Extension 24 Information, Review, Specs

Sailing Performance & Handling

The Extension 24 was engineered as a light-displacement racer (D/L ratio of approximately 112), specifically optimized for off-wind speed and light-air performance. According to archival racing records at Histoire des Halfs, the model participated in competitive events like the 1975 Quarter Ton Cup under names like Minestrone.

Under sail, the boat is known for its agility and ability to surf readily. Editorial testing published by Practical Boat Owner describes the Extension 24 as a boat that "surfs readily" due to its flat aft run and light displacement, with owners reporting speeds of up to 17 knots in heavy weather under control. However, while the technical ballast ratio is reported to be nearly 50%, the boat is often described as "tender" in a breeze because its fin keel lacks a bulb, resulting in a lower righting moment than modern performance keelboats. The fractional sloop rig provides a high sail-area-to-displacement ratio (SA/D), making it a formidable performer in light winds but requiring early reefing as the breeze builds.

Interior Comfort & Variations

Despite its racing pedigree, the Extension 24 offers surprisingly spacious accommodations for a 24-foot vessel. The design’s significant beam and relatively high freeboard create an interior volume that rivals many 27-to-28-footers of the same era. While specific layout details vary among the few custom-built units, the interior is typically described as functional and open, prioritized for a racing crew but capable of weekend cruising.

The boat’s design lineage is closely tied to other "Tension" series yachts by De Ridder. While the Extension 24 is the primary hull, it shares DNA with the Blue De Ridder (a 1972 prototype) and larger siblings like the Tension 31 and the High Tension 36. These models were all focused on the IOR (International Offshore Rule) handicap system, though the Extension 24 specifically sought to maximize "spaciousness" within the narrow confines of the Quarter Ton class.

Known Issues & Buyer’s Checklist

Due to the small production run and the era of construction, buyers should prioritize the following technical inspections:

• Deck Core Integrity: Unlike many production boats of the 1970s that used solid fiberglass or balsa, some Extension 24s (notably Minestrone) were built with fiberglass-sheathed plywood decks. These are highly susceptible to freshwater ingress and rot if deck hardware has not been meticulously re-bedded.
• Rudder Bearing and Stock: The boat utilizes a large transom-hung or partially balanced rudder positioned forward of the transom to maximize control. Owners have noted that the steering system requires regular inspection for play in the bearings, especially given the high loads generated during high-speed surfing.
• Keel-to-Hull Joint: The high ballast ratio puts significant stress on the hull grid. Any signs of "smile" cracks at the leading edge of the fin keel or compression in the bilge should be professionally surveyed.
• Rig Tension: As a fractional rig designed for racing, the mast is often pushed to its limit. Check for evidence of mast-step compression or chainplate movement in the deck.

Community & Resources

Due to its rarity, no dedicated owner’s association exists. However, technical history and data on individual hulls like Mascotte, Slow Motion, and Nimrim are maintained by the Dutch Quarter Ton Class and European racing archives. Enthusiasts often share maintenance insights through broader IOR-era forums and the Quarter Ton Class Facebook community.

The Verdict

The Extension 24 is a "pocket rocket" for the sailor who values historical racing pedigree and surprising interior volume over the convenience of a mass-produced cruiser.

Pros:

• Exceptional surfing capabilities and light-air performance.
• Spacious interior for a 24-foot boat due to the 9-foot beam.
• High-quality design by a respected Dutch naval architect.

Cons:

• Maintenance-heavy construction (especially plywood-cored decks).
• Tender handling in heavy weather requires active sail management.
• Extreme rarity makes sourcing model-specific parts difficult.