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When sailing off the wind we normally use a spinnaker. This sail is probably the most misunderstood sail on board. Most good sailors can look at mains and jibs and have fair idea of what is a fast or slow shape. Spinnakers on the other hand are a big mystery. Unfortunately it is difficult to tell a good spinnaker from on board the boat. It is far better to be four or five boat lengths away looking at the profile when both leeches are lined up. A good spinnaker has a nice even curve from head to foot. Any lumps or bumps in the profile indicate too much fullness. This could be caused by excessive broad-seam or use in too much wind (blown out).
In designing the spinnaker, Lidgard sailmakers have two objectives; first to build the fastest all-round shape into the sail and second to build in that shape so the sail flies in a stable manner and is easy to trim. A sail that has a fast shape will not produce speed if it is continually bouncing around and needs to be over trimmed to settle it down. Speed and stability go hand in hand.
Stability comes in the form of the overall depth of the sail and the shape of the leading edge. If the sail is too flat or if the leading edge is too straight the lift needed to support the sail and make it project will not be produced. The luff will "wash out" and to maintain a constant curl in the luff would be difficult. An unstable sail will collapse right when the sheet is eased and a slight curl is seen. If you see these symptoms in your sail, have Lidgard Sails take a look at it.
Most spinnakers are made of .75oz nylon. The decreased loads off the wind allow the spinnaker to be much lighter than their upwind counterparts. But unlike a main or jib which has a luff and leech a spinnaker has to be reversible and has two luffs. Most of the racing rules require spinnakers to be symmetrical. This is not the fastest way to build the sails but it does challenge the sail designer all the same.
Spinnakers are only fixed at two points: the head by the halyard and the tack by the pole. Everything else on the sail is free floating, relying on its own lift to stay aloft.
Aerodynamically the spinnaker becomes a foil producing lift whenever there is air flow across the sail.
The height of the pole, the sheeting angle and even bouncing over waves change the shape. Be aware of the small changes in wind velocity and angle. The smallest change in either of them means a change in the way the sail should be trimmed.
First, let us consider the use of the spinnaker pole as a control. The poles importance must not be overlooked. Do not just set the pole height to the old rule of keeping clews level. If properly set many times the tack will be lower than the clew.
The vertical component of the pole determines the draft placement and leading edge shape of the luff while the fore and aft component determines the angle of attack.
Because the spinnaker has to be symmetrical the deepest part of the sail is in the middle. But because you want the chute to act as a foil, the draft has to be moved forward. The pole acts as a cunningham in the sense that the more luff tension applied, the more the draft will move forward. Draft placement through pole height is combined with having the sail luff evenly. If the pole is too high the top of the spinnaker will be allowed to lift and it will twist off, collapsing over itself. If the pole is set too low the bottom of the spinnaker will be pulled too tight causing the break to be low.
When the pole height is just right and the sheet is eased a bit the sail will maintain a smooth even curl through the middle of the luff. As the wind speed changes the pole will have to be adjusted to match the spinnakers new shape.
Pole position fore and aft will determine just how effective your spinnaker is. It controls the angle of attack on the luff of the chute. If too far forward the angle will be too great and there will be little attached flow. If the pole is squared too far back the angle of attack will be too narrow causing you to over-sheet the sail and create stall. Basically the spinnaker luff should be vertical and at right angles to the pole.
Proper trimming requires not only trimming the sheet when a slight header comes but also easing the pole forward to maintain the proper angle of attack. The whole sail should be rotated around the boat to the changing apparent wind.
Once the pole location is established the sheet is eased to the point the luff of the spinnaker has a slight curl. If the curl increases pull the sheet and take it out. Trimming the spinnaker is more of a full-time job than trimming any other sail on the boat.
There are fewer controls available to shape the genoa than there are for the mainsail, so the sail shape built in at the loft is critical. Unlike the main the genoa is supported only by the luff; both the foot and leech are controlled by the sheet alone. When the boat becomes overpowered it is best to change to a smaller jib. Failing that there are some tricks that can be used to make the sail more efficient.
Cloth selection is critical. Mylar is better than dacron because of its stretch to weight ratios. Kevlar is even better but does have certain drawbacks, including price! The low-stretch qualities allow the sailmaker to build in a predetermined shape that the sail will take. The sail is less susceptible to wind speed changes so trimming is less. New Mylar and Kevlar sails are made to be set in a relaxed state. When you first put the sail up use only enough tension on the halyard to remove the wrinkles. Later the halyard can be fine tuned.
Once the sail is hoisted, it is time to get it trimmed properly. First check the fore and aft until the tell tails lift evenly from top to bottom as you slowly head up into the wind. If the lead is too far forward, the leech will be tight and cause more back-wind in the main than normal. Also, the tell tail will lift first at the bottom. If this is the case, move the lead aft one hole on the track, and sheet the sail in. Continue this process until the whole sail breaks evenly. If the top tell tail lifts first, then move the lead forward.
When all the tell tails break evenly you are ready to go upwind. there are times when you will be overpowered and will want to change jibs but cannot, move the lead back to induce more twist. This will let the top of the sail luff, spilling off the extra power. Also this will flatten the bottom of the sail, making it more efficient for a higher wind velocity.
The draft location is another important aspect to good jib trim. Ideally the maximum draft should be at 35% to 45% aft. By this we mean the deepest part of any horizontal section of the sail should be over one-third, but less than halfway back from the luff towards the leech. As the wind increases the draft tends to move back. Increasing the halyard tension will pull the draft forward. One thing to note is that as the halyard is pulled, the sail in effect is lifted up off the deck, so the jib lead will have to be moved aft to keep the same relative position. The helmsman can often tell if the halyard is not tight enough, as the sail will be draft aft and hard to steer too. The tell tails will easily stall and the sail will appear to have no groove. Pulling the halyard up will make the draft move forward, and the front of the sail rounder, making it much easier to sail to.
Headstay tension controls how full the jib is. It is much like mast bend but rather than bending forward like the mast, a headstay sags the fuller the jib gets. On most boats the backstay is used to tension the headstay and reduce sag. It is very important, since pulling the backstay will flatten both the jib and main, that the two sails are matched. This way they will both be the correct depth at the same time. In light wind the jib needs to be fuller so the headstay should have sag. Some boats, like SOLINGS, never sail with the headstay tight. Even though there is a lot of headstay sag, SOLINGS are one of the closest winded boats. Reducing sag is not the key to pointing higher; the sectional shape of your jib is. The headstay should be at the correct tension to make the jib full enough for the conditions.
On boats with swept-back spreaders, the cap shrouds take most of the headstay load. There is very little you can do to get increased headstay tension while sailing. The backstay really only bends the top of the mast, doing little to the headstay sag. Usually we like to set these boats up with very tight cap shrouds to keep the sag from becoming excessive in windy conditions.
The genoa sheet is the most important control for the sail. As mentioned earlier, the genoa does not have boom to support the foot, so the sheet has to act as the boom, vang, outhaul and traveller as well as the sail tension device. More than any other control the sheet has a greater proportional effect over all the aspects of the genoa trim.
Once the halyard has been set and the lead positioned properly, the in-and-out action of the sheet will change the shape of the genoa in relation to the changes in wind velocity. When a puff hits the genoa will stretch and distort somewhat. The leech will open up and the sail will become deeper. By trimming the sheet more you will reverse these reactions by tightening the leech and bringing the sail back closer to the midships of the boat.
Exact sheet tension for upwind conditions is hard to specify. But, as a rule the maximum sheet tension should be so the genoa kisses the upper spreader.
When reaching with a genoa, the first thing to do is to move the lead as far outboard as possible. This will open up the slot or gap between the main and the leech of the genoa, tossing less back-wind in the main, allowing it to be eased more. To make the genoa luff evenly from top to bottom, the lead will have to be moved forward. When the wind is 90 degrees apparent there will no longer b any benefit in moving the lead further forward because the sail will be so eased and twisted. Moving the lead far enough to fix this will cause the bottom of the sail to be too full and the leech excessively tight.
Good genoa trim has to be in harmony with the main trim and helming of the boat. Communication between all parties is critical to sail trim and thus the speed of the boat.
When you bend the mast to flatten the sail, though the effective height of the mast becomes shorter so you have to re-adjust the Cunningham to get to the original luff tension and draft placement. Normally the Cunningham should be pulled on just hard enough to take any horizontal wrinkles or sag out of the luff. It is far better to sail with too little mainsail luff tension than too much. Off the wind you should always ease the Cunningham off.
The leech line is a small line that runs inside the leech fold from the top of the sail to the clew where it exits out of the sail. It is used to control any flutter of the leech between the battens.
The mainsheet is used to control the amount of twist in the leech of the sail. Twist is the amount the sail is turned to leeward at the top. If you sight up under the boom comparing the boom to the top batten you will note the difference in the angle of the two, this is called twist and is measured in degrees. In light or medium wind and smooth water the batten and boom should be parallel or zero degrees twist. In windy conditions or rough water three or four degrees of twist is preferable. Leech tell tails are helpful in deciding how much sheet tension to use. These tell tails are streamers off the leech at each batten and indicate the flow at the back end of the sail. In an untwisted sail the top one or even two should be stalled 50% of the time. Tell tails are stalled when they curl back around the back of the sail. In a twisted condition they will be flowing out straight back from the leech.
The traveller controls the athwartships position of the boom and thus the mainsail. A good traveller can be pulled to weather in light air so the boom can be on centre-line with a minimum of sheet tension. When the sheet is pulled in or when the weather helm becomes too much, the traveller should be let down to leeward. This will help to keep your boat on itâs feet and efficient. Effectively the traveller allows the main to keep the air foil shape while changing the angle of attack.
The boom vang is used to keep the boom down much like a mainsheet. When sailing off the wind particularly reaching, the boom will be out of the range of the traveller. In this case you will be forced to use the mainsheet. The problem is that the first thing that happens when you ease the mainsheet is that the boom goes up, not out. In turn this puts too much twist in the sail. Enter the boom vang: it is used in place of the mainsheet (to control the leech tension and twist) and the mainsheet becomes the traveller controlling the in and out positioning of the boom and sail. The boom vang can also be used up wind to induce bend in the bottom of the mast. By using the vang as the mainsheet, there is a great deal of forward pressure put on the gooseneck. This forward pressure bends the mast flattening the mainsail. This can be a very effective mainsail control but the boat must be set up for it as this technique is hard on the boat equipment.
Good mainsail trim requires good communication with the helmsman. The helmsman can feel through the tiller the amount of load on the helm. If he has too much helm the main is probably over-sheeted (not enough twist) or too full. If he cannot seem to get the boat on the wind or even has lee helm try sheeting the main or making it fuller. The main has to make the boat feel right if the boat is going to be fast. The most important main controls are the sheet and fullness (mast bend and outhaul).
The mainsail is the hardest and most fun sail to trim. You cannot change a mainsail as you can jibs. The one main has to look full and powerful in three knots of breeze and become flat and efficient in twenty. The main on a masthead boat is more like an aeroplane flap or an extension of the wing. This flap has a great effect on the lift versus drag of the whole sail plan. On a fractional rig the main makes up a large part of the driving force and is part of the wing itself not just an extension.
The mainsail trimmer has more controls at his disposal than anyone else on board. The mainsheet, traveller, Cunningham, outhaul, mast bend, and reefs all help to give this sail the necessary range. The main can also act like a rudder balancing the helm and keeping the boat tracking.
Mast bend is probably the most effective way to change the shape of the mainsail while sailing, so it is important to have the right luff curve of the sail to fit your mast. Luff curve is the round in the front of the sail which matches the bend in the mast and offsets the broad seaming (shaping) in the panels. At Lidgard Sails, computers match luff curve, cloth stretch, broad seaming and mast bend to make sure your main is easy to trim and has maximum range. Bending the mast will flatten the main and allow the leech to open off. On boats with an adjustable backstay you have the ability to bend the mast. Even the boom vang can be used to get bend in the bottom of the mast when the mast is stepped on the deck.
The outhaul controls the foot and up to the bottom quarter of the mainsail. When the outhaul is eased a small shelf will appear next to the boom. This will add considerable depth to the bottom of the sail for sailing in light air or off the wind. often the outhaul adjustment will have an effect on how the boat is pointing. Easing the outhaul adding fullness to the main will cause the main to have more lift (and more drag) creating more weather helm. The end result is that the boat will point higher and go a little slower through the water. In windier conditions the main has got enough lift due to the amount of air passing by the sail. The boat has weather helm, by tightening the outhaul the main is flattened the drag is reduced and the boat will go faster.
A flattening reef is a cringle placed about eight inches above the clew ring. This is really an extension of the outhaul and continues to flatten the sail. The area it takes out is insignificant. Flattening reefs are not used as much today and hardly ever used on boats with masts that can be bent.
The Cunningham (named after Briggs Cunningham who invented the device in 1958 on the 12 metre "Columbia") is used to adjust the draft location through luff tension. The tighter the luff tension the further forward the draft will come. The main should fit perfectly between the black bands when the halyard is just tight.
In general, the purpose of the mast is to support the sails and to aid their shape through controlled bend. To do this the mast has to have proper hardware with which to hoist the sails with minimum friction and to be able to change bend so that the crew can vary the mainsail depth for different wind conditions.
Masts, like any part of the boat, should have regular inspections. Every three months or so the whole mast section should be carefully checked for cracks. Often shroud attachments will get a lot of wear even to the point of tearing through the metal. Halyard sheaves should be free turning. Any excess weight should be taken out, like flag halyards, boom topping lift and unused halyards. Spreaders should be checked for sharp ends and chafe protection.
When your mainsail is designed at Halsey Lidgard Sailmakers care is taken to calculate the exact amounts of broad-seaming and luff curve so you can get a sail which sets properly and is easy to trim. The broad-seaming is applied to every seam and is matched and balanced by the luff curve in the front of the sail. All things being equal you should get a smooth, fast sail except when a sail is set on a mast that is improperly tuned. A mast out of tune can make your perfectly shaped mainsail look horrendous and detract from the boats performance. Before you make a call to the loft check your mast tune. The mast and the main must work together.
There are no mysteries to proper mast tune. Simply, the free-standing spar is supported by the shrouds and spreaders. They control the sideways or athwartships movement of the mast. Athwartships bend cannot be adjusted during racing so it is important that it is done the same for all sailing conditions. Fore and aft control and bend can be set up to change the mainsail shape for different conditions through use of adjustable backstays, mast partners and to a certain extend the boom vang.
When tuning your mast you should first start with the headstay. The headstay controls the amount of rake or aft lean your mast has. This in turn effects the amount of weather helm you feel while sailing upwind. The longer the headstay the more rake and the more helm. On most boats we use two or three degrees of rake. Once you have decided on the forestay, pin it and forget it.
You need to get the mast lined up, athwartships along the centre-line of the boat and then adjust the rigging so that the entire mast stays in column when under load. To accomplish this, start at the bottom and begin by making sure your mast is centred in the boat. Measure the distance from the mast to the gunwale at the mast partners using a zero stretch tape measure. We've seen stock boats that do not have the deck partners in the middle. Once the mast is centred at the deck, wedge in some hard rubber chocks to keep it in place.
The next step is to get the jib hounds centred over the mast step and partners. With the rigging fairly loose, hoist the tape measure up a jib halyard (be sure to check if the halyard is on the centre-line of the mast) and measure from the jib hounds to the gunwale. Adjust and tighten the rigging so the distance on both sides is equal.
Now that the mast is straight in the boat, the upper shrouds should be tightened. A good rule of thumb is to tighten the shrouds enough so the leeward shrouds just become loose when the boat is heeled 20 degrees. Do this in a moderate breeze after you have done the dockside centring. Start off on the starboard tack and tighten the port shrouds on the leeward side. Make sure you count the number of turns you take up so you can duplicate the adjustment on the other side after you tack. You should end up with an equal number of increased turns on both sides so the mast remains in the centre.
The final step is to tighten the lower shrouds so the middle of the mast has the proper support and will not sag to leeward. Sight up the luff track to eyeball the mast to make sure it is as straight as possible. Normally the lower shrouds will be looser than the uppers.
Most smaller boats have rigs with single sweptback spreaders, one upper shroud and one set of lowers. Often experimenting with different shroud tensions and mast positions can have a large effect on the boat. Check with your local fleet champion to find out his latest mast-tuning techniques. A good tool to have on board is a shroud tension meter, which measures the actual load the shroud is under.
These devices are also handy if you trail your boat to different regattas. When you re-step your mast, you can use your tension meter to duplicate your previous tension settings. Failing this you should count the number of turns that you loosen on the shroud when you take the mast down so that when you put it back again you can tighten it by the same number of turns and end up with the same correctly tuned mast.
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