The Sliding Gunter:
A versatile Traditional Sailing Rig
by David Nichols
www.arrowheadboats.com

Traditional sails can be a very efficient, low tech engine for your boat. In fact, in some cases, a traditional sail can be better suited to your particular boat than the standard jib headed Bermuda rig.

The Sliding Gunter is a traditional rig that has always been more popular in Europe than on this side of the Atlantic, but it’s hard to find a better sailing rig for small boats. One of the main advantages of the Gunter is the use of a mast and vertical spar to achieve the same mast height and sail area as the Bermuda rig would set. This means the un-stepped mast and all the spars can fit inside the boat when under oar power or traveling on a trailer.

Figure 1a	figure 1b
(click thumbnails to enlarge)

Many whale boats—a real study in efficiency—used the Sliding Gunter, particularly in the Azores. The whalers found a long mast hanging over the end of the boat was not an asset when attached to several tons of a very angry whale. Also, stepping and un-stepping a shorter mast was easier and faster for the whalers and that, of course, applies to the recreational boater, as well. Yet all this convenience and ease comes in the same size and shape as the Bermuda sail.

The sail is convenient but is it fast? Yes, according to Jeremy Howard-Williams in Small Boat Sails. He found that wind tunnel tests showed the Gunter was as fast on the wind as the Bermuda and actually faster off the wind. Also, C.A. Marchaj in Sail Power gives the Gunter very high marks for aerodynamic shape and lower induced drag. According to Marchaj, the Gunter achieves the same effect as the Bermuda with a bending mast. But the Gunter does it without all the high-tech gear that comes with a bending mast Bermuda. This allows the Gunter sailor to get high-tech results with low-tech gear.

Figure 2

Detractors of the Gunter rig are quick to point out that the yard falls off from the mast on a beat to the wind, creating turbulent air flow and is therefore slower than the Bermudian sail. The debate on this can be complicated with both sides quoting data to make each case. Perhaps the main question the builder must ask is “Do the advantages outweigh the disadvantages?” And an understanding that choosing any sailing rig is always giving up an advantage to gain another.

One of the main advantages of the Gunter rig doesn’t become obvious until the sail is reefed. Then the spar comes down as well and brings its weight with it. The photos in figures 1a and 1b illustrates how this not only maintains a low center of effort for the sail, but also eliminates the extra weight of the mast aloft. This has a very positive effect on a boat in strong winds.

figure 3a

figure 3b

The Sliding Gunter is a good example of the low-tech versatility of traditional sails. The number of rigging variations with this sail is amazing. The builder can rig the boat with a simple combination of mast, spar, and sail- or a carefully thought out system that is perfectly suited to his or her sailing needs. Such a system can be crafted with the builder using nothing more than wood, rope, needle, thread, and marlinspike skills

A Gunter yard or spar can be as simple as a square piece of light-weight wood, with or without a taper or as Willits D. Ansel indicates in The Whaleboat even a piece of bamboo. At the other end of the spectrum is the graceful, curved bird-wing yard. The use of the curved yard and full length battens allows this Gunter sail to come very close to the RAF Spitfire wing. The Spitfire wing shape provides the most amount of lift with the least amount of induced drag. Figure 2 shows a comparison of the Bird-wing Gunter sail and the elliptical, u-shaped RAF wing. Yet, for all its high-tech appearance, it is nothing more than wood, cloth, and rope.

figure 4

Modification doesn’t stop with the shape. The yard can use jaws or it can be jawless. The jaws can wood, plywood, or a simple piece of line. The yards in Figure 3a and 3b use a simple toggle and a roband. Both are easy, effective methods of keeping the yard captive at the mast; yet allow the yard to slide freely. If either of these systems are used on boats in the 18 to 20 foot range are larger, it will be better to use parrel beads and service the line. The parrel beads and the stiffness added by the service will help keep the yard from jamming. The Drascome Longboat, a British 22 foot fiberglass production boat, uses parrel beads with the jaws of its Gunter rig (figure 4) and even though the jaws are made of metal, the general shape would be easy enough to reproduce.

figure 5

All the rigs, simple and complex, start with the sail laced to the Gunter yard. The luff should be tight but not stretched hard. A little experimentation will determine the proper tension. The next step is to lace the sail to the yard. The marlin hitch shown in figure 5 is probably best if the sail is left bent to the yard. It’s fast and holds the sail securely. Actually, there is really no reason to remove the sail each time the boat is used. Round lacing or back-and-forth lacing is faster but doesn’t secure the sail as well. Robands can be fast but allow even more sail movement.

Not only are there several possibilities of attaching the sail to the yard but there are several ways of attaching it to the mast as well. It can be loose-luffed, that is attached to the mast only at the tack, which according to Phil Bolger is more correctly a Solent Lug Sail rather than a Gunter variation. Or the luff can be bent on with robands, toggles, or wooden hoops. The Drascome Longboat uses toggles, which is simple and fast and the Mirror dinghy, Jack Holt’s famous design, uses lacing. Over 60,000 Mirror dinghies actively racing means there are a lot of owners lacing the sails to the mast. Other racing designs use tracks to eliminate the gap between the luff and mast. The owner can be as simple or complex as he or she wishes to be.

figure 6

This variety carries over to the sheeting of the sail as well. There are at least three sheeting possibilities with a loose-footed or boomless sail. A bridle and a single sheet allow the tiller to operate without fouling the mainsheet. A block, a brass thimble, or wooden lizard can be used for the sheet to feed through but a block produces the least drag on the mainsheet. It’s also possible to use two mainsheets. The leads can be as simple as wooden pins or thumb cleats on the rail (figure 6) or brass thimbles seized into line. Using two mainsheets has the advantage of allowing the sail to be sheeted pass the center line of the boat—acting like a traveler on a modern rig. While this will improve the boats pointing ability it adds the complication of more line to tangle. On some boats it maybe necessary to use a purchase on the single mainsheet. Most small sails won’t need this but if the sail area dictates it, this system will do nicely. The systems main draw back is the block at the clew can raise a lump on the head of the unwary crew member.

Where the mainsheet lead falls might, in fact, determine which system is used on the boat. To find the sheeting angle, pick a point in the middle of the luff and imagine a line from there down through the clew to the sheer of the boat. That will be the starting point for the sheeting lead but some fine tuning will probably be required.

figure 7a

figure 7b

All the sheeting systems do have one thing in common; the main sheet is not cleated off. In small boat the sheet should always be in hand to be quickly eased in puffs. And when the puffs get too much to handle, a brailing line provides a fast way to douse the sail without dropping the yard. This useful piece of traditional rigging can be found on several kinds of loose-footed sails. On the loose-footed Gunter the brailing line should start at the luff and loop around the leech to the luff on the other side and then lead aft (figure 7a). Brass thimbles sewn to the sail will act as fairleads for the light line. As the brailing line is hauled in the loop collapses pulling the leech to the mast (figure 7b). With the sail collapsed against the mast, dropping the yard can wait until a more convenient time. Now the boat can be rowed, work can be done or a sandwich eating. To get under way again, just reverse the process.

figure 8

Variations don’t stop with the sheeting, as the halyards can be rigged in several ways as well. But regardless how the halyard is rigged, raising and lowering the sail will be much easier if the halyard is attached at a point that makes the yard bottom heavy. A bottom heavy spar will be more likely to behave when it’s quickly run up or lowered. The simplest system is a single halyard belayed at the mast. The main problem with this occurs when trying to reef the sail. Unless the boat is beached, the spar will start to swing wildly as the halyard is eased to put in the reef. This can be over come somewhat by adding a toggle below the point the halyard attaches to the spar as shown in figure 8. The toggle holds the yard captive as the reef is put in or the sail dropped. A similar method in figure 9 is found in John Leather’s Spritsails and Lugsails. If the parrel line and halyard are led aft and belayed at the center board trunk, the sail can be raised and lowered from the helm. While this can be an advantage it does add more line in the boat.

figure 9

Either method will help control the sail and yard. And control is very important in small boat. The sailing canoes of the 1890’s and early 1900’s developed quite a few very clever ways of controlling sails as well as yards and quickly shortening sail. Several of these small craft made some impressive and incredible voyages. S. R. Stoddard made a 2000 mile journey down the Hudson River, up to the Bay of Fundy, through the St. Lawrence Seaway, and back to Lake Champlain in Atlantis, a 20 foot sailing canoe. No less impressive is Frederic Fenger’s 500 mile voyage through the Caribbean in his 17 foot Yakaboo. These narrow, unballasted and tender craft demanded almost instant reefing, particularly in the open waters encountered by Stoddard and Fenger. Dixon Kemp in his Manual of Yacht and Boat Sailing details three or four of these types of rigs. A variation of a rig on Nautilus, another famous sail canoe of the 1890’s, is shown in figure 10. Control is provided with two lines, battens and a topping lift. To reef this sail the halyard is eased as the reefing line is hauled in and made fast, then a final tug on the halyard tightens the luff.

figure 10

Sailing canoes of the St. Lawrence River and other areas used another wrinkle called a “Batwing” sail. With the addition of not more than two battens, the shape takes on the highly efficient shape of the RAF wing (figure 11). All of this is done with straight battens, a straight Gunter yard and components made by the builder. It looks very similar to sailboard and catamaran sails but pre-dates them by about 100 years.

The “Batwing” and related sails may be too complicated for the needs of some builders but just adding a sprit boom to the basic mast, yard, and sail still keeps the system simple. The biggest advantage of the sprit boom is the “self-vanging” effect off the wind. As the mainsheet is eased, the angle of the boom tightens the leech. This helps stop the boat rolling when sailing off the wind. Also the sprit boom can control the camber of the sail by adjusting the snotter (the line that attaches the sprit boom to the mast). As the wind kicks up, the snotter is hauled in to flatten the sail and the process is reversed to increase the camber in light winds. The photos in figure 12a and 12b shows a rig that leads the line aft allowing adjustments to be made from the helm. On larger boats it will probably be necessary to have a purchase on the snotter in order to flatten the sail.

figure 11

A sprit boom can be added after the fact to a loose-footed sail, but it’s better to decide the way the sail will be rigged before it’s ordered or made. A sail for a sprit boom can have a little more camber because the control the sprit offers and the foot will need to be cut flat or with very little round. Obviously, the more complicated the sailing rig, the more information the sail maker will need. The “Batwing” or the “Birdwing” Gunter will need much more thought from the builder and the sail maker than the simple loose-footed sail.

Also, with a little thought from both the builder and sail maker, a boat that has an existing Bermuda rig can be changed over to a Sliding Gunter. Because the sails are the same shape, the center of effort will be the same-or about the same- with both sails. This means the same mast step can be used without changing the balance of the boat. In some cases the existing sail might be re-cut, making the transition even easier. The process is even simpler if the boat is not completed. However, the builder should check with the designer before changing the type of sail to avoid changing the balance and performance of the boat.

figure 12a

figure 12b

So, whether you’re retrofitting an existing sail or rigging a new one, the Sliding Gunter has a great deal to offer. The advantage gained with the short mast and spars, by itself, make this sail worth considering. But perhaps its greatest appeal is the ability to design and construct a sailing rig that is perfectly suited to the builder’s or your personal needs. Also, another advantage of the Gunter Rig-and traditional sails in general-is they are made by the builder and therefore repairable by the builder. This makes the Sliding Gunter a versatile and effective sailing rig with a great deal to offer.

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arrowheadboats.com