giving the sail the chance to move around a lot more.”

On the down side, however, with a low-clewed sail, the leech will twist open as soon as the sheet is eased, so that you have to adjust the lead by moving the sheet car forward to compensate. This , of course, means more work, something cruisers like to avoid.

With a higher clew, on the other hand, the foot will ease and the twisting will be less noticeable. “Having a higher clew means you don’t have to move your jib leads as often,” says Hodges. “So for a cruiser who is reaching a lot it makes sailing a lot easier.”

Beyond that, no matter what headsail you have, there are a number of things you can do to improve performance while sailing offshore. One of the most effective is to add a means of easily moving the sheeting position as you reef and unreef the headsail. It’s simple and relatively inexpensive to add a block-and-tackle system that can pull the genoa lead car forward when the sail is reefed, and ease it aft when the sail is unreefed. With a raised clew, you won’t have to do this as often, but if you make the effort and change gears with the headsail and staysail you will be sailing efficiently.

A large overlap on a small cruiser

Charter boat headsails are often cut so they will be easy to see under

If you opt for a 130 percent headsail and find that your boat lacks power in light conditions, you can always turn to a small asymmetric spinnaker that can be set and doused with a single-line furling unit. These sails have an anti-torque line running up the luff of the sail which makes setting and dousing them very easy. The anti-torque line is soft and easy to stow when the sail is not being used, but as soon as there is some tension put on it, it becomes rigid and rotates when the furling unit is turned. The lines are built into the luff of the spinnaker and just as a headsail can be rolled away, the spinnaker can also be rolled away.

Bluewater cruisers usually carry sails with overlaps no greater than 130 percent

Bluewater cruisers usually carry sails with overlaps no greater than 130 percent

If you are planning an offshore voyage it would be best to sail with your working headsails for a while and note where you lack performance. Sailmakers can design spinnakers so that they can sail quite close to the wind, but you will lose some downwind performance. Then again, it may be that you don’t need to sail that close to the wind, in which case your sailmaker can design a larger, more powerful sail that will give you a broader range of sailing options.

These days there is so much more versatility in sails, and despite sailing being about trade-offs, we have never had it better. Modern fabrics and sail engineering greatly extend the wind range of each sail, meaning that we don’t have to change them as often. The sails are lighter, meaning they easier to handle and easier to set and trim, and there is one other point that is often overlooked—light sails mean less weight aloft, and less weight aloft means less heeling and pitching. This reduces fatigue on the crew and makes for a happier passage. s

Brian Hancock is a veteran cruiser and racer and author of the book Maximum Sail Power—The Complete Guide to Sails, Sail Technology, and Performance

July 2015

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