Manufacturing technology for cruise laminate sails

In the second part of our cycle on sails, we will talk about the current state of technology of modern cruise laminates, their production and durability... In addition, we will give you some useful tips for choosing and buying these sails.

Everything membrane sails are piece goods made by individual tailoring. That is why they can be optimized and adapted for a specific yacht, its character, conditions of a particular sailing region and the wishes of the owner.

This custom work achieves a high level of perfection and quality in customization that cannot be achieved with roll sails. Indeed, with these fabrics "from the poles" the sailing master can only use the ready-made laminates of different weights and qualities that are available to him and try with their help to improve the sail as much as possible.

The result of these efforts: characteristic "Patchwork method" with numerous stripes and seams in radial cut. At the same time, laminates and membrane sails are getting cheaper every year and can compete with high quality Dacron sails - regardless of the size of the yacht. Especially on small yachts, quality sails are truly incredible sailing pleasure - after all, because then you feel the action and operation of the sails directly on the tiller.

Since in membrane technology strips of taffeta (thin polyester fabric), mylar (polyester film) and scrim (non-woven spun sheet of high modulus fibers) mainly serve as the basis for those fibers that bear the main load, these strips can be arranged in parallel and connected to each other. Compared to radial cutting, it is possible to reduce the number of seams by 70 %, several times the stress zones and, accordingly, errors during cutting.

Different technologies - or many roads lead to Rome

All leading manufacturers of membrane fabrics create their products, albeit using different methods, but similar principles: a program-controlled machine-automatic machine arranges on taffeta / film strips of high-modular fibers yarns according to the directions of the load. Depending on the requirements, they can be reinforced with scrim and then covered with a film in the case of cruise laminates, and additionally with taffeta to take the form of a finished sandwich laminate.

To hold all this together firmly and lastingly, you need a lot of know-how and practical experience, the details of which are protected by many manufacturers as the most terrible secret. But the principle is the same everywhere: under the influence of temperature, the glue applied to the canvases and contained on the film and taffett is activated and at the same time the laminate is pressed under the influence of a multi-ton load of press pressure, or with the help of a vacuum, both of these options can also be used. At the same time, there is one fundamental problem that all manufacturers of membrane sails face: to activate the adhesive, it is necessary to heat up to a temperature of 120 degrees, and then maintain pressure on the laminate until it cools down to a temperature of 50 degrees to get strong connection.

In the case of roll-to-roll laminates with their fixed width, the production process is relatively simple: the glue on the bottom layer (film with or without taffeta) is heated, the scrim canvas, the filaments and the top layer of the sandwich are machine applied and bonded together in this way way: under a multi-ton press, the laminate is rolled on rollers. After that, the resulting connection should set within a few hours. The disadvantage of this method is that it is impossible to avoid getting air into the fibers. Especially in the case of laminates with thick filaments and laminates in which the filaments are of high density. After all, the fewer air inclusions, the better the adhesion of the layer and, consequently, the life of the laminate.

However, in membrane technology, it is possible to significantly reduce the amount of air entrapment by means of a vacuum. How this happens in detail, we could not find out from North Sails (3DL)nor at Dimension-Polyant (D4).

The exception was the development of membrane tissues Elvstrom Sails - "EPEX". The production of sails using this technology began in Denmark in 2009, and we were allowed to look into production for the first time. Layers of taffeta, film and filaments, placed exactly along the load lines, with or without a scrim, are prepared on a huge table and the adhesive is eventually activated by a plotter element moving above the table. During the process, an extremely high vacuum of 79 tons is applied to the entire porous work surface and, thanks to this, every square millimeter of the laminate is processed. In this way, up to the setting of the adhesive, a particularly efficient evacuation of air and, at the same time, a firm connection of the filaments and scrims is achieved.

At the same time, excess glue is pumped out, which allows the production of very lightweight fabrics. According to Elvstrom, this technology is unique and rivals methods in which air inclusions are pumped along the edges of the fabric. The disadvantage of these methods is that due to the increasing resistance of the webs to the center of the laminate, the vacuum is reduced so that in the case of very wide laminates or filaments that run tightly to each other, air inclusions are less efficiently removed. If we take and compare a rolled laminate with a laminate produced using membrane technology, then with an increase we will see that the air inclusions in the latter next to the fibers are much smaller.

3DL technology (North Sails) in turn uses a flexible working surface that can be reshaped by multiple hydraulic pistons so that it precisely matches each specific sail profile. Above this form, strips of fabric treated with glue are then laid out, filaments of fibers are mechanically placed, depending on the type of fabric, a scrim canvas is applied and all this is glued together under the influence of temperature. Since the laminate cannot be secured by the pressure of the rollers due to the flexible backing, this is ultimately due to the vacuum.

The advantages of this method, according to North Sails: The finished, profiled sail fabric remains a single whole, it does not need to be cut into separate strips, as a result of which the carrier threads of the fibers pass from corner to corner without breaking. In addition, the sail fabric comes out of the form already profiled, so that errors of manual cutting of strips are excluded. This method, however, has no effect on the durability of the sail, since the bond strength of the filament yarn corresponds to ten times the possible load in the sail.

The main advantage of these "shape-finished" sails is that they can provide riders with a big edge on the road to victory - which is, however, contested by other sailing makers.

Parallel cut: less effort, longer profile

In addition to these membrane technologies, there are also compromise solutions that allow achieving similar qualities as in membrane sails, such as technology "Tape Drive" from UK Sailmakersconstantly evolving for over a decade. In this case, roll-to-roll laminates with a lightweight “scrim” canvas made of durable polyester, equally strong in the weft and warp directions. Once the panels are cut and connected to each other in the sail, tensioned fiber bundles (Tapes) made of fiberglass or carbon fiber are additionally glued to them in the direction of precisely calculated load lines.

They mainly take over the main acting forces, while the scrim canvas additionally supports the profile in the laminate. Therefore, with Tape Drive technology, lighter fabrics can be used as a base. In order to make the fabric lighter and more stable in shape, UK interlays in the fabric "Tape Drive Titanium" inside the laminate, twigs are stacked in structure. The bundles of fibers in this case 80 % consist of carbon, the remaining 20 % of aramid, which significantly increases the shelf life of the profile. In addition, it makes the sail more convenient to operate and set up. UK recommends Titanium sails for performance cruisers from 35 feet. In addition, the sailmaker can only offer parallel cut sails due to the

Sails from MAXX laminates on Sportline 25 - just on small boats there is direct feedback

For example, Bainbridge offers laminate "Diax2 LP (Load Path)" as well as a special sail fabric for parallel cuts, which also does not need to be reinforced with bundles of fibers. The weft-reinforced scrim is further reinforced with fibers in the diagonal direction of 45 and 65 degrees of tensile force and significantly adds dimensional stability. In addition, Bainbridge can also adhere strands of high modulus fibers in the direction of the load lines, thereby reducing the weight of the base fabric and increasing the shelf life of the profile.

Dimension-Polyant also produces various fabrics optimized for parallel cuts in the weft direction. Similarly as in "Diax2"Dimension-Polyant uses in Flex Pen Cruise not only in the direction of the weft and warp, but additionally in a diagonal direction of 20 and 30 degrees of pentex fibers to absorb the forces acting in the area of the head, clew, tack and leech.

Laminates series "MAXX"offered by the third leading manufacturer of sailing fabrics, the Dutch company Contender, operate on a similar principle: in addition to the usual scrim, this laminate can be reinforced with high-modulus fibers in up to four diagonal directions. This also achieves a longer profile retention, as noted by the manufacturer.

For lovers of cruise yachting Contender also recommends branded laminate flooring MAXX VoyagerCoated on the outside with polyester taffeta, which protects against UV radiation and rough use. The advantage of this fabric, reinforced in several diagonal directions (for example, 30, 60 and 75 degrees), is that its fibers can carry loads in many main directions. This advantage manifests itself primarily when the sail trim is changed. For example, if the depth of the profile of the genoa is shifted back, at the same time, making the leech flatter, and thereby relieving the upper part of the sail, then the main acting forces are displaced from the leech to the middle of the sail. As a result of this maneuver, they change the direction of the tensile force. It is then that the fibers skipped in the laminate asymmetrically along the diagonal show their purpose, since they take into account the changed directions of the load lines and thus contribute to maintaining a functional profile.

Disadvantage of rolled laminates: they are generally slightly heavier than membrane fabrics due to the very high density of fibers in some areas, more densely packed and, accordingly, less convenient to adjust. In addition to all of the above, the use of a vacuum to remove air inclusions.

Summary and tips:

Sail fabric quality is defined in the same way as a prepared dish: the better the quality of the “ingredients”, the more professional handling and the high-quality “tools” for production, the better the menu will be - but also (almost always) and more expensive. This comparison does not fully apply to cruise yachting, since it is not necessary that “high culinary art” should be in the first place, sometimes simple “homemade food” may be enough. This statement applies, for example, to the everyday basic set, in which the durability of the fabric plays an important role during long sea voyages, rather than a decrease in tacking or an increase in speed. For this reason, Dacron sails with large reinforcement areas are still recommended for these purposes so that they can withstand rough exploitation longer. Because of this, they are generally considerably heavier than laminates.

But even for yachtsmen who prefer not only cruise yachting or do not want (or cannot!) Pay more for laminate sails, high-quality dacron fabrics are still the number one choice.

A little tip: Dimension-Polyant offers a special polyester canvas fabric that has dyneema gratings woven into it. Thanks to this, this sail from the so-called Hydra-Net additionally obtains a very high tensile strength and a particularly long service life. Since dyneema, in addition to the highest tensile strength, also has increased protection against UV radiation, is resistant to rough cleaning and use, this durable fabric is ideal for swimming with long-term transitions. The only drawback: it is very expensive!

For yachtsmen-cruisers who sail in regions more or less close to their place of residence throughout the season and enjoy the ability to optimally maintain the course of their yacht with the help of sheathing, gikshkat shoulder straps and headstock adjustments, laminate sails, without doubts are the best solution.

But then a logical question arises: which of the many varieties of sail fabric then guarantees the longest service life at the lowest cost?

If we weigh and compare all the pros and cons of various technologies for the production of laminates and sail cutting, then everything speaks for the still expensive membrane sails: their profile holds its shape longer, they are more durable and lighter, which guarantees the pleasure of yachting.

"EPEX", "D4" or "3DL" - which of these laminates retains its original shape longer? In this regard, we do not want, and we can not provide any data, because for today there are no control values yet. According to the various sailing makers who offer these membrane sails to customers, sail durability can be expected for 15,000 miles or as much as 8 years. So, for example, most of the riders of the finished race  Vendee globe  had no problem with the D4 sails.

On the other hand, sails wear significantly during the normal season as they are set and rolled more often. But, despite this, the announced durability period is striking - but it, however, strongly depends on the quality of the materials used (see graph) and the accuracy of handling the sail.

The most affordable alternative is parallel cut laminate sails like the MAXX-Voyager from Contender, Flex Pen Cruise from Dimension-Polyant, Diax2 LP from Bainbridge or Tape Drive Titanium from UK Sailmakers. Laminates, additionally reinforced with bundles of fibers, although they increase the durability of the profile, but lead to an increase in the cost of the sail (see price comparison).

On the other hand, radial sails and the laminates used for their production have by no means become obsolete due to many years of development and accumulated experience, so when choosing such a sail, a mistake will hardly be made. One thing is clear: radial sails should be more expensive due to the difficult cutting and the large number of seams.

Price comparison

We asked three manufacturers: North Sails, Elvstrom Sails und UK Sailmakers calculate the cost of producing a mainsail with an area of about 33 square meters for a cruising yacht type Bavaria 38 in three versions:

1. the best dacron, 2. radial cut at the best, 3. membrane sail.

North Sails:

1. Grotto. Fabric: Polyester Premium NSP 5.8 H. Armament: 2 rows of reefs, with through-battens, sliders, Cunningham guy-rope attachment. Price: 4085 euros
2. The mainsail is triradial cut. Norlam Cloth 2000 XP Gatorback 6.2 XP TF2. Laminate structure: polyester taffeta / Mylar sandwich, scrim lattice for reinforcement in the weft and warp direction, diagonal X-fibers. Armament: as in 1. Price: 4588 euros
3. Membrane mainsail "Marathon 3DL". Laminate structure: Polyester taffeta and Mylar sandwich, with X-shaped and grid scrim. The load bearing fibers are made of Twaron (aramid) with a protective impregnation to improve UV resistance. Armament: as in 1. Price: 6341 euros

UK Sailmakers:

1. Cruise grotto. Fabric: Dacron "challenge high modulus" Dacron. Armament: 2 rows of reefs, with through armor, sliders. Price: 2665 euros
2. Tape Drive Silver parallel cut cruise mainsail. Laminate structure: Mylar sandwich with a narrow "scrim" lattice, one-sided taffeta application and external fiberglass fiber bundles in the load directions. Armament: as in 1.

Price: 3950 euros

3. "Tape Drive Titanium Offshore" cruise mainsail. Fabric: Base material as in 2., but with a double layer of taffeta and interlaced fiber bundles (80% carbon and 20% aramid). Armament: as in 1. Price: 6190 euros

Elvstrоm-Sails:

1. Cruise grotto. Fabric: Dacron 360 AP ES. Armament: 2 rows of reefs, with through battens, attachment for the Cunningham guy. Price: 2965 euros
2. Triradial grotto "Trioptimal". Fabric DC 66 (DP) and lighter DC 55. Laminate structure: polyester taffeta / Mylar sandwich with scrim (see test chart) reinforced in the warp direction, made of high tenacity polyester filaments ... Armament: as in 1. Price: 3738 euros
3. Membrane mainsail "EPEX". Laminate structure: Polyester taffeta and Mylar sandwich, with X-shaped and grid scrim. The load bearing fibers are composed of Twarone (aramid). Armament: as in 1. Price: 4379 euros

Proper handling is key to maintaining the durability of your laminate sail. Activity number 1: Immediately after the sail, the sail must be folded or twisted, avoiding folds if possible, and placed in covers that do not transmit ultraviolet light. UV radiation is still the number one enemy of any laminate flooring. The fabrics covered with taffeta on both sides, while increasing the durability of the sail and making it easier to maintain, at the same time make the sail heavier and more expensive. Those who appreciate the lightness of the sail should use a tuffet covering on one side and take the sensitivity of the bare side of the sail into account. These sails weigh about 30 % less than taffeta sails on both sides.

No sail, regardless of the method of production, should dry hanging in the wind if it hits other structures in the process. Therefore, the mainsail with through battens is an ideal sail for laminates, since the damage from strong blows is reduced with the help of a runner, and the sail is grooved or lowered almost without the formation of sharp bends of the sail.

Certain death awaits any laminate when stored in an overheated room, such as in a car that is in the scorching sun for a long time. This can lead to tissue delamination.

After all, the quality and type of fibers used to make it are strongly influenced by the durability of the laminate and the stability of the sail profile (see info table). Otherwise, our flutter test unambiguously refutes the following prejudice: laminates are less durable, as impacts or rough exploitation leads to their delamination.

One final tip: Having bought a new yacht (especially for modern cruising yachts with fast hull lines and appropriate sail setting systems), choose not the standard sails supplied with the kit, but the sail package offered as an extra option "Performance", which can cost you less than ordering separately from a sailor. This way, you will enjoy customization right from the start. And those who are thinking about buying a new sail must decide in advance how actively he will race on his yacht. After all, if it turns out that the standard sail you selected two years ago turned out to be unsuitable for loads, and only after that you decide to buy the optimal sail, then the “cheap” one will be expensive.

Test:

Although it is believed that laminate sails provide a yacht with excellent traction and propulsion, it is also generally accepted that they are hardly suitable for cruising yachting - they are too short-lived, not adapted for intensive use and whimsical to operate. This prejudice still keeps many sailors from buying laminate sails, even if they are willing to spend 60 % more on them than for regular sails.

We, too, were skeptical about claims by some sailing makers that the latest cruise laminate sails could last up to 15,000 miles. To verify this data, we ran a flutter test, a process that is the most efficient way to check fabric for wear.

For this test, we requested samples of their cruise laminates from leading manufacturers and ran the test in the laboratory of the world's largest sail fabric manufacturer. Dimension-Polyant (DP).

DP testing conditions are international standard: for flutter, two strips 50 cm long and 5 cm wide are cut from a fabric sample in each direction: warp, weft and diagonal.

The test is carried out in three stages:

At first one of both strips in each direction is clamped in a device that subjects it to 10, 25, 50,100, and 200 lb (1 lb = 0.45 kg) loads. In this case, the indicators of the resulting longitudinal deformation in inches (2.54 cm) are measured. The force required to stretch the strip by 1 percent is then calculated - that is, 0.16 inches, which corresponds to 4 mm, since the test length after fastening the strip of fabric is 40 cm.

Second phase: the second strip of fabric is fixed in a special device, which for 20 minutes produces a vortex effect on the strip using a powerful fan.

Stage three: this strip is now also subjected to a tensile test. The computer then calculates the stretch values before and after flutter and prints them out as curves and tables.

Summarizing: Of the many parameters that characterize sailcloth, only the parameters of the force load required to stretch the strip before and after flutter by 1 % were relevant for our test. Indeed, the data on the difference between the indicators before and after the conducted flutter test provide the most accurate data on the extent to which the laminate can suffer during wind and vortex overload and lose tensile strength.

On the other hand, the sailing master first of all needs data with which he can assess the quality or performance of the fabric: how little stretch fabric with a certain weight and different loads in the direction of the warp, weft and diagonal, and how much their strength indicators differ. The table of parameters will help him to answer these questions. Laminate Stretch Test Reports.

For example, a particularly lightweight laminate GPL 14 (DP)Reinforced in the warp direction with very thick carbon fibers, it is characterized by high strength values and almost zero wear in the warp direction, but relatively weak diagonal strength. Since this "warp-oriented" fabric is used exclusively for radial cuts, other measures play a secondary role.

If a sailmaker chooses a fabric for a parallel cut, then he can opt for a cruise laminate "MAXXVoyager", since it is reinforced with aramid fibers (technora, twaron) in the direction of the weft, which gives the sail a special strength in this direction.

And if he needs a fabric that is “oriented on the basis”, which has relatively low extensibility in other directions, then the laminate Diax2 TT Cruise would be the best solution.

With regard to the ability to resist flutter, cruise laminates CL 90P (Bainbridge), GLP 14 DT (DP), MAXX Voyager (Contender), and Flex 16 Aramid Cruising (DP)taffeta coated on both sides showed the best results - they were found to be almost insensitive to this effect. The laminate has experienced a serious impact of flutter Diax CL 95CFG (Bainbridge)which has lost about 160 pounds in strength towards the warp.

It was also interesting to establish how much the weight of lightweight laminates increases when taffeta is applied on both sides:  laminate "GLP 14" from DP has a weight of 241 g / m2 - with a double-sided protective taffeta, it rises by almost 50 % to 359 g / m2.

Those for whom the weight of the yacht and sail plays a role should turn their attention to laminates with a single-sided layer of taffeta. Polyester fabric from Dimension-Polyant, tested for comparison with laminates, once again confirmed its endurance and resource: unlike laminates, it did not show any signs of wear after the flutter test. When it comes to tensile strength, the laminates are far ahead, as expected. For example, Dimension-Polyant 'GLP' cruising laminate is thirteen times stronger at tear in the weft direction. When used in a radial sail, it accordingly can help maintain the sail profile longer.

Test results:

After the vortex test, we did not detect any traces of delamination. A fact that surprised us, but was obvious to the manufacturers. As far as strength loss is concerned, as already mentioned, there were some differences among the tested samples. The extent to which they can affect the durability of the profile cannot be unambiguously judged by these numbers. But one thing is for sure: the fewer differences in performance before and after the test a certain fabric had, the more wear-resistant the sail made of it and the more optimal its profile. And in the end This test reflects the current state of development of sail fabrics from new cruise laminates: reliable sailing fabrics for cruising yachting that maintain long-term profile stability and make yachting enjoyable - all at prices that become more affordable every year.

Text: Michael Bohmann

08.01.2013