Design Brief & Intent
The core mission of the Supercat 20 was to deliver maximum velocity without the terrifying bow-burying tendencies common in early multihulls. To achieve this, Bill Roberts integrated a patented elliptical hull shape. This innovative geometry provides high-volume forward sections that generate dynamic lift as the boat accelerates, virtually eliminating the classic "pitchpole" or "nose-dive" common to narrow-bow designs of the 1970s and 1980s.
Another defining characteristic of the Supercat 20 is its extraordinary twelve-foot beam. While competing designs of similar length adhered to the standard eight-to-eight-and-a-half-foot beam limit for easy trailering, the Supercat 20 was intentionally widened to twelve feet to vastly increase its righting moment and structural stability. Because there is no heavy lead ballast, the boat relies entirely on this wide stance and crew weight on the trapeze to keep its massive sail plan upright. The deck configuration is minimalist and purely functional, featuring a heavy-duty trampoline stretched over aluminum crossbeams (or akas). There is no cabin or interior joinery; this is an open-platform daysailer where the crew is fully exposed to the elements, emphasizing visceral connection to wind and water.
Variations & Configurations
Throughout its production history—which saw the boat built by Formula Catamarans, briefly marketed by Boston Whaler, and ultimately built and supported by Aquarius Sail Inc.—the Supercat 20 was offered in two primary rigging configurations:
- Standard Rig: Designed for general recreation and high-speed daysailing, this setup featured a mast height of just over thirty-three feet. It carried a generous but manageable sail area of approximately 292 square feet.
- Tall Rig: Optimized for competitive racing in light-to-moderate air, the Tall Rig featured a towering mast of thirty-eight feet, six inches. This configuration carried an aggressive 344 square feet of sail area, giving the boat an immense power-to-weight ratio.
The underwater profile utilizes high-aspect vertical daggerboards. This configuration allows for highly adjustable draft options, ranging from a minimal six inches with the boards fully retracted (allowing the boat to be sailed right up to a sandy beach) to three and a half feet when fully lowered for maximum lift and pointing ability upwind.
Over the years, the major configuration challenge has been road transport due to the twelve-foot beam. To address this, owners utilized specialized telescoping trailers that could expand from an eight-foot legal trailering width to the full twelve-foot sailing width, or tilt trailers that transported the boat at an angle. Some owners chose to permanently modify the aluminum crossbeams to reduce the beam to nine feet, sacrificing a portion of the righting moment in exchange for straightforward trailering and ramp launching.
Sailing Performance & Handling
The sailing physics of the Supercat 20 are defined by its jaw-dropping power-to-weight ratio. With an ultra-light displacement of just 450 pounds, the boat possesses an astronomical sail area-to-displacement ratio of 74.92. This translates to instantaneous acceleration; the boat responds to the slightest puff of wind and can easily achieve double-digit speeds, regularly cruising between fifteen and twenty knots in favorable conditions.
Its displacement-to-length ratio of 29.29 underlines its sleek, easily driven hull form. The hulls slice through waves rather than pushing them aside, resulting in a smooth, low-drag gliding sensation. Helming the Supercat 20 is a highly engaging experience. Because of the twelve-foot beam, the helm remains incredibly balanced even when flying a hull, giving the skipper precise, responsive control via the twin rudders.
The motion comfort ratio of 1.32 is expectedly low, meaning the ride is highly active, wet, and physically demanding. The crew will feel every wave contour, and staying on the trapeze requires strength and concentration. The capsize screening ratio of 6.26 indicates that while the boat is incredibly stable up to its tipping point, once it goes over, it is highly prone to inversion. Righting a capsized Supercat 20 is a serious undertaking; the massive twelve-foot beam and heavy mast can make it nearly impossible for a solo sailor or lightweight crew to right without a righting bag, a strong breeze, or powerboat assistance.
Market Snapshot & Economics
In the modern brokerage market, the Supercat 20 is a rare find. Production numbers were relatively limited compared to mass-market brands, meaning they do not change hands frequently. They command a dedicated following among vintage multihull purists and speed enthusiasts who recognize the genius of Bill Roberts' design.
From an economic standpoint, the Supercat 20 represents an incredible value-to-performance proposition, allowing sailors to experience modern multihull speeds for a fraction of the cost of a contemporary carbon-fiber racing catamaran. A major benefit to owning a Supercat 20 today is the continued support of Aquarius Sail Inc., which acquired the company in 1984. Unlike many orphaned vintage beach cats, original replacement parts, heavy-duty trampolines, and specialized sail plans remain accessible through the builder, which greatly simplifies the modernization and refit process.
Known Issues & Triage
While the Supercat 20 is a robustly engineered craft, potential buyers should perform specific triage on older models.
- Daggerboard Trunk Stress: The massive lateral loads generated by the deep daggerboards can cause stress cracking around the daggerboard trunks, particularly if the boat was run aground with the boards down.
- Beam-to-Hull Connections: The aluminum crossbeams and their mounting saddles must be thoroughly inspected for corrosion, hairline cracks, or loose fasteners, as these joints bear the immense torque of the twelve-foot beam.
- Mast and Rigging Wear: On Tall Rig models, the rotating spar and high-tension shroud lines put extreme compression loads on the mast step. Inspect the mast step base and the surrounding fiberglass deck layup for compression damage or spiderweb cracking.
- Hull Delamination: As with any vintage fiberglass catamaran, check the hulls for soft spots, particularly on the decks where crew members frequently stand, and along the keel line from dragging the hulls on sandy beaches.
The Verdict
The Supercat 20 remains a masterclass in beach catamaran design, offering a thrilling combination of raw speed and engineered stability that few boats of its era can match. It is not a casual beach toy, but rather a high-octane daysailer that demands respect, skill, and active athletic participation from its crew.
Pros:
- Immense speed and acceleration with a massive sail area-to-displacement ratio.
- Patented elliptical hull design prevents the terrifying pitchpoling common in other classic beach cats.
- Extreme twelve-foot beam provides outstanding stability and a highly balanced helm.
- Continued manufacturer support for replacement parts and sails through Aquarius Sail Inc.
- Deep daggerboards provide excellent upwind pointing capability.
Cons:
- The twelve-foot beam makes trailering highly complex, requiring specialized telescoping or tilting trailers.
- Visceral, wet, and physically demanding ride with minimal comfort in a seaway.
- Extremely difficult to right after a capsize without a large crew or dedicated righting aids.
- High-tension rig puts significant structural stress on aging hulls and crossbeam joins.
