The next Big Thing?

We take a close look at the Transpac 52 class

Farr Yacht Design

With the new Farr Yacht Design Transpac 52s completed recently at Goetz, Patrick Shaughnessy (right), Senior Designer at the Annapolis-based design house says their latest trio represents a move to get back into the European and Mediterranean keelboat markets, having spent so many years concentrating on the America's Cup and Volvo Ocean Race. To this end some both Russell Bowler and Jim Schmicker are racing regularly on their new Transpac 52s.

While the Transpac 52 is mostly US-based at present Shaughnessy says they are receiving much interest in the class from Europe, where it is believed the highly influential King Juan Carlos of Spain is looking favourably on the new class. "We've had a huge amount of interest. We're quoting for builds in the Med, the West Coast and as far afield as Asia. The only place we haven't had any interest is the UK...

"There has been a group of owners who want to be able to customise their boats and have their choices make a difference and they have been sitting aside waiting for something for them to do. This class may be the place for them, particularly if it gets a foothold in the Med that will ensure the longevity of the class, provided the rules aren't changed."

One of the fears in the class at present is that different versions of the Transpac 52 may come into being, with for example Med boats being optimised for light wind conditions.

Farr Yacht Design's new trio of TP52s are not their first foray into the class. This was Karl Kwok's Beau Geste, launched last year. Shaughnessy says that this boat was more orientated towards offshore racing, particularly with the Transpac in mind but changing her appendages could make her competitive round the cans.

Aside from racing in the TP52 class events, Shaughnessy says that Beau Geste has proved competitive under IRC, which will be useful for this year's San Francisco Big Boat Series were at present nine TP52s are expected to take part, and in the future for events like the Rolex Fastnet Race and Sydney-Hobart.

Shaughnessy says that the present Farr 52s have very similar dimensions to the TP52 equivalents, but unfortunately they won't fit into TP52 class rules as there are a couple of dimensions they don't meet (the Farr 52 is heavier and proportionally has slightly more ballast). The Farr 52 varies in its concept with the TP52 in that it was designed to offer owners a relatively low-tech carbon fibre boat at a good price point.

Building the three new boats at Goetz allowed for bulk purchasing and saved on the cost of tooling. While their hulls are the same, there are minor differences in their interior and deck layout.

The cost of a Transpac 52 from Goetz was US$ 1.3 million.

Basic performance comparison between a Transpac 52 and an IMS53.

	Upwind vs		Downwind vs
10m ws	TP52	IMS53	TP52	IMS53
4	5.0	4.7	5.1	4.4
8	7.5	7.2	8.4	7.3
12	8.2	7.7	9.9	8.5
16	8.4	7.9	13.2	9.2
20	8.5	8.0	16.0	10.4

Farr Yacht Design on their new design:

Within the bounds of the otherwise tightly controlled Transpac 52 rule there is some room to set the balance between upwind and downwind performance. Displacement and VCG are limits set by the Transpac 52 rule so we were left to choose the optimum beam to draft ratio to produce optimum upwind and reaching power versus downwind slipperiness. While the overall length of the boat is set by rule we were free to optimize the waterline length and shape details to best suit the boat's expected race schedule.

To determine the optimum hull characteristics FYD conducted a research program employing a combination of VPP studies and computational fluid dynamics experiments. We developed a series of candidate designs to explore the available rule space. The performance predictions for each of these designs were then combined with wind distributions for the various targeted races to determine the optimum hull parameters and the consequences of being off optimum.

This research program addressed the following principal areas:

Selection of optimum beam waterline.
Maximum beam and hull flare effects examining the trade-off between heeled drag and increased crew righting arm.
Selection of displacement within rule range.
Effects of being above rule VCG.
Transom immersion and effective length.
Forward section shaping to improve the onset of planing and boat handling in waves.
Appendage size refinement and optimization for particular event priorities – offshore versus around the buoys etc.
Bulb shaping and style for particular event priorities.
Hull

We have chosen the beam waterline to give the boat exceptional upwind and reaching speed. We have carefully crafted a beautifully fair hull shape, a by-product of the freedom of the box rule format, to minimize the wetted surface that accompanies higher beam. Crew weight supplies a significant proportion of the overall righting moment so the hull exhibits a close to rule maximum beam at the deck. We have examined the average boat speed profiles for a series of events and built upon our extensive knowledge base in this area to select an appropriate level of transom immersion in sailing conditions that we feel balances the competing demands of round the buoys racing and high speed offshore sailing. The waterline is maximized at the bow leaving just enough distance to the upright stem to fit a reasonable knuckle radius.

Appendage Geometry & Sizing

There is a wide range of freedom in the design of the appendages. Within the restrictions of overall draft, permitted materials, and minimum keel fin strength we were free to develop low drag, good handling solutions. The rudder was sized to provide sufficient lift and good handling characteristics with minimal area and drag. The combination of optimized planform shape and our own foil sections, designed in-house, produce a high lift/low drag rudder that gives the helmsman plenty of warning of an imminent stall. The keel fin was sized to provide sufficient lifting area for starting and other maneuvering situations while balancing the competing concerns of upwind and downwind sailing.

The bulb concept also reflects efforts to balance upwind sailing and manoeuvring issues with the desire to minimize viscous drag. We chose a chined bulb shape to improve the upwind performance and achieve the deepest centre of gravity. The bulb shape was optimized using our understanding of transitional flow mechanics that contributes to reducing the bulb viscous drag.

Deck Geometry and Layout

The deck geometry combines the minimalist coach roof and flattish deck camber of our previous design work with an aggressive cockpit aimed to position crew not hiking as far outboard as possible. Substantial weight savings have been achieved in the aft cockpit by continuing the cockpit sole out to the hull, thereby eliminating the cockpit sides. The cockpit sole has been sloped down aft of the traveller to minimize its surface area while enhancing its draining properties. Our vertical transom style has been maintained to position the topmast backstay fittings as far aft as possible, minimizing the mainsail roach and topmast backstay interaction.

Advances in the deck layout are focused on a winch system designed for forestay-less gibing, where two after guys are required to be loaded throughout the manoeuvre. In this case, the secondary winches, by careful positioning can be used for after guys downwind and topmast backstay upwind. The mainsheet system is a 2:1 “half German” style system led aft to a single pedestal driven winch on centreline. The mainsheet grinder pedestal and primary pedestal are linked below deck to provide maximum horsepower during highly loaded manoeuvres.

Hydraulic tensioning systems are in place for both forestay and “code 0” tack line. These systems both utilize through deck sheaves and below deck strops intended to position the actual hydraulic cylinders as far aft and low in the boat as reasonable possible.

Longitudinal jib tracks are combined with in-hauler systems to provide ample sheeting range along side the relatively large class required coach roof. Mainsheet traveller and other control lines are led below deck to maintain clutter free deck space.

Rig

The fairly standard 20-degree swept spreader rig has been combined a cathedral style topmast stay system to support “code 0” style upwind spinnakers. In this case the combined stay envelope has been carefully optimised to allow close sheeting of those sails.

The mast has been designed to class rule minimum weight and VCG targets. Where possible, IMS friendly mast and boom dimensions have been pursued to help ensure that the yacht can be competitive in other outside class events.