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NORTH SAILS J-105 Tuning Manual

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Summary of Contents for NORTH SAILS J-105

  • Page 2 This tuning guide has been developed over years of J-105 sailing and sail development. It is intended to serve as a starting point for new boat owners and new North Sails clients. Once your boat is set up to the basic principles of this tuning guide, you can use our Quick Tuning Guide to make on-the-water adjustments to your rig to make adjustments for various wind conditions.

  • Page 3: Table Of Contents

    Contents Part 1 — Rigging Preparation Part 2 — Rig Set — Up Part 3 — Mainsail Trim Part 4 — Jib Trim Part 5 — Crew Weight Placement Part 6 — Downwind Sailing Quick Tuning Guide...

  • Page 4: Part 1 - Rigging Preparation

    North Sails and make the boat easier to sail and set up. Head swivel shackle: The North Sails jibs come with a webbing loop at the head. It is critical to have a 90-degree “twist” shackle to attach the sail to the swivel. A standard shackle will cause a hard spot at the top of the jib as the sail is torqued.

  • Page 5: Part 2 - Rig Set - Up

    50’ metric tape measure. Part of the success of growth of the J-105 Class is the tight class rules and limited sail inventory. With the J-105s limited sail inventory of only one headsail, aggressive rig tuning is essential for performance throughout the full range of wind conditions.
  • Page 6 Measuring Rig Tension with the RT-10m Gauge Advanced Tuning — Beyond the Numbers The North Sails J-105 Tuning Guide is very refined, and has been used to the letter to win many events. In fact both the 2000 and 2001 North American Champions use the Quick Tuning Guide as their bible.
  • Page 7 The final D1 and D2 rig tension will be dictated by mainsail shape. The light air performance of the J-105 can be dramatically improved with leeward mast sag in under 12 knots. This is side-to-side sag from the partners to the hounds. This can only be seen under sail and will not happen at the dock.
  • Page 8 The image at the right shows what the mainsail will look like with no backstay if the D1s and D2s are too tight. The sail is too deep and the draft is too far forward. Rig is tuned for 15 knots and there was actually only 8 knots.

  • Page 9: Part 3 - Mainsail Trim

    Part 3 — Mainsail Trim The J-105 relies on much of it’s power from the mainsail with the class inventory. The mainsail is very easily adjusted because there are many shape controls including mainsheet, traveler, backstay, cunningham, vang and outhaul. Proper mainsail trim is achieved by balancing the speed and pointing with its twist, angle of attack and overall power.
  • Page 10 It is much easier to depower the J-105 than is to power it up, so ALWAYS TUNE FOR THE LULLS!
  • Page 11 As the mast bends it has an immediate effect on the luff and leech tension, so other controls must be adjusted in conjunction with the backstay. When you pull the backstay on, the mainsail will twist more so more sheet will have to pulled on to reset the twist. More backstay will also loosen the luff, so mo cunningham will be needed.
  • Page 12 Light Air Upwind — Traveler is high, boom is slightly above centerline. Crew is low and forward. The boat is balanced nicely with a good heel angle. Blasting Upwind in San Francisco Bay — Nice heavy air upwind form here. The traveler car is centered and speed is being controlled with the mainsheet fine tune.

  • Page 13: Part 4 - Jib Trim

    Part 4 — Jib Trim The J-105 Class Jib has a very tough job. It has to be fast in all wind conditions, where other 35’ offshore one-designs allow 3 headsails! The single jib inventory presents a tough challenge for sail designers to create a sail that is versatile enough to cover the entire wind range, while being constructed so that it can be light enough to perform well in light air, yet being strong enough to handle heavy air.
  • Page 14 leech more closed and the foot rounder. Moving the lead aft will make the upper leech more open and the foot flatter. The median jib lead position is slightly aft of the middle of the jib track, which is about 9” aft of the chainplate.
  • Page 15 The image at the left shows the AP jib set up perfectly in 17 knots of wind. The camber and draft measured by North Sails SailScan program is: Top Stripe: 14.76% @ 41% Mid Stripe: 14.45% @ 40% Bot Stripe: 11.25% @ 39%...

  • Page 16: Part 5 - Crew Weight Placement

    Part 6 - Downwind Sailing Sailing the J-105 downwind can be one of the more difficult things to do well. Paying small attention to the minor details can make a huge difference. The key to fast sailing downwind is good communication between the trimmer and the helmsman.
  • Page 17 2.5’ The North Sails J-105 Tuning Guide has been developed by the North Sails Class Development Program. The J-105 Class Leaders are Tim Dawson (tim@sales.northsails.com) and Will Keyworth (will@sales.northsails.com). Feel free to contact Tim or Will at any time if you have questions or...