Design Brief & Intent
John B. Brooke’s design mandate for the Sunbird 25 was to bridge the gap between spartan, day-sailing trailer boats and heavy, permanently moored coastal cruisers. Built for families looking to graduate from smaller trailer sailers, the boat’s primary mission was to provide weekend and extended cruising capability across varied environments, from shallow estuaries to open bays and semi-protected coastal waters. What distinguished the Sunbird 25 from its competitors was its emphasis on liveability. While many contemporary 25-foot trailer sailers felt like scaled-up dinghies, the Sunbird 25 boasted an impressively high cabin trunk and a wide, stable beam of 8.17 feet. This geometry allowed for an interior with a genuine six feet of standing headroom—a rare luxury for a trailerable boat of this era.
The interior layout was meticulously planned by builder Chris Hall and Brooke to maximize every square inch. Utilizing a full internal GRP liner for structural rigidity and easy maintenance, the cabin felt remarkably bright and open. It featured accommodation for up to six berths, including an enclosed forward V-berth for privacy, a four-seater dinette that converted into a double berth, a fully functional galley, and a dedicated, enclosed compartment for a marine toilet. Rich timber trim and high-quality joinery elevated the interior beyond the utilitarian standards of many fiberglass production boats of the late 1970s, making it a highly comfortable platform for live-aboard weekends.
Variations & Configurations
The Sunbird 25 was offered in two distinct configurations that fundamentally changed the boat’s handling, propulsion, and cruising profile: the Trailer Sailer (TS) and the Motor Sailer (MS). The standard Sunbird 25 TS featured a fractional seven-eighths sloop rig and a pivoting steel swing centerboard. This centerboard drew just 1.67 feet with the board fully raised, allowing the boat to navigate extremely shallow waterways, run up onto sandy beaches, or slide easily onto a custom multi-axle trailer. With the board lowered, the draft extended to 4.00 feet, providing the necessary lateral resistance for upwind sailing. A key design triumph of the TS version was that the centerboard casing was completely integrated beneath the cabin sole and interior furniture, leaving the saloon cabin entirely unobstructed.
The Sunbird 25 MS, released in 1978, was a bold departure designed for a relaxed, sheltered cruising lifestyle. Rather than a swing centerboard, the MS model utilized a shallow fixed ballast keel with an aperture for a propeller, paired with a heavy skeg-mounted rudder. It traded the trailerable versatility of the TS for a permanent mooring lifestyle. It featured a prominent cabin doghouse or pilot house that offered superb weather protection for the forward end of the cockpit. Under this hardtop, a wheel steering station replaced the standard tiller. To accommodate the higher boom required to clear the doghouse, the mainsail area was reduced. The MS variant prioritized reliable mechanical propulsion, typically carrying larger inboard diesel engines—such as Volvo Penta or Bukh units producing 10 to 13 horsepower—and was highly favored by sailors who valued mechanical reliability and shelter over pure sailing performance.
Sailing Performance & Handling
On the water, the Sunbird 25 delivers a reassuring, stable ride that belies its trailerable classification. Its sailing characteristics are defined by a moderate displacement of 3,505 pounds, with a significant 1,199 pounds of lead ballast representing a ballast-to-displacement ratio of 34.21 percent. This high ballast ratio, combined with 1,000 pounds of the ballast poured and sealed internally within the hull's lower skeg, gives the boat excellent initial stiffness. Under sail, it resists rounding up in sudden gusts and carries its momentum well through light chop. With a displacement-to-length ratio of 137.37, the hull is relatively light and easily driven, though its moderate sail-area-to-displacement ratio of 15.88 means the boat can feel slightly underpowered in light airs. To optimize performance in light breezes, experienced helmsmen rely on a large overlapping genoa or a spinnaker.
The boat’s comfort ratio of 14.19 reflects its relatively light trailerable displacement; while it is highly stable, it exhibits a quicker, more active motion in a seaway than a heavy, full-keeled offshore cruiser of the same length. With a capsize screening ratio of 2.15, the Sunbird 25 is mathematically classified as a coastal and inland cruiser rather than a blue-water passage maker. It has a lower ultimate righting capability if completely knocked down compared to deep-draft keelboats. Despite this, the boat’s seaworthiness is highly respected; fleet cruises of Sunbird 25s successfully crossed the notorious Bass Strait to Tasmania, proving that in competent hands and favorable weather windows, the design is highly capable. At the helm, the TS version is balanced and responsive, utilizing a transom-mounted rudder that leaves the cockpit uncluttered.
Market Snapshot & Economics
On the brokerage market, the Sunbird 25 occupies a unique niche as a highly desirable, classic pocket cruiser. It commands a relative premium over smaller, more spartan trailer sailers of its era due to its generous standing headroom, inboard engine configurations, and robust construction. In regions like the Gippsland Lakes and Western Port in Victoria, Australia, where the design has a dedicated owner’s association, clean examples are highly sought after and trade quickly.
When evaluating a Sunbird 25, the economics of ownership are heavily influenced by two major factors: the trailer and the auxiliary power. Because a fully laden Sunbird 25 TS on a trailer carries an average towed mass of approximately 3,000 kilograms, towing requires a heavy-duty, dual-axle road trailer and a powerful tow vehicle. A trailer in poor condition, requiring brake, axle, or structural frame replacement, can easily equal or exceed the purchase price of the boat itself. Additionally, many units still feature their original Lister Petter 6-horsepower or Volvo Penta inboard diesels. If these engines are nearing the end of their service life, buyers must budget for either a costly diesel rebuild or a conversion to an outboard motor mounted in the cockpit well.
Known Issues & Triage
Prospective buyers of a Sunbird 25 must pay close attention to several known, age-related technical vulnerabilities. The most critical area of concern on the TS version is the swing centerboard mechanism. The heavy steel plate is raised via a winch and wire cable system. Over decades of immersion, the lifting cable can fray, and the steel loop welded to the top of the centerboard is highly susceptible to galvanic corrosion. If this loop fails, the plate can drop completely or jam in the trunk. Triage requires accessing the inspection port under the cabin sole to check the cable, shackle, and attachment eye. Dropping the plate during a haul-out to inspect the pivot pin, replace the cable, and re-galvanize or paint the steel plate is highly recommended.
Another common issue lies in the deck construction. The deck is built using a GRP sandwich core with foam and timber (or plywood) reinforcement. Over time, water can penetrate the core through poorly bedded deck hardware, such as the chainplates, stanchion bases, or around the mast step. This leads to localized rot and soft spots. Buyers should perform a thorough "tap test" across the side decks to check for delamination. On the TS version, the rudder is housed in an aluminum box with laminated plywood cheek plates. If the rudder blade is allowed to kick up or swing back even slightly while sailing in heavy weather, the leverage on the tiller increases dramatically. This force can split the plywood cheek plates away from their core, requiring a complete rudder box rebuild.
Modernization & Upgrades
Modern owners of the Sunbird 25 are active in updating these classic boats to improve single-handed handling and comfort. One of the most popular upgrades is the modernization of the electrical system. Replacing the original, heavy lead-acid battery banks with modern Lithium Iron Phosphate (LiFePO4) batteries significantly reduces the boat’s overall weight—an important consideration for trailer towing—while providing reliable power for modern refrigeration, electric anchor winches, and electronics.
Repowering is another common modernization pathway. For owners of the TS model looking to retire aging raw-water-cooled inboard diesels, some choose to install lightweight, fresh-water-cooled modern diesel engines like a Beta Marine 10 or 14 horsepower unit. Alternatively, some owners seal the old shaft log and convert the boat to run on a high-thrust four-stroke outboard engine mounted on a transom bracket or within the existing cockpit well, utilizing remote controls at the helm. Lastly, upgrading the deck layout by leading all halyards, reefing lines, and control lines aft to the cockpit cabin top with modern deck organizers, rope clutches, and self-tailing winches makes the Sunbird 25 an exceptionally easy boat to sail single-handed.
The Verdict
The Sunbird 25 remains one of the most successful and practical compact cruisers of its era. Its clever design, massive interior volume, and genuine standing headroom make it feel like a much larger yacht once step aboard, yet it retains the flexible, cost-saving advantages of trailerable ownership. Whether configured as the agile, shallow-draft swing-keel TS version or the heavily protected, pilot-house MS motor sailer, the Sunbird 25 stands as a testament to John B. Brooke's vision of comfort and seaworthiness in a 25-foot package. While aging systems and potential deck-core issues require careful vetting, a well-maintained or modernized Sunbird 25 offers an unmatched gateway to family coastal cruising.
Pros
- Generous interior layout with an exceptional six feet of standing headroom.
- Versatile swing-keel (TS) configuration allows for beaching and shallow-water exploration.
- Robust fiberglass hull construction built to standards exceeding Lloyd's requirements.
- Excellent initial stability and stiff sailing characteristics due to a high ballast ratio.
- Functional, fully enclosed head compartment and private forward V-berth.
- Excellent weather protection and cruising comfort on the Motor Sailer (MS) doghouse variant.
Cons
- Steel swing-keel winch, cable, and attachment loop are prone to severe corrosion and require regular maintenance.
- Plywood and foam deck cores are highly susceptible to localized rot and delamination if hardware is poorly sealed.
- High towing weight (approaching 3,000 kg fully laden) requires a heavy-duty tow vehicle and a high-maintenance dual-axle trailer.
- Underpowered in light wind with standard sails, necessitating a genoa or spinnaker.
- Narrow side decks make moving forward from the cockpit to the bow tight under foot.
