Code

The Code 0 was originally developed for the Whitbread Race where a restriction on the Whitbread 60 rule limited the size of the head- The asymmetrical spinnaker has an efficient shape for reaching. The wind is able to remain attached all the way across the sail, providing drive as well as lift. The Code 0 on this trimaran works well on a number of points of sail. Because this sail is a hybrid between a spinnaker and genoa, tending more toward the headsail, it generates headsail-type loads...

Naming Nylon

Nylon was actually named after the cities of New York and London, where Du Pont had offices at the time the fiber was being developed. Du Pont did not register nylon as a trademark, choosing instead to allow the word the enter the American vernacular as a synonym for stockings. that results from weaving it. From a chemical standpoint, Dacron is a type of long organic molecule called a polymer manufactured from ethylene glycol - the same stuff used as automobile antifreeze - and terephthalic...

Guide for InBoom Furling Systems

To help you determine some of the details you will need for your system to work better, the following are suggestions for three different size ranges of boat size At the low end of the size range, say 35 feet, it is much easier to install and operate an in-boom furling system. The loads are not that great and any reefing system is quite manageable. Woven Dacron can still be the fabric of choice unless the boat has a high righting moment thereby increasing the load on the fabric. If this is the...

Loads In Highaspect Headsail

When sailing on the wind, a high-aspect sail like a blade jib will have the bulk of the load travel almost directly up the leech of the sail with less stress along the foot. Loads travel up the leech and along the foot pf the sail. being used within its designed wind range sailing hard on the wind and see what loads the sail encounters. If, on the other hand, he is designing a headsail to be used on an Open 60 sailing in the Southern Ocean he would know that the sail would never be used in a...

The History of Cuben Fiber

During the 1992 America's Cup, the U.S. syndicate America3 began some highly secret fabric development in an attempt to find a technological edge that would help it win the Cup. Bill Koch, the syndicate head, was sure there were some gains to be made not only in sail design, but in fabric engineering, so he set his design team about creating something radically different. The result was a fabric manufacturing process that was so advanced when compared to the way conventional sailcloth was being...

Storm Preparation

It's human nature sometimes to deny the obvious, especially when work is involved and that work is dangerous and means getting soaked. We are all guilty of it. The forecast is for a gale, yet the conditions are still manageable and we convince ourselves that it will not be as bad as forecast. My experience is that storms take people by surprise, and that is when they do their most damage. It's true that often the forecast is wrong and the wind does not blow like expected, but sometimes the...

Is Cuben Fiber Cost Effective

When considering Cuben Fiber it's important to keep another point in mind the bigger the boat, the higher the loads. At some point the cost differential between conventional fabrics like Spectra, Vectran and Kevlar, and Cuben Fiber becomes less noticeable. You simply need so much regular fabric to manage the loads that the Cuben Fiber option begins to look reasonable. For smaller boats, the gap is still quite large. For example a high-tech Kevlar mainsail for a 55-foot racing boat might cost...

Running Backstays

Running backstays come in pairs, one to a side, and are not permanently fixed. Instead they can be eased off or removed on the leeward side when not in use. In most cases, running backstays will run from the aft weather side of the boat to a point on the mast usually two-thirds of the way up the spar. If the mast is sophisticated there might be two, or even three sets of running backstays on each side that can be independently adjusted. In this case the lower running backstays are called...

Basic Concepts

If you are scratching your head right now, don't worry. Much of this theory is counterintuitive - again, its pretty controversial stuff - and involves some fairly esoteric aerodynamic theory. Still, if we break things down into separate parts, they are much easier to understand. There are also a number of ancillary points we need to come to terms with, including such concepts as lift, drag, boundary layers, attached flow, separation, pressure gradients, and angle of attack. Note that in the...

New Clew Height

When you wind the backstay on, you not only bend the mast, you move the top of the mast aft a few degrees. This movement will in turn have an effect on the clew height of the headsail. Looking up the back of the mainsail on this multihull reveals a flat shape perfect for a boat that sails at high speeds. Looking up the back of the mainsail on this multihull reveals a flat shape perfect for a boat that sails at high speeds. Rule No. 4 - The part of the boat under water has a lot to do with how...

Lazy Jacks

The simplest mainsail handling devices are lazy jacks. These pieces of rigging have been around for decades and over time have become more sophisticated. At their most basic, lazy jacks are a series of lines running from the boom to the mast that keep the mainsail on top of the boom when the sail is lowered. On some rigs they can be removed or lowered when the boat is sailing, then deployed at the end of the day. To increase their effectiveness some lazy jacks are attached to wings running...

New Generation of Sailmaking

Of course, now that you have finally figured out how the fibers and fabrics are used to make sails, the sailmaking world has taken another giant leap forward leaving you behind once again. The days of cross-cut and radial sails are slipping into the past as new sailmaking technologies find a foothold in the industry and become more widely accepted. Once the exclusive domain of the racer, exotic construction techniques like North's 3DL, UK's Tape Drive, and Doyle's D4 are becoming mainstream. In...

The Spinnaker Sock

Some spinnaker socks (Figure 12.1) are full-length contraptions that are equal in length to the spinnaker leeches. Others are shortened versions with a diaper (Figure 12.2). The latter type is made from a light nylon and is closed by a zipper that runs its length starting at the head of the sail and working down toward the leech. Just as we ended the leech stops half the foot-length up from the clew when banding a spinnaker, the sock ends at the same place. This is because for spinnakers that...

Sailplan Jargon

Most of the names of sail parts have been covered in previous chapters (and they are explained in full in the glossary), but if you look at a sailplan you will see some new and strange letters, namely I, J, P, E, Ii, Ji, Py, Ey, and LP. Let's start by explaining these characters. Note that these are broad explanations only. The exact measurements are quite complicated and not necessary for this discussion. I - The height of your mast above the deck. J - The distance from the front of your mast...

Luff Curve

Because the mainsail is attached to the mast, it follows that the way in which it is attached will have an influence on the shape of the sail. For example, the sail designer designs a luff curve on a mainsail that he assumes will match the curve of the mast. In some cases he might add more luff curve than there is mast bend so that some of that excess curve can be fed into the body of the sail in the form of sail shape. Imagine, however, what would happen if the sail is set on the mast and the...

From Flax to Cotton

It may seem foolish for any modern look at sails and sailmaking to be discussing cotton and flax sails. On the other hand it would also be foolish not to look back to the very beginnings of sailcloth, if only to illustrate how and why progress and change takes place, since it is sometimes for the most unusual reasons. In the early 1800s, for example, American warships had sails made from flax, at least until the Navy decided it needed to find something new. It did so not because it was...

What can be done to minimize induced drag

Keeping the lower sections of a sail flatter than the body of the sail effectively funnels wind across the sail rather than allowing it to escape under the sail. It's more important to have flat sections at the bottom of the sail where there is a long chord rather than at the top where the sail comes to a narrow point. You can also have the sail sweep the deck if it's a headsail, since by being right up against the deck the wind can't escape under the foot of the sail. But this is not possible...

Jibing an Asymmetrical Spinnaker

This is not a difficult maneuver to perform, but like all sailhandling techniques it requires practice. Jibing an asymmetrical without a spinnaker pole is actually quite easy. It's only when a spinnaker pole is employed that it becomes more difficult. Let's look at a pole-less jibe first. Just like jibing a symmetrical spinnaker, the helmsman plays a key role in the process. It's up to him to jibe the boat in concert with the speed at which the spinnaker is able to be moved from side to side....

Chord Depth or Sail Draft

This is probably the single most important feature of any sail. The chord depth, also called the camber or draft, is determined by running an imaginary line or chord from the luff of a sail to the leech (Figure 6.1), and then measuring the distance from this line to the deepest part of the sail. The chord-depth ratio, often expressed as a percentage, refers to the ratio between the length of the chord and the depth of the sail. Because sails taper toward the head, it is important for the draft...

Crescent Cut and Saw Tooth Sails

Partly out of a desire to save overall weight in the boat, and partly in an effort to engineer more efficient sails, sailmakers started to manufacture sails that had a relatively light base fabric, then added a second ply of woven Dacron along the high load area, i.e., the leech. This development took place in the early 1980s and initial forays into two-plied sails, or sails that had heavier fabric up the leech were not a total success. The point where the different fabric strengths came...

Setting a Spinnaker

Now that you have all your gear in place it's time to get ready to hoist the sail. First, the leeward sheet and the lazy guy (if the boat is rigged with one) are run aft to a turning block, and the afterguy and lazy sheet are led around the windward side of the boat. While doing this, the afterguy is led through the beak, or jaws of the spinnaker pole, through a turning block on the windward side and to one of your largest winches. When the spinnaker is set there will be a lot of load on the...

The Laminating Process

The basic lamination process is a relatively simple one, although there are many variables. First, a thin film of adhesive is spread on a Mylar film. Then the Mylar and the base fabric, be it a scrim or a woven fabric, are passed between heated rollers that both set off the adhesive and force the adhesive into the fibers. If the fabric calls for more than two layers, the Mylar film, covered with adhesive, and a base fabric are passed between heated rollers that set off the adhesive and bond the...

Thank Goodness for Ted Hood

In the early 1980s I was fortunate enough to be part of the crew of the maxi-boat Nirvana. At the time the boat was a cutting-edge design that held true to my theory that beautiful boats also sail fast. David Pedrick drew the lines, and the boat was a pleasure to behold. It was also fast, despite the built-in dishwasher, washer and dryer, and full-size bathtub in the master stateroom. We raced the boat all over the world in places like Sardinia, Mallorca, Scandinavia, Malta, the Caribbean, and...

Trim Stripe

To make it easier for you to trim your sails, your sailmaker should add a trim stripe at the clew of the sail. The trim stripe is a line that roughly splits in half the angle made by the leech and foot. This stripe is a good average reference point for you to use when you are trimming your sails. Sight down the stripe to your sheet and if the sheet is in line with the stripe, you can be sure that your sail is trimmed correctly. A UV sunshield down the leech and along the foot of a headsail can...

Alternative Mainsail Handling Systems

Despite these modern advances in mainsail handling hardware, there remains a constituent of sailors that scorns in-mast and in-boom systems, opting instead for a compromise between no system and a fully-fledged hardware package. For Lazy jacks are an easy and effective way of handling a mainsail, and when combined with a boom with a recessed upper surface (left), the system is neat and efficient. Lazy jacks are an easy and effective way of handling a mainsail, and when combined with a boom with...

Bias Stretch

While the bobbins holding the warp and the shuttle holding the fill are important, it's actually the beater that plays the most important role in weaving sailcloth. As noted above, the finished fabric has strength both along and across the cloth, since pulling in those directions means pulling along the length of the yarns. But it is weak along the diagonal since forces working in this direction are pulling at an angle to the yarns and can distort the weave. To minimize this bias stretch as...

Using Symmetrical and Asymmetrical Spinnakers

One advantage of asymmetrical spinnakers is that they are often much easier to set and douse when under sail. Conventional spinnakers can be fairly complicated to use requiring a number of different sheets and guys attached to the sail, to say nothing of a spinnaker pole that has its own topping lift to hold the outboard end of the pole up and downhaul to hold the outboard end down. It's no wonder the sail can sometimes be intimidating. In the chapter on sail handling we will discuss some basic...

A conversation with your sailmaker

Is polyester only used to make cross-cut sails 229 Is there a limit to the size of boat that can have Dacron sails 229 Nylon has some give to it. Is that good for spinnakers 229 Pentex is also a polyester How is it that Pentex sails perform better than regular Dacron 230 What are the attributes and drawbacks of Spectra 230 Why would you not use Kevlar for cruising sails 230 What about Vectran Where does this fiber fit in 230 Is there a future for PBO in sailmaking 230 And carbon. Does it have a...

Introduction

In the fading light of a South African summer evening we took off from a small airfield and flew along the coast watching the bays and harbors unfold as we skimmed the treetops. A strong wind was blowing, lacing the ocean with white streaks of spindrift and buffeting our small helicopter. Table Mountain cast long shadows as the sun dipped slowly over the western horizon. Where the water was shaded, the whitecaps stood stark against the dark sea, but toward the horizon they sparkled like small...

InBoom Furling Mainsail

In contrast to in-mast furling systems, in-boom furlers, as the name suggests, have a mandrel running the length of the boom so that the sail can be rolled up horizontally as opposed to vertically in the mast. As a result, you can maintain a reasonable amount of roach on the sail since you no longer have a problem with conventional horizontal battens. There is one important point to consider, however with in-boom furling mainsails the devil really is in the details, and you would do well to go...

If the boat starts to become overpowered

Bend the mast more to flatten the mainsail. Lower the traveler a little. Move the lead on the headsail aft to allow the top to twist open. Moderate to strong air (15 to 25 knots) - You have taken up on the backstay and added bend to the mast, tightened the outhaul and flattening reef (if there is one), used the cunninghams on both sails and started to twist open the top of the headsail. But you are still feeling a bit overpowered. That can only mean one thing It's time to make some changes....

Warp and Fill

The warp refers to the yarns running the length of the fabric while the fill refers to the yarns running across the fabric (Figure 3.1). Another name for the fill is weft, but most sailmakers and sailcloth manufacturers prefer to use the more modern name. A fabric engineer can design a fabric to be warp-orientated by using heavier yarns running the length of the fabric or he can design a fabric to be fill-orientated by using heavier yarns along its width. Balanced fabrics, as their name...

Measuring for a Headsail

Height of I - If you do not have a sailplan and would like to know your I dimension, attach a tape measure to your Genoa halyard and hoist the halyard to the top of the mast. Be sure to attach a retrieval line so that you do not have to rely on the tape for pulling the halyard back down again. Now measure to the base of the mast for your I dimension. This is an estimated I dimension. The lower point of I is relative to the height of your freeboard and some other factors, but for a sailmaker's...

Stopping a Spinnaker

Unless you are setting the lightest of spinnakers or on a fairly small boat, the sail should be in stops or in a spinnaker sock. Stops are either elastic bands or light pieces of yarn that are used to lash the sail to keep it from catching wind and setting prematurely. Larger boats (or spinnakers that are going to be set in a lot of wind) should be stopped with yarn. The yarn is more time consuming, but definitely worth the effort. It is the only safe and secure way to ensure that the spinnaker...

Induced Drag

In terms of the physics of how a boat sails, there are a number of different types of lift and drag that are fundamental to performance. Two obvious types of drag are form drag, which occurs when any object presents a surface to the movement of air, and frictional drag, which is a function of the amount of friction between any surface and the surrounding air. Race cars and airplanes, for example, are streamlined in an effort to minimize the former, and their surfaces are kept smooth in order to...

In very light air

Keep the sails relatively flat so air flow can stay attached. Move crew weight forward and to leeward. Watch out for wind shear and twist your sails accordingly. You would, do better to concentrate on boat speed and let the lift come from the foils rather than trying to stuff the boat as high as it will sail. Light air (6 to 10 knots) - Once you have at least 6 knots of true wind you should be generating some apparent wind of your own, allowing you to concentrate on sail trim and make fine...

Measuring for a Mainsail

Maximum luff length (P dimension) - Measure by attaching the tape to the halyard shackle and pulling it to the top of the mast until it stops. Secure the halyard and measure to the bearing surface of the tack pin. If your mast has black bands, raise the tape until it is just at the lower edge of the band. You will probably have to site the position of the tape from off the boat. Be sure to note that this is a black band distance when submitting the data to your sailmaker. 2. Maximum leech...

Separate Trysail Track

Many offshore sailors insist on a separate trysail track running up the trailing edge of the mast, and I tend to agree with them, especially aboard larger vessels. For a racing boat where weight and windage are a consideration, however, sharing the track with the mainsail is acceptable, providing there is a simple and secure way of loading the trysail's slides without having to remove the mainsail. Boats below 30 feet in length do not need a separate trysail track. The sails are a manageable...

The History of the Spinnaker Sleeve

Spinnaker Sock

The first spinnaker retaining device was invented in Germany about 35 years ago. It was called the Blue Max and was a very simple cloth tube with a rigid opening at one end and a closed-loop line running along the inside that was used to control the up and down of the tube. Nobody paid much attention to it back then since flying spinnakers was not very popular at the time. Then along came Eric Tabarly, the French singlehanded sailing ace who recognized the need for such a device and asked his...

Making Cuben Fiber

There are various steps to making Cuben Fiber with the number of steps dependent on the engineering of the finished fabric. For example, a heavy fabric for use on a megayacht mainsail will have more steps than a light fabric for use as spinnaker material. The basic process is the same it's just that the heavier fabrics require more layers, hence more steps. The foundation of all Cuben Fiber fabrics is tapes of pre-preg fibers 30 meters long and 30 centimeters wide. The fibers can be either...

Downwind Sails Explained

There is nothing quite like a day in the trades with a warm wind at your back and the horizon ahead stretched in a wide arc like open arms just waiting for you. You are romping downwind with every inch of sail set, your boat rollicking and revelling in the conditions. Unfortunately for many sailors this is not a reality. They are wobbling downwind wing-and-wing, or worse, with the engine on and the spinnaker neatly stowed in the sail locker. Sailing with a spinnaker should not be a scary thing....

Spectra

Spectra is also made by Honeywell Performance Fibers and is a highly processed ultra-high molecular weight polyethylene or UHMWPE, according to the literature put out by Honeywell. This outstanding fiber has been used to build sails for megayachts and for numerous racing sailboats competing in offshore My own boat, Great Circle, had an inventory of Spectra sails that served me well for many years and many offshore miles. races like the Volvo Ocean Race, the Vend e Globe, and the Around Alone....

Backstay

Manual Backstay Adjuster Manual

In Chapter 6 we discussed how a sail designer adds curve to the luff of the mainsail to match the curve of the mast. He anticipates the amount of bend and designs the sail accordingly. If you are able to bend the mast more than the anticipated amount, the luff of the sail is pulled forward and the fabric stretches to accommodate the bend. This pulls shape from the rest of the sail and effectively flattens the chord of the mainsail. Conversely, if the mast has less bend than anticipated, the...

Inflatable Battens

The third alternative is one that has been around for quite a while, but never really caught on. That solution is inflatable battens. It makes perfect sense since we all know you can get a very rigid batten just by adding air pressure, and of course when the pressure is removed the batten is as flexible as the sail itself. The reason, I feel, that inflatable battens have not caught on yet is that they add a whole new level of complication to a sail. Cruisers are looking for simplicity, and...

Crosscut Radial Spinnaker

In the cross-cut radial spinnaker, a radial head on a cross-cut body addressed the problems caused by the cross-cut panels. The tri-radial spinnaker revolutionized spinnaker design by allowing for more stable sail shapes. The tri-radial spinnaker revolutionized spinnaker design by allowing for more stable sail shapes. ment in the head, reasoned that the clews could also benefit from being radial. This resulted in what became a true benchmark sail the tri-radial spinnaker Figure 8.3 . Despite...

Step Broadseaming and Sewing

There are two ways to add shape to an otherwise flat surface. The first is to draw a convex or positive curve down the luff of the sail so that when the curve is placed up against the straight edge of a mast or headstay, the extra fabric is pushed into the sail as shape. While this sounds rudimentary, it's actually quite effective, although it does not give the sail designer much control over the overall shape. To create a more consistent shape throughout the sail, designers can also employ a...

Power up sails in light air by

Keeping main traveller at or above centerline. Allow headsail draft to move aft in order to create a narrow angle of attack. Keep lower third of sails flat to minimize induced drag. Keep the boat footing and minimize rudder use. Moderate air 8 to 15 knots - Once the true wind is blowing steadily over 10 knots you can get the boat fully up to speed and the sails trimmed perfectly to match not only the conditions, but whatever it is the helmsman wants to achieve....

InMast Furling Mainsails

Along with roller-furling units for headsails, the in-mast furling mainsail is largely responsible for the growth of cruising in the last two decades, as well as the fact that larger and larger cruising boats are being sailed short-handed. Up until Ted Hood first introduced what he called the Stoway Mast in the late 1970s, sailors lived in trepidation of their mainsails, especially aboard larger boats. They were large, unwieldy and difficult to manage, and many cruisers in particular simply...

Early Theory

When I first learned about boats and sails, I read a number of the simple theories that were eventually upgraded by Mr. Gentry. They certainly seemed to make sense at the time. But while many of them were grounded in hard scientific fact, they overlooked some basic problems that both research and common sense later revealed. For example, while most sailors learn that a sail is shaped like the wing of an plane, and that since planes can fly it must hold true that a sailboat will sail, this line...

Loads Catenary Versus Isotropic

There are two principal issues at work here, and they represent the primary differences between molded sails and paneled sails made from Cuben Fiber fabric. Since the early days of sail engineering there has been an underlying assumption that the loads in a sail radiate out from the three corners of the sail and then travel along catenary curves much like cables strung between two endpoints. The common thinking was that if you placed a fiber or bundle of fibers along this catenary, such as in a...

Tape Drive

Tape Drive, for example, has been around since the beginnings of molded sails and is the exclusive domain of UK Sailmakers. In fact, UK Sailmakers was one of the first sailmakers to acknowledge the Airframe patent, immediately applying for a licence to build sails using this new technology. Instead of laying thousands of individual fibers along load paths, however, Tape Drive uses high-strength tapes to accept the loads in the sail in a two-step process in which a base fabric or membrane...

Spinnaker Handling in Heavy Winds

One of the areas where large gains can be made, as well as where spectacular wipe-outs can occur, is running downwind in strong winds. It's not as hard as it looks, but it does require teamwork and co-ordination to pull it off success- fully. As previously mentioned, it's important to mark sheets, guys, and halyards so that you can pre-set the running rigging before you deploy a spinnaker. This is doubly important in heavy air. You want to be sure that when a spinnaker fills you do not have the...

Spinnaker Handling Techniques for Racers

As noted above, for the cruiser it is better to err on the safe and steady side when playing with spinnakers rather than take chances. But for racing sailors it's a different game. They expect to have occasional problems, and the trade-off between a quick spinnaker set and one that might possibly go wrong is a worthwhile risk. In this section we will look at four maneuvers in detail A bear-away set with a conventional symmetrical spinnaker. A jibe-set and a regular jibe with a symmetrical...

Hypothetical Look at Buying Sails

It was not so many years ago that buying a new sail for your boat meant a pleasant trip down to your local sailmaker. You made a call e-mail was not yet invented , set up an appointment, and then spent a few wonderful hours looking at bolts of cloth, talking boats, and settling on a price. If you were a good customer a handshake would seal the deal, the sail would be made, and a few weeks later it was delivered to your boat an invoice would arrive by mail. Your sailmaker knew you by name - both...

Daisy Staysail

There is one sail that I am particularly fond of, a sail that is often found on racing boats, but hardly ever carried by cruisers, a sail with three names and a number of purposes. To some it's known as a Daisy Staysail. To others it's a Tall Boy while others simply call it a Windseeker Figure 10.2 . Regardless of the name, it is a high-aspect, loose-luffed sail usually made from a light fabric. Cruising sailors pre- fer the sail to be made from nylon, while racers will opt for a light...

The Design Process Turning Theory and Fabric Into Flying Shapes

Each sail goes through a number of design steps before construction can begin. Some steps, like sail geometry or the basic shape of the sails, are reasonably simple while others, like computing stress strain pictorials, require much more thought and deliberation. Ultimately, the shape of each sail will be drawn from a database of known sail designs and manipulated until the designer is satisfied that the sail he is creating for your boat is perfect for your purposes. Before we look at the...

Streamlines

Let's go back to the front of the sail again. Before any circulation was created you had a circumstance as shown in Figure 15.14. We now need to label some parts of this diagram, and I have done so using the terminology created by the scientists. The lines of wind flowing across the sail are known as streamlines. Between the flowing streamlines are two stagnation streamlines, i.e., streamlines that end or begin abruptly. These are created by the vacuum that arises when the flowing streamlines...

Biradial Mainsail

Panels ra nid clew be used f dcwnwini A bi-radial main with load-bearing gores radiating out of the head and clew only - bi-radial meaning that there are only two sets of panels Sails have become far more sophisticated than a simple tri-radial configuration. Here the panels change direction along the load lines in the sail. downwind leg, as soon as the racing sailor reaches the windward mark and bears away, the loads on the sail immediately decrease so that even though the loads may be...

The Spinnaker Turtle

Yarns, rubber bands, the spinnaker sock, and dousing sock are devices generally used on larger boats, say 30 feet and longer. On smaller boats it's not necessary to go to all this trouble because the spinnakers are much easier to manage. That's not to say you should not be careful, but you most certainly do not need to stop the spinnaker on a Hunter 26. Instead you should launch it from a spinnaker turtle, basically a round bag with a plastic hoop at the opening and a cover that has a bungee...

Case Study Transatlantic Race

Two sailors are planning to compete in the Cape Town to Rio Race aboard different boats one a 60-foot IMS design with a reasonable budget and a strong will to win the other a 60-foot performance cruising boat that is planning to continue on after the race and sail to the Caribbean. The owner of the cruising boat wants his sails to be good for the race as well as for cruising afterward. For the owner of 60-foot IMS boat there are a number of options Low stretch - use the latest technology....

The Slot Effect

The mainsail also creates somewhat of a slot effect at the very end of the head-sail where the air is squeezed between the leech and the lee of the main. This is not the large slot effect that earlier studies pointed to because the circulation around both sails negates each other to some degree. But the wind does still speed up as much as 30 percent. In fact, studies have shown that the air coming off both sides of the headsail has an increased velocity and the Kutta Condition is met not at the...

Factors That Affect the Price of Dacron Sailcloth

In order to provide a yardstick by which fabrics can be compared, fabric makers rate the performance of different sailcloths by dividing the modulus of a fabric by its weight to determine a number called the specific modulus. In most cases fabric makers are striving for a high modulus low weight fabric, in which case they might incorporate some exotic yarns into a fabric to give it more strength. On the other hand, there are some occasions where durability needs outweigh performance, and in...

What is Cuben Fiber

You may recall from the introduction to this book, that the sails for the mega-catamaran Team Adventure were made from a revolutionary new sailcloth called Cuben Fiber, which we chose after weeks of rigorous testing of a number of different types of fibers and fabric engineering techniques. Some of this testing was The thing that sets Cuben Fiber apart is the way in which these raw fibers are turned into sailcloth. Once they are laid down the entire matrix is inserted into an autoclave . . ....

Dousing the Spinnaker

Now that you have the sail set and all is right with the world, you need to consider how to get it down. There are a number of simple methods and we're going to look at the asymmetrical first because it's the easiest to douse. Bear in mind, however, that no matter what spinnaker you are flying, your mainsail is your best friend, since as was the case with the hoist, it can reduce the force of the wind on the sail when it comes time to douse. In fact, the lee it provides is invaluable. It's true...

Tips for Using a Dousing Sock

When using the control lines to lower the hoop over the sail, lead them through a ratchet block mounted on the rail at a point forward of the boom and to leeward since this will allow you a measure of control over the lines, and you will be pulling up from the turning block on the deck rather than down on the sock. This way your feet will be squarely on the deck and you will not be dangling at the end of the sock hoping that the sail does not accidentally fill and flip you over the lifelines....

The Flattening Reef

This reef is found only on cross-cut sails and is located a short distance up the leech from the clew. When cross-cut sails are designed they have a very important seam originating just above the tack of the sail called a tack seam that runs perpendicular to the leech and plays an important role in adding shape to the sail by feeding a large amount of sail shape into the body of the sail. Once you take up on the flattening reef by winding up on the reef line, it cinches the leech and...

An Effort to Improve Dacron

Despite the fabric engineers' best intentions, for example, after a while all those fillers and finishes added to woven sailcloth begin to break down, and what starts off as crisp, low-stretch fabric becomes a softer, more easily manipulated sailcloth that begins to stretch and distort the sail shape. Therefore alternative means of creating a tight weave were sought. In the late '70s and early '80s Hood Sails believed it had solved the problem by producing its fabric in 24-inch-wide panels,...

The Dousing Sock

This invention has done for the cruising spinnaker what roller-furling did for cruising headsails, i.e., made the sail more manageable and less intimidating Figure 12.3 . The dousing sock is similar to the spinnaker sock except that it does not have a zipper. Instead, the sock is pulled down over the sail with a rigid fiberglass hoop that collapses the spinnaker and feeds it into the sock. The hoop has flared edges, and when a takedown line is pulled it gathers the spinnaker fabric and the sock...

Mitre and Cross Cut Sails

Before we look at some of the latest sail designs, it's once again important to look to the past. As was the case with sail fabrics and yarns, if we understand how we got to where we are today, we will have some idea of where we might be going. Sail engineering is all about making good use of raw materials, both raw fibers and sailcloth. Back in the days of square-riggers and trading schooners all sails were made in much the same way, i.e., with their panels laid parallel to the leech of the...

Luff curve to be no move than oercent more than mast prebend

If the roll size is uniform, the sail can roll up evenly and not travel forward or aft as you reef. If you have ever tried to roll up a carpet, you will know what I mean. The top ply added to the leech can also be a UV-resistant fabric to protect the sail once it is furled away in the boom. It works the same way as the UV cover on your rollerfurling headsail. Another important part of the sail is the luff tape, or bolt rope. In fact, the boom maker will usually supply a bolt rope...

Case Study Fabric for High Latitude Sailing

I recently had two customers who were building boats for high latitude sailing. One was building an 80-foot sloop and the other a 50-foot sloop. It's interesting that both customers had firm views on what they wanted, and both went against conventional wisdom with their choices. Since both boats would be sailing in areas where the conditions were harsh and repair facilities nonexistent, rugged and durable were the principal requirements. Both owners were presented with similar fabric choices,...

Fulllength Battens

Full-length batten mainsails have all the battens running from luff to leech. when it comes to battens they will extend the life of your sail since battens add support to the fabric and dampen the flogging that is one of the principal causes of fabric degradation. Full-length battens also assist in keeping the shape of the sail looking good after years of service, whereas with conventional battens wrinkles start to appear at the inboard end of the batten pockets after heavy use. Mainsails that...

To drop the sail

Ensure that the pole guy is fixed in place. The pole guy holds the spinnaker pole in place. The trip line opens the snap shackle. Gather the sail under the boom. secures the afterguy to the clew of the sail. You may have to modify your existing pole. Beyond that you need to run a trip line through the fairlead at the end of the spinnaker pole and loop it through the trip mechanism on the Sparcraft shackle, i.e., the one on the afterguy. When the spinnaker is flying the trip line just dangles...

Spinnaker Trip Mechanism for Easy Takedowns

There is an easy takedown system that the crew of Alaska Eagle developed during the 1981 Whitbread Race that served us very well, especially when the boat was sailing along on the edge of control. I have since used the system when cruising and introduced it to others. The consensus is that it takes away one element of concern when sailing with a spinnaker that all-important element of releasing the sail to get it down. In order to use this technique you will need a pole guy, and a spinnaker...

Explain how the mainsail trimmer can drive the boat

The mainsail is a huge sail that has a large effect on the weather helm and heel of the boat. If the sail is sheeted on too tight or if it is too high up the traveler, the helmsman will have to turn the wheel to compensate and this can slow the boat down, especially if there is a sudden puff of wind. Rather than wait for a puff of wind to hit the sails before easing the sheet, the mainsail trimmer can ease it before the wind hits the sail and save the helmsman from having to turn the wheel.

Foam Luff Pads

More turns more girth more shape removal flatter sail To compensate for a sail bagging out when reefed, sailmakers add a foam luff pad that runs the length of the luff Low-aspect sails need a foam luff pad more than high-aspect sails because they have more shape over a larger area to remove. While there may be less need for a foam luff pad on a high aspect sail, all sails will benefit from having one Figure 7.7 . Even though it can remove shape, the luff pad does nothing to help keep the shape...