Please select your home edition
Edition
Upffront 2020 Foredeck Club LEADERBOARD

Sailboat Composite Standing Rigging - Material Options

by Phil Anniss 5 Nov 2020 09:00 GMT
Composite rigging benefits © Future Fibres

Having established the significant advantages of reducing rigging weight, next we would like to look at the composite rigging options available on the market. However, before we get to that point, we need to take a little diversion into basic material properties to provide some background context.

Physical material properties are a technical subject and numbers vary considerably depending on manufacturer, test procedures and samples used. The table below represents a correlation of data across multiple sources and reflects the relative characteristics of a range of different materials. N.B. These are theoretical numbers for the material itself and finished products (cables, rods, wires) will have their own unique properties which will generally be lower than theoretical.

FibreYoungs Modulus (GPa)Density (kg/m3)Strength (Mpa)Elongation at Break (%)Source
T800 Carbon294180058802Toray T800
PBO275156055002.5Toyobo Zylon Datasheet
N50 Steel193780069035Matweb
316 Stainless193800058060Matweb
Dyneema SK991309804100100DSM Dyneema Datasheet
Dyneema SK751169803300100DSM Dyneema Datasheet
Aramid K49112144030002.4Matweb
Hemp321490300 Matweb
Polyester131390784 Matweb
Cotton81540225 Matweb
Nylon41140616 Matweb

Terminology

  • Youngs Modulus - this is a measure of the stiffness of the material. The bigger the GPa number - the stiffer the material.
  • Density - provides an indication of relative weight for the given strength/stiffness
  • Ultimate Strength - is the amount of load to failure
  • Elongation at Break - this is the % increase in length to failure point (of a lab sample)

Discussion

Nylon/Cotton/Polyester/Hemp are shown for interest. Hemp and Cotton were traditional sailing ship materials for standing rigging and sailcloth and show just how far things have moved forward.

Steel wire replaced Hemp standing rigging from the mid 1800s and is still the default material for boats sailing around today. Wire is 6x stiffer than Hemp and double the strength, but this does come at a significant weight penalty. Durability, reliability, ease of use and mass production techniques led to wire's domination. However, in pure strength-weight terms, Hemp was not a bad material!

The performance metallic standing rigging option is Nitronic 50 rod. Nitronic is a nitrogen-strengthened steel alloy and was developed in the 1960s. The basic material properties are stronger and lighter than stainless wire plus the fact that it is a solid rod, rather than a twisted wire, leads to a significant diameter reduction for equivalent stiffness, which reduces windage.

The synthetic rigging revolution started quite slowly with the introduction of Aramid fibres in the early 1980s. A Kevlar 49 cable, built to the same stiffness, would be approx. 70% lighter and 7x stronger than Nitronic 50. The other major development was the extremely low elongation at break (2,4%) which means that the fibre will sit under high load and not deform / lengthen until it breaks. This is very important for standing rigging in terms of maintaining rig tune. The one downside with Kevlar is that it takes a lot of fibre to achieve the same stiffness, which adds significant diameter compared to rod.

PBO (Zylon) arrived on the sailing scene in the early 1990s with carbon rigging products coming in the early 2000s. These two materials have very similar properties and are approx. 45% stiffer, 80% lighter and 8 times stronger than Nitronic rod. There are challenges in manufacturing these materials into standing rigging cables but, for a stiffness equivalent cable, they are comparable in diameter to wire/rod, whilst providing major weight and strength gains.

For the last 20 years therefore, Carbon, PBO and Kevlar have established themselves as options for lightweight, high strength standing rigging cables. Whilst it is possible to build lateral rigging from Kevlar, it is relatively uncommon due to its diameter. For example, a Nitronic Dash 17 rod has a diameter of 8,4mm - in PBO the stretch equivalent cable would be approx. 9,5mm but Kevlar would be more like 14mm. Kevlar is mainly limited to backstays on larger yachts where it can still deliver a 70% weight saving over wire/rod.

Dyneema®, which is a household brand name for an Ultra-high-molecular-weight polyethylene (UHMWPE), was developed around the same time as Aramid fibre. It is a bit stiffer than Kevlar (depending on the type), similar in strength but extremely light. However, UHMWPE has not been widely used in standing rigging, to date, due to one weakness - it creeps. At 30 degrees under constant load (10% of break load) it physically grows (SK75 - 0,02%/day, SK78 - 0,006%). On a 15m cable that equates to approx. 8% / 1.1m in 365 days for SK75, and 2.2% / 330mm for SK78.

Having said that - Dyneema is a cost effective and incredibly reliable / durable fibre and, on smaller boats (under 45ft), there is a growing community of sailors who are adapting and finding ways to manage these challenges. This can be done by using long lashings for terminations, so that creep can be taken up, and also by over-building the cable, which reduces the rate of creep. On larger boats it becomes physically impossible / impractical to develop the required rig tension using a lashing.

Summary

For performance sailors and larger yachts - PBO and Carbon are the primary material choices available for standing rigging. For sportsboats and smaller yachts these materials/products can become cost prohibitive and there is an increasing trend towards DIY Dyneema® rigging solutions.

If you would like to explore the options for a retrofit to composite rigging on your boat, please use the Composite Rigging enquiry form or contact us at

Related Articles

Mantagua's Certified NAVIPRO Navigation Lights
Products enabling lighter, faster and safer sailing from upffront.com Lighter, faster and safer sailing is our mantra. Thus, we're excited to launch our new product category - Navigation Lights - on Upffront.com, to keep you safe at sea. Posted on 6 May
Karver KF V3 Furler Accessories Guide
upffront.com help you identify what will fit best into your set-up The Karver KF V3 range is now available at upffront.com and with this latest iteration of their popular KF furlers, Karver have moved away from dedicated top-down drums in favour of a more flexible modular system. Posted on 29 Apr
The LOOP Boa Constrictor Clutch
Maximise your deck space - build vertically! Deck space is prime real estate on a sailboat, with clutches and jammers vying for space, often on narrow areas such as the cabin top or mast. So what do you do if you can't fit any more clutches to your deck? Build vertically! Posted on 22 Apr
Horizontal, Vertical or Compact Motor?
Electric sailboat winch options examined by upffront.com You've chosen to upgrade from a manual winch to an electric winch. Now, you need to decide on motor placement. This is a critical design decision which largely depends on your boat's available space below deck. Posted on 15 Apr
MORFRAC and 3D Printing
A success story, investigated by upffront.com In recent years, 3D printing has revolutionised manufacturing processes. Expiring patents have caused 3D printing costs to plunge and quality to soar, granting opportunities for small-scale manufacturers to experiment - and excel - with 3D printing. Posted on 9 Apr
Lewmar EVO Winches - Made to Last
Flagship winch range is an evolution of 'the most popular winch ever made' Lewmar's flagship EVO® winch range is an evolution of their Ocean range which they claim is the most popular winch ever made. This is due to their widespread use by volume boat builders who prioritise ease of use / maintenance and reliability. Posted on 2 Apr
A Truly Unique Proposition
Karver winches seamlessly change between 4 gears without any switch Karver are relatively new to the world of sailboat winches but they are bringing something completely different to the market. Their KSW Speed and KPW Power winch ranges can offer some dramatic advantages. Posted on 25 Mar
What size electric sailboat winch do I need?
upffront.com consider application and load When choosing an electric winch, there are four main factors to consider: speed (1, 2 or 3), motor placement, drum material and size. In this article, we'll focus on size. Posted on 18 Mar
The nke Multidisplay
All your boat data in one place GPS, navigation data, wind data, boat speed, heel, rig loads etc. Onboard electronics are far more accurate and capable than ever before, so sailors are able to charge and depend on more electronic systems. Posted on 11 Mar
Andersen's Electric Winch Range
Quality cruising with elegant, stainless steel winches that last a lifetime Andersen Winches are iconic. Often considered the benchmark for quality, Andersen's elegant, stainless steel winches take pride of place on the foredeck. Underneath the stainless steel exterior, an internal construction manufactured from aluminium bronze. Posted on 4 Mar