• Last Updated: July 5, 2017
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The current North Sails inventory for the Shark is a result of years of design research and testing as well as numerous National and International victories. This tuning guide is meant to be a good starting point in setting up your boat. Depending on your crew weight, strength, sailing style and local conditions you may have to alter your rig tune slightly. As you read this write down any questions you may have and we will be happy to discuss them with you in more detail.

Our main goal is to help you achieve a rig set-up that is fast in all conditions; upwind, reaching and running and which is very easy to adjust or change gears while sailing. Your new North sails are designed around this all-purpose philosophy.

It is important to mark all your shrouds, sheets, halyards, tracks, outhaul, backstay, etc. Keep records of your tuning set-ups, the conditions you sail in, and how your speed is. It is essential to be able to duplicate settings from race to race, and also to know exactly how the boat was set up when you were going fast. Experiment during practice races and clinics.

Tuning at the dock


Measure to ensure both spreaders and jumper struts are of equal length and cut to the class minimum.

Install jumper stays and adjust the tension so that they are hand tight tensioned.
Fine tuning of the jumpers must be done after the mast is stepped.

Note: It helps to not tighten the lock nuts on the jumper turnbuckles before stepping, so that you won’t need to loosen them after the mast is up.
Check that there is no horizontal movement in either the spreaders or the jumper struts and if there is pin them and/or epoxy them securely in place.
Check that all sheaves are clean and lubricated and fittings securely attached.


Rake Setting: 55 -56”
Once the mast is up attach your jib or spinnaker halyard to the bow of the boat and tighten. Disconnect the forestay and bring it back to the mast. Pull the forestay tight along the front of the mast and with a black marker make a mark on the forestay at the location of the bottom of the black band.

Re-connect the forestay and apply enough backstay tension to straighten the forestay and measure from the black mark on the forestay to the deck right beside the forestay pin.

If you are sailing really light on crew weight, and the breeze is up you might want to go closer to the 56” mark and if you are often sailing in lighter conditions the 55” setting may be better.”

Why do it this way? Because it’s the most accurate way and the measurement is the same for new and old style decks and is independent of the size of your main shackle or the length of your mast above the upper black band. There are so many versions of Sharks around and actively racing now and they all have slightly different equipment.
(The old measurement from the masthead to the deck at the transom is in the 29’10 -30’ range).

Next, make sure the top of the mast is centred in the boat. The best way to do this is to ensure that the keel and mast are vertically lined up but the easier way is to measure from the mast head to a point on the deck at the same location on each side of the boat, equi-distant aft of the tack fitting. Make sure your lower shrouds are loose. With the upper shrouds hand tight hoist a tape measure on the main halyard and measure down to the deck on each side. Keep measuring side to side and tightening or loosening the upper shrouds until the tip is centred.

Set your jumper tension by sighting the mast. The jumper stays will be hand tight, not enough to invert the mast forward but enough to support the upper leech of the mainsail when backstay is applied.

The range of tension is between being able to easily pull both jumper wires together to the mast above the attachment point 3 – 5” up the mast. At 3” up the upper mast will be quite stiff and at 5” up the top section of the mast will be fairly flexible. Be sure to do this with no backstay tension or the boom hanging from the topping lift. The idea here is to end up with a fairly straight mast when the main is up but not pressurized.

The jumpers stays should be hand tensioned and shouldn’t require tools to get the desired tension. In most conditions the correct setting is that the jumpers stays can be squeezed together to touch the mast just above the turnbuckles or about 5” above the bottom attachment point. In windy conditions they can be tightened 1-2 turns so that the mast does not over bend and the mainsail gets too flat in the top. Sight the mast to ensure that the upper section is straight and not pulling to one side.

Hand tension the lower shrouds until they are evenly tensioned. Sight up the mast track/ groove along the back side of the mast to see if it’s straight from side to side. You may find it helpful to take the main halyard and hold it stretched tight as a reference on the aft side of the mast. Use the wire as a straight-line reference with the track. Tighten or loosen the lower shrouds until the mast is straight and the middle of the mast is in column with the mast tip.

We recommend investing in a Loos Tension Gauge Model PT-1. This gauge can hang on the shrouds as it is adjusted and won’t stretch out like the Model A gauge.

Using the tension gauge adjust the upper shrouds to the base setting of about 300 lbs Once the mast is centred it is important to take the same amount of turns on the port and starboard shrouds while adjusting tension in order to keep the mast centred. If the port and starboard spreader tips are at different heights above the deck, the mast will not be straight side to side or the shrouds will have different tension from the port side compared to the starboard side. The shrouds will feel just snug and the lower shrouds will feel slack. In 12 knots of breeze the upper shrouds will start to go very slack on the leeward side.

Set up the rig at the base setting before you leave the dock, adjust the rig as conditions change but remember to keep track of any changes. Just to make sure there is no confusion, all the changes reflect turns on or off from the base setting – not from the previous setting. Also, mark your deck with an arrow and a ‘T’ for the tightening direction and replace any cotter rings/pins with turnbuckle nuts or simply a small rope tied between both turnbuckles through the open barrel – they’re much easier to adjust!

Upwind Trim

Light air (0-5 Knots)

In these conditions keeping the boat moving fast and not worrying about pointing makes bigger gains around the racetrack. Therefore set the boat up to maximize boat speed instead of pointing ability.

The golden rule in all conditions is “If you want to point you have to be going fast first!” In light air set your sails up for maximum power.


The lowers shrouds are set at a position so the mast is slightly sagged to leeward yet there is enough tension that when the backstay is pulled the mast will not bend down low. Get into a habit of sighting up the backside of the mast to see how the mast is bending. Next, sheet in the main sheet so that the top batten just comes parallel to the boom. You will not need any backstay tension in this condition. Make sure the tell tail on the top batten is not stalled. The boom vang should be eased all the way and the traveller pulled to weather usually up to the seat or enough so the lower battens are just to leeward of the backstay. The boom should be on centreline. The outhaul should be 1- 1.5” from maximum. The more chop there is, the looser the outhaul should be set. The cunningham should be slack.


Tension the genoa halyard enough to leave a few of the luff wrinkles. This will ensure that the draft is pulled a bit forward and will open the leech of the sail. With the draft slightly forward the boat will be easier to steer. The open leech will help air flow across the sail without stalling. The foot of the genoa should be 2-3” from the shroud turnbuckle, and the leech should be 4-6” from the spreader tip. Make sure the leech lines are eased.

Remember in these conditions keep your head out of the boat and sail towards better wind velocity on the course.

Light to medium air (6-12 Knots)

These conditions call for a good amount of power as well as the ability to point.


The traveller should be pulled to weather with the boom on centreline to help the boat point (about half way upto the seat), but eased to leeward if too much weather helm is felt, or if the boat starts to heel too much. The outhaul should be eased ½” from the maximum position. The cunningham should be pulled tight enough to remove some of the wrinkles from the luff. The boom vang should be pulled in just enough to snug up the line (preset for downwind). Start with the main sheet set with the top batten parallel to the boom. If your boat speed is good and you want to point higher, try pulling harder on the mainsheet and stall the top batten tell tail 50-80% of the time. (One click in on the ratchet is often enough!)

Beware, if your speed starts dropping off ease the mainsheet.


Set the halyard so some wrinkles show in the luff of the genoa. (the cunningham is tightened slightly but a bit looser than the very light setting) This will flatten the genoa entry and move the draft aft in the sail, allowing for more power and higher pointing. Set the leads so the foot is 1–2” from the shroud turnbuckle and the leech is 2-3” from the spreader tip.

Medium to heavy air (13-18 Knots)

Once the wind has reached this level, it is time to start thinking about de-powering the sails to keep the boat from healing too much.
The shrouds should be tightened according to the matrix listed above. This allows more backstay to be pulled on letting the top of the main twist to leeward, while at the same time placing more tension on the forestay which improves pointing and flattens the genoa. In order to determine backstay tension, pull the main sheet in enough so that the top batten twists to windward even while the backstay is at it’s medium setting. Then pull just enough backstay to let the top batten twist to leeward about 15 degrees. The cunningham should be pulled tight enough to remove all wrinkles from the luff. The boom vang should be tightened enough to hold the boom down at its sheeted height even without mainsheet tension. The outhaul should be at its maximum position.


These conditions are at the upper wind range for the 180 Genoa. The decision to switch to the 150% Genoa or the jib will depend on crew weight, consistency of the wind and waves. Choose the size of your headsail based on the strength of the wind during the lulls. The larger the waves the larger a headsail needed to power through them. If the Genoa is used tighten the halyard to move the draft forward and open the leech. Set the leads so the foot is against the shroud turnbuckle and the leech is 4–5” from the spreader tip. To de-power twist the genoa by easing the sheet 1–2”.

150% Genoa

This sail is designed for winds ranging from 15 to 25 knots. Sheeting of this sail can be done on the toe rail but slightly higher pointing can be obtained with an inboard track mounted approximately 5” from the outer edge of the hull. This sail cannot be sheeted from the 180% lead. In winds ranging from 15-18 knots the rig setting from the matrix are OK. If the wind is in the lighter range while you have this sail up the medium rig settings are better to ensure enough headstay sag is obtained. This will make give the sail the most possible power. Cloth tension is determined by the wave conditions. In flat water allow some creases to appear around the hank positions. This will give you a flatter entry for high pointing. In big seas and chop remove the wrinkles.

The 13-18 knot range of apparent wind can really separate the fleet. Make sure the boat is tuned for the conditions and the headsail. The key is to keep the boat moving fast and pointing high, you should roll the boat up to speed and keep the weather tell tails at about 45 degrees for maximum VMG to weather.

Heavy air (19+ Knots)

In these conditions the sails need to be flattened as much as possible and set up so the boat is as easy as possible to steer.


Begin vang sheeting by pulling the boom vang on hard, which bends the lower section of the mast thereby flattening the lower part of the main. The cunningham should be pulled in enough to remove all wrinkles and move the draft forward. Set the outhaul at it’s maximum setting. Let the traveller down to the leeward seat to help balance the boat and maintain a low heel angle.


The crossover to using the class jib can be found in this wind range. Lighter crews, or sailing in flatter water can allow you to go to the small jib and still be fast.
If the wind is under 20 knots or there are large seas, keep the lead forward to make the bottom of the sail full while twisting off the leech a little. The top batten should lie 10-15 degrees below centreline.

As the breeze increases or the water flattens out you can trim harder. Now the top batten will lie 0-10 degrees below centreline. If the breeze increases further move the lead back one more hole.

Keep the boat powered and don’t strap the jib in! The Shark likes to be rolled up to speed and a strapped headsail won’t get you there!

In the heavy air condition you will probably see all styles of headsails used effectively. The heavier crew will still manage the 180% genoa, they can manage the tacking and are good at keeping the boat on it’s feet and moving. The 150 provides almost the same amount of power but is easier to handle and tack. The jib is the ultimate in tactical advantage high pointing and easy tacking. But you have to make sure that the wind is going to stay up in the 20 knot range and above

The jib should be sheeted to tracks mounted 5” inboard of the toe rail and about 12” aft of the shroud base.

Pull the jib halyard tight enough to remove the wrinkles in the luff. Set the jib so the top tell tails break slightly before the lower tell tails. If the boat needs a little bit more power move the jib lead forward to give the bottom of the sail some depth and sheet the sail so the leech is pointing straight aft. To de-power move the lead aft to flatten the bottom of the sail and twist the top off.

The main and headsail need to work together. If the genoa or jib is twisting off at the top, so should the main. If the genoa or jib is sheeted hard, so should the main. When the wind is blowing hard adding twist to the main and jib will help give the boat a larger groove to steer in.


Downwind Trim



Downwind the main should be set at its fullest settings. The backstay should be eased. In breeze over 15 knots it is a good idea to keep the backstay tensioned a little to prevent total mast inversion. The outhaul should be 2” from maximum tension. The cunningham is always eased all the way on a run. Boom vang should be set so the top batten is parallel with the boom or slightly forward.


While reaching the main should be powered up most of the time. The backstay should be eased, cunningham loose and outhaul eased. A little bit of twist in the top of the main is okay. Make sure the top tell tail is not stalled. Once the boat starts to be overpowered on the reach it is time to depower the main. Pull the backstay on a little to keep the mast in column. Ease the vang to allow the top of the sail to twist off. Pull the cunningham on to open the leech of the main. Tighten the outhaul.


North’s spinnaker likes to be flown with the spinnaker pole lower to project more area. The pole should be flown parallel with the horizon. The halyard should be raised as high as it will go to increase projected area and stabilize the sail. Only in fully powered up conditions can the halyard be eased a few inches. When running, square the pole so it is perpendicular to the apparent wind.

The trimmer should keep a slight curl in the luff of the sail. Remember that an under trimmed spinnaker is much faster than an over trimmed and stalled spinnaker. Spinnaker trim needs to be constantly adjusted due to the changes in apparent wind caused by velocity changes, steering, waves and changes in boat speed. To help the boat accelerate faster be ready to ease the sheet 5–12” when a puff hits. The ease of the sheet will move the driving force of the sail forward instead of healing the boat to leeward.

When running concentrate on steering your optimum down wind angle. Good drivers are sensitive to small changes in boat speed. When the boat is going slow head up a little to increase boat speed. If the boat is moving fast, or in a puff, bear off to ride the puff longer and use your extra boat speed to sail lower. Good communication between helmsman and trimmer is important.

Make sure one of the team (not the spinnaker trimmer) is constantly watching for puffs and velocity downwind.

If you have any questions, comments or suggestions about your new Shark sails, we will be glad to discuss them with you.

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