Farr Ropes UK

Choosing Your Rope Technical Information

ROPES TECHNICAL INFORMATION

Purchasing a new ‘rope’ should be a simple process, however it can be confusing when there are so many alternatives on offer. Sometimes the terms used don’t often help your selection process.

Simply put, you need to be able to make the correct choice for your particular application, it is pointless purchasing a rope with a specification that is way in excess of what you need – you will be wasting your money, conversely buying an inferior rope will produce the same result.  

This particular section will hopefully provide you with some basic technical information covering some of the more popular ropes that we supply, and explain why we make certain recommendations for a variety of applications.

If you need further information just give us a call.

GENERAL OVERVIEW OF ROPES and TERMINOLOGY

Rope basically means “thick cord” and most of our ropes used in yachting, sheets, halyards, warps etc are manufactured with an  inner core and outer protective sheath, sometimes called braided rope, however the correct term is ‘kernmantle’  rope-  the inner core being the ‘kern’ and the outer sheath being the ‘mantle’ similar to climbing and mountaineering rope, although the particular characteristics can vary somewhat . For example if a climber takes a fall he needs to be arrested on a rope that is relatively ‘elastic’ thereby reducing the forces on the body, NYLON kernmantle rope is ideal.  POLYESTER rope on the other hand is not suitable, as compared with NYLON it is far less elastic with minimal extension.

Generally speaking NYLON kernmantle rope is 30% more elastic than comparable POLYESTER kernmantle rope. Given the basic difference in characteristics between the two it is clear both materials have advantages and limitations. For example NYLON is not suitable for halyards because it is more ‘elastic’ and will extend too much when under load, POLYESTER is the material of choice for such an application because it is far less elastic with very little extension.

DYNEEMA, often used in yachting ropes will extend even less than POLYESTER.

Other examples are mooring lines and warps, generally NYLON is used because being more elastic, it will absorb the energy generated when a vessel moves, POLYESTER on the other being far ‘stiffer’ will not absorb the energy as effectively as NYLON subjecting the vessel to unnecessary shock loads.

Textile lifting slings used for lifting cargo and boats are extensively manufactured from POLYESTER where elasticity or stretch must keep to a minimum. NYLON would be unsuitable as the slings would stretch and cause the loads to bounce and become unstable. For the same reason lifting slings for carrying loads beneath Chinook helicopters are POLYESTER and not NYLON.

In addition POLYESTER is more resistant to abrasion compared with NYLON so clearly there are sometimes advantages to be made in combining the two materials to generate the ‘best of both worlds’  Our DOCKLINE is such a product, the inner core being NYLON to absorb shock loads with a loose braided POLYESTER outer sheath offering better wear characteristics.

DYNEEMA and POLYESTER (Racer 3003) is another often used combination.

The Kern (inner core) can be made up of virtually straight parallel strands or a braided construction, more parallel strands reduce elasticity but is slightly stiffer, braided (basically meaning interwoven strands) is more elastic but is more flexible.

The mantle (outer sheath) is braided with a combination of strands, ropes that we supply are braided with either 32 or 24 braids. The number of braids will determine the feel and wear characteristics of the rope. Generally the more braids the tighter the weave and the stiffer the rope, less braids the looser the weave and more flexible the rope.

With our rope, combinations of materials are put together to produce the best product for a particular application. Unfortunately no one has yet been able to produce one rope that will do everything.

polybraid 32POLYBRAID 32, with parallel 3 strand core and 32 braided sheath, is the first choice for halyards with minimal stretch and a tightly woven sheath.  This produces a relatively stiff rope with good abrasion resistance which is ideal for use with load stoppers and clutches. Polybraid 32 is not best suited for applications where the rope passes through pulley systems or blocks i.e. mainsheets, kickers, etc.    A more flexible rope is required for these applications

polybraid24POLYBRAID 24 with a braided core and 24 braided sheath, this construction produces a rope with slightly more stretch than Polybraid 32 but with excellent flexibility, ideal when the rope has to pass through several pulleys or blocks such as mainsheets kickers etc without kinking.

racer 3003RACER 3003 is the optimum rope with minimal stretch recommended for halyards, when used in heavy demanding conditions on load stoppers and winches. This rope is constructed with a braided outer sheath with an inner and mid core.  The outer sheath is braided POLYESTER the inner core is 100 % DYNEEMA the mid core is braided spun polyester specially treated to increase the friction between the inner core and outer sheath. The finished rope is pre stretched and heat set to ensure minimal stretch.

dockline mooringDOCKLINE MOORING WARPS, the ultimate mooring rope for all conditions, no kinking, and no hassle tough double braided POLYESTER outer sheath with NYLON inner core.

GLOSSARY

DYNEEMA.

High Modulus Polyethylene is the collective name for Dyneema fibres.

This material is characterised by extremely high breaking strengths with minimal stretching. For example a rope of 10 mm diameter braided entirely in Dyneema will typically have a breaking strength of 10,000 kg. Not even extreme racing conditions require these strengths; the load on a genoa sheet on a 33 foot yacht in extreme conditions will rarely exceed 500 kg

NYLON.

Is the generic designation for synthetic polymers known as polyamides, limited applications when used in the manufacture of ropes due to relatively high elongation. Good for applications when shock loads need to be absorbed.

Typically a Nylon rope will stretch approximately 30% more at breaking point than a comparative rope made from Polyester 

POLYESTER.

The most widely used rope in the world, in UK sometimes called Terylene in USA called Dacron in Germany called Trevira, in the end they are all Polyester.

Polyester is a relatively heavy fibre with a specific gravity of 1.38 (it does not float) very resistant to sunlight and ultra violet light, extremely strong with minimal stretch, especially when pre-stretched during the manufacturing process.

Typically a polyester rope will only lose 10% of its breaking strength after 2 years of outdoor use, excluding cuts or severe abrasion.

 

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