The world of ropes is much more full o variations than we might think. When we enter in the territory of racing ropes, things get even more complicated. The ropes for a sailboat seem at first glance all the same except for the colour. Nothing could be that far from reality. Some ropes have truly remarkable technical properties. Others are not quite as noble and we need to understand the differences.
Ropes, with some exceptions, are all made up of a core and a cover. The basic lines for cruising boats are often made with a polyester core and cover. Racing ropes mostly have a Dyneema ® or UHMwPE or HMPE core – which is to say the same thing. The cover, on the other hand, is usually a mix of two or more fibres where polyester is used to create the range of colours. The “noble” fibres used in racing lines usually have a limited range of colours.
Racing ropes: the world of noble fibres
Noble fibres distinguish themselves from common polyester for characteristics such as resistance, stretch and melting temperature. In fact, a polyester lines can be cut with a hot knife and finished with a lighter. For many of the high performance fibres this would not be possible. The melting point of Vectran™ is 350°C, that of Nomex® is 350°C – they are not even yet aramids. For aramids such as Technora®, Kevlar®, Twaron® we reach 500°C for Zylon® (PBO) at 650°C.
Among the high performance fibres everyone knows Dyneema®, this is just a registered trademark of the DSM company. Saying Dyneema is like saying Sellotape (a brand) instead of sticky tape. Dyneema is in fact composed of fibers of UHMwPE (ultra-high molecular weight polyethylene) or HMPE produced by Dupont. UHMwPE is 15 times stronger than steel and 40% stronger than many aramids of the same weight. This makes it an extraordinary fibre for making racing ropes.
HMPE also has extraordinary properties in terms of resistance to abrasion and chemicals. However, its melting point is just 150 ° C, even lower than polyester which melts at 260° C. For this reason, most racing lines have a Dyneema core (UHMwPE / HMPE) and a mixed fibres cover. This is to remedy the fact that in many applications, such as spinnaker sheets, a low melting point would be a problem.
Cruising ropes
For cruising ropes, the extraordinary holding properties and very low stretch of Dyneema are often useless. If, for example, we have Dacron sails, therefore able to stretch with every gust of wind, the HMPE rope becomes a bit wasted. On the other hand, when we have a sail that is also built with Aramids such as Carbon and Kevlar® fibres, we have no stretch. If we used a Polyester halyard for a noble fibres sail, it would be the halyard that “pumps” and stretches in a gust.
With a Dacron sail, on the other hand, the lengthening of the halyard and the sail are comparable, however they add up. In addition, both the Dacron of the sail and the Polyester of the rope stretch when left under tension. This lengthening over time is called creep, which differs from stretch, which is the instant elastic lengthening. So with polyester ropes and Dacron sails we have to be much more careful when we return to port not to leave everything in tension.
The typical example is that of the halyard of a furling jib. Many, once the sail is hoisted, tighten the halyard and do not touch it for the whole season. On many cruising boats the genoa halyard is not even led back to the coachroof winches. However, it would be good to remove the tension from the halyard when the boat is not in use, due to the creep the sail and rope will lengthen over time. Obviously this is nothing serious for the line, but the sail with a stretched leech will slowly lose its shape.
High tenacity polyester
Speaking of polyester, we cannot make a bundle of all fibres. In fact, even polyester can have very different properties depending on its quality. Polyester is part of that family of plastic materials made of polyethylene terephthalate. These include Sustadur Pet, Zellamid 1400, Arnite, Tecapet, Impet and Rynite, Ertalyte, Hostaphan, Polystar, Melinex and Mylar films, and the Dacron, Diolen, Tergal, Terital, Terylene and Trevira fibres.
It is also indicated with the abbreviations PET, PETE, PETP or PET-P. The first polyethylene terephthalate fibre to be patented is Mylar, in 1943. PET plastic bottles are a 1973 patent. PET can therefore be transparent to make a film such as Mylar, or opaque to make a woven fibre to obtain Dacron. With reference to ropes we simply speak of PET but here too a world opens up.
The measurement of the density of the material expressed in grams per kilometre will inevitably indicate its final holding power. This density is measured in dTex, what we call “deniers” in other fields of yarn and fabrics. The greater the dTex grading of the single fibre, the greater the weight per meter and the breaking load of the finished rope. We therefore refer to high tenacity PET or HT (High Tenacity) for dTex values beyond a given threshold. So not all PET lines are the same and not all Dacron sails are the same!
Pre-stretched polyester
As long as we talk about polyester, we must be aware of the poor elongation properties of this fibre. At its breaking point, PET can reach a stretch equal to 12-15% of its length before tearing. Think, this is half the stretch of a Nylon fibre. Material that we find in our spinnakers and gennakers where the stretch actually absorbs and distributes the gusts. The actual stretch of the finished rope can be significantly reduced during the processing phase.
The elongation of the polyester over time is called creep and takes place by leaving a line under tension. However if we apply a programmed tension during the spinning of the fibre that we will use to weave the finished rope, it will have a reduced residual elastic stretch. This is why we speak not only of high tenacity PET but also of pre-stretched PET. Combining a high initial density that has also been pre-stretched we will obtain a PET rope with better properties.
However, neither stretch nor creep can be completely eliminated. But, it is important to understand that there are very low quality polyester lines even for a cruising boat. I realise that the price will not always help you make the choice. There are low quality products sold at the prices of completely different rope. Unfortunately, you will realise this at your expense as you find yourself having to continually which in a rope that continues to stretch and that will ruin quickly.
Evolution of cruising ropes towards racing ropes
Over time, therefore, the cruising ropes have changed a lot. Even among those in polyester, the stretch has been greatly reduced and the resistance has increased. However, to make step up in quality we are forced to change fibres. If, as far as the cover is concerned, it is rare to find anything other than PET, the core of the rope can vary in the cruising world too. If you think of a hoisted sail, on one side you have all the stretch of the sail.
This is still made of polypropylene terephthalate (Dacron) even of the best quality, like the one produced by Bembridge. On the other hand, you have the halyard which, although pre-stretched and with high tenacity, will still have residual stretch. The sum of the two components certainly does not help the shape of the sail in a gust. As wind pressure temporarily increases, the simultaneous lengthening of the halyard and luff will carry the camber of the sail aft making it less efficient upwind.
Dyneema was invented in 1963 but marketed by DSM starting in 1990. Another well-known brand that preceded Dyneema is Spectra. Many still today talk indifferently of Dyneema and Spectra, and to be honest they are both UHMwPE fibre ropes. However, even in the world of UHMwPE there are distinctions. In this case the unit of measurement is the atomic mass of the UHMwPE called Daltron. Many years ago also in the cruising world and especially in the racing ropes one saw the first ropes with a Spectra core.
Racing ropes: Dyneema and other UHMwPE fibres
Without going into too much technical detail, let’s say that Spectra is to Dyneema as a low quality Polyester is to a high tenacity one. Without speaking of atomic mass we can limit ourselves to making comparisons on the breaking loads between Spectra and Dyneema to see the superiority of the second. However, things get further complicated, even DSM that produces the Dyneema has introduced gradations. So you will hear about Dyneema SK75, SK78, SK99.
Since this is a proprietary measure used by DSM, not referring to any unit of measurement in physics, unfortunately it helps us little in making comparisons. In other words, when we have a UHMwPE line of a brand other than Dyneema in our hands, how do we compare it to DSM’s Dyneema? For simplicity, it is best to compare the breaking loads of the braids with the same diameter. From this exercise it is clear that the Spectra does not reach the breaking load of an SK75 Dyneema braid. Other brands and products such as Southern Ropes’ Super-12® exceed the specifications of the SK75.
Therefore, when comparing the cores of two racing lines, if they are UHMwPE (also called HMPE), you will need to compare the braking loads. That is, just because a line says Dyneema instead of HMPE or UHMwPE doesn’t mean it’s better. Dyneema has simply become so well known that it replaces the name of the fibre that constitutes it. However, we have seen that those that have been sailing for long still speak of Spectra. In the end we all talk about UHMwPE or HMPE with better or worse properties.
Racing ropes: UHMwPE core treatments
The UHMwPE fibre can be treated before becoming a braid, a bit like PET which is pre-stretched. In the case of UHMwPE or HMPE there are two treatments that further improve its properties. The first is a hot pre-stretch process often referred to as HPS (Heat-Pre-Stretch). The second treatment is a protection with a polyurethane resin often indicated with PU Coating.
The HPS treatment reduces both stretch and creep of the line. The PU Coating in addition to protecting the braid from fraying makes it more compact and easier to splice. The ease with which UHMwPE splices is one of its greatest strengths. When you find a braid treated with PU Coating, the work is further simplified. The PU coating is particularly important where we leave the core uncovered. The treatment prevents it from snagging and fraying.
So when you go from a cruising rope to a racing one, the first change is the core. On a racing boat, with racing ropes, there are few applications where we find lines with polyester cores. As for the cover, we will now see how the reasoning is even more complex. If the superiority of the core in UHMwPE compared to PET does not raise doubts, for the cover we have to put together various considerations, from use to price.
Racing ropes: the cover
Why add a cover to a racing line if the UHMwPE, be it Dyneema or another brand, is so performing? The melting point of UHMwPE is only 130 ° C, worse than polyester melting at 230°C. Furthermore, the PU Coating treatment makes the UHMwPE line very slippery. Perfect for sliding in a low-friction ring or thimble but absolutely not suitable for use in stoppers and winches.
If you’ve ever broken the cover of a rope with a Dyneema core, you’ll know what I’m talking about. The HMPE braid cannot be stopped either in a stopper or in a cam-cleat. And, if we used it uncovered on a winch it would have bad grip. That is, we would have to give a lot of turns on the drum for this to take hold. However, even if we managed to tighten it with the winch, we would not be able to block it in the self-tailer, effectively making the line unusable.
To all this, we have to add the heat factor, as friction could heat the line until it melts. For example, if we kept a line in pure Dyneema with several turns on the winch as a spinnaker sheet, at the first serious ease out it would melt. The friction on the drum and the many revolutions would mean that the temperature would easily exceed 130°C. So, while HMPE represents the perfect core, it represents the worst cover where we need grip and heat resistance.
Racing ropes: clutches
In order for a line to be locked into a clutch, we will need to have a line composed of core + cover. In a lot of applications, it may seem strange to you, but a good HT polyester cover is all you need. A quality polyester still costs very little compared to alternatives, especially if we think of the entire length of the rope. The point where the rope is stopped often represents a very small section of the line.
For this reason, on many racing boats we see how the whole section that will never reach clutch left uncovered. This is done to reduce the overall weight of the rope, moreover HMPE has a better resistance to UV rays than Polyester. In other words, where the cover is not needed, it may be removed, it adds nothing. The ropes are always sized with breaking loads referring to the core alone, the contribution of the cover is often almost irrelevant.
So why are there other coves besides the plain polyester ones? Although PET is respectable in its properties in the long run it tends to wear out at the working point of the stopper/cleats/clutches. For this reason we can protect the working point without upgrading the entire cover for its entire length. Those who are familiar with splicing and have good dexterity can apply a protective cover on the work points.
Cost/benefit of protective covers
Logically it would seem the perfect solution, however there are contraindications. First of all, the work must be professional to avoid changes in diameter that prevent the rope from easily passing through clutches. Secondly, if we are talking about a mainsail halyard, we must have taken very precise measurements. In fact, in addition to the working point of the fully hoisted mainsail, we will have another three working points for each reef point.
It is clear that if we do not do the work we have to take into account the complications of placing the order. In addition to having to provide all accurate measurements we will have to pay for all the splices. The exercise could erode the savings compared to a better cover along the entire length of the rope. If you don’t want to take this step, I’ll give you a much more trivial piece of advice. Buy the line 2-3 metres longer than needed then periodically cut and re-tie the halyard shackle.
In this case it is better not to have the a splice at the shackle because you will not be able to cut a small section at a time. If you repeat the operation at the very first signs of rope fatigue at the wear points, you can slide everything by 30-50cm. By doing this you can extend the life of the rope by several seasons. This is particularly suitable for halyards where there is no “dynamic” use of the line on the winch. For sheets we must also take into account grip and friction related temperature.
Racing Ropes: the winches
Sheets heat up when they are eased out. Not only sliding between our fingers but also on the winch drums. For all sheets we have two additional considerations which are related. The grip on the winches (which is ultimately given by the friction) and the heat resistance. If you’ve ever been on a racing boat with heavy workloads you will know what I’m talking about. If you take a low quality line and use it as a spinnaker sheet at the first big ease out in a gust the rope will melt on the winch.
This is because, as mentioned, the melting temperature of PET is 230°C. This is sufficient on cruising boats but not for racing ropes. In this case, to improve the properties of the rope, we start with a melange of PET + Aramid or 100% Aramid covers. Obviously, as the share in Aramid (noble fibre) increases, the price and performance also increase.
If we wanted to increase the grip only we find covers in PET + Cordura. If it is true that it improves the grip on the winch, the melting point of Cordura is only slightly higher than that of Polyester. It is therefore fine as a solution for the Genoa sheets but not for the spinnaker sheets. However, the use of Cordura is passing somewhat in disuse due to the difficulty of splicing the Cordura covers. Kevlar® remains very common but undoubtedly it is Technora® that is becoming even more used.
Racing ropes: the top of the range
On most racing boats the spinnaker sheets are melange with a Kevlar® or Technora® component. On top-level boats we find 100% Technora® or even Zylon® (PBO) covers. We are talking about ropes that we will never find even on a Class40 and instead we see from the TP52s to the America’s Cup.
Racing ropes: your hands
Some racing ropes are easier to handle than others, not only on dinghies but also on larger boats. For example, the spinnaker sheets on a Mini 650 are often worked by hand up to a certain wind intensity. On larger boats we have control lines such as barbers, cascades, track control lines and others which are simply adjusted by hand. For these you need to choose a cover that has an excellent grip on the hands, to prevent them from slipping and burning you.
To obtain racing rope that are easy to work by hand, special processes are carried out. This makes the ropes slightly “hairy” or with a texture that is easily manageable. It becomes clear that for every racing rope we have to consider many factors. Stretch, creep, grip in cleat and clutches, grip on the winch, heat resistance, possible grip on the hands.
The important thing is to choose the right racing rope for the right application. And, if we are on a cruiser, we can rely on high quality lines in high tenacity pre-stretched polyester. However, with the improvement of technology even in the cruising sector, some upgrades cannot be ruled out. Fibre laminated sails have now become common even on boats that are not really pure racing ones. In this case we will probably have to change the related halyards as well. If we start to do some races, a better cover for genoa sheets and spinnaker / gennaker sheets is not to be excluded.
Racing Ropes – Mixed covers with colour point
