Hirondelle Mk I Buyer's Guide
The Hirondelle Mk I is the early-1970s iteration of a 23-foot British catamaran designed by Chris Hammond and built by Brian Carvill & Associates, with more than 300 sold across the family line. On the used market it shows up as a small, beamy cruising multihull whose twin-hull layout and bridge-deck cabin still read as practical weekenders rather than toys. Because a high percentage of Mk I boats were home completed, no two will present identically, and the buyer should judge each hull on its own finish and systems rather than assume a production standard.
Layouts on the Used Market
Most Mk I interiors follow a predictable plan: two generous single quarter berths aft in the hulls, a single berth forward in the starboard hull, and a large convertible double on the bridge deck formed by lowering the dinette table. The heads sits to port in the bow, commonly a sea toilet with a small stowaway wash basin. A two-burner galley abaft the dinette and a molded sink in the starboard hull round out the cooking space, while doorless cubbies handle stowage. The forward area between the hulls is mostly solid glass with a short trampoline forward, and that solid deck carries lockers for ground tackle and fenders.
Equipment and Common Upgrades
Original auxillary power is an outboard in a well aft in the cockpit, rated up to 25 horsepower, with fuel tanks under the port and starboard helm seats. The stock rig wore a roller-furling boom and a tall mast over 30 feet, and many boats carry the widely used 150 percent genoa to lift sail area from 250 to 330 square feet. Steering runs through a bar linking the two lifting rudders. Buyers should treat the outboard well and tank stowage as the core power detail, and view the genoa and furling boom as the principal sail-handling equipment; beyond those, individual boats vary by how the home builder finished them.
What to Inspect
The Mk I uses twin daggerboards and lifting rudders that raise but do not kick up; the after rudder-trunk ends are designed to break away on impact, so check for prior strike damage and makeshift repairs. A long-shaft outboard projects below hull level and risks running aground if left down, so confirm the motor tilts and the well is sound. The builder's sailing instructions warn that catamarans can capsize without returning to level, which is a handling fact rather than a defect but speaks to how the boat must be sailed. Where an owner reports balsa-cored deck over single-skin hulls with no liners, probe for soft spots and fastener leaks since all deck hardware is accessed from inside.
Availability and Buyer's Takeaway
Regional availability should be confirmed locally, as no specific market list is provided here. For the walk-through, focus on rudder-trunk integrity, outboard well and tilt function, deck-core condition, and the state of any home-completed interior work.
- Verify rudder trunks and break-away ends for past groundings
- Confirm long-shaft outboard tilts clear of hull depth
- Sound the deck for core damage around fasteners
- Assess home-completion quality of hulls and bridge deck