All About Rope

With many new materials to choose from, let's look at the range of ropes now available.

The Introduction of Spectra, Kevlar and more recently Vectran has changed the way we rig our boats just as significantly as the introduction of Nylon and Polyester in the 1950's. But choosing the right rope from the bewildering election available is not as hard as it seems. Selecting the correct fibre is fundamental. Pick the wrong one and you will either end up with a rope that is inadequate for the job, or more expensive than it need be. In most applications high strength and low stretch are priorities. Don't go mad though; there are applications where a little bit of give can be a good thing. Anchor warps are the obvious example but there is a place for some shock absorption in other places too. Six materials are commonly used to make ropes. These fibres can be used alone or in combination to produce ropes of widely differing properties and price. The most common fibres are:

Polypropylene
A lightweight fibre that is also cheap. Farmers use it for bailer twine. From a sailor's point of view polypropylene has the great advantage of being less dense than water. Not only does it float, but it refuses to absorb water too. Unfortunately it is not very strong and doesn't offer much resistance to stretch. Left outside in the sun it deteriorates quickly. Polypropylene melts at a low temperature and it's easy to generate sufficient frictional heat to cause damage or failure.

Despite its many apparent weaknesses, polypropylene finds many applications on dinghies and yachts. Where it is necessary to have a large diameter rope for handling purposes polypropylene is ideal due to its low weight and minimal water absorption. Where strength is not an issue (eg dinghy mainsheets) it can be used alone while more demanding applications will use a high strength core inside a polypropylene cover.

Polypropylene's ability to float on water is, however, its most valuable attribute for the sailor. Used in applications from rescue lines to dinghy tow ropes it remains on the surface resolutely refusing to get dragged into propellers or lost under boats. While most users will be interested in the fine spun soft finished family of polypropylene ropes, dinghy sailors whose class rules require them to keep a tow line on board should look out for the harder finished rope intended for water-ski tow lines. Apart from being slightly stronger than the fine finished material, it traps minimal amounts of water between the fibres, keeping weight to a minimum.

Nylon
One of the original synthetic fibres, nylon has been replaced in many applications by newer fibres. Its combination of good shock absorbing properties, wear resistance and its imperviousness to UV light and chemicals still make it the fibre of choice for anchor warps and dock lines.

Polyester
If one were limited to just one fibre for all uses this would be it. It is strong, resistant to UV light and chemicals, kind on the hands and stretches just moderately when loaded. This is the fibre to choose in any application where ultimate performance or minimum weight is not absolutely essential.

Aramid (Kevlar, Twaron, Technora)
First into the market as a high performance fibre, Aramids were for many years the only viable high performance yarns. Offering about twice the strength of polyester and only half the stretch it found wide application on racing yachts especially in applications where weight saving was important.

Despite their impressive properties, Aramids do not make ideal ropes. Poor resistance to UV light can be overcome with careful construction and ensuring that the core is always covered and never exposed to daylight. Low breaking strength when knotted can also be overcome by always ensuring the ends are terminated in a splice, though this is not always a practical solution in real life. Problems with internal friction in the rope core have, however, proved to be the fibre's downfall. Repeated bending causes the strands of the core to rub together and this in turn causes friction damages. Unseen and undetected the core steadily gets weaker until one day, bang! Without any apparent explanation the rope breaks. Unsurprisingly, Aramids are not any longer widely used in sailboat applications.

HMDPE (Spectra and Dyneema)
Though it starts out life as something not much more complicated than the material that your supermarket carrier bag is made from, High Molecular Density Polyethylene is a remarkable material. In fact, the carrier bag provides a good example of just why HMDPE is so strong. Try this; lightly load a piece of supermarket bag in the main body of the material by pulling it between your fingers. It stretches easily and shows little strength. Now fill the bag with heavy groceries and lift it up. By some apparent miracle the all too thin looking handles stretch a bit before stabilising and supporting what can be quite a high load (yes, I know they split when you put too many bottles in). What has happened is that the molecules in the material making up the handle aligned themselves in the direction of the load during the initial stretching process. Thus organised they are much better able to support a big load than in their original random orientation.

The manufacturers of HMDPE exploit the phenomenon of molecular alignment to produce their super strong material. In the case of HMDPE fibres the alignment process takes place by means of chemical and mechanical processes during manufacturing rather than when you, the user, apply the load for the first time.

Unfortunately, the process is not quite perfect and this leads to a phenomenon known as 'creep'. Though the initial stretch of HMDPE is very low, if one leaves a HMDPE rope loaded for a long time it slowly but inexorably stretches, never to return to its original length. While this is not a problem in lines that are adjusted regularly it can be irritating in applications where stability is important (eg the main halyard).

In the early days, the very slippery surface of HMDPE gave rise to some problems with keeping the various parts of the rope stable. Highly loaded the core would slip inside the cover, leaving the highly loaded outer part well and truly shredded when used on winches or in clutches. More sophisticated manufacturing processes have largely alleviated the problem, though in winching and rope stopper applications the cover will likely as not still fail before the core.

These small problems aside, HMDPE is an excellent material for ropes as it is light enough to float, takes up no water and offers a very high degree of UV light and chemical resistance.

Vectran
Latest in a line of high strength materials, Vectran looks like an almost perfect rope maker's material. It is as you might expect frighteningly expensive.

Vectran takes the molecular alignment principle used in making HMDPE one stage further, using electric currents to align the molecules in what, for the technically minded, is called a napthalene-based thermotropic liquid crystal polymer. In English, this is a very strong fibre with minimal stretch and no propensity to creep. Excellent abrasion resistance is complimented by good fatigue strength so sudden failures such as those seen in Aramids should not be a problem. On the downside, Vectran does not exhibit very good resistance to UV light so needs to be used inside a cover.

Natural Fibres
Used only by the traditional boating fraternity, ropes made from natural fibres are now virtually impossible to obtain. Several substitutes exist and various manufacturers have synthetic ropes dyed, spun and finished to look like natural hemp.

Types of construction
Selecting the correct type of rope construction is the next decision. Though in many cases there may appear to be little choice there are subtle differences between the various construction systems employed by the various manufacturers.

In the beginning all rope was laid or twisted from individual fibres. Originally performed on rope walks, long narrow areas where the rope could be laid out full length. Rope making was essentially a manual process. The length of rope that could be produced was limited to the length of the rope walk and production of large ropes was complex and time consuming. Individual fibres were made into yarns; these yarns were twisted into threads, these threads were in turn twisted into strands and finally the strands were twisted together to form the rope. The twist in each thread and strand served to hold the rope tight and a whole tradition of knot work and rope craft was developed to utilise the properties of laid rope. Machine manufacturing followed and with it came the ability to produce infinite lengths.

Widely used for the manufacture of nylon rope for dock lines and anchor warps, laid rope is still a very cost effective solution for ropes where ultimate handling characteristics or flexibility are not key issues.

Laid rope is simple to splice or knot and offers good strength. The process does produce a stretchy material with a hard and nobbly finish that is neither free running nor easy on the hands. This led to the development of braided ropes which though produced in short lengths and at great expense by hand can only be made in economic quantities by machine. While there are a few ropes made simply from a single braid - polypropylene is often made up using this construction - the majority of braided ropes consist of an outer cover and an inner core. Similarly there are some super-specialised fourplat construction nylon ropes designed specifically for use as anchor lines. Soft and flexible they offer a better handling though slightly more expensive alternative to laid equivalents.

The core and cover of braided ropes are often of different materials allowing optimum properties for each. There is no reason why the core and cover should be of the same construction. The core for example may be a twisted design or constructed from a simple eight plait construction while the cover is a soft 16 plait design. In some instances there may even be three layers with an intermediate layer between the main load bearing core and the wear resisting outer cover. Generally used in the manufacture of ropes with a HMDPE core the intermediate layer helps to stop slippage between the core and the cover.

Braided ropes offer an inherently lower stretch design, a softer feel and less friction. With the exception of anchor warps and dock lines virtually all ropes used in modern sailing have some kind of braided cover while many also use a braided core. To achieve a good balance between flexibility, cost and ease of use virtually all manufacturers produce their covers in 16 plait form, using 16 individual yarns for the cover. In the smaller sizes the number of yarns is sometimes reduced to eight, and though more economic to produce and harder wearing these ropes are noticeably less flexible and harder on the hands.

Where combinations of material are used, it is reasonable to expect that the properties of each will be reflected in the finished rope. For example, an HMDPE core with a polypropylene cover will be very light and very strong but will not exhibit good abrasion or UV resistance. The same core within a polyester cover will provide better abrasion resistance but at the expense of increased weight. The ratio of core material to cover thickness will also have a substantial impact on the performance of the finished rope. Take two different nominal 8mm HMDPE ropes.

One may have a 6mm core and a 1 mm cover while the the other has a 5mm core and a 1.5mm cover. Though they look the same the one with the 6mm core will be 40 per cent stronger. Unsurprisingly the one with the thinner core will almost certainly be the cheaper one.

Though requiring a different technique, braided ropes are not significantly more difficult to splice than laid rope. You will however need some special tools and a set of instructions for your particular rope. Beware that the tools and techniques that are suitable for one make of rope may not be directly transferable to another make.

Size?
Having selected a fibre and the most suitable construction, it remains only to determine the size required. This is not always as easy as it sounds. Calculating the loads on sailing boats is a notoriously difficult thing to do and it is as well to remember they are not often as big as you might imagine. On bigger boats the designer may be able to give some guidance. Smaller boats need some simple rules.

If it is a rope you pull on, it's a fair bet that the load will not be more than about 20kg, perhaps 50kg top whack if you are a big man. Multiply this up through the various purchases and it's easy to work out what the load is at any given point. Take care though with lines that are cleated Off. It's easy to pull the kicker in with one hand when the sail is flapping but just think what the load might be when it's locked off and the boom end smacks into the back of a big wave. That's when things break.

Alternatively look at the size of blocks you are using. Check the manufacturer's data to see what the breaking load is. Assuming the existing blocks don't break, it would be wise to choose a rope with a similar breaking load. You will probably be surprised just how small you can go. Smaller sizes bring lots of benefits. Not only are they cheaper and lighter but they take up less (weight increasing) water when wet and run more freely through the blocks.

Spectra or Dyneema?
Neither actually. Spectra and Dyneema are simply different brand names for the same thing made by two different companies. A marketing arrangement between the two companies means that only Dyneema yarns are sold in Europe. That doesn't mean you can't buy Spectra rope here in the UK... but if you do it will have been manufactured outside Europe and imported.

Similarly Dacron is a trade name for DuPont Polyester while Aramids are variously known as Kevlar, Technora and Twaron depending on their source.

Tapered lines -- Where once a simple piece of rope cut and whipped at each end would suffice for most jobs, no modern racing yacht or dinghy is complete without a selection of varying thickness ropes. The theory is simple; make the rope as thin and light as possible where it does not come into contact with hands, winches, cleats or clutches while building it up to provide sufficient wear resistance and handleability where required. In practice there are a number of ways the job can be accomplished.

Strip the Cover -- Here the outer cover of the rope is removed to expose the core. This only works with ropes of mixed construction where the core provides almost all the strength and the cover simply provides protection and additional thickness. In practice this technique is used almost exclusively with HMDPE cored rope. At high wear points such as winches and cleats or where the rope comes into contact with your hands, the cover will need to be retained. The ends of the cover need to be tucked neatly inside the core and whipped in place. A stripped cover also simplifies the splicing process for most Dyneema lines and for this reason you will often see apparently bare ends where ropes are spliced into a shackle.

Add a Cover -- High load areas can just as easily be built up using an additional layer of cover. Again the end will have to be tucked inside the main body of the rope and secured in place. This method allows a wear resistant cover to be introduced over a polypropylene rope at the appropriate point, for example where a halyard regularly passes through a clutch.

Bulk Up the Core -- The neatest solution is also often the most difficult to execute, especially in the middle of a long length. By introducing an additional core into the rope it is easy to make it thicker while at the same time keeping the outer cover smooth and free running through blocks etc. If you can find a rigger who is prepared to do this kind of work it will often prove the best solution for spinnaker sheets and other lines where the change in diameter has to pass round a block.

Pre-Tapered Sheets -- Several manufacturers make rope where the thickness changes mid-length. Extra yams are introduced at the weaving stage to make the rope thicker at one end than the other. These offer a very neat solution always provided you can buy the exact combination of lengths and thickness you require.


How Much Line Do I Need?

Halyards. Add the height of the mast, plus the length of the headstay, plus the distance to the winch, plus about 10' for a tail.

Jib and Genoa Sheets. For the working jib you need just slightly more than the length of your boat for each sheet. For genoas, figure 1 1/2 times boat length.

If you have a staysail, add in some extra length to accommodate the staysail stay.

Mainsheets. Your best bet is to remove the existing sheet and measure it for a replacement, since there is so much variation in purchase ratios and attachment points along the boom.

Spinnaker Sheets should be two times the length of the boat, plus about 4' for both eye splices.

COMMON ROPES

CAJUN ROPES
XLE Top-quality, double-braid polyester. UV Stabilized cover, low elongation, abrasion resistant 3/8" - $0.46/FT
XLE-Z-FEEL Double braided polyester. Manufactured with an easy grip polyester yarn. 3/8" - $0.65/FT
SPECTRAŽ Outstanding toughness and extraordinary visco-elastic properties allow SpectraŽ fiber to withstand high-load strain-rate velocities 3/8" - $1.76/FT
NEW ENGLAND ROPES
STA-SET® Top-quality, double-braid polyester 3/8" - $0.64/FT
STA-SET X™ A high strength, low stretch line made with a patented polyester parallel core with a braided cover of blended spun and filament polyester. The strongest and lowest stretch polyester line available. 3/8" - $0.80/FT
STA-SET X PLUS™ A Vectran and multifilament polypropylene core, with a polyester cover. Minimum stretch and low creep. 3/8" - $1.15/FT
REGATTA BRAID™ A 12-strand single braid of spun and filament polyester. Flexible and easy to handle. White. 3/8" - $0.55/FT
T-900™ This line has a mix of Spectra and Technora in the core with a polyester cover. The mix gives the line low stretch with the least possible weight. 3/8" - $2.04/FT
ENDURA BRAID ™ Endura Braid is the latest double braid high tech rope. This double braided construction consists of an Endura 12 core and a durable, twill polyester cover for increased abrasion resistance and better handling. The core is vinyl coated to increase durability. 3/8" - $2.43/FT
STA-SET X LITE™ Spectra parallel core with a polypropylene cover. Due to its unique construction resulting in good stretch resistence, it's great for spinnaker sheets, topping lifts, and foreguys. 3/8" - $0.96/FT
SAMSON ROPES
ULTRA-TECH™ 100% braided Technora core with a polyester cover. Low stretch and great for halyards. 3/8" - $1.87/FT
WARPSPEED™ Spectra core with a dacron cover. Very low stretch, but Spectra will creep slightly when loaded beyond 50% of its tensile strength. 3/8" - $1.89/FT
SPECTRON 12™ 100% Spectra single braid with a urethane coating. High strength-to-weight ratio and great abrasion resistance. Doesn't absorb water; some creep. Spectron 12 is slippery, it's usually covered at the cleat, stopper, or winch. 3/8" - $1.77/FT
XLS™ This top-quality double braid polyester has been around for years. Great for sheets and control ines. 3/8" - $0.60/FT
LST™ Polyester cover, polyester core. A general-purpose, low-stretch double braid. 3/8" - $0.50/FT
YALE CORDAGE
ARACOM T 100% Technora braided core with a polyester cover. 3/8" - $1.19/FT
PORTLAND BRAID High tenacity polyester. 3/8" - $0.48/FT
CRYSTALYNE™ A Vectran core coated with Maxijacket urethane and with a polyester cover. This is one of the lowest stretch of any of the high-tech lines -it's very strong and has little creep. Moderate abrasion resistence. Excellent halyard material. 3/8" - $2.28/FT
YALELIGHT™ Braided composite core of Spectra and multifilament polyester and a polypropylene cover. Repels water; ideal where light weight and low stretch are critical. 3/8" - $1.41/FT
VIZZION™ Braided composite core of Spectra and filament olefin, with a braided polyester cover. 3/8" - $1.59/FT
MARLOW ROPES
MARLOW BRAID All polyester line. Size for size, is 40% stronger than conventional braid. 3/8" - $0.59/FT
EXCEL MARSTRON The lightweight floating mainsheet for small dinghies. A braided core and smooth profile 16 plait braided cover of polypropylene. 3/8" - $0.61/FT
EXCEL PRO Low-stretch polyester core with a smooth cover. Excellent flexibility around tight radii turns. 3/8" - $0.48/FT
MARSTRON 8 plait, highly visible, floating line. 3/8" - $0.59/FT