Tuning Manual – Stiletto Catamarans

Introduction

The purpose of this manual is to assist you in learning how to properly tune your Stiletto and to explain how to get the best performance from the boat using the various sailing adjustments. The manual is organized into two sections: sailing adjustments which are normally made as conditions and course change, and tuning the boat and rig which are adjustments affecting the safety and sailing qualities of the boat that are not routine in nature. The tuning of the mast and standing rigging are particularly important on a new boat, as improper adjustment can result in poor performance and even failure of the mast.

Section I- Sailing Adjustments

The following sections on sailing controls are obviously interrelated. When sailing, the adjustment of one or more others. We will attempt to describe the effects of each sailing control on the Stiletto in terms of what it does and how the result will change the “feel” of the boat. In the end, though, sailing a boat is like playing an instrument- you are a very essential part of the whole. Speed and handling depend on your ability to get in tune with your Stiletto and sense what adjustments are needed. In general, if it feels better- it is!

RUDDERS

The rudders provide one of the primary sensory inputs to you through the tiller. The rudders tell you whether or not the boat is in balance. The boat is perfectly balanced when there is slight weather helm so the boat wants to turn slowly into the wind if the tiller is released. For example, if the traveller to too far away, or the centerboard is too far up or forward, the tiller will pull strongly against your hand, a condition called “weather helm” in which the boat wants to turn into the direction of the wind. On the other hand, if the main sheet is too loose, the headsail or jib too tight, or the centerboard is too far down or back, “lee helm” will result in which the boat wants to turn away from the direction of the wind and the tiller pushes against your had. In this sense the push or pull of the rudders through the tiller tells you which list of adjustments needs to be considered. NOTE: When sailing away from the dock or beach, be sure the rudders are all the way down, even ½ inch at the rudder will give you a false reading of the helm conditions.

CENTERBOARD

The centerboard is both the underwater balance point of the boat and the surface against which the water pushes, just as the overall sail plan is the balance point and surface against which the wind pushes. The centerboard is adjusted both by raising and lowering as well as tilting the board forward or aft in its bracket. If the boat were being sailed in a perfectly balanced condition and the top of the centerboard was then pushed all the way forward, the bottom of the board which is in the water would move aft. The boat would then have “lee helm” or would turn away from the wind. If on the other hand, the top of the board were pulled aft, pushing the bottom of the board forward, the boat would develop “weather helm” or would turn into the wind direction. Consequently the board can be moved around to rebalance the boat when it is developing weather or lee helm and the sails are properly trimmed. If again the boat were being sailed in a perfectly balanced condition and the centerboard were pulled up in its mounting several inches, the stern of the boat would begin to slide sideways slightly away from the wind direction, resulting in the feel of weather helm, or if the board were pushed several inches further down in its mounting, the stern of the boat would slide sideways less, and the feel of the lee helm, or turning away from the wind would result. This represents another way of balancing the boat often used when reaching and running with the wind. The above paragraphs are true sailing in any direction relative to the wind. There are certain board positions, however, which tend to be normal for sailing in a particular direction in a Stiletto. When sailing ot windward we keep our board all the way down. This gives maximum resistance to sliding. While reaching the board is pulled up far enough to get rid of the lee helm. Running downwind at slower speeds the board is again pushed down. Board position is always secondary to proper sail trim.

MAINSAIL CONTROLS

The mainsail controls are the main sheet, traveller, downhaul, outhaul, mast rotation, and batten tension. The battens should all be in their pocket tightly enough so that there are no vertical wrinkles in the mainsail. On the top most batten this means very tight.

The mast rotator should be adjusted so that the long axis of the mast section is pointed into the apparent wind direction while sailing. This means some rotation sailing upwind (approximately 30 degrees from center) and a lot of rotation sailing downwind (approximately 60 degrees.) Under other than racing conditions we set it correctly in the upwind position and don’t bother readjusting for different points of sail as it is not critical.

The downhaul adjusts the draft location in the mainsail. The more downhaul tension the farther forward the draft, the farther forward the draft, the less weather helm. The downhaul should be tight enough to prevent any horizontal wrinkles in the mainsail. On a Stiletto this usually means that the main sheet is pulled in very tightly, then the downhaul is tightened as much as possible, and then the main sheet is let back out again. Under very light wind conditions the downhaul can be eased out, making the sail a little fuller and more powerful. This would also be desirable when sailing downwind for a long while.

The outhaul is used to control the fullness of the bottom third of the sail. Sailing upwind the bottom of the sail should be very flat because it is sailing backwind of the jib. This means the outhaul car should be al the way aft. When reaching and running the jib is farther away from the main, so the bottom of the sail can be fuller (more curve) and consequently more powerful. At this point ease the car forward such that the curve in the bottom of the sail matches that in the panels above. This usually means easing the car forward about 4-6 inches. If you forget to tighten the outhaul sailing upwind, some weather helm may result.

The main sheet and traveler are the two primary mainsail controls. The goal in trimming the main sheet must be kept tight enough on all points of sail to achieve the desired sail shape. The most common mistake in trimming Stiletto sails is to allow the main sheet to be too loose, allowing too much twist in the sail. The main sheet when very tight pulls in the upper part of the leech, adding power to the upper half of the sail, and bends the mast away from the sail, causing the mainsail to flatten which is desirable in heavier winds. In strong winds the man sheet is also acting as a backstay supporting the mast.

The main sheet tightness also affects the tightness of the forestay to which the jib is attached and thus the shape of the jib, so it also affects the ability of the boat to point upwind when sailing to windward. When sailing downwind the main sheet should be loose providing as much curve as possible in the mainsail and also relieving tension on the forestay, thereby adding fullness to the jib. When reaching the main sheet should be fairly tight to keep power in the upper part of the mainsail as well as keeping tension on the forestay.

The traveler is used to adjust the overall angle of attack of the mainsail relative to the wind over the boat. If, when the main sheet is properly adjusted there is too much weather helm, the traveler should be let out until the helm is reduced. When sailing to windward the traveler should normally be centered or even up to 6 inches towards the windward side of the boat. In very heavy winds it should be let out as necessary to reduce the weather helm and heeling of the boat (about 6-18 inches.) Reaching the traveler will normally be about half way out the track, but might be anywhere from 6 inches out when close reaching to almost the end of the track while broad reaching. When sailing downwind the traveler should be all the way out to the end of the track.

JIB CONTROLS

The jib controls, in addition to the main sheet tension, are the jib sheets, the jib cars, and the jib downhaul lacing at the tack of the sail. The downhaul should be laced just tight enough to give the luff a taut, wrinkle free look. This will require lacing it mush tighter in heavy winds, but it should not be over tight in light breezes as it will cause vertical wrinkles in the luff of the jib. On any point of sail except hard on the wind, the jib sheets should be as slack as possible without luffing the jib, or inducing a reverse curve in the leading edge of the sail. When sailing to windward close hauled, the jib sheet should be as tight as possible without causing the slot between the mainsail and the jib to close up. Or so tight as to cause the leech or trailing edge of the jib cloth to curl toward the mainsail. The jib lead to the deck is adjusted by moving the jib car fore and aft along the track. The jib car is in the correct position when the entire leading edge of the jib from top to bottom luffs at exactly the same time when the boat is turned slightly upwind from the course which you are sailing. Again, the goal is to get all of the telltales flowing aft.

REACHER

The reacher is really a very full shaped jib which can be used on all points of sail from a close reach to downwind. In extremely light breezes it can even be used upwind but can easily become overstressed if the breeze picks up. The controls are the halyard, the reacher bridle, and the reacher sheets. The halyard is set up tight when the sail is raised. The tack should be centered on the bridle to keep the leading edge taut. When close reaching the tack should be eased off to the leeward bow to open up the slot between the reacher and the main. When broad reaching or running downwind the tack should be pulled to the windward side to get the leading edge of the reacher out from behind the mainsail. The reacher sheet should be trimmed so as to keep a nice airfoil shape in the sail with the draft in the forward half of the sail. Be careful, though, not to over tighten the sheet, especially when sailing downwind.

SPINNAKER

The spinnaker is a huge, powerful sail designed to be used downwind and broad reaching in light to moderate air. The spinnaker is about 2 ½ times larger than the mainsail alone. As such, it is the one sail which, more than any other, must be used with proper caution as its power in heavier air van make any boat, including Stiletto, uncontrollable and subject to capsize. On the other hand, when used properly it can add large measures of speed an enjoyment in more moderate or light conditions. Unlike Monohull sailboats, the Stiletto requires no spinnaker pole and this simplifies the use of the spinnaker. On Stiletto the spinnaker has its own halyard and running backstays, but otherwise uses the same controls as the reacher. Sailing downwind it may be desirable to slack off the halyard about 1-1 ½ feet from the mast, but it should be tight against the masthead when reaching. It is very important to remember to always tighten the windward running backstay firmly before raising the spinnaker and before each gybe. After gybing the leeward running backstay can be slacked off to allow the mainboom to be eased farther out. The running backs are the only support for the top section of the mast against the tremendous pull of the spinnaker and failure of the mast can result if they are not properly used! As on the reacher, the bridle can be moved to the leeward side when reaching and to the windward side when running downwind to get more of the spinnaker out from behind the main. The spinnaker should be sheeted as loosely as possible, allowing approximately 8-12 inches of the leading edge of the sail to actually curl in towards the mast. Normally, the spinnaker sheet requires continual adjustments to be set properly. While cruising, however, we will sometimes trim it in just a little too tight to avoid having to constantly adjust it even thought a little boat speed will be lost.
Both the reacher and the spinnaker can often be used with another jib in a double head rig. This is a matter of experimentation to see if speed is gained under particular conditions.

Section II- Tuning the Boat and Rig

The balance and tautness of the rig of any boat affects the sailing qualities in terms of speed, pointing ability and steering or helm balance. The section below entitled mast is of major importance.

THE STANDING RIGGING

Consists of the forestay bridle, the forestay, and the port and starboard shrouds. The purpose of the standing rigging is to hold the mast in the proper upright position. The only adjustments are the forestay turnbuckle and the shroud adjuster which have a series of six holes for adjustment. With the boat floating in the water on its normal lines the mast should be in a vertical position and the rig should be as tight as possible without being so tight that the mast does not rotate on its support. Normally the shroud adjusters will have the pin in the 2nd or 3rd hold from the top when the mast is vertical. Note that both the port and starboard shroud adjusters must be in the same hole or the mast will lean slightly to port or starboard. The forestay turnbuckle controls the overall tightness of the standing rigging.

THE MAST

Is supported like a column by the port and starboard diamond stays and jumper stay attached to the upper and lower mast sections and held away from the mast by the spreaders. These diamond stays are adjusted by the turnbuckles at the lower end of each on newer Stilettos and by an adjuster at the spreader tip on earlier boats. The port and starboard diamond stays should be tight enough to completely prevent any sideways bending or motion of the mast while sailing. We sight up the little groove in the front of the mast to verify that it does not arc to either side when sailing. The jumper stay should be tight allowing only a slight bending of the mast, along its fore and aft axis, and should only bend away from the main sail. This bend will become apparent when the main sail is sheeted in tightly. The reason for allowing a slight bend in the mast away from the mainsail is that, when sheeted in tightly in heavy winds the bend of the mast will flatten out the mainsail slightly and both reduce the power of the sail and reduce the amount of weather helm or the tendency of the boat to turn towards the wind.

THE DOLPHIN STRIKER

The purpose of the dolphin striker is to take some of the mast compression loading on the center of the main beam and spread it out to the ends of the main beam. This is necessary only in extreme conditions such as high winds or waves. The dolphin striker should be adjusted by backing out the adjuster screw until the dolphin striker is snug against the dolphin striker strap. Then tighten the lock nut against the dolphin striker rod to secure the adjuster screw. You may need to readjust the dolphin striker from time to time.

THE RUDDERS

The alignment of the rudders is preset at the factory and normally would not require adjustment. If a rudder were seriously damaged or replaced, the alignment can be checked with the blades in the full down position and the tiller cross arm connected and centered so that the rudders point straight ahead. The distance between the trailing edges of the rudder blade should be within ¼ inch of the distance between the leading edges of the blades.

HULLS

As in any sailing craft the smoothness of the underwater surface affects the overall speed capability of your Stiletto. This is particularly true as the boat accelerates into the upper speed ranges. The Stiletto is delivered with a smooth, fair bottom, but if you are racing the boat you may wish to make further improvements such as wet sanding the bottom paint. Even if you are cruising, however, from time to time you should check the bottoms for marine growths such as barnacles and for minor damage from rocks if you beach the boat. If these surface imperfections are permitted to accumulate, performance will naturally suffer.

In closing, may we suggest that before you sail you perform “preflight check”, which should include the following: snug standing rigging, tight diamond and jumper stays, mast rotator set, do all of the pin shackles have rings or cotter keys and are all of the screw shackles tight and wired if critical? The tightest rig in the world wont stay up if a shackle comes apart. With these adjustments and checks made, you are now ready to go sailing with confidence that your Stiletto is ready, too!

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