Olimpic Sails J24 Tuning guide.pdf - Sailmaker.org

j24australia.com :: International J24 Class Australia* Slowly pull the mast step aft using the tail from the genoa sheet, tied just above the mast base and leading it back aft toyour port primary winch. Inscribe a line at 13 mm (No1) 26 mm (No2) and 39 mm (No3). These are your mast stepsettings. You must able to pin your step at these positions.* Now set your step on 39 mm or (No 3) measuring from the bow fitting along each gunwall, make a mark at 3200 mm.* Using a tape measure pull it up using the Genoa halyard and centre the mast side to side.* Slowly take up the turnbuckles (caps and lowers) until you reach a light tension on each shroud, centre the mast as yougo.* The mast must be perfectly straight whilst looking up the mast track.* Counting your turns accurately, tighten your caps to 24 using the ‘Model B Loo's Gauge’ and set thelowers at 21.* The backstay should be loose during the process.* With no backstay tension there should be 45 to 55mm of pre-bend.Shroud TensionSail shape is governed by shroud tension. Use the chart below to set up the sails through the entire wind range. As theshrouds become tighter in the windier conditions, the turnbuckles on the split backstay bridle need to be tightened so youcan get adequate tension, and then loosened again in light air to allow the headstay to sag when the backstay is off.Step Position Cap and Lower SettingsTrue WindConditionsMast stepCapsLowersBackstay0 - 6 KnotsChoppyNo. 31411Loose0 - 6 KnotsSmoothNo. 3129Loose6 - 12 KnotsChoppyNo. 32421+ 10 Turns6 - 12KnotsSmoothNo. 3241912 - 18 KnotsNo. 22828+ 8 Turns18+ Knots JibNo. 13132+ 8 TurnsA Loo’s Gauge should be kept aboard at all times. It is also essential to know how many turns are required on thecaps and lowers to bring them up and down to these figures. This can be written on the deck alongside the shrouds forease of reference and rapid adjustment between races.Speed ControlsThe following controls: Genoa sheet, Mainsheet and Backstay share equal importance and need constant adjustment.These control the gear changes necessary for optimum speed upwind. The Genoa sheet should never be cleated assmall increments of adjustment ( to 2cm) can make the difference, whilst the mainsheet should stay out of the cleat 50%of the time.Genoa TrimThe Genoa covers the range of 0-17 knots of true wind speed. In conjunction with the proper rig tune, the Genoa isaffected by halyard tension, car position and sheet tension.Halyard tension affects the draft position of the sail. On our Genoa, the draft is designed four percent farther forward thana normal genoa, so in light air we set the draft back by sailing with small scallops between each hank. This allows thedraft to move aft to 43%, the proper position for light air.As the breeze builds, halyard tension should be slowly tightened until the wrinkles just disappear in 13 to 15 knots of truewind.A mark on your halyard with a numbered scale will help you duplicate fast settings.We use the genoa Cunningham to fine-tune the luff tension and the draft position when the wind is increasing anddecreasing.The Genoa tracks should have an extra hole drilled between each standard hole in the front half of the track; this allowsyou to adjust the Genoa lead in half-hole increments. When using the light air setting in under 5 knots of wind, the carshould be positioned so when the Genoa is overtrimmed the leech hits the spreader while the foot remains 7 to 8 cm offthe chainplate. In medium air, move the lead aft one to two holes. At this setting the overtrimmed genoa will touch thechainplate and spreader tip simultaneously. At the heavy air setting (one to two holes further aft) the over-trimmed genoawill touch the chainplate while the leech is 5 to 7 cm off the spreader tip. (Remember, these trimming distances are tocheck the car position, not for sailing upwind).You need to get creative with your car position in between shroud adjustments, as the mixture of twist induced by easinghttp://www.j24australia.com Powered by Joomla! Generated: 17 December, 2007, 01:47

j24australia.com :: International J24 Class Australiathe sheet or by moving the lead aft is critical for maximum speed.Mainsail TrimThe shroud tension and mast step position have the most effect on your mainsail shape. Once the rig is set, the mainsailis trimmed (or overtrimmed) to assist the balance of the boat. We trim the mainsail tighter on a J/24 than any other typeof boat we’ve ever sailed. In up to 12 knots, the top batten points as much as 5 degrees to windward of parallelwith the boom, and the telltale on the top batten is stalled as much as 50% of the time, but the boat doesn’t seemto slow down it just points higher!Position the traveler all the way to windward to center the boom in breeze up to 12 knots.At this point it’s important to remember that J/24’s hate to heel, and should be sailed flat, or with less than15 degrees of heel. Once the traveler is centered in the building breeze, the backstay / mainsheet trade off begins.At times you can de-power by easing a little sheet, and the Mainsail will flog. You may avoid this by easing the genoasheet so that the leech of the genoa is at 15 to 19cm off the spreader tip. This allows you to play the mainsheet and keepthe boat on its feet. Also, remember that the backstay affects the leech twist of the Mainsail dramatically, so every timethe Backstay is adjusted, the Mainsheet must also be adjusted accordingly.OuthaulThe outhaul controls the depth in the lower half of the sail. In 0 to 6 knots the maximum foot depth should beapproximately 5cm away from the boom, as the breeze builds and sea conditions become choppy, ease the Outhaulslightly to a depth of 5 to 7cm thereby making the mainsail deeper and more powerful in it’s lower section. Above15 knots + start cranking it out towards the band so the sail de-powers and becomes flatter.CunninghamThe Cunningham is rarely touched. We sail with a floating tack (a sail slide webbed on the tack of the sail) so downwindthe sail can move up the luff groove. The halyard is simply cleated with the headboard at the masthead black band, andwe only pull on the Cunningham as we need it, with just enough tension to smooth out the luff wrinkles as the breezefreshens.Boom VangMake sure you have a marked calibration so you can duplicate your fast settings. Upwind in airs from 0-6 knots zerotension, 6-12 knots hand firm, then in 12-18+ knots, we tighten the vang very firm to control the leech twist and stop theboom lifting when the Mainsheet is eased. Once you have changed down to the Jib, be sure that you are not overvanged, then as the breeze builds again shift back to your fast settings by vang sheeting. Downwind in heavy air, makesure you ease it as you approach the top mark. (this prevents you breaking a vang fitting) Ease it to your calibrated markso as the top batten area is a little open.Jib TrimThe Jib halyard is always tightened enough to pull the luff cloth flat between the hanks. The lead is set at one of twoholes; an ‘all-purpose’ setting, used 80% of the time, then in 28 + knot range the setting is moved an extrahole aft.The ‘all-purpose’ car position sets up the sail with 15 to 18cm of depth from tack to clew, with the jib leech4 to 10cm inside the spreader tip. When using the ‘all purpose’ setting, sheet tension should be varied sothat the leech moves from 10cm inboard of the spreader tip in 18 knots to 7cm outboard of the spreader tip in 25+ knots.In the aft hole the leech will be trimmed between the spreader tip to 12cm outboard.Spinnaker TrimPole height is important and changes in increments of 2cm have a significant effect on the shape. In general the pole end(tack) should be kept even with the clew whilst keeping the center seam square to the water.Be sure you have tweakers on both sheet and brace. These need to be adjusted in varying wind strengths. A goodgeneral setting for both is the top rail height. In a building breeze move them down 20 to 30cm to control the shut. (Thisposition needs to be maintained for heavy air gybes.) J/24’s now only use the windward / leeward courses.Light airAlways sail with windward heel as this will project the spinnaker and reduce the wetted surface of the hull.Communication between the trimmer and skipper is imperative. The goal is to be able to sail as deep as possible whilemaintaining good pressure in the sheet and speed in the boat.Heavy airTry not to brace the pole too far aft as this makes it easier for the spinnaker to roll out to windward and cause a Chinesegybe. Do not let the clew go further than 30cm past the forestay. Have the crew stay on their haunches so in the big puffshttp://www.j24australia.com Powered by Joomla! Generated: 17 December, 2007, 01:47

j24australia.com :: International J24 Class Australiathey can move from side to side and keep the boat under the rig.ConclusionWhen it comes to experience few people know more about the J/24 than Gary Gietz. He has sailed in the J/24 classsince its introduction to Australia in the late 70s and has won 5 National championships, and countless State and Clubevents. Gary has represented Australia at international level for more than 25 years. He is an Australian OlympicRepresentative, AYF Coach and AYF Sailing Master. Gary is currently the coach for the Iain Murray / Andrew Palfrey2004 Olympic Star campaign.For any further information please don’t hesitate to call on the above number, or email atggproyachting@ozemail.com.auhttp://www.j24australia.com Powered by Joomla! Generated: 17 December, 2007, 01:47