Design Brief & Intent
The Cougar Mark III was conceived during an era when the fiberglass medium was in its infancy and multihulls were still establishing their architectural vocabulary. The Prout brothers aimed to create a boat that offered the thrilling speed of their earlier racing catamarans but with a vastly improved level of comfort and utility. While competing designs of the era, such as the Carter-designed Tiger Cat or the MacAlpine-Downie Shark, leaned heavily toward either raw racing performance or heavier cruising capabilities, the Cougar struck a rare, highly functional middle ground.
The defining characteristic of the Cougar Mark III is its hybrid construction. The hulls—or pontoons—are constructed of molded fiberglass, which was highly advanced for the early 1960s and made Prout a global pioneer in GRP construction. However, the bridge deck, cockpit, and structural crossbeams are built of marine plywood, spruce, and mahogany. This design choice yielded a solid, continuous deck area measuring nearly seven feet square. Unlike modern beach catamarans that utilize flexible trampolines, the Cougar’s solid wooden deck provides a dry, stable platform capable of carrying up to six passengers comfortably during casual day cruises. This hybrid layout, combined with built-in watertight storage hatches in both hulls, gave the Cougar a utility that pure racing monohulls and early beach cats simply could not match.
Sailing Performance & Handling
Under sail, the Cougar Mark III is a testament to the power of a high sail-area-to-displacement ratio. With a standard rigged displacement of 620 pounds and a total sail area of 225 square feet, the boat boasts a staggering sail-area-to-displacement ratio of 49.51. In physical terms, this high ratio translates to explosive acceleration and the ability to generate its own apparent wind in light-air conditions. In just five to eight knots of breeze, the Cougar can easily match or exceed wind speed, slipping through the water with minimal drag.
The boat’s capsize screening ratio of 3.75 reflects its lack of ballast and its reliance on form stability. While a ratio of this magnitude on a monohull indicates severe instability, on this 19-foot catamaran, it highlights the lightweight, highly dynamic nature of the platform. Stability is derived entirely from its 7-foot-11-inch beam and the active positioning of the crew, who must utilize hiking straps or a trapeze to keep the hulls flat in heavier air.
The rig is a highly efficient 7/8 fractional sloop featuring a rotating aluminum mast stepped on a hinged base. The rotating spar aligns with the airflow to significantly reduce turbulence along the luff of the fully battened mainsail. Upwind, the Cougar points remarkably well for a vintage multihull, thanks to its pivoting, removable aluminum centerboards. When lowered, they draw 2.5 feet, providing the necessary lateral resistance to prevent leeway. Downwind, the boards can be completely retracted, reducing the draft to a mere 5 inches. This makes the Cougar exceptionally easy to beach, launch, and trailer, allowing sailors to explore thin-water bays and shorelines that are inaccessible to keelboats.
Variations & Amateur Sister Ships
While G. Prout & Sons produced the molded fiberglass Cougar Mark III hulls at their UK facility, the design gained massive traction in North America. Licensed builders, such as Rebcats and Technical Enterprises Limited, marketed and assembled the boats in Canada and the United States, catering to a booming class association that thrived throughout the 1960s and 1970s.
To accommodate home builders who wanted to participate in the multihull craze but lacked access to expensive fiberglass molds, the Prout brothers designed a sister ship called the Jaguar. The Jaguar was essentially a hard-chine version of the Cougar Mark III, sharing nearly identical dimensions and sail areas but utilizing a chined hull shape that could be easily constructed from flat sheets of quarter-inch marine plywood over spruce frames. While the factory-built Cougar Mark III, with its rounded "soft-chine" fiberglass hulls, offered superior hydrodynamics and less resistance in a chop, the plywood Jaguar allowed the design to proliferate among amateur shipwrights across the globe.
Known Issues & Restoration Triage
Acquiring a vintage Cougar Mark III today requires the discerning eye of a restorer, as these boats are now decades old and feature a vulnerable wood-to-fiberglass structural interface. The primary concern for any prospective buyer is rot within the wood-composite bridge deck and structural framing. The spruce crossbeams that tie the fiberglass hulls together are subjected to immense torsional loads when sailing in a seaway. If water penetrates the fiberglass encapsulation or the fastener holes for the hardware, these beams can rot from the inside out, severely compromising the boat's structural integrity and leading to hull misalignment.
The mahogany plywood cockpit sole and bridge deck are similarly prone to delamination. Any softness underfoot, especially around the chainplates, mast step, or hatch openings, indicates water ingress. The mast step itself is a critical triage point; because the heavy compression loads of the rotating rig rest directly on the wooden bridge deck, any underlying rot in the spruce support structures can cause the step to sag or collapse entirely.
The centerboard trunks also require close inspection. The pivoting aluminum boards can wear out their pivot pins or wear down the interior fiberglass walls of the trunks, leading to structural leaks or jammed boards. Finally, early GRP layups from this era, while thick, can suffer from gelcoat crazing, stress cracking around the shroud chainplates, and minor osmotic blistering if left in the water for extended periods.
Modernization & Refit Trends
For dedicated classic multihull enthusiasts, the Cougar Mark III represents a highly rewarding restoration project, and veteran owners have established standardized pathways for modernization. The most critical modern upgrade involves stripping the old varnish or deteriorating gelcoat from the wooden cockpit and deck, replacing any soft spruce framing, and encapsulating the entire wooden structure in modern epoxy. Utilizing lightweight fiberglass cloth saturated with epoxy resin creates a durable barrier that stops moisture penetration while retaining the beautiful aesthetic of the mahogany brightwork.
Rigging modernizations are also common. Many owners choose to replace the original stainless steel wire shrouds with modern Dyneema standing rigging. This modification reduces weight aloft, which is highly beneficial for minimizing the heel angle and reducing pitching in a chop. Upgrading the deck layout with modern, high-load roller-bearing mainsheet travelers, cam cleats, and self-tailing blocks significantly reduces the physical effort required to trim the 225-square-foot sail plan. Finally, replacing the original, heavy wooden hatch covers with modern, watertight composite hatches ensures that the dry storage compartments in the pontoons remain truly dry.
The Verdict
The Cougar Mark III is a masterfully designed classic that represents the golden age of early multihull development. For the sailor who values historical pedigree, the elegance of classic mahogany brightwork, and the pure thrill of light-air speed, this 19-foot catamaran is a rare and rewarding find. While it requires more structural vigilance and maintenance than a modern rotomolded beach cat, it rewards its crew with a dry, spacious cockpit, excellent sea-keeping capabilities for its size, and a sailing experience that is both fast and comfortable.
Pros
- Exceptional light-air performance and acceleration driven by an impressive sail-area-to-displacement ratio.
- Extremely shallow draft with centerboards up, allowing for effortless beaching, trailering, and thin-water sailing.
- Spacious, solid mahogany cockpit deck that comfortably accommodates family day-sailing, unlike modern mesh trampolines.
- Generous dry storage options within the watertight hatches of both fiberglass hulls.
- Efficient, rotating 7/8 fractional rig that optimizes aerodynamic efficiency and reduces sail-handling friction.
Cons
- High maintenance demands due to the vintage hybrid construction of fiberglass hulls joined by spruce and mahogany woodwork.
- High susceptibility to structural rot in the crossbeams, bridge deck, and mast step if water intrusion is left unchecked.
- Extreme sail area requires active mainsheet management and crew weight placement in heavy wind to prevent capsizing.
- Rarity of surviving parts and specialized class hardware requires custom fabrication or creative sourcing for refits.
