First launching in 1974, the Extension 24 was designed to compete at the highest levels of the competitive IOR Quarter Ton Cup circuit. Its pedigree was cemented on the international racing stage, with notable sisterships like Minestrone competing in the 1975 Quarter Ton Cup in Deauville, and Balletent—built by Jim Lensvelt at Jachtwerf Middelharnis in the Netherlands—finishing an impressive seventh at the 1977 Quarter Ton Cup in Helsinki. While mass-market Quarter Tonners like the San Juan 24 or the Ron Holland-designed Eygthene 24 went on to sell in the hundreds, the Extension 24 remained a more exclusive, semi-custom affair. It offered discerning Corinthian racers a highly optimized racing platform that, crucially, retained enough interior volume and structure to double as an active weekend cruiser.
Design Brief & Intent
The core mission of the Extension 24 was to exploit the measurement loopholes of the IOR Quarter Ton rule while providing a rigid, lightweight, and aerodynamically advanced racing platform. In an era when many Quarter Ton designs were stripped-out, hollowed "machines" with barely enough headroom to sit, de Ridder opted for a relatively high freeboard and a wide, stable deck beam. This choice created a surprisingly airy, open-plan interior layout.
Down below, the boat eschewed heavy, cosmetic joinery to keep displacement to a minimum. Structural bulkheads were built using marine-grade plywood bonded directly to the hull to provide necessary torsional rigidity. The accommodation plan typically offered four berths—including two quarter berths running under the cockpit sides and a V-berth arrangement forward—along with basic galley provisions, such as a space for a two-burner stove. This layout distinguished the Extension 24 from its more Spartan competition, making it far more practical for short-handed coastal cruising and overnight stays once the racing marks were cleared.
Variations & Configurations
Because the Extension 24 was produced in small numbers by both George Stead Yachts in the United Kingdom and Jachtwerf Middelharnis in the Netherlands, variations across the fleet are common. The primary difference lies in the building materials and construction methods. The standard production run utilized hand-laid solid fiberglass (GRP) for the hull, whereas several of the highly optimized racing prototypes and later Dutch builds were constructed using lightweight foam-core epoxy composites to maximize strength-to-weight ratios.
Draft and keel configurations also varied. While the standard design featured a high-aspect, deep fin keel drafting 5.09 feet (1.55 meters) with a ballast weight of 1,003 pounds, some European variants utilized slightly modified keel profiles designed to optimize their performance under specific local handicap rules.
Rig choices represent another major area of variation. The initial 1974 launches utilized the massive masthead sloop rigs common to early IOR rules, which relied on huge, overlapping genoas to generate power. However, later configurations and subsequent owner conversions shifted to a modern 7/8 fractional rig. This fractional setup, often featuring dual spreaders and a keel-stepped mast, significantly modernized the boat's handling dynamics.
Sailing Performance & Handling
On the water, the Extension 24 behaves like a purebred, highly responsive racing machine. The boat's physical dimensions explain its lively character: a displacement of just 2,006 pounds paired with an exceptionally generous sail area of 247 square feet. The resulting Sail Area-to-Displacement ratio of 24.84 indicates an incredibly powerful sail plan. In light to moderate air, the Extension 24 is exceptionally agile, accelerating out of tacks almost instantly and showing a remarkable ability to point high into the wind.
The high Ballast-to-Displacement ratio of 50.0% is a critical element of its design. With half of the boat's total weight concentrated in its deep fin keel, the Extension 24 exhibits excellent initial stiffness. However, because the hull itself is so light—as reflected in its ultra-low Displacement-to-Length ratio of 111.94—the boat feels incredibly active. At the helm, the feedback through the tiller is immediate and tactile, requiring a concentrated, active helm hand.
Its Motion Comfort ratio of 7.72 confirms that this is not a heavy, sea-kindly cruising yacht; the motion in a chop is quick and lively, which can be tiring for a novice crew over long passages. Furthermore, its Capsize Screening ratio of 2.87 is typical of the wide-beam, lightweight racers of this vintage, meaning the boat is highly suited for inshore, coastal, and closed-sea racing, rather than blue-water offshore voyaging. Downwind under spinnaker, the wide beam and deep fin keel help control the classic "IOR roll," though the boat still demands timely sail trimming to maintain optimal trim and avoid round-outs.
Market Snapshot & Economics
Today, the Extension 24 occupies a highly specialized niche on the brokerage market. Hulls are exceptionally scarce, particularly outside of European waters, meaning they rarely change hands. When they do emerge on the market—primarily in England, Wales, and the Netherlands—they are typically priced as highly affordable entry points into the vibrant and prestigious classic Quarter Ton Cup racing circuit.
Due to the age of these vessels, buyers should prepare for classic "project boat" economics. While a solid hull can be acquired for a very modest outlay, bringing an Extension 24 up to modern, competitive racing trim can quickly add up. Replacing older standing and running rigging with modern Dyneema, investing in high-performance carbon or black laminate sails, and updating deck hardware like self-tailing winches and high-load clutches can easily dwarf the initial purchase price. However, for the sailor who values historical significance, exceptional sailing feedback, and the camaraderie of the classic racing scene, the total investment represents excellent value compared to modern, sterile sportboats.
Modernization & Upgrades
The most successful Extension 24s sailing today have undergone significant modernization, many of which were documented during high-profile refits, such as Rupert Holmes’ long-term restoration of the class racer Minestrone in the late 2000s.
The most universally accepted upgrade is the conversion from the original masthead rig to a 7/8 fractional setup. Modern owners often utilize donor rigs—such as keel-stepped aluminum spars from Etchells or custom-built Selden twin-spreader masts—paired with a redesigned deck layout. This allows the boat to run non-overlapping headsails, drastically simplifying short-handed tacking, reducing crew fatigue, and significantly improving the boat’s rating under modern handicap systems like IRC.
Keel modifications are also common among serious racers. Over time, some owners have cast heavier or more hydrodynamically efficient lead keels, often shifting the keel’s position slightly aft to match de Ridder's original design specifications, which corrects the trim imbalances introduced by early IOR modifications.
On the auxiliary front, the heavy, unreliable inboard petrol engines of the 1970s have almost universally been replaced. Most owners prefer to run a lightweight 3.5 to 5 horsepower four-stroke outboard motor on a heavy-duty transom bracket, keeping the weight out of the stern when racing. More recently, the boat’s light displacement and primarily racing-oriented mission have made it an ideal candidate for conversion to lightweight electric outboard systems, which easily handle the short transits from slip to racecourse.
The Verdict
The Extension 24 is a compelling, high-performance historical artifact that offers an incredibly rewarding sailing experience for those who appreciate the design philosophies of the 1970s IOR era. It is not a boat for beginners, nor is it a comfortable family cruiser. However, as a fast, rewarding club racer with overnight capability, it stands out as an exceptionally stiff, well-engineered, and historic little yacht.
Pros:
- Outstanding sailing performance with exceptional light-air agility and responsiveness.
- Highly impressive 50% ballast ratio provides excellent stiffness and safety on the racecourse.
- Surprisingly spacious, open-plan cabin layout compared to other highly stripped-out Quarter Tonners of the era.
- Strong, passionate community support and class eligibility within the historic Quarter Ton Cup circuit.
- Light displacement allows for easy, cost-effective auxiliary power solutions, including electric outboards.
Cons:
- Extremely scarce on the brokerage market, requiring patience and search effort to locate a well-preserved hull.
- Lively, motion-heavy ride in a seaway can be physically demanding and exhausting on longer transits.
- Original masthead rigs are labor-intensive to sail and require conversion to fractional setups for optimal modern handling.
- High Capsize Screening ratio limits its safe operation to coastal and inshore waters.
- Bringing a neglected hull up to competitive racing standards can carry high refit costs relative to the boat's ultimate market value.
