STANDING TALL – GUNBOAT 68 RIGGING

August 2, 2018

Article #7 in our series about the design and build of the Gunboat 68.

The new Gunboat 68’s rig is one of the most performance-critical parts of the boat – a network of high-aspect and super-strong components working in carefully engineered compression and tension. It is designed to deliver a finely balanced and highly optimized sailing system.

We knew from experience that our customers would want two distinctly different rig options, either fully integrated just as precisely onto the same platform; a Performance Cruising package for fast but safe ocean passage-making, and an ultra-competitive Regatta package for race-focused owners who want to leave maxi monohulls trailing in their wake. Both rigs had to maximize performance and outperform the competition while staying within pre-defined safety margins.

Gunboat 6801 CONDOR with the Regatta Rig option (built by Hall Spars)

Gunboat 6802 DASH with the Cruising Rig option (built by Lorima)

Routinely, high-performance sailboat owners have endured a costly, time-consuming process of tweaking and adapting the rig to suit their style of sailing, hiring the top experts privately to arrive at the product they want. For the Gunboat 68 we wanted to streamline this, build upon the fleet’s preferences, and deliver the Gunboat 68’s rig comprehensively optimized straight out of the box.

A CALCULATED SHIFT

One of the first decisions made, with our naval architects VPLP, was to move the mast and its associated structures aft, along with the daggerboards. You only have to look at the host of sailing records their boats have broken to trust their philosophy. And VPLP’s Xavier Guilbaud explained:

“The mast is positioned further aft than on the previous Gunboat models to increase the aspect ratio of the mainsail. It also allows easier fine-tuning on the mainsail trim with smaller loads to handle. Adding rake to the rig gives the main a near-vertical leech, which makes it a better-looking and more efficient sail when it’s reefed. It’s a more efficient sail plan, gives better helm balance in any sail configuration, and is easier to handle and trim.”

Gunboat 68 CONDOR, photo by Gilles Martin-Raget

Next, we worked with VPLP to identify sail areas for use in VPP analysis. Safety is paramount, so we gave the boat a wide platform (9.1m/30 ft) and crucially considered max righting moment. To choose to fly a hull with the Performance Cruising Rig, you would need to go on a reach with full sails up and full boards down in over 20 knots true wind speed, or in over 16 knots with the Regatta package. From there we worked out the sail area and determined the rig heights (standard rig 25m/82ft tall, Regatta rig 29m/95ft tall). Confident with the design brief, our rigging experts pushed forward.

AHEAD OF THE CURVE

We partnered with Rigging Projects for their superior focus on performance as well as reliability. Having worked on several Gunboat rigs and decks, they have deep knowledge of performance optimization and extensive practical experience integrating our boats’ above- deck sailing systems. They know which components have performed most effectively over the years, right down to the types of locks or cables, and help to ensure we always source the best of the best.

Nick Black, Co-Owner of Rigging Projects, managed a full-scale rig definition and procurement project for the Gunboat 68 as he often does for some of the world’s top yacht racing teams. ”We worked very closely with Gunboat and VPLP to calculate the critical parameters of performance and safety. It’s extremely important to get the sail package and rig parameters right early on in the design process. Too much sail and mast height lead to a tweaky boat that is hard to sail safely, while not enough gives you an underpowered platform.”

Rigging Projects has been the go-to for Gunboats in refit and many other projects of this caliber. It made sense and streamlined the path to the finish line to have Nick extensively involved from the start – from the tender process involving all major spar providers all the way to fine-tuning the 68 on the water.

Rigging Projects working on Gunboat 6801 CONDOR

ENGINEERING THE RIG PLAN

The two rig plans took shape through a collaborative design loop. We ran different iterations of VPP and explored the rig plans to optimize and improve efficiency from every angle. We simulated performance with different mast rake angles and single or double diamond stay configurations, examined a range of sail, rig and deck plan parameters, then built a theoretical sail crossover chart to know exactly how this rig would perform across wind speeds and angles.

The design that resulted for the Gunboat 68 includes a three-cable, single-spreader mast with single diamond stays. We built it in high-modulus carbon fiber, which adds cost but is in line with our mantra about spending money to save weight in the most important places. The Regatta package comes with a rotating mast, while the Performance Cruising package features a non-rotating mast – a decision made based on the limited performance gains available (just a few percent in the mainsail), that in our view didn’t merit the extra cost and the complication involved in each tack on a cruising package.

The standing rigging employs the material that best fits the mechanical requirements of each application. For the diamond stays, PBO handles static loads better than almost anything else. The shrouds and forestay are Kevlar, which is optimized for dynamic loading, and the martingale stays are ECsix carbon because it has the lowest possible stretch and smallest cable diameter for very high loads. Instead of a V-boom, 50% weight savings was achieved by using a box-section carbon boom with ‘hayracks’ supporting a self-draining mesh and a zip-on mainsail cover. It’s simple, lightweight, and efficient.

Mandrel-style boom, showing external patching

Rotating gooseneck fitting on forward end of boom

This high level of consideration and quality carried throughout all of the details. The forward structure features a crossbeam as well as a longeron, both made of pre-preg carbon – the simplest, lightest, and strongest solution. While some catamarans do without a crossbeam for purely aesthetic reasons, the large amount of structural carbon that needs to go into the hulls to handle the resulting torsional loads has an impact on performance, trim, cost and a host of other key factors. The anchor box is positioned as far forward as possible, right under the forestay. Putting the chain entry here gives more control when anchoring in a cross-breeze. The anchor chain runs back through the longeron to a  windlass recessed below deck.

Efficiency and functionality were also persistent driving forces. For example, most catamaran owners will be familiar with the foot of the J1 headsail being deformed by martingale stays. To solve that problem, the Gunboat 68’s martingale stays run through the crossbeam and attach to the hulls lower down. We’ve eliminated an annoying inefficiency and effectively added sail area where it matters most.

For those who choose the Regatta rig package, the mast is 4m (13ft) taller at 29m (95ft)  and rotates. All standing rigging is ECsix carbon. The longeron is extended by about a meter (3ft 4in) and the boom is half a meter (19in) longer, though the mainsheet exits the boom at the same point above the aft beam. A simple hydraulic package is recommended to take care of the mainsheet, rotation, and cunningham – freeing up time and space and adding safety to maneuvers. The Performance Cruising version of the Gunboat 68 has more than enough sail power to win line honors in many racing events, and the Regatta rig offers a further step up. Our VPP studies show that the Regatta rig, combined with the longer daggerboards, will give you boat speed increases of up to 12% upwind and up to 20% downwind.

SPARRING PARTNER

Gooseneck and Mast Base of the Gunboat 68 Regatta Rig

We commissioned Hall Spars to build a Regatta rig package for Hull #1 in the Netherlands. Hall Spars normally produces male mandrel-type tubes but we wanted to use female tooling; the extra patching that is applied for reinforcement around penetrations in the spar can be done internally, within the tool. Unavailable off-the-shelf, Hall offered to build a custom section to get the perfect spar for the boat.

Female mold layup, showing internal patching

FROM THE BOATBUILDER

Rig package design itself was a complex process, but we couldn’t look at it in isolation – it had to work in harmony with the design and engineering of sail and deck plans, particularly in the forward cockpit where most of the line handling is done.

William Jelbert, Gunboat COO explains, “Getting movable bits like sails and sheets to all line up while they all come from different factories is tricky. We have 3D models for everything, verifying the models with scale one mockups, and we encourage multiple loops between teams. Nobody was working in a bubble. Effectively this greatly minimized sailing systems tweaks during sea trials on Hull #1.”

Find out more about the Gunboat 68 and read the rest of the series here!

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