Thanks to improvements in materials technology, and the innovative work of some of the industry's sector leaders such as North Sails, Hall Spars, Rondal and Ocean Yacht Systems, such projects will continue to be feasible. The question "how big can we go" can perhaps only be answered by a corresponding question "how deep is the water"?

Man-made materials

The continuous development of high performance man-made materials, such as carbon fibre, PBO, Vectran, Spectra and Kevlar, has contributed much to the dramatic improvements in yacht performance in recent years. The ability to simply build many of today's Superyachts is principally down to the use of these materials.

Typical of this is the almost universal change from alloy to carbon masts and the current trend towards composite rigging.

Carbon fibre seems to have been around forever. However, it is not so many years ago that it was fraught with early teething problems when used in mast construction. These have been successfully overcome and its use has revolutionised spar design in recent years and even conservative builders such as Rondal and Perini Navi have now embraced the carbon revolution and it shows in the product's performance.

The secret of using any new material is not to reverse engineer the old design in the new material, but to radically utilise the new material's inherent properties to enable the maximum advantage of its underlying properties to be achieved in the final design.

As one problem is solved, another arises. The use of carbon reduced weight aloft and allowed relatively shallower drafts to be achieved for the same size of boat. However, in parallel, boats got significantly bigger, masts became much higher and the draft problem arose once more.

The development of lifting keels has certainly helped contain the problem, but currently Superyachts such as Mirabella V, with her 90m mast, cannot transit the Panama Canal due to mast height. The problem is now above deck, as well as under the keel.

The Pedrick designed MITseaAH, utilises an unsupported 9m carbon fibre extending telescopic top mast. Carbon fibre's unique stiffness is critical to being able to engineer this section. OYS's chief designer, Mike "Jaffa" Orange, was deeply involved in the design of this mast.

"It was a unique challenge to get the boat under the Brooklyn Bridge whilst keeping the performance required by the design, " he said. "The topmast system has been thought of in the past I am sure, but was unfeasible until materials such as carbon fibre came along. Not much else could cope with a headboard load of 17 tonnes over 9m away from any support and still be able to slide inside the main body of the mast."

Wing masts are also being tried again. Such masts typically rotate hydraulically each way to trim and also feather quickly. One of the first prominent examples of this was Dennis Conner's Stars and Stripes America's Cup campaign of 1988. A controversial beginning, but definite proof that the concept could work effectively in the right circumstances.

A more recent example is Mike Golding's well-proven Open 60 Ecover, which won the 2004 Transat.

Composites - rigging's future Composites (high tensile manmade fibres) and in particular PBO, Kevlar, Spectra/ Dyneema and Vectran, which can be made into extremely strong, lowstretch ropes and cables, are the future. There are several technical characteristics as well as price to consider; creep - the tendency to permanently elongate when held under tension, stretch - the elastic elongation, which disappears when the load is removed.

Spectra or Dyneema fibres have reasonable stiffness, so they are cost effective replacements/upgrades for polyesters as sheets or halyards, but they creep too much under load to hold a mast up.

Kevlar creeps less, but stretches more. This is fine where large adjustments are available so Kevlar is used extensively for runners and checkstays. This applies to even the largest of projects, with Mirabella V rigged using 120 tonne break load runners to support her 90m carbon mast.

PBO and Vectran have very low stretch and almost zero creep and are thus perfect for standing rigging and halyards, where constant loads are generally present. PBO (Zylon) theoretically has a tensile strength approximately 10 times that of steel and yet weighs 80% less, however this simple equation is slightly reduced when construction and attachments are taken into account.

PBO is now being incorporated into standing rigging, although conventional Nitronic 50 rod rigging will continue for some years to come, as it is a well-proven material which is reliable and takes on-board abuse well: composite rigging is on the way.

For PBO rigging it is usual to find a combination of different fibres in the construction of a rope or stay. A core of PBO - perfect for minimum stretch, but susceptible to UV and abrasion - might be covered with a polyurethane cover to protect from UV with an additional braided Spectra or Technora cover to protect against abrasion.

Some top end race and performance boats are already sporting PBO cable and this will filter down. Already Aramid Rigging, Future Fibres, Navtec and Ocean Yacht Systems have composite and PBO products available.

Recently

Decision SA of Switzerland re-rigged its fleet of 35ft one-design racing cats with PBO standing rigging. It will be interesting to see how PBO enhances what are already pretty extreme machines. Carbon rod rigging has also been developed, but currently manufacturing issues remain to be resolved before this really becomes a costeffective solution.

Lower keel weight Where does this allow designers to go? Less weight aloft can enable reduced draft, lower keel weight, and reduce rig loads on the hull. A perfect example is Mirabella V, where the conventional rigging package supplied weighed in at 14 tonnes. Had this been PBO, as had once been reviewed, the weight saving would have been around 75%. This could be translated even into massive fuel savings over the life of the yacht.

At least two new major Superyacht projects are now seriously considering use of PBO standing rigging on 40m+ yachts. After considerable interest from rigging manufacturers, Germanischer Lloyds, one of the leading maritime classification societies, is writing a set of rules for individual companies to gain type approval for their type of composite standing rigging.

This will provide a level of assurance for composite rigging that was lacking when carbon spars were initially introduced to the market. It is also likely that any composite rigging outside the racing world will not be insured without this approval.

PBO is also being used in furling headstays, perhaps the most difficult application of all due to combined requirements of a tension stay and the torsional effect of furling sails.

PBO is currently really only used on detachable sewn soft luff reaching sails, but it's now being developed for critical stand-alone headstays/boltrope headfoils.

New materials are on the way and the present deficiencies of PBO and other materials will no doubt be improved upon when these are introduced to the market.

There is already one such material at the application development stage.

Until recently the use of composite fibres for standing rigging had been restricted to open class boats and other race boats where aesthetics have not been an issue. For PBO, in the past, traditional Kevlar style friction based terminals were used, this didn't work well due to the slippery nature of PBO, which had to be held onto very tightly to avoid it slipping out of the terminals, but this lead to excessive wear on the fibres.

Continuous loop

One common answer is to use a continuous loop construction, where the fibres are continuously wound around thimble terminals avoiding the friction hard points. This kind of idea can also be seen in the short loops, available as shackle alternatives, most noticeably from companies like Aramid Rigging (also licensed to Harken) and Equiplite.

At least one company has since developed the design of their compression cones and this has now led to a realistic choice between continuous loops and parallel cables.

Loops are very well established, but the parallel cable system has some specific benefits as well. Notably and very importantly, it is directly interchangeable with existing rod rigging, such that any boat currently in service can be retro-fitted without incurring any additional work.

Secondly, it is significantly easier to service, repair and replace, anywhere in the world, even in areas without proper docking or maintenance facilities.

Sail Technology

Sail technology is also moving ahead in leaps and bounds, with many more yachts using sails made on 3-dimensional moulds and other pseudomoulded panelled sails. The sailmakers are keeping pace with composites and it is the norm to see Kevlar, carbon, Vectran, Spectra and Cuben fibre in sail ingredients.

Current composite sails have proven to be the way to go for ultimate performance, but this technology leap has not been without its problems.

It has not been unknown for the occasional winch to pull out of the deck, or shock loadings from ultra-stiff sails and halyards cause breakages elsewhere on yachts.

Unquestionably, everything is now being looked at anew and it is no surprise to find that some traditional sail plans have been reviewed again, using advanced rig design technology.

A current in-build example of this is the Perini-Navi 289ft, three-masted, junk-rigged clipper Maltese Falcon.

Whilst this configuration eliminates much of the conventional standing rigging, it will have Kevlar 49 stays, as cross braces on the masts to provide extra rigidity. Break loads will be 15 and 25 tons.

This unique "DynaRig" is a modern development of a traditional Chinese rig, which originated more than a thousand years ago.

The use of three-dimensional fluid dynamics and precise wind tunnel testing make it relatively easy to design sails with remarkably accurate aerodynamic contours, that will power a yacht extremely efficiently, relative to given wind strengths and angles. The America's Cup proves that optimising sail shape for a known set of conditions, using moulded composite sails, produces exceptional performance increases over a conventional multi-purpose sail.