All about rope - Part I

What kind of lines are suitable for YOU SW

Dyneema-Yacht-Rope © SW

Spectra/Dyneema: These are both trademarks for high-molecular weight high modulus polyethylene (HMPE) fibre. Spectra is a US-sourced product, while Dyneema comes out of Japan; Spectra has virtually become a generic term for these products, and it’s not uncommon to see a Dyneema-based line referred to as “Spectra”.

They are most commonly available as “double-braid” products, covered with a high-tenacity polyester fibre sheath or 'jacket' for easier handling.

Applications include halyards, sheets, guys, runners, downhauls, outhauls, etc.
HMPE fibre is tremendously strong; an HMPE line is 10 times stronger for its equivalent weight than steel, and it has minimal (although some) stretch or creep.

These low stretch and high-strength characteristics make Spectra/Dyneema suitable for halyards, jib and spinnaker sheets, keel uphauls on trailer sailers, and similar applications.

Advantages include much easier handling (and replacement, with a knot or splice sufficing in place of the swaged eyes required on wire ropes), and equivalent or greater strength, according to Phill Bate, of rigging specialist Riggtech: 'These ropes also have very good abrasion resistance.

Sometimes just the core goes through the sheave © SW

'Frequently you'll see areas where a rigger has removed the polyester jacket so it's just the core going through the sheave or spectacles, as these synthetics can handle the abrasion better than the polyester jacket,' he says.

However, high-tech synthetic lines as a rule don't like going through tight curves, so they tend to need larger diameter sheaves with wider profiles when using them in place of wire halyards.

Otherwise, the result can be early fatigue and unpredictable breaking.

'In my view, HMPE lines require a sheave diameter at around eight to 10 times that of the rope – the larger, the better,' says Bate. 'If you are replacing a wire halyard with rope, it’s a good idea to replace the sheave at the same time, and most important to ensure all exits from the mast are smoothed off. This minimises the chances of wear and fraying on sharp edges.

'Sheaves for ropes have a flatter groove than those for wire, plus over a number of years, the wire halyard is likely to have cut a deeper groove into the sheave as well as sharpening its edges,' he says.

HMPE single braid © SW

“Single-braid” HMPE products are, as their name suggests, braided HMPE alone, and are designed as a wire replacement.

Advantages include high strength, minimal stretch, good abrasion resistance and very light weight. They are generally only available through professional riggers and spar makers.

Single braid products are often used aboard racing dinghies and sometimes also used as trapeze wire replacements, for control lines, high-load strops and tackles.

Single braid blends of fibres such as Dyneema/polypropylene are also becoming more widely accepted for use as lightweight or lower-diameter sheets, control lines for their fast handling characteristics and trailer winch ropes (if you use that blue trailer winch rope for your trailer/sailer or stinkboat, that’s a Dyneema single-braid product).

Vectran © SW

Vectran:
This is the trademark for polyester-polyarylate, also known as “liquid crystal fibre”. Again, it’s a high-strength, low-stretch line – within even less stretch than HMPE lines, making it more suitable for halyards.

Applications include halyards, control lines, running backstays, sheets, genoa car controls, topmast backstays, leech lines, after guy/braces, vangs, checkstays and outhauls.

It's generally been argued that Vectran has less UV resistance than HMPE, so it’s sold as a double-braided product with a high-tenacity polyester cover.

However, Bate doesn't necessarily agree. 'Coatings that have been developed for Vectran these days give it very good UV resistance. We reckon it's even better than Spectra,' he says.

Applications on a cruising boat include anywhere that heavy steel wire can be replaced with a lighter, equally strong and more user friendly product giving an advantage for the end user, whether in performance or ease of handling – although Bate believes Vectran is probably a little expensive for most cruising boat applications.

However, some sailmakers are also offering Vectran luffs on storm jibs (staysails), particularly on boats with a furling jib.

One of these is Ian Short, of Ian Short Sails. Rather than unfurling and removing the jib or genoa in storm conditions, the sail is simply furled, and the storm jib shackled on at the foot of the forestay then hoisted with the jib halyard.

'Vectran's minimal stretch and high strength make it suitable for this high-stress application,' says Short.

Double-braided polyester: These ropes have been around for many years, and are not regarded as 'high-tech' lines.

Double-braid polyesters remain commonly used for cruiser and cruiser-racer running rigging applications such as genoa/jib sheets, mainsheets and traveller lines.

While these lines are durable and easy to handle, they do tend to absorb water and are heavy.

However, some argue their time is drawing to an end because of the advantages of the stronger high-tech synthetics.

Bate sees them as a 'budget rope' that is on the way out. 'Polyester is really very stretchy rope, and you should never use it in a stretch-critical application such as for a spinnaker halyard or brace.

'Take the example where you've set your spinnaker pole 2 feet from the forestay; I'd bet my bottom dollar that when a bit of pressure comes on – say a gust up over 20 knots – that pole will be hard against the forestay.

'In my view, it's too stretchy, it absorbs water, and it's heavy,' he says.

But for many cruisers, double-braid polyester is likely to remain the rope of choice for many years, according to Bruce Clark of yet another rigging company. 'Many cruisers are happy to have a bit of stretch in their sheets and lines. Because the boats are often fairly heavy and not super responsive, a bit of stretch eases the loads on the boat and crew,' says Clark.

Switching to a Spectra/Dyneema rope allows you to drop several millimetres in diameter (say from 16 mm to 12 mm); the rope's easier to handle and there's less friction through the blocks.

Other types:
Double-braided polyester, HMPE and Vectran-based lines, along with the traditional nylon and polyethylene lines, are likely to cover most cruisers’ cordage needs.

High-performance racers are now using synthetic lines based on poly-paraphenylene-2 6-benzobisoxazole (PBO or Zylon) as replacements for standing rigging and halyard runners.

However, their expense and maintenance requirements mean they are not suitable for most cruising yacht applications.

Having said that,high-end cruising yachts (100 ft plus) being built in New Zealand are now using PBO standing rigging in place of running rigging.
'The last America's Cup campaign really changed the upper end of the market,' says Phill Bate of RiggTech. 'Because of the reputation of NZ sailors and boat builders, there's a lot of building going on there, and they are really pushing the boundaries.

'Certainly the use of high-end synthetic ropes is increasing, particularly at the top end of the market. Ultimately, it all depends on your budget,' says Bate.