Boat rigging: a guide to switching to composite
Are you considering changing your boat’s rigging to composite but are confused by the options? Sam Fortescue examines the pros and cons of various solutions
âLike the switch from wooden spars to alloy spars after WWII, we are moving to carbon spars and composite boat rigging for cruise ships,â says famed surveyor Kim Skov-Nielsen. âWe are living on the cusp of a major shift towards all-composite platforms. “
Four broad options for modern boat rigging range from Ultra High Molecular Weight Polyethylene (HMPE) to Aramid, PBO (Poly-Benzoxazole) and finally Full Carbon.
Compared to steel, all of these options offer a much lighter weight, which reduces pitch and roll in the sea. Greater rigidity of the rig improves the trim of the sail and transfers forces more efficiently, by especially in lighter winds. And synthetic fibers resist the invisible fatigue that undoes stainless steel systems.
On the other hand, the cost can be two to four times higher than that of the rigging of the wire boats, and the repairs are delicate outside the large nautical centers. Some fibers degrade quickly with exposure to UV or moisture, so damage to the coating will shorten the life of the stay.
Carbon in particular is also sensitive to side impacts. Each sailor will evaluate the options differently, but here are your choices:
HMPE (Dyneema / Spectra)
Dyneema and Spectra have extraordinary toughness and very low weight, but many riggers are reluctant to use it on cruisers because they consider it too elastic.
However, US specialist Colligo Marine says it’s just a matter of choosing the right grade of Dyneema and sizing it correctly. âA lot of people mistakenly sized the Dyneema for breaking strength and ended up with a very stretchable rig,â says John Franta of Colligo Marine. âThe stretch is a function of the cross section, so all you have to do is choose the right diameter for your application. “
This means that you are going to end up with a Dyneema line that is larger than your original yarn, causing slightly more drift, albeit at a fraction of the weight. For example, the 8mm wire that is standard on many 40ft cruisers should be replaced with 11mm Dyneema in a Colligo Dux system, but this should slip less than 3mm per year.
The variety of HMPE you use is also vital, as the strands in the line line up with the load.
âA 50-foot-long backstay made from normal Dyneema can grow to a length of 4 to 6 inches,â says Franta. This is why Colligo only uses hot-drawn Dyneema SK75, where the fibers are already very tightly aligned, instead of high-tech grades like SK99 and DM20.
A typical HMPE seatstay is spliced ââaround a lightweight aluminum thimble, which easily fits the traditional fork at the end of the bridge. You will need a special Colligo stemball aloft fitting or a CheekyTang, spliced ââinto a loop at the top end of the shroud, then bolted through the mast.
Friction and UV are the main enemies of Dyneema platforms. “It’s easier to cut and has a low melting point of 100 Â°, so a fast moving sheet could cut it in seconds,” warns Marlow’s sales manager Paul Honess. Colligo is PVC wrapped for this reason and is expected to last eight to 12 years without incident.
Aromatic polyamides (Kevlar is a registered trademark of Dupont) have low creep and high toughness, but they also resist abrasion well, which is important when pitching and rolling across the Atlantic, for example. .
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Aramids are five times stronger than weight-for-weight steel cables, but those multiple drops if the fibers get wet and UV light quickly damages them, so the cables need to be well sealed and protected.
OYS has been designing Kevlar backstays with stainless steel terminations for years and recommends a maximum working load of 40% of rope breaking tension to minimize creep, so aramid shrouds are a bit larger than the equivalents of the rods.
For example, an 8.5mm cable can withstand loads of 3000kg while weighing only 60g per meter. Compare that to Nitronic, where the 7.5mm rod with the same workload weighs 350g per meter. âYou size it for stretching, and then you get a much higher safety factor,â says Robbie Sargent of OYS. âIt’s flexible and you can roll it up, plus it’s relatively competitive in price and looks smart. Aramid is for all intents and purposes a cruise product.
Black jacket is standard, but lighter custom colors may reduce the UV resistance of the cable. OYS does not recommend using aramid shrouds on a monohull. âThe rod and wire are pretty resistant to bullets in terms of friction and physical damage,â says Sargent. âThe composite rig is much more fragile. A medium-sized oyster or swan has solid slats – can pass through the fabric sheath very quickly. ‘
The material works well in backstays and backstays, inner skids and shrouds, or as a side rig on a multihull, he adds.
Aramid Rigging, based in the Netherlands, uses an advanced endless winding machine for tailor-made stays. The fiber bundle is in turn wrapped in heat shrink film to keep water out, then an outer protective braid with a UV resistant coating. The metal lugs at each end are then sealed inside a polyurethane molding, eliminating a common point of failure for steel platforms.
Developed in the 1980s, polybenzoxazole or PBO was considered an advancement over aramid for racing boat rigging, with nearly twice the strength and modulus – stiffness. It weighs less than 20% rigging wire, and the manufacturers have developed a cruising product that is easy to install.
Westmarine in the US worked with Applied Fiber to develop the Powerlite brand – fully compatible with normal mast and deck terminations, so it can be swapped out for an existing guy line.
A jacket is extruded over pre-stretched PBO bundles at the manufacturing stage, protecting the fibers from UV, water and abrasion. It can even be passed through spreaders like steel.
Allspars is the UK supplier of the Dutch EasyRigging system, but both manufacturers agree the rig should be replaced after eight years – sooner if the boats have run hard. Removable babystays, slides and forestay should be replaced after only four years. Some riggers, however, say PBO has been eclipsed by carbon for performance, while Dyneema and Aramid shrouds are cheaper and stronger. “PBO has been shown to be unreliable, inexplicably brittle, and very sensitive to UV damage,” says surveyor Skov-Nielsen. “It’s not even discussed these days when considering a new rig.”
The state of the art remains carbon, where Future Fibers dominates. Before you turn the page laughing, know that costs have plunged and manufacturing has improved, putting carbon rigging within reach of cruise ships.
“ECthree is an entry level for those who want to move away from rod rigging for better performance and more comfort at sea,” said general manager James Austin. “Our mission is to democratize this and make it a more accessible product for someone in the 30-60 foot category.”
ECthree is made of pure carbon rods, bundled, sheathed and fitted with stainless steel terminations, making them easy to retrofit. It is similar to the peak performance ECsix product. âIt’s 20% less modulus but one-fifth the cost,â says Austin. “We think it’s a good compromise.”
Carbon boat rigging saves 65% of the weight of rod rigging. It is invulnerable to water or UV, so it is ideal for use on a yacht. Granted, carbon doesn’t handle lateral forces as well as steel, but the construction allows the fibers to move and flex inside the sheath.
Stainless steel fittings are designed to be replaceable, but the cable should be inspected and maintained regularly – a service provided by Future in the package.
âIt’s unrealistic to think that we can hit the same price as the rod, but we would hope to be less than double,â Austin says. âIt’s definitely an extra cost to have a composite rig, but you have to consider it over a 15 to 20 year life cycle of the boat. The side rigging of a recently refitted Grand Soleil 46 cost around Â£ 15,000.
LightSpeed, a smaller US manufacturer that is also trying to fit the carbon rig into the under 80ft cruising bracket, uses the same Toray T700 as Future, with smart titanium terminals that fit most standard turnbuckle and mast attachment types. âWe are unique in building a Technora blend integrated into the cable hoop structure, which provides unparalleled protection and durability against cable chafing without adding bulk of coverage,â says technical specialist Mike Wasten.
Comparison of boat rigging costs
- Wire and rod – to rig a Dehler 38 with a standard 1 Ã 19 wire or Nitronic rod, would cost around Â£ 2,280 for the wire and around Â£ 5,000 for the rod.
- HMPE (Dyneema /spectra) – The cables to rig a Dehler 38 would cost Â£ 2,900 to Â£ 3,700.
- Aramid – costs around Â£ 7,500 for the Dehler 38 are 40-60% higher than rod rigging
- DPB – Powerlite claims its cables cost only 30% more than the rod, citing $ 8,525 (Â£ 6,210) for a Dehler 38 with backstay.
- Carbon – $ 20,000 (Â£ 14,600) for a full set of stays with runners to suit a Dehler 38.
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