Thistle Tuning Guide
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Thistle Tuning Guide For any question you may have on tuning your Thistle for speed, contact our experts: Ched Proctor 203-783-4239 [email protected] Brian Hayes 203-783-4238 [email protected] onedesign.com Follow North Sails on... NORTH SAILS Thistle Tuning Guide Introduction to your diamonds. Always be sure to check 1/8” Cable Forestay Tension your diamond tension and straightness of LOOS LOOS PRO the mast while it is supported at both ends This tuning guide is for the Greg Fisher TENSION MODEL A GAUGE with the sail track upwards. design and the Ched Proctor design Thistle 240 28 21 sails. These designs are the result of hours 260 30 22 If while sailing in marginal hiking of boat on boat sail testing and racing 280 31 23 conditions (10 - 12 mph breeze) you experience. 300 32 24 notice slight diagonal overbend wrinkles in 320 33 25 the upper part of your mainsail, your upper The following tuning guide is meant to 340 34 26 diamonds are most likely too loose which be a comprehensive guide for setting and 360 35 27 is allowing the upper part of your mast trimming your North Sails. Please read it to bend too much. On the other hand, if thoroughly before using your sails for the your mainsail in the upper third appears first time. 1/16” Wire Diamond Tension fairly round and is difficult to flatten out in We urge you to read the section on sail With North Proctor model sails a breeze, your upper diamonds are most care in order to prolong the life of your likely too tight. sails. DIAMOND MODEL A PRO For Proctor’s main when sailing above Thank you for purchasing North One Top 12-13 9-10 490 pounds of total crew weight, set the Design Thistle sails. We enjoy working with Middle 15 11 diamonds close to 18 (number scale on you and the Thistle Class. We hope you’ll Bottom 15-16 11-12 the Loos gauge—the numbers do not consider us your personal sailmakers. correspond to pounds) top to bottom. Set them progressively looser for lighter Good Sailing! 1/16” Wire Diamond Tension crew weights to a minimum of 10 on the With North Fisher model sails Loos gauge, e.g. top crew weight of 490 pounds, scale 18; to crew weights less DIAMOND MODEL A PRO than 430 pounds, scale 10. Top 4-8 2-4 For Fisher’s main, set your diamonds at Boat Preparation and Middle 9-13 5-10 approximately 6 - 14 - 9 (not pounds and Rig Tuning Bottom 4-8 2-4 measuring from bottom to top). The lighter the crew weights, the lighter the tension on the top diamonds. Set the top diamond DIAMOND TENSION at 4 or less when sailing below 430 LOOS TENSION GAUGE Before you step the mast, set the diamond pounds in crew weight. The Loos tension gauge is a relatively tension to achieve proper mast bend. accurate instrument that will help measure Diamond tension, not only has an effect On wood masts, the diamond tension the tension of your standing rigging. The on the sideways bend in the mast, but should be slightly less than the standard newer Loos Pro gauge is spring loaded and also on fore and aft bend. The suggested aluminum mast because of possible some sailors have found it to be slightly numbers that we offer here will, again, get compression problems that could develop more accurate and reliable than the Loos you very close so that your mast and North from excessive tension. Never tension any Model A. Following is a comparison of the mainsail will work well together. Due to of the diamonds on a wood mast to more numbers between the Model A and the the nature of the aluminum extrusion than 16. Pro gauges. We have broken down the and in some cases the way the masts are numbers for both 1/8” forestay tension rigged, some masts are stiffer and some On the older, stiffer, gold aluminum and 1/16” diamond tension. masts are softer than others. This is not a masts the diamond tension should be problem; it just requires slight adjustments considerably looser to allow the mast to Visit our web site at OneDesign.com for the latest Thistle news and tuning tips. 1 © North Sails One Design. All rights reserved. NORTH SAILS Thistle Tuning Guide bend as easily as possible. You should Position the mast on the step so that it (forward at the middle, aft at the head) drop the tension on all the diamonds is even fore and aft. In other words, the shim the front of the step between the approximately 4 numbers from top to mast butt does not protrude out over the step and the grating. This is better than bottom. front or back of the mast step. We have putting thickness (coins, stainless tangs, found that it works well to have the step etc.) between the casting on the mast and While the Thistle mast looks fairly positioned at minimum “J” dimension the casting on the grating because it still complicated with three sets of diamonds, when the mast is set squarely on the step. allows the mast to remain flexible. these adjustments listed above will make The mast should rest on the mast step it fairly easy to properly tune your mast to in such a way that it has nearly 1/2'' of It is important that the mast butt casting your mainsail for all crew weights and all positive prebend will develop when the be securely fastened to the bottom of the wind velocities. If you have any questions rig is properly tensioned (we'll discuss mast. Any slop whatsoever can greatly about the proper bend in your mast, this later). Measure prebend by pulling affect the mast's ability to bend properly. please don't hesitate to call us. the main halyard down all the way to the A quick check to verify if the mast is set up gooseneck so that the wire is up against properly is to push the mast forward from (Note: The numbers above relate to the Model A the back of the mast. You will notice the behind, halfway between the spinnaker gauge. Refer to the conversion chart under Loos prebend as the gap between your main pole eye and the lower diamonds. If the Gauge section for new Pro Gauge.) halyard wire and the mast as it bends mast feels stiff or it's bend restricted, most forward. likely the mast butt is not set up well. MAST STEP/MAST BUTT A telltale sign that the mast is bending Position your mast butt casting so that the There should be a slight gap (nearly correctly is that when all the crew weight mast will be positioned at the minimum 1/8”- see picture) between the casting on is positioned on the weather rail (about “J” —or 4' 9" measured from the forestay the mast and the casting on the grating 8 mph breeze), there will be evidence to the front of the mast on an aluminum at the forward edge. The gap at the front of overbend wrinkles developing in the mast or 4' 8 1/2'' measured from the will help the mast bend easier because it mainsail running from the area of the forestay to the front of the wood mast. rocks slightly aft of the central axis of the lower diamond diagonally down towards mast. If the mast prebends more than 1" the clew of the main. In heavy winds (over 15 to 18 mph) or in flat water, these overbend wrinkles could be quite pronounced and should actually run back to the near the aft edge of the windows. If not, check your mast butt and diamond tension as there is most likely not enough mast bend developing. On the other hand, if the overbend goes past the aft end of the window, then you have too much pre- bend and should add another shim under the front of the mast step. RAKE Mast rake is measured by hooking a tape measure on the main halyard and hoisting it all the way to the top of the mast until the shackle just hits the sheave. The measurement point on the boat is located at the back edge of the bottom of the tiller hole (not the traveler). Adjust Visit our web site at OneDesign.com for the latest Thistle news and tuning tips. 2 © North Sails One Design. All rights reserved. NORTH SAILS Thistle Tuning Guide For those boats still rigged with the smaller 3/32" forestay the reading should be 5 numbers lower. Too much rig tension will tend to increase prebend. Too little tension will tend to reduce it. (Note: Refer to conversion chart under Loos Gauge section for new Pro Gauge.) Rigging the Sails and Sail Trim MAINSAIL MAIN HALYARD The halyard should be pulled all the way up to allow for correct leech and luff tension. When hoisted, the top of the sail must pass the bottom of the sheave box. your shrouds and forestay so that your Note: In order to allow sufficient sheeting You may check your main halyard lock rake measurement (with the rig properly with a long leech and rake, the mainsheet position with the mast down to be sure tensioned and the correct amount of pre- needs to be properly arranged at the the shackle is tight against the sheave bend) is: 26' 11 1/2'' to 27' 1/2'' for both end of the boom.