North Sails Tuning Guide

Tuning guide graciously provided by North Sails One Design.

On-shore Adjustments

Mast Placement

The mast step should be positioned so that the mast is near maximum aft position. In this position the back edge of the mast should be 16″-16½” forward of the centerboard pin. Most commercially built Y-Flyers since 1975 were built this way.

Mast Rake

The best method for measuring the mast rake on the Y-Flyer is by hoisting a 25′ or longer tape measure to the mainsail halyard shackle and raising the halyard all the way up as if the mainsail were attached. Then measuring the distance from the top of the mast to the intersection of the transom and the center of the back deck. With the jib sail up and tensioned as if sailing (tension discussed later), this measurement should be 23′ 10½”-24′ 1″.

Corresponding the above method to the method of the bubble level on the top of the centerboard trunk, the distance from the main halyard, with a weight on it, to the lower mast band above the gooseneck should be 30″-31″.

While the tape measure is hoisted to the top of your mast it is important to check that your mast is set up straight on your boat laterally (i.e., side to side). With the tape attached to the mainsail shackle and the shackle still at the top of the mast, measure the distance to the bottom of each upper shroud chainplate. There should not be a difference of more than ¼”-½” difference from side to side.

Rig Tension

The Y-Flyer performs best in medium winds with the rig set up fairly tight. It is best to use a powerful jib halyard adjustment system (a lever, magic box, block and tackle, drum, etc.) so that the leeward upper shroud just begins to go slack when sailing in winds of 10–12 mph.

To verify proper rig tension, it is strongly suggested that you use a Loos tension gauge. When using the Loos gage, and checking the tension on your ⅛” upper shrouds, the gauge pointer should indicate 34–36 (this is a Loos gauge number, not lbs of tension).

In light winds without changing the shroud position, it is advantageous to ease off the jib halyard slightly so the tension is reduced in the rig. This will allow the jib luff to sag slightly, making the jib slightly fuller. Using the Loos gauge to check the tension on the shrouds, you should find a number of approximately 28-30. If you still have your tape hoisted on your main halyard, you can check the rake number and see that it will become less by 1″-2″ indicating more rake. In heavy winds, when the boat is overpowered, it is found fastest to rake the rig farther aft. If you set your mast up at 24’ 1” for medium winds, it is suggested that you allow the mast to drop back nearly as far as 23′ 9″-23′ 10″. Ideally, it is best to also drop the shrouds in their channel adjusters so that the rig, when raked farther aft, would still be close to the proper 34-36 Loos gauge number on the shrouds. However, if the breeze comes up during a race and since it is impossible (and illegal) to change the shroud length while racing, it is best to compromise and sail with a looser rig with the mast raked farther aft.

Loos Tension Gauge

The Loos tension gauge is a very helpful guide in tuning your Y-Flyer. A Loos tension gauge can be purchased online from various sources (APS, Layline, West Marine, etc.) or directly from North Sails.

Mast Bend

When the rig is properly tensioned with the proper rake and spreader settings, the mast should develop a positive prebend, where the middle of the mast will move forward at the spreaders and the top of the mast will come aft. In medium winds with the rig tensioned at 34-36 on the Loos tension gauge on the upper shrouds the mast should develop nearly 1″-2″ of prebend. Prebend can be observed by pulling the main halyard down tight and holding it at the gooseneck so it will develop a straight line as a reference from the top of the mast to the gooseneck. In light winds with less rig tension, there will be less prebend of approximately ¾”.

Listed below are suggested spreader positions for the various popular masts used on the Y-Flyer. It should be noted that masts of a particular section may have slightly different bend characteristics depending on spreader height, rigging placement, and any differences in the mast extrusions themselves. Because of this, the following measurements should be used as starting points with only small adjustments being made to the mast bend and then tested while sailing.

Spreaders for the stiffer mast (W2, H2): Non swinging spreaders need to secure the cable at 35″-36″ from cable to cable to give the proper mast bend. They must be swept back to the same angle on each side to provide the same mast bend for both starboard and port sailing. Swinging spreaders must have their swing limited such that the cable to cable dimension is never less than the 35″-36″. This spreader length dimension is for spreaders that are located on the mast at 9′ 1″-9′ 2″ from the deck. Spreaders that are mounted higher than 9′ 1″-9′ 2″ on the mast will need to be shorter to give the same mast bend.

Spreader for the bendy mast (DP1, C1): These masts require spreaders which measure 38″ cable to cable and located approximately 10′ above the deck. To make adjustments to the mast bend, the “cant” of the spreaders must be adjusted forward (greater cable to cable distance) for less bend and aft (less cable to cable distance) for more bend. Greater cable to cable distance can be made by lengthening the spreaders. Lesser cable to cable distance can be made by shortening the spreaders.

Sailing Adjustments

Main and Jib Cunningham

For both the main and the jib, never pull the cunningham tighter than to just leave a hint of wrinkle along the luff of both sails. On the main, these wrinkles will appear in the lower ⅓ to ¼ of the luff and appear as small wrinkles approximately 2″ long perpendicular to the luff of the jib.

Note: do not attempt to pull out your overbend wrinkles by tensioning your main cunningham. Again, remember that the overbend wrinkles are a necessary guide in showing that the mast is bending properly and pulling the cunningham tight enough to pull these wrinkles out will pull the draft too far forward in your main, robbing the boat of necessary power.


The outhaul adjusts mainsail depth in the lower part of the mainsail. As the outhaul is eased, the shelf on the bottom of the sail opens and the seam that attaches this shelf to the sail moves away from the boom. To gauge outhaul tension, judge the distance from the seam to the side of the boom at roughly the center of the mainsail foot.

The outhaul should be pulled tight enough so that there is just a ½”-1″ gap between the side of the boom and the shelf foot seam in the middle of the foot. In breezes above 10-12 mph when the boat becomes overpowered the outhaul needs to be pulled tighter until the seam is snug against the side of the boom (max outhaul).

When reaching, ease the outhaul until vertical wrinkles appear across the seam perpendicular to the foot into the body of the sail. Tighten the outhaul until the wrinkles are just removed. When overpowered on a reach, tension the outhaul as you did for upwind. For downwind sailing, leave the outhaul on in the tensioned position for maximum sail area.

Jib Sheet Trim

Unfortunately, there is not an easy guide for jib trim. We are looking for a parallel slot between the exit of the jib and the entry of the main. A guide that has been used with some success is to imagine a middle batten on the jib at mid-leech. Set this “batten” parallel to the centerline of the boat, making the upper batten of the jib twist outboard slightly and the lower batten twist inboard slightly. In extremely flat water and winds of 8-12 mph, it is possible to trim the jib in slightly tighter so that the top batten is nearly straight back parallel with the centerline. This trim can be used for short periods of time when the boat is traveling at near maximum speed.

In light winds, or when acceleration is needed, ease the sheet out slightly so that the top batten is angled outboard approximately 15 degrees from parallel with the centerline of the boat. The imaginary middle “batten” will be angled outboard just slightly from parallel to centerline and the jib will be fuller and less apt to stall.

Mainsheet Trim

The mainsheet on the Y-Flyer should be pulled so that the upper batten is parallel to the boom. This is sighted underneath the boom looking up the sail, lining the batten and the boom parallel on a horizontal plane. In very light winds, it is usually impossible to keep the upper batten from hooking slightly to weather because of the weight of the boom hanging on the leech. In these conditions, ease the sheet out so that the top batten is parallel with the centerline of the boat.

In choppy conditions in winds above 2-3 mph, ease the mainsheet approximately 6″-8″ to slightly open the upper batten out from parallel to the boom. This will make your mainsail fuller, more powerful, and like the jib, less apt to stall.


When sailing upwind in medium to heavy winds, the boomvang should be kept on hard enough to keep the upper batten parallel to the boom. This may require a good deal of vang tension but this will also help to bend the mast and flatten the sail. In light winds, never use any vang tension upwind. Downwind the vang should be tensioned only tight enough to maintain the upper batten parallel to the boom position. There may be a tendency to overvang downwind in light winds and undervang downwind in heavy winds. Basically, look for the main to set downwind as it does upwind. Upwind when the boat becomes overpowered, the traveler should be eased to leeward, with the boat slowly feathering up into the wind to help keep the boat level and the helm neutral. In the lulls, be sure to quickly pull the traveler back up to centerline, but be ready to ease it back down to leeward in the puffs.


When sailing your Y-Flyer downwind with the whisker pole up, it is best to ease off the jib halyard as much as 10″ to allow the luff of the jib to sag greatly. A loose luff, when sailing with a pole, will allow the jib to basically ”turn around” with the leech becoming the luff and the luff becoming the leech. You need to remember that you are trying to create airflow across the jib with the wind entering the jib from the actual leech of the sail. Not attaching your jib to the forestay (except at the jib head as required by class rules) with the snaps or velcros will make this procedure much easier. Instead, set the forestay so that it is loose enough to just allow the rig to lean back to the heavy air setting of approximately 23′ 9″. There will be slop in the rig, but that is necessary for top performance downwind. A shockcord retainer can help minimize the slop in the headstay when sailing upwind.

In addition, it is also suggested to sail with a longer whisker pole which will help with better performance on beam reaches. A longer pole may just barely fit into the cockpit of some fiberglass Y-Flyers.

Once again, a powerful jib halyard adjuster is helpful to make it easy to adjust the halyard tension properly and easily before rounding the leeward mark when the pole is dropped.

When sailing on a close reach without the pole, be sure to use your barberhaulers and move the jib lead outboard. The proper position of the barberhauler lead, forward and aft, is determined by the trimline on the clew of the jib. This time, position the barberhauler lead so that the sheet is angled slightly forward of parallel to the trimline. This will make the jib slightly more powerful and help to support the upper leech.