Hammond chose symmetrical hulls wide enough for single berths and used a fairly flat sheer with some reverse curve to make the most of the interior. The result is a small, versatile family cruiser suited to short passages and lively daysails. In its original form, it was faster than most monohulls of similar length.
Design and Construction
The hulls are deliberately symmetrical. Their single-skin fiberglass shells have no liners in the hulls or beneath the deck, leaving the structure visible and easy to survey. Overall, construction is adequate but dated by modern standards.
The area between the hulls forward is mostly a solid fiberglass deck, with a trampoline net spanning only the foremost foot or so. This solid deck adds weight, but it was a conscious concession to cruising utility. It contains several lockers sized for ground tackle, fenders, and lines.
One owner reports that the deck is balsa-cored, while the hull itself is single-skin fiberglass. Either way, all deck-hardware fasteners are easy to reach from inside.
Rig, Performance, and Handling
The original Mk I had a tall rig, with a mast exceeding 30 feet and 250 square feet of working sail area. With the widely used 150 percent genoa, sail area increased to 330 square feet. A stock roller-furling boom simplified shorthanded sail handling, while the twin daggerboards provided superior upwind ability.
Owners have found that the boat tacks through about 130 degrees. When she loses power midway through a tack, a gentle turn of the helm preserves way better than throwing it hard over. One reported way to clear a stall is to sail backward with the helm reversed.
The rudders lift but don’t kick up. If they strike the bottom, the after ends of their trunks are designed to break away rather than damage the hulls. A steering bar links the two rudders and tillers so they work as a unit.
The manufacturer’s sailing notes warned that catamarans can capsize without self-righting and urged crews to shorten sail early. The boat also accelerates better when held straight through a gust than when borne away.
A Hirondelle once won the multihull class in the Around the Isle of Wight race. The source’s editorial review rated the boat’s sailing performance excellent in its day and still good for its size, particularly in Mk I form.
Accommodations
The bridge deck centers on a U-shaped dinette seating four. Its table drops to form a large berth, though the mast compression post interrupts it. The post also carries the clamp that holds the table up. Fixed backrests run along the outboard side.
The remaining berths are spread through the hulls: two single quarter berths aft and one single berth forward in the starboard hull. Together with the convertible dinette, the standard layout sleeps four or five.
The head is forward in the port hull, with a portable toilet, although most Mk Is were fitted with sea toilets and a small stowaway basin. A small galley with a two-burner stove sits abaft the dinette on the bridge deck, served by a molded sink in the starboard hull. Storage consists of a network of doorless cubbies.
Auxiliary Power and Grounding Risks
An outboard of up to 25 horsepower mounts in a well aft in the cockpit. Fuel tanks are stowed beneath the port and starboard helm seats.
The daggerboard-and-lifting-rudder arrangement requires attention when operating under auxiliary power. A long-shaft outboard projects below hull level and can run aground if left down. The rudders lift but, because they don’t kick up, rely on the breakaway after ends of their trunks if they hit bottom.
Variants, Refits, and Ownership
A high percentage of Mk I hulls were completed at home, so finish and systems vary from boat to boat.
Later versions differed substantially. The Mk II had a shorter mast, while the late-1970s Mk III adopted fixed keels and upgraded interiors. The subsequent Hirondelle Family retained the same length but added two feet of beam, moved the cabin forward, and offered the Aero Rig, with headsail and mainsail carried on a single rotating boom.
The Verdict
The Hirondelle Mk I is a thoughtfully arranged pocket catamaran that sails beyond what its 23-foot length might suggest. It combines strong performance with a genuine cruising interior, and the builder was candid about the limits of a small multihull.
Its dated construction and the variable quality of home-completed boats call for careful inspection. Even so, the underlying design remains a quick, roomy weekender.
Pros
- Symmetrical hulls and reverse sheer provide useful interior volume for the length
- Twin daggerboards and the tall rig deliver strong upwind and all-round performance
- Practical bridge-deck dinette, accommodation for four or five, and sheltered forward stowage
Cons
- Single-skin, dated construction, with many home-completed hulls of uneven finish
- Long-shaft outboard can ground if not tilted; rudders lift but don’t kick up
- Capsize without recovery is a stated risk, so sail must be reduced early
