Design Brief & Intent
The Australis was designed with a single, uncompromising mission: to be the fastest, most efficient single-handed racing machine on the water under the strict parameters of the IYRU A-Division. This box rule permitted a maximum length of 18 feet, a maximum beam of 7.5 feet, and a sail area capped at 150 square feet. Within these tight confines, Johnston sought to optimize hydrodynamic efficiency and structural stiffness. Unlike the heavier, more utilitarian recreational catamarans of the era, the Australis was aimed squarely at elite, athletic racers who possessed the skill to manage a highly responsive, easily powered platform.
Architecturally, the boat featured exceptionally narrow, symmetrical hulls with clean, fine entries designed to slice through chop with minimal drag. In an era when many beach cats relied on heavy solid trampolines, the Australis prioritized weight reduction, featuring a lightweight mesh trampoline stretched over a rigid frame of aluminum crossbeams. The interior of the hulls—accessible only via small inspection ports—was strictly structural, devoid of any accommodation, and focused entirely on providing buoyancy and longitudinal stiffness. Early versions were built from marine grade plywood using the stitch-and-glue or stressed-skin method, yielding a warm, classic aesthetic that demanded careful maintenance. As production modernized, builders transitioned to glass-reinforced plastic (GRP) shells, offering greater durability at the expense of the ultra-stiff, hand-crafted feel of the original wooden hulls.
Variations & Configurations
Though conceived as a strict one-design to foster fair racing, the Australis saw significant variations in its construction and rig setups during its production lifespan. The primary choice for buyers and home builders lay between the traditional wooden construction and the newer, production-molded fiberglass hulls. The cold-molded or marine plywood hulls, constructed using high-quality timber like West Australian cedar, were highly prized by purists. These wooden boats possessed a unique flex profile and were often lighter and stiffer than early solid-fiberglass counterparts, though they required a level of dry-storage discipline that molded GRP hulls did not.
The underwater profile of the Australis remained highly consistent, utilizing dual, high-aspect vertical daggerboards that dropped through tight trunks in each hull. These daggerboards allowed the draft to vary from a mere six inches when raised for beaching or downwind runs, to a deep three feet when fully deployed for maximum lift on a beat. The rig configuration was classically a cat-boat setup, utilizing a single, fully battened mainsail on a rotating spar. Early boats shipped with highly flexible, pear-section aluminum masts of roughly 28 feet in length. This bendy mast technology was designed to work in tandem with a heavy downhaul to control sail twist and flatten the draft in heavy air. Over time, as the strict Australis class blended back into the open A-Class development, owners began retrofitting stiffer, more modern carbon fiber or specialized aluminum wing-masts to handle the high-tension loads of modern racing sails.
Sailing Performance & Handling
On the water, the Australis is a pure, sensory-driven experience that demands undivided attention. The physical reality of this design is written directly into its performance metrics. With a staggering sail area to displacement ratio of 86.16, the boat possesses an almost explosive power-to-weight dynamic. In light air where other boats stall, the Australis accelerates effortlessly, flying a hull in as little as six knots of breeze. The displacement to LWL ratio of 11.58 highlights an ultralight hull form that presents virtually zero hydrodynamic drag. This allows the boat to glide over the water rather than pushing through it, translating every puff of wind into immediate forward kinetic energy.
However, this blistering speed comes with a complete absence of physical cushioning. The comfort ratio of 0.87 is a stark reminder that this is an off-the-beach racer, not a cruiser. The ride is raw, wet, and highly immediate, requiring the helmsman to use their body weight actively on a trapeze or sliding seat to balance the immense heeling forces. The capsize screening ratio of 5.68 underscores the wide, stable platform inherent to its 7.5-foot beam, but in a lightweight catamaran, this number must be interpreted differently than in a monohull. While highly resistant to rolling in moderate conditions, the boat's ultra-low displacement of 147 pounds means that once the critical tipping point is breached, capsize is swift and definitive. Handling the boat in a seaway requires delicate rudder inputs and constant sheet trim; the vertical daggerboards provide exceptional pointing ability upwind, but failing to raise them slightly when sailing deep downwind can lead to tripping over the bows in a steep swell.
Market Snapshot & Economics
Today, the Australis Catamaran occupies a highly specialized, vintage niche on the brokerage market. It is a rare find, sought after primarily by classic multihull enthusiasts, historic racing class preservationists, and collectors of mid-century maritime design. Because it was superseded by the highly developed, carbon-dominated modern A-Class catamarans, it no longer competes at the cutting edge of contemporary fleet racing. Consequently, surviving examples are valued less for raw competitive utility and more for their historical significance and vintage charm.
Financially, acquiring an Australis is typically a low-cost entry point into classic sailing, but the real economics lie in the post-purchase refit and preservation. A buyer should expect to invest significant sweat equity or professional restoration capital, particularly when dealing with older wooden hulls. The cost of sourcing authentic vintage spars, restoring decayed plywood bulkheads, or replacing worn-out high-tension rigging can quickly exceed the initial purchase price of the boat. Nevertheless, for the dedicated preservationist, the Australis represents an affordable, highly rewarding piece of Australian and international yachting history that commands immediate attention and respect on any beach or race course.
Known Issues & Triage
Operating a vintage high-performance catamaran requires a proactive approach to structural triage. For wooden Australis hulls, the primary threat is freshwater rot, which routinely takes hold in the enclosed bow and stern compartments where condensation accumulates. Owners must regularly inspect the areas around the bulkheads, deck joints, and daggerboard trunks using a plastic hammer to tap for dead, soft spots. Any soft timber must be thoroughly dried, cut out, and repaired with marine plywood and epoxy resin before the boat is subjected to the high torsional loads of sailing.
In early GRP hulls, delamination and stress cracking are the most common failures. The high rig tension required to keep the forestay tight places immense compressive loads on the aluminum crossbeams and the hull shoulders where the beams attach. Over time, this can lead to hairline fractures or structural crushing in the fiberglass laminate around the beam receivers. Furthermore, the daggerboard trunks are subject to extreme lateral forces when sailing hard upwind; leaks or cracks at the hull-to-trunk joint are common and must be reinforced with extra layers of fiberglass biaxial cloth. The rudder gudgeons and transoms also require careful scrutiny, as decades of beach landings and high-speed vibrations frequently work the mounting bolts loose, leading to water ingress into the stern tanks.
Modernization & Upgrades
Veteran owners who continue to sail the Australis often implement a series of thoughtful modernizations to improve both safety and performance. The most significant upgrade involves the spars and sail plan. Replacing the original, highly temperamental pear-section aluminum mast with a modern, stiffer carbon fiber section or a tapered Needlespar dramatically improves rig control and reduces weight aloft, which in turn enhances the boat's stability and reduces the tendency to pitchpole. This is usually paired with a transition from traditional Dacron sails to modern Pentex or carbon laminate sails, which hold their shape far better under high downhaul loads.
The deck layout also benefits immensely from modern hardware upgrades. Replacing vintage, high-friction blocks with modern, ball-bearing mainsheet systems and low-profile travelers allows for effortless, precise sail adjustment while on the trapeze. Many owners also discard the heavy, water-retaining original trampolines in favor of modern, high-strength mesh fabrics that shed water instantly, reducing weight and wind drag. Finally, retrofitting modern, high-aspect rudders and kick-up cassette systems prevents damage during shallow-water beaching while providing a much lighter, more responsive feel at the helm.
The Verdict
The Australis Catamaran is a legendary, historically vital design that captures the pure, unadulterated thrill of early high-performance multihull racing. While it may no longer match the hydrofoiling speeds of modern carbon-fiber A-Class machines, it remains a beautifully balanced, lightning-fast classic that rewards skilled seamanship with an unmatched connection to the water. For the vintage enthusiast or the sailor seeking a raw, athletic single-handed challenge, the Australis is a timeless masterpiece of Australian design that still flies a hull with grace and authority.
Pros
- Exceptional light-air performance and acceleration due to an incredibly high sail area to displacement ratio.
- Highly responsive, tactile helm feedback that rewards precise trim and active weight management.
- Historically significant pedigree as a former IYRU International class winner.
- Simple, elegant cat rig that is easy to step and rig single-handed.
- Shallow draft with fully retracting daggerboards and rudders, perfect for beach launching and exploring shallows.
Cons
- High physical demand requiring active trapeze work and constant athletic movement in moderate to heavy winds.
- Vulnerable to freshwater rot in vintage wooden hulls and stress cracking near crossbeam connections in early fiberglass models.
- Complete lack of interior amenities or comfort, offering a wet, exposed ride.
- Strict vintage class parts can be difficult to source, requiring custom fabrication or modern retrofits.
- Highly volatile in gusty conditions with a narrow margin for error before capsizing.
