North Sails RESOURCES
Knarr Tuning Guide
Download – Knarr Trimguide (Danish)
The purpose of this tuning-guide is to give our clients in the Knarr class some guidelines on how to get the most out of their North Sails. This tuning-guide was compiled by Henrik Søderlund and Theis Palm.
Always experiment and try finding your own trim using these guidelines. The weight of the crew, the balance of the boat together with specific local wind and sea conditions all have influence on the fastest and final trim.
Before stepping the mast in the boat, some very important measurements have to be checked to follow this tuning-guide correctly:
- Lead the upper shrouds and forestay along the mast, the upper have to be out of the spreader tips. Pull them as hard as you can and put a mark on all three wires at the top at the black near the gooseneck on the mast. These three marks are now used to check if the mast is centered in the boat, and to check the mast rake.
- Place the mast foot the following way. First measure 1.21 meter from the bow and place the forestay here. Move the foot of the mast aft, until you measure 2,00 meter from the forestay position (this is the maximum J measure to the class rules) block the mast on the backside. Leave 20 mm free space on the front side of the mast.The mast foot adjusts the following way: In light winds (0-8 Knots) the mast should be relative hard on the aft edge and pressed 10 mm aft along the mast foot rail for the mast to bend smoothly, and make the forestay loos. In winds above 8 knots move the mast foot back to basic position.
- Set the mast rake. Pull the permanent backstay until the forestay stays straight. Then measure the distance from the black mark on the forestay to the deck (along the forestay) the distance is 1,13 meter. Control the distance from the deck to the upper black band at the gooseneck measured on the backside of the mast, the measurement is 80 cm. If there is a difference it should be adjusted on the forestay measurement.
- The upper shrouds proper position is located measuring perpendicularly from the center of the mast to the attachment point on the shroud base.
- The marks on the upper shrouds (from step 1) are now used to verify that the mast is vertical. This is best done by measure from the mark on the upper shrouds to where the turnbuckles enter the deck – the distance should be the same on both sides. It is very important, that the mast is straight from side to side and not being distorted at deck level.
- The lower shrouds are placed 35 cm behind the upper shrouds according to the class rules.
- All rig tension measurements we used a Loose Gauge PT-2. The upper shrouds should read 11 as a base setting. In 9 – 15 knots tighten 1½ turn and from 16 knots and up, another 1½ turn.
- The lower shrouds are tensioned, so that the mast is completely straight in the boat. The lowers is tighten in the same time as the upper shrouds. In general the rig is very slack to get the mast as fare forward as possible on the downwind leg.
- The jumpers are adjusted by pulling the permanent backstay. Then look up along the sail track and check that the jumpers are equally tight on both sides. If this is not the case, they should be adjusted till the mast is completely straight. When the mast is relaxed it will bend slightly forward.
The mainsheet is critical in setting the shape of the sail and small adjustments can have a big effect on speed and pointing. If the mainsheet is sheeted tight, the leech will close and put more pressure on the rudder – on the other hand pointing ability is improved. This can be used in medium winds and flat water, where the boat can be kept flat by hiking. In light winds the mainsheet is eased so that the top tell-tale flies straight. In heavy winds, sheet tight and pull the backstay until the rudder feels light again (but without losing pointing). In large waves, let the leech twist a little more to have a wider steering angle. This increases speed, and therefore pointing, at the same time. As a thumb rule the top batten is trimmed parallel to the boom in almost all wind strengths.
The outhaul is also an important factor when trimming as it controls the draft in the bottom of the sail. In very light winds (0-5 knots) the sail should be 2 cm from the mark. In medium winds (5-12 knots) about 1 cm from the mark and in more wind than this pull the sail all the way to the mark.
Do not set the cunningham in light winds. In medium winds set the cunningham so that the wrinkles along the luff disappear. When the wind exceeds 15 knots pulled it hard to open the leech and keep the draft forward in the sail.
Always to windward in any condition
The backstay has two functions: To control draft in the mainsail and to control forestay sag. When the backstay is tightened, the mainsail flattens, the leech opens, and there is less forestay sag and therefore, a jib with less draft. It is a good idea to put marks on the backstay, e.g., every 5 cm, to facilitate finding the right trim after mark roundings, etc.
The kickingstrap is used when sailing upwind in strong wind and also downwind. Upwind, the kickingstrap push on the mast and opens the leech in the bottom part of the mainsail and keeps the boom down when easing in the gusts. Never use the kickingstrap upwind in less than 18 knots and use caution. Remember always to ease the kickingstrap for downwind sailing when bearing off, otherwise the boom might break. Downwind the kickingstrap is trimmed so that the top batten is parallel to the boom – on all sailing angles and in all conditions.
North Sails jibs are made for sheeting points both on deck and cabin top. However, we recommend sheeting from the cabin top to make the jib-leech twist more freely and thus allowing the gap between main and jib to be as wide as possible. Furthermore, the control of the jib is improved (particularly in heavy winds) because of the shorter distance from clew to block. The jib-lead track is placed with its center 48 cm (fig2A) from the boat’s centerline.
When sheeting from the cabin top, we recommend using a swivel block on the deck, so that the jib sheet does not create an overwrap on the winch.
The position of the jib lead is crucial for the jib trim. As a reference point measure 2.68 m from the pin in the forestay to the centre of the block (if the lead is on the cabin top). The jib shall luff evenly, i.e. tell-tales must fly at the same time in top and bottom.
As a general rule sheet the jib so that the middle batten is parallel to the centerline in most conditions, but in light winds (0-5 knots) leave 2-3 degrees of twist. If the sea is lumpy, move the jib lead 2 – 3 “holes” forward to get more draft and power in the jib (the middle batten shall still be parallel to the boat’s centerline). In heavy winds move the lead 1 – 2 “holes” back without letting the foot of the sail become tight and flutter.
Never pull the halyard too tight. This will cause the draft of the jib to move too far forward. Pull it until the wrinkles in the luff disappear. In light wind the best shape is obtained when leaving small wrinkles in the luff.
Good luck on the water!