North Sails RESOURCES

T-10 Tuning Guide

  • Last Updated: Agosto 23, 2017
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This guide is intended to help you realize the full potential of your new North sails. It discusses rigging, tuning and trimming procedures that we have found to be the fastest over a wide range of conditions. We do encourage experimentation, but the following instructions should give you a great starting point.

Keep in mind as you read through Part 1, that class rules prohibit moving factory installed hardware. We strongly agree with the class philosophy that it is the intent of the rule to prevent deviation from the one design specifications, assuming the factory hardware is properly and symmetrically located to begin with. If you find significant differences from the suggested numbers in Part 1, we suggest contacting the Chief Measurer before attempting an alteration.

If you have any questions about any of the numbers in this guide or sailing your Tartan Ten fast, please don’t hesitate to call any of your North Tartan Ten team representatives. Good luck and good sailing.

PART 1 – HULL, MAST RIGGING

HULL 

Maintaining a fair and smooth keel, rudder and bottom is a bit of work, but is well worth the effort. Make your keel and rudder as fair and symmetrical as possible and try to keep a square, sharp corner on the trailing edge (class specs say 1/4” thickness is minimum). Try to keep your bottom clean and smooth!

FORESTAY

Your forestay should be class max allowable length. To determine this measure the height of the attachment hole on your mast and compare this measurement to the table in the class rules. Remember that total length includes link plates and is eye to eye.

MAST BUTT POSITION

Your “J” dimension (measured from the pin at the bottom of your forestay link plates to the front face of the mast at the deck) should be close to 12’ 0” which is a class minimum specification. Mast butt position and forestay length have a great effect on the rake of your mast. Ideally with the forestay as long as possible and the butt as far forward as possible, you will be sailing with maximum mast rake.

JIB TRACKS

Ideally your jib tracks should be symmetrically placed fore and aft and 53” apart. If they are much over 53” apart, you are giving up some potential sheeting angle. We suggest talking to the chief measurer if the distance is greater than 54”.

MARK YOUR SPREADERS

Your new North mainsail is built with a spreader window which will enable you to see the position of the jib leech in relation to the spreader from the windward side of the boat. We suggest placing contrasting stripes of tape on your spreader at the most inboard points of 30” from the side of the mast. We suggest placing 2 more sets of tape marks 1 1/2” outside these marks to help gauge your jib leech position when the sail is eased for power.

MAIN SHEET SYSTEM

Your mainsheet system should consist of 4:1 gross tune with and integral 16:1 fine tune capability. You should adjust your main a great deal and be able to do so with ease.

BACKSTAY

The backstay system should be double-ended and not more than a 4:1 purchase. Ideally an uphaul on your backstay tackle in the backstay triangle will be added in order to help raise the tackle in light air reducing any load on the backstay. This allows the backstay to loosen as much as possible for maximum headstay sag.

BOOMVANG

Ideally the boomvang should be at least 15:1. You will use your boomvang upwind in many conditions over 16 mph of breeze. You should be able to adjust it quickly and easily both on and off for best performance. A powerful system is necessary to accomplish this. Be conscious of easing the vang when rounding the weather mark, as a great deal of boomvang tension can permanently bend or break the boom if it is too tight when the mainsheet is eased!

SPINNAKER GEAR

Hoisting is made easier with the halyard exit hole on the mast about 8’ off the deck and cleated to a big cam cleat about 1’ below. Take downs are less risky, if after the set the halyard is cleated aft on the deck and taken out of the mast cleat. The foreguy is more available if double ended and led aft to cam cleats on either side of the companionway. Lead your double foreguy directly from the pole bridle to fairleads at the mast step and then aft to the cleats. This helps eliminate the need to constantly adjust the foreguy with each adjustment of the spinnaker pole/guy.

The use of a spinnaker turtle is extremely effective and eliminates the need to repack the spinnaker after each takedown. While you may need to rerun the sheets if hoisting from the opposite side, in the long run it is much faster and safer.

PART 2 – TUNING

Before starting the tuning process, completely relax the shrouds and sight the length of your mast up the slot. Make a mental note if it has a permanent bend or S shape, as this may come into play later when tuning the mast.

Next, hand tighten your upper shrouds as evenly and as much as possible. Hoist a tape measure on your jib halyard. Measure down to your upper forward chainplate on either side. Adjust the upper shrouds from side to side until the mast is close to centered. We suggest using the jib halyard instead of the main halyard because in the end it may be difficult to tune a slight amount of hook or S shape out of the mast and the tip of the mast may not be perfectly in line with the deck and the hounds (where the upper shrouds and the forestay attach to the mast). It is most important that the hounds are centered. Throughout the tuning process the backstay should be completely slack and the boom unhooked from the topping lift and resting on the traveler.

Snug up the lower shrouds and tighten evenly, being conscious to maintain close to lateral straightness while sighting up the back of the mast.

Tension the backstay very hard and tighten your upper shrouds 10 more turns initially. Recheck your straightness in the mast again through your measurement on the jib halyard to the upper chainplate.

Now check and retension your upper and lower shrouds using an older model Loos tension gauge Model B. (We will have numbers with the new style tension gauges soon.) With the backstay completely relaxed the upper shrouds should be close to 46, the lower shrouds close to 41 and the forestay close to 30. With this standard tune your mast should develop nearly 1” of positive prebend at the spreaders. This can be sighted easily by pulling the main halyard down taught holding it at the gooseneck against the back of the mast. This is your standard medium wind sailing tune. A properly tuned rig while sailing upwind will see an apparent 3” to 4” of sag in the jib luff when sighting up the forestay with this tuning in medium winds.

For light winds a looser rig is in order. For winds less than 5 mph back off the upper shrouds approximately 2 turns. For winds of 5 – 8, back off the upper only one turn. Adjust your lower shrouds accordingly, so that a 1” positive prebend is maintained and the mast is straight laterally side to side when sailing upwind.

In heavier winds the uppers will be turned tighter from our base setting. With winds of 12 – 15 tightens the uppers 1 turn tighter. In winds 15 + tighten the uppers 2 full turns tighter.

In all conditions the lowers will be tensioned to maintain the 1” positive prebend and a straight mast laterally.

Hint: Adjusting the uppers up or down will be much easier on you as well as your turnbuckles, if you lubricate them well and pull the backstay hard. (Ease to adjust the lowers) If you are sailing adjust the leeward side and then tack. Be prepared by having clear marks as to the number of turns necessary to reach the proper tune and the job will be much easier.

Another hint; tuning the mast doesn’t need to be exceptionally complicated. In all conditions (except in winds less than 7 – 8) when the rig is properly tensioned, the leeward upper shrouds should just barely be slack. The leeward lowers will appear considerably slacker.

Tensioning the rig up or down from the base setting results primarily in a correspondingly more or less powerful rig for different conditions. Ideally, tension decisions are made race by race and generally we try to tune as tight as comfortable while retaining the ability to power up adequately in lulls and waves.

PART 3 – SAIL TRIM

JIB LEADS

The basic guide for setting your jib lead position is so your luff breaks evenly as the boat luffs slowly into the wind. As there can be differences in rake and height of the jib tack off the deck due to the various tack shackles, it is difficult to give a precise measurement from the bow to the lead position. You may find that your new North jib leads slightly farther forward than other jibs you have sailed in the past. For most sailing conditions the lead should be set so the luff breaks evenly top to bottom. Only in winds of 5 – 10 with a lot of chop would the lead ever be moved forward of this position and then only 1”. As the boat becomes overpowered the lead is moved aft from the standard “even breaking” position never more than 2”. When the lead is aft the top of the jib will break earlier than the bottom.

SHEET TRIM

In 10 knots of breeze, trim your jib sheet when the lead is in the “break even” position, so that the middle batten at the spreader is parallel with the centerline of the boat. This will position the leech about at the first mark outside the 30” inboard mark on the spreader. In conditions where the crew is fully hiked with smooth water or with waves which match the wind strength up to 18 m.p.h., the jib sheet will be trimmed tight enough so that the leech will be lined up with the most inboard mark on your spreader. In breezes above 18 or between 10 and 5 m.p.h. trim your jib so that the leech is at the most outboard tape on the spreader. In winds below 5, especially if there is chop, the jib may be trimmed so that the leech is at the end of the spreader.

JIB HALYARD TENSION

The North Tartan Ten jib is fitted with a “stretchy luff”. This means that only in heavier breezes will it be necessary to use a winch to develop the proper tension on the jib luff.

In light winds set your jib halyard so there are fairly good-sized wrinkles (i.e. “crow’s feet”) off of each hank. Wrinkles should be nearly 11” long and there should be a small amount of sag between each hank. In medium winds the halyard should be tensioned so that the wrinkles are much less evident and only 4” – 6” back from the luff. There should be little sag between the hanks.

In heavy winds the halyard should be tensioned so the jib luff is nearly smooth and the wrinkles are almost gone. There should be no sag between the hanks.

If there is question of whether to be tighter or looser on the jib halyard, always err toward the loose side.

Your new North jib has a cunningham grommet just above the tack grommet. Ideally a jib cunningham adjustment system would be rigged so that the tension on the luff of the jib could be adjusted from the rail while the crew is in a hiking position. If the cunningham is not rigged, adjustment to the jib halyard accomplishes the same goal except the halyard is a bit less convenient than adjusting with the cunningham.

Be careful of overtensioning the jib halyard when approaching the leeward mark with the backstay fully eased in medium to heavy winds. As the boat rounds a mark, the rig moves back as the backstay is applied and the loads increased on the jib luff. 

UPPER BATTEN TENSION 

Your new North jib and main are fitted with full length top battens. It is very easy to overtension these battens and make the sails too deep in the upper sections or hook the leeches or both. Be sure to put the battens in with very light tension, so there are very slight vertical wrinkles in the pocket perpendicular to the batten. Battens should never be so tight that the battens “pop” from side to side.

OUTHAUL

The shelf foot of your new North main is an extra piece of fabric that adds fullness to the main when the outhaul is eased. We have found that the seam that forms the top of the shelf in its joint to the body of the sail is an excellent point to measure the tension in the outhaul. We judge the outhaul tension from the shelf seam to the side of the boom. Often it is difficult to “eyeball” the band, so this system makes it easier for the crew to judge and tension the outhaul properly at the same time.

In flat water and winds below 10 m.p.h., or choppy conditions and winds below 15, the outhaul should be tensioned so that the shelf seam is 2” to 2 1/2” off the side of the boom. The outhaul is gradually tightened until maximum with the shelf fully closed when the breeze is over 15 mph or more in flat water or 20 or more in chop.

When reaching, the outhaul will be eased until the seam is 3” to 3 1/2” off the side of the boom. Downwind the seam will be 4” off the side of the boom. However, when the boat is overpowered when reaching, usually the outhaul will never be eased from its trimmed upwind position.

MAIN TACK PIN POSITION

Most Tens are fitted with a gooseneck that has different options for positioning the tack pin. The distance from the forward and aft position is nearly 1”. Where your mainsail is pinned can have a substantial effect on the sail’s “look” and performance. Most of the time your main will be pinned in the forward tack hole, but in flat water with wind below 12 m.p.h. it is advantageous to move the tack aft. This flattens the lower forward 1/4 of the main helping to open the slot between the main and the jib.

MAIN CUNNINGHAM

Under 5 m.p.h. of wind there should be obvious luff wrinkles from head to tack. From 5 to 10 the cunningham should be tensioned just enough so there are wrinkles in the lower half of the main. In winds from 10 – 15 wrinkles would be limited to the lower quarter and from 15 – 20 all the wrinkles would be removed. Above 20 m.p.h. wind the cunningham should be tensioned about 1/2” past the point where all the wrinkles are removed from the luff.

Downwind be sure to totally ease the cunningham, and if necessary to develop wrinkles from head to tack, ease the main halyard.

BOOMVANG TENSION – UPWIND AND DOWNWIND

Because the boom is so long and bendy the boomvang is not very effective for true vang sheeting upwind. The primary effect of using a great deal of boomvang tension upwind in a breeze is to promote bend in the lower sections of the mast. Any time the boat is still overpowered with the traveler eased past the leeward seat edge and a lot of backstay on, the vang is tensioned hard. It is also effective to vang hard in smooth water with as little as 18 m.p.h. breeze. In puffy, breezy conditions work the vang hard powering and depowering with the big puffs and lulls. It is effective in helping to keep the boat upright when used in conjunction with other controls, but requires constant attention. If in doubt, use less vang. Be sure to ease the vang off at the weather mark or when doing a heavy duck around another boat, as the loads are greatly increased on the boom and the gooseneck and, again, some damage can occur.

When reaching use just enough vang so that the last 2’ of the top batten is parallel with the boom. In a big puff that overpowers the boat and loads up the helm, ease the vang completely – basically dump it! Once the puff subsides and the boat is back under control, be sure to trim it back in to power up. A crew member on a windy, tight reach should tend to the vang constantly. When running the vang also needs constant attention. It tends to be set a bit looser than when on a reach. The last 2 feet of the top batten should be angled slightly outboard from parallel to the boom for top performance.

MAINSHEET TENSION

The mainsheet is perhaps the most important adjustment on the boat. Easing the sheet makes the mainsail fuller, opens the leech, powers up the boat and relieves weather helm. Trimming the main tighter helps the boat point higher, flattens the main, tightens the leech and increases windward helm. The sheet should be constantly played to put the boat in the proper gear for every condition. The basic positions are determined in the relationship between the last third of the top batten and the boom. Probably 70% of the time this portion of the batten will be trimmed so that it is nearly parallel to the boom. At this point the telltale off the top batten will fly. When the boat is starved for power, when sailing in light winds and chop, accelerating out of a tack or getting up to speed at the starting line, the mainsheet will be eased so that the top batten will be angled outboard 5 – 10 degrees from parallel to the boom. The telltale will always fly off the leech when the sheet is eased for acceleration.

In “ideal boatspeed conditions” (when the waves match the wind and the water is fairly flat) the mainsheet can be overtrimmed for short periods and the upper batten will actually hook in relation to the boom. This trim would be good for a high pointing mode of sailing with some compromise to overall boatspeed. When the main is trimmed hard and slightly overtrimmed, the telltale will be stalled and flipping behind the backside of the main much of the time.

The mainsheet will be constantly played in and out of these 3 “batten positions”, which will help the boat accelerate through critical conditions, sail at top speed or pinch when conditions allow.

TRAVELER

The traveler is a balance adjustment that is judged by heel angle and degree of weather helm. Easing the traveler to leeward will help “depower” the boat, but at the same time windward helm will be minimized and the boat will sail faster. The traveler is the first adjustment made in puffs or overpowered conditions. Sometimes the traveler may be eased only 4” to leeward to balance the helm or as much as 20” to leeward to depower the boat and keep the boat tracking and under control. Keeping the traveler too low through lulls will cost valuable pointing ability, while keeping it too close to centerline will result in excess heeling and excessive windward helm.

Try to maintain the upper batten parallel to the boom position while playing the traveler in the puffs and lulls to keep the boat on its feet.

In light winds (below 6 mph) it is necessary to trim the traveler to windward of centerline to bring the boom up to or near centerline while easing the mainsheet in an attempt to maintain the upper batten parallel to the boom position. When the breeze increases, lower the traveler car. The boom should never be trimmed to windward of centerline in any condition.

BACKSTAY

As the boat becomes overpowered and it is necessary to ease the traveler to leeward, the backstay should be tensioned. Small adjustments to the backstay will correspond to large changes in the shape of the main up high above the spreaders. More backstay bends the top of the mast flattening the top of the main and opening the leech. Each adjustment of the backstay requires a corresponding adjustment of the mainsheet to maintain the proper upper batten parallel to the boom position. In heavier breezes enough backstay tension will be applied so that subtle “overbend” wrinkles will develop in the main below the spreaders. These wrinkles will be angled 45 degrees from the mast toward the clew and indicate that the main and the mast have reached maximum mastbend. If the backstay is pulled to the point where these overbend wrinkles appear near the hounds and through the T-10 logo, then too much backstay is applied. Be sure as the wind lightens to ease the backstay quickly to power up the main and the jib. Again, be sure to ease the mainsheet quickly as easing the backstay will quickly straighten the mast and tighten the leech on the main up high.

In addition to changing the fullness of the main, the backstay also has a large effect on the shape of the jib. Less backstay tension means more headstay sag and a fuller jib. More backstay tension means less headstay sag and a flatter jib. For this reason we strongly suggest having some sort of positive uphaul for your backstay tackle that is rigged in your backstay triangle. Ensuring that the tackle is loose and high and the backstay, therefore, is as loose as possible will generate the most headstay sag in light to light-medium winds. Except in very breezy, puffy conditions on a tight reach with the spinnaker up, ease the backstay completely when sailing downwind.

SPINNAKER TRIM

Like your main and jib it is easy to overtrim the spinnaker. We suggest as a guide trimming the sheet until the luff of the spinnaker has 6” to 12” of curl at all times. Once you have developed the curl, a steady, gentle ease and trim to maintain it is fast. Anticipate the break of the luff and don’t ease any more sheet than you must to maintain the curl. Trim your guy to maintain the pole nearly perpendicular to the wind. Adjust the height of the pole so that the 2 ends of the spinnaker are even. An even better guide is that the center seam (from the head to the middle of the foot) is parallel to the mast. Pole height adjustment is nearly as important and should be as consistent as sheet and the guy trim.

In light winds the pole should to be lowered quickly and when the breeze is back, the pole raised to maintain the center seam parallel. We suggest easing the halyard off the top of the mast about 1’ at all times to open the slot between the spinnaker and the main upper sections.

In puffy, breezy conditions on reaches it is important to have a crew member calling the puffs and the waves, so that the spinnaker trimmer is prepared to ease the spinnaker as much as 3’ which allows the helmsman to bear off smoothly. Be sure to trim again as the helmsman steers the boat back up and the apparent wind moves forward.

PART 4 – GENERAL SAILING TIPS

ACCELERATING WHEN SAILING UPWIND

As stated above, fine tuning the trim is centered around the base trim point with battens parallel to the centerline and boom. To accelerate as quickly as possible, you’ll ease both sheets slightly until the battens in both main and jib point slightly to leeward (5 – 10 degrees). Here is where sewn-in trim marks on the jib sheet are useful. Once you establish how much ease it takes to twist the jib leech off 5 degrees, you can do that from the windward side by looking at your sheet trim mark and the position of the jib leech through the spreader window. The main is easier to judge by sighting the top batten and observing the tip leech telltale, which will flow strongly aft. Raise the traveler as much as possible without inducing excess heeling and without causing the boom to cross to windward of the centerline. Steer with jib telltales streaming aft and as the boat speed comes up, the sails will be gradually trimmed and traveler adjusted to keep the boom centered and the boat on its feet. It is most effective to work both sails together, but in practice we end up doing most of it with the main. For example: if we hit a bad wave, we’ll ease the main sheet slightly to get a little twist. This will relieve the helm a little, induce sag in the forestay which powers the jib (which eased the helm a little more) and the boat accelerates. The trim comes back in and we have lost very little.

POINTING 

As the boat gets up to speed, sails are trimmed for max pointing for the condition. We define max pointing as as high as you can go with minimum loss of speed. During most of your upwind sailing (except in very light winds) your windward jib telltale will just stall, flowing back and up about 60% of the time or more. T-10’s don’t seem to sail faster when headed off 3 to 5 degrees and certainly not fast enough to net a gain. The straight exits on your North main and jib allow you to “overtrim” and sail very fast and high, so except for tactical reasons(driving into a header or a puff, etc.) footing is not effective. In conditions where the crew is fully hiked with smooth water or with waves which match the wind strength up to about 16 mph., the jib leech will be trimmed to the inboard trim mark on the spreader. The main batten will “hook” 3 to 5 degrees to weather of parallel to the boom and the top leech telltale will stall about 50% of the time. The traveler should be as high as possible with the boat on its feet. Once the boom is lowered below centerline, we start trimming with some backstay which flattens the jib and main entry, depowering both sails slightly and allowing an even higher angle of pointing. When you apply backstay, remember to trim the mainsheet again to the “overtrimmed” position. You may be able to raise the traveler slightly to maintain the proper helm balance. When the boat feels a little sluggish, ease the mainsheet a little as well as the backstay to repower. If your timing is on, you can keep the top telltale stalling full-time, powering and depowering as needed, while still going high and fast. If you overdo the “pinching” and slow too much, you’ll need to ease enough mainsheet to get the telltales streaming and get your speed back up.

This combination of pointing and speed results in a third condition we refer to as height. Height is defined as the distance to weather you gain on a competitor. Imagine: You are sailing side by side with a competitor who is 8 boat lengths abeam to windward and bow to bow. Five minutes later you are still bow to bow, but only separated by 2 boat lengths. You have gained 6 lengths of “height”. This will only occur because you are sailing a high angle with speed and the only way to do that is to sail as flat as possible. When the boat is flat, maximum projected area of the keel is exposed, resisting sideslip and creating lift. When you sail fast, but heeled, you will lose height because you will slide sideways. When you “aim” too high in order to keep the boat flat, you will go slow and sideways. When you sail high enough with the windward jib telltale just “dancing”, the battens just “overtrimmed” and the backstay and traveler set to allow the boat to stand up a little straighter without losing speed, you will be gaining maximum height. Others may “aim” higher than you, but if you gain height, you win.

Sailing this way requires a great deal of concentration on the part of the helmsman. The skipper won’t use much rudder (which is just a big brake), but will anticipate and guide the boat around waves and allow it to ease up in flat spots and help it down to accelerate. The main trimmer will help facilitate this by easing the mainsheet momentarily to help bear off and then trim slightly to develop the helm (boat’s desire to turn up) necessary to head up. Communication between helmsman and main trimmer is important to accomplish this smoothly. It come down to a lot of small, consistent adjustments which allow the best speed and pointing.

MAIN AND SPINNAKER TRIM DOWNWIND

Downwind speed is remarkably equal in Tartan Tens with few significant speed differences. However, we have some tips that may get you an edge.

Main

On reaches, trim the main for balance. Make it as powerful as you can, depower as much as you have to and trim to keep the boat under the sails. Flogging the main is hard on the sail and makes a lot of drag, but is not as slow as rounding up. Try easing more vang and driving on the lower part of the main in heavy breeze. Pay attention to the puffs and ease ahead of time to allow the boat to bear off. Trim to the apparent wind angle constantly which changes dramatically on waves and in puffy conditions. Watch the vang. When running, trim again to the apparent angle until the boom is against the shrouds. Pump the main in surfing conditions – it works.

Spinnaker

When reaching and running, trim diligently with a constant 3” to 12” of curl in the luff. Once you have the curl, a steady, gentle ease and trim to maintain it is fast. Anticipate the break and don’t “give” any more sheet than you must to keep the curl. When you must trim quickly, try to be smooth and steady. We often put 2 or 3 crew on the sheet in lieu of a winch because it is faster. Adjust the pole height and angle as needed, which on some days is a full-time job. Small changes of 2” or 3” can prove worthwhile by the end of a leg. Pump on broad reaches and runs in surfing conditions. Keep the clews level and the pole angle just forward of square to the apparent wind. In surfing conditions, we over-square the pole slightly to avoid pumping the spinnaker into the main shadow. In puffy conditions on reaches, have someone calling puffs and waves so the spinnaker trimmer is prepared to ease up to 3’ or more on the sheet. This is critical to enable the helmsman to turn the boat downwind for acceleration and control. Trim again as the speed comes up and apparent wind moves forward.

Thank you for joining the North Tartan Ten team. As always, if you have any questions we urge you to call any of your North Tartan Ten team members. Good luck and good sailing!