Sloop to cutter

Making a Tartan 34 sloop into a cutter can be very cost effective from a performance and sail-handling point of view. When a staysail is added to a sloop, the number of headsail combinations is increased without the need to change either the foresail or the staysail until wind strengths get above 35 knots.

Designing and installing a staysail stay can be a relatively inexpensive do-it-yourself project, particularly if a heavy hank-on sail is used rather than roller-furling staysail. I believe a hank-on staysail is better than a roller-furling staysail on mid-sized boats because it can be doused easily during heavy weather and replaced by a hank-on storm staysail. Also, the staysail stay and staysail can be moved aft to the shrouds when at anchor in order to clear up the foredeck.

Running backstays

I have had several discussions about the need for running backstays when a staysail is installed on a masthead sloop. Running backstays are normally required to counteract the unsupported strain on the mast caused by staysail and staysail stay, which, on our mast, is attached about midway between the spreaders and the masthead. The Tartan 34 has a single spreader rig and a very beefy seven-inch oval aluminum mast. The angle of the staysail stay with the foredeck is steep67°meaning that most of the strain is pulling down on the mast and up on the foredeck. I have looked up the mast a number of times when the staysail is flying in 35 to 40 knots of wind and observed no major mast bend or any other signs of undue stress.

At a 67° staysail stay angle with the foredeck, a 500-pound tension on the staysail stay means about a 160-pound forward force on the mast about halfway between the spreaders and the masthead. A 500-pound staysail stay tension seems reasonable on voyaging boats when backstay/forestay tension is generally 1,500 pounds or less when close reaching.

The staysail stay tension can be controlled by the staysail tack turnbuckle and should be set considerably less than the tension on the backstay/forestay to prevent creating a force greater than 160 pounds and bending the mast forward at a point between the spreaders and masthead. A 20-foot unsupported length of seven-inch oval aluminum mast can support a perpendicular force of 160 pounds. Of course, tensioning the staysail stay to the point at which the mast bends between the spreaders and masthead is asking for trouble. If we planned to sail the boat in the roaring forties I would probably install running backstays just to be on the safe side.

Staysail location

The location of the staysail tack, the halyard exit and the staysail mast tang, and the size and weight of the staysail, were determined with help of our sailmaker. The tack is located first at the most convenient and strongest point just forward of the anchor locker bulkhead. Using the Tartan 34 side view scale drawings, a line was drawn from the staysail tack location parallel with the headstay to a point on the mast. The point on the mast locates the halyard exit point and the tang for the staysail stay. The staysail stay was 32 feet long with the tang located about 10 feet below the masthead and about 11 feet above the spreaders. The tack is located about 5 1/2 feet aft of the stem. As it turns out, the angle between the foredeck and staysail stay is 67°.

Staysail design

With the help of our sailmaker, a 7.25-oz Dacron staysail was designed that was slightly shorter on the luff than the foretriangle created by the staysail stay and the mast. When flying, the staysail foot just overlaps the mast. The area turns out to be 142 square feet with a luff of 27.75 ft and a foot of 11.5 ft. The staysail was cut as a yankee with a moderately high clew for offshore work.

Different boats will require different size staysails, but the location and size principles are the same. A hank-on 90-square-foot, 10-oz Dacron storm staysail was made at the same time the staysail was made. The storm staysail is also cut with a high clew to work with a double- or triple-reefed main. We particularly liked the idea of keeping the storm sails close to the mast so the bow is less likely to blow off when reaching. The staysail cars are also used with the storm staysail.

Foredeck reinforcement

Foredecks on sloops are not designed to handle the 500-pound upward pull of a staysail stay. To prevent distortion and cracking of the foredeck, the foredeck was reinforced. A four-inch aluminum I beam was cut to fit athwartships just forward of the anchor locker bulkhead. The I-beam was pre-drilled in the center to accept the on-deck four-bolt tack-eye fitting. It was also fiberglassed in place under the foredeck and also against the sides of the hull.

The I-beam is out of sight forward in the anchor locker. Fiberglass tape and resin was liberally applied to ensure the staysail strain was distributed evenly across the foredeck and by the sides of the hull.

If I were to do it again, I would use a carbon fiber I-beam rather than aluminum to save weight. The holes in the I-beam were located to the foredeck and the tack plate bolted to the deck using liberal amounts of sealing compound. After two Atlantic crossings and frequent use of the staysail, neither the mast nor the foredeck shows signs of stress.

Staysail sheet leads

The Tartan 34 has a sail track on deck inboard of the toe rail. We use it for both the staysail and headsail sheet leads using separate cars. Both headsail and staysail sheets are led outboard of the shrouds. Because of the narrower sheeting angle, the staysail cars are forward of the headsail cars; they don’t interfere with each other. Because of the much narrower sheeting angle, the storm staysail sheet is led inboard of the shrouds and uses the inboard sail track and staysail car.

Staysail stay

A 1/4-inch 1 x 19 wire stay with a 3/8-inch open turnbucklerigging screwat the tack end is used for the staysail stay. The head end of the staysail stay uses a 1/2-inch swage eye fittinga 1/2-inch Sta-Loc eye fitting could be used just as well. The fittings are considerably overdesigned given 500 pounds of staysail stay tension.

The staysail stay mast end was connected first to the mast tang fitting with the mast up. The forestay and backstay were tensioned as they would be when close reaching. The staysail stay was measured by first installing the 3/8-inch turnbuckle at the tack and opening it 3/4 of the way. The stay was cut to length, including a 1/2-inch Sta-Loc eye fitting installed and pinned to the turnbuckle. The turnbuckle was tightened, locked, and pinned by hand. A 1/2-inch pushpin was used at the tack fitting to allow the staysail stay to be easily disconnected.

The turnbuckle is sailed hand tight so as not to cause slack in the headstay or bend the mast at the staysail tang; the staysail luff is set reasonably tight depending on the wind strength. The staysail tack fitting was made of 1/8-inch stainless steel plate sandwich. The custom-made stainless steel tack fitting bolts around the tack-eye cost about $15.

Staysail mast fitting

The staysail stay mast fitting was designed to serve both the staysail halyard and the staysail stay. The fitting was designed to conform to top of the angle made by the mast and the staysail stay. The side view boat drawings were used as a guide. The fitting was attached to a beefy tang located just above the internal halyard exit hole. Again, a custom sandwich of 1/8-inch stainless steel plate was made to contain the halyard block and 1/2-inch tang pin and stay pin. The custom-made stainless steel fitting cost about $35.

Staysail halyard & stowage

The staysail is left hanked on and is either flown or bagged on deck during passages and stowed by the mast when in harbor. The staysail bag has a hole in the bottom to allow the stay to feed through the bag. The halyard is left attached to the staysail head and tied off. The staysail sheets are fed aft and left in place during passages and stowed below when in harbor.

At wind strengths above 25 knots the headsail is left tightly furled and either the staysail or the storm staysail is used with a single or double reef in the main.

Clearly we are believers in cutter rigs for offshore work. Many production sloops offer roller-furling headsails only, probably because most sailors don’t make offshore passages in heavy air.

The entire staysail project can be done for less than $300, plus the cost of the staysail. We have a separate staysail halyard winch on the mast, but one could tie off the foresail halyard and use the foresail winch. An internal halyard is nice but an external halyard will work. It’s even possible to do the project without unstepping the mast. The mast tang can be installed with the mast in the boat; it’s much easier with the mast unstepped, however.

The design and layout is done first with the help of your sailmaker and even the boat manufacturer. The biggest task is properly reinforcing the foredeck and fabricating the tack and mast fittings. As for running backstays, each boat is different, and some may require "runners" to safely reinforce the mast.

By Ocean Navigator