Design and Construction
Thames Marine built the 670 in fiberglass, and the era's heavy hand-laid solid hulls gave the boat a substantial feel for her length. The twin-keel arrangement is the defining geometry of the design: by splitting the ballast into two lateral foils the boat draws only 2.67 feet and can take ground upright on a drying mooring, a practical advantage in the tidal estuaries the British market favored. A ballast-to-displacement ratio near 45 percent places her firmly in the stable, forgiving end of the spectrum for a 22-footer, and the 19-foot waterline against 22-foot overall length shows a modest overhang rather than a stretched planing hull. David Feltham, who would later develop the builder's Mirage 28 and 37 lines in the mid-1970s, shaped a conservative pocket cruiser here rather than a racer.
Rig and Handling
The masthead sloop rig carries 238 square feet of reported sail area, a moderate inventory for a boat of this displacement that yields enough drive to move her in a breeze without demanding a large crew. The 5.84-knot hull speed is the natural limit imposed by the 19-foot waterline. With twin keels and a short draft, the 670 trades pointing ability to windward for the security of standing where a fin-keeler would tip, and the 8-foot beam gives her the form stability to carry that rig without nervousness.
Accommodations
The interior arrangement of the 670 is not described by the available sources, and the builder context supplies only the broad fact of 1960s solid-GRP construction rather than joinery detail. What can be said is that at 22 feet overall with an 8-foot beam she is a two-person coastal camp cruiser by proportion, not a weekender for four. The twin-keel hull leaves a central dead-flat floor amidships where a fin would intrude, a layout consequence of the keel choice rather than a documented plan.
The Verdict
The Snapdragon 670 is an honest early-1960s Thames Marine product: a shallow-draft twin-keeler of conservative rig and reassuring ballast fraction, designed by David Feltham at the start of his association with the builder. She asks little of a short-handed crew and can dry out where deeper boats cannot, but she is slow by modern standards and small by any measure of cruising comfort. As a first classic pocket cruiser she remains a sensible, well-built introduction to the marque.
Pros
- Twin-keel hull draws only 2.67 feet and grounds upright
- Ballast fraction near 45 percent gives high stability for length
- Solid hand-laid fiberglass construction from a known British builder
Cons
- 5.84-knot hull speed limits passage pace
- 22-foot length restricts accommodation to coastal use
- Masthead rig with modest sail area is underwhelming in light air
