Hirondelle Mk I Information, Review, Specs

Sailing Performance & Handling

The Hirondelle Mk I is frequently described as a "spirited" performer, particularly in light to moderate winds where its low displacement and narrow hulls allow it to outpace monohulls of significantly greater length. Unlike many modern cruising cats that rely on fixed shallow keels, the Mk I features retractable daggerboards. This configuration allows for exceptional upwind tracking and a reduced "sideways slip" common in multihulls, while also providing the ability to venture into extremely shallow estuaries.

In heavy air, the boat’s handling is predictable, though its light weight requires early reefing to maintain a flat, stable platform. According to archival reports from Practical Boat Owner, the Mk I is capable of speeds exceeding 12 knots under the right conditions, though it is most comfortable cruising at 6 to 8 knots. The helm is typically responsive, though owners often note that the original kick-up rudder assemblies require regular maintenance to ensure they remain play-free. Because the boat is a catamaran, it lacks the "heeling" feedback of a monohull, requiring the skipper to be more attentive to rig loads and wind speed changes.

Interior Comfort & Variations

The interior of the Mk I is modest, reflecting its 23-foot footprint and performance-oriented hull shape. The accommodations are split between the two hulls, with the bridge deck serving primarily as the cockpit floor rather than a living space (a feature that would change in later siblings). The Mk I typically offers four berths—two singles in the midships section of each hull and a double formed by the bridge deck area in later Mk II and Mk III iterations, though the Mk I is generally more restricted. Headroom is limited, requiring a "sitting-up" lifestyle below deck, which is the primary trade-off for the boat's excellent bridge-deck clearance and reduced windage.

The lineage of the Hirondelle grew significantly over its production run. Following the Mk I, the Mk II introduced extended transoms and a slightly revised coachroof to improve buoyancy and space. The Mk III (often referred to as the "Family" version) represented the most radical departure, featuring a significantly larger bridge deck cabin that offered standing headroom and a more unified interior layout. There was also a "Hirondelle 23" variant and later the Simpson 26, which further refined the hulls for increased payload.

Popular Mentions & Media

The Hirondelle's most notable cultural contribution is its role in proving the durability of small catamarans through the 1968 Round Britain Race and subsequent ocean crossings. It gained further recognition through the technical writings of designer Chris Simpson, who advocated for the safety of the "low-aspect" rig and wide beam (10 feet) on a small platform. While it does not have a large-scale Hollywood footprint, it is a staple of British multihull literature and remains a frequent subject of "classic boat" features in UK-based nautical media.

Known Issues & Buyer’s Checklist

Prospective buyers should focus on several specific structural areas inherent to the Mk I's age and construction methods:

• Bridge Deck Integrity: Inspect the underside of the bridge deck for stress cracking or delamination, particularly where the hulls join the deck. The Mk I was built during an era of evolving GRP (glass-reinforced plastic) techniques, and flexing over decades can lead to structural fatigue.
• Daggerboard Trunks: These are high-stress areas. Check for "smile" cracks at the base of the trunks and ensure the trunks themselves are watertight.
• Rigging Points: The shroud chainplates are under significant tension in a multihull. Ensure the mounting points are reinforced and free of water ingress.
• Osmosis: Like many British boats of the 1970s, the hulls are susceptible to osmotic blistering. A moisture meter test on the gelcoat is highly recommended during a survey.
• Window Seals: The wrap-around windows on the Mk I are prone to leaking if the original rubber seals have perished, which can lead to interior wood rot.

Community & Resources

The Hirondelle remains supported by a dedicated group of enthusiasts. The Hirondelle Association is the primary repository for technical drawings, tuning guides, and historical data. This group is essential for new owners looking to source parts or understand the nuances of the various Mk I, II, and III configurations.

The Verdict

The Hirondelle Mk I is an ideal entry-level catamaran for sailors who prioritize performance and shallow-draft versatility over luxury.

Pros:

• Excellent speed-to-length ratio and light-air performance.
• Retractable daggerboards allow for beaching and shallow-water exploration.
• Easily trailered compared to modern wide-beam catamarans.
• Strong, proven seaworthiness for coastal and occasional offshore passages.

Cons:

• Limited interior headroom and living space.
• Requires active sail management due to light displacement.
• Aging GRP components require a diligent survey and ongoing maintenance.