harryproa/articles/ Extraordin-harry

Extraordin-Harry Design Concept

Article by Bruce Cartwright (Feb 2002)

click to enlarge	Extraordin-Harry is the extrapolation of the proven Harryproa concept to a size suitable for challenging long distance records. It is a high-powered, easily driven, minimal-crew boat for serious long-distance races, such as the Jules Verne Trophy attempts. Background The current breed of boats competing for long-distance records all perform admirably in the Southern Ocean, but are struggling in the light winds of the equatorial zones. It is apparent that if a real challenge to these records is to occur, it will come from improved light air performance. Extraordin-Harry is designed to perform equal to the existing breed of mega-catamarans in a heavy sea and strong breeze, but show marked improvements in light air performance. This is achieved by a lightweight and easily driven boat that can be powered up to handle the big stuff.
The Concept The concept is a boat that is easy to sail, requires a minimum of crew, has high reliability, and is a true ocean racing boat. The concept is based on the proven Harryproas of Rob Denney. Like all Harryproas, Extraordin-Harry has the rig in the leeward hull, and all accommodation and stores in the windward hull. The windward hull remains dry and at all times provides a clear view of the rig and the sea forward - an ideal place from which to sail the boat. The primary sail controls lead to the spacious crew position in the windward hull. The windward hull also houses the navigation, comms and all crew conveniences. As for all Harry Proas tacking or gybing is achieved by shunting. As the crew/accommodation hull is always to windward, and the rig fully rotating, there is minimal risk of being caught aback, or performing an accidental gybe. The ideal crew size for Extraordin-Harry is 4-6 people.
click each view to enlarge above front side	Platform - The main hull is 33m long, the accommodation hull is 11m long, and the beam a conservative 20m. - The mast is a wingmast, freestanding and fully rotating, located midship in the main hull. - Rudders are located in both ends of the main hull. These rudders are fully rotating, and provide unparalleled directional control for a boat of this size. The boat has no dagger-boards. - The trampoline between the two aerodynamically shaped crossbeams provides a large and safe working area for the crew. The two crossbeams split to provide four equi-spaced attachment points on the main hull. These four attachment points provide an even distribution of load into the main hull, and reduce the length of unsupported bow - resulting in a stiffer structure.
Sail Plan A balanced Balestron rig reduces sheet loads compared to conventional rigs, thus minimal deck hardware is required - reducing cost, weight and bananas for the gorilla pit. The freestanding rig is a logical decision for shorthanded long-distance races. It has no stays or running rigging, providing the following benefits;
a) improved aerodynamic efficiency by eliminating the aerodynamic drag of stays; b) greater rig reliability, through fewer 'critical' components in the rigging; c) easier rig maintenance; d) fail-safe ability to 'dump' sail power, as there are no stays to restrict the mainsail - no snapped battens, or chaffed sails from side-stays. e) self-regulating 'power-dump' by the top of the mast falling off to leeward in gusts
The main is fully battened and relatively flat, developing depth through rotation of the wingmast.
click to enlarge	A two-metre wide "Boardwalk" boom acts as an efficient end-plate in light-winds, and provides a wide base for reefing in heavier weather. It is envisaged crew at the mast base would do the first two reefs, but additional reefs could be performed remotely from the windward hull. Thus in heavy weather sailing, the crew should not have to venture to the leeward hull at all.

The clew of the headsail is self-tacking on a curved track attached near the base of the mast. A number of design options are on the drawing board to allow for shifting the centre of effort of the headsail to maintain a balanced rig when reefing the main. A screacher called the "Doldrum Solution" is proposed for light-air conditions. This masthead sail is flown from a telescoping prodder-pole protruding from the forward end of the Balestron boom, and is sheeted to the back end of the Balestron boom. Hulls Perhaps the only difference between the traditional Harry Proa and Extraordin-Harry is the shape and proportions of the leeward hull. True Harry Proas have an ultra-minimalist wave-piercing leeward hull that is extremely long and slender. This concept is well proven on Rob Denney's developmental Harry Proas up to 40'LOA - U, W, Harry, and Harrigami. The extrapolation of the long slender wave-piercing hulls was tried on a recent mega-catamaran with much-publicised disastrous consequences. Although the experience of the existing Harry Proas suggests the concept is worthy, we are suggesting a more conventional hull form at this stage to ensure the publicity from this boat is achieved through its success. We are convinced a conventional hull form combined with the other novel features of Extraordin-Harry will provide performance without risk. Consequently, the main hull of Extraordin-Harry is narrow with a high freeboard at the bow - ie a wave-slicing form. High bow freeboard reduces the tendency to bury the bows, whilst the appropriately profiled crossbeam and attachment points will minimise slamming should they hit a wave. The windward hull has a waterline beam of less than 1m, and a cross-section that eliminates slamming when skipping across wave tops. The narrow windward hull has a significant blister for crew accommodation, kitchen and communications. The blister is located well above the waterline, and bridges out between the crossbeams. Bunks are located athwartship, below the crew deck. Thus the crew are at all times in close proximity to each other - ensuring safety and ease of communication. Displacement Weight estimates indicate a racing trim of around 11 tonnes for a non-stop around the world attempt. Approximately 60% of the weight is in the main hull, and a mere 40% in the windward hull. This distribution of weight is ideal for the light wind conditions where wetted surface area can be reduced by lifting the windward with confidence. The stability curve for Extraordin-Harry shows a high point-of-no-return. This stability coupled with the easily controlled power of the sailplan means flying the windward will be achievable with confidence for extended periods. In heavy seas, 3+ tonnes of water ballast can be added to the windward hull, significantly improving the stability and power of the boat. Water ballast can be also added in the main hull for improved motion of the boat in heavy weather. Conclusion Extraordin-Harry is not your average racing multihull. It is a workable, simple, reliable boat that has the potential to break race records in long distance sailing. The components are simple and the stress-concentrations manageable with current technology. This boat will be simple, quick and cost-effective to build using current boat building technology. This ain't rocket-science - just commonsense. We'd love to work with any design group, team or individual that is interested in this boat. Please, contact us to discuss this project further. We believe it is truly extraordinary.

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