Design and Construction
Karlsson specified a solid-fiberglass hull, a foam-cored deck, and a lead fin keel. Depending on load, the keel draws roughly 5.4 to 5.7 feet.
Displacement is near 7,700 pounds, and the ballast ratio is 46 percent. The Mamba 311’s capsize screening value is 2.04—a figure that would bar her from sanctioned ocean racing, while also indicating a stable form for coastal work.
Her length-to-beam ratio of 3.05 and displacement-length ratio of 191 place her among “moderate racers.” The immersion rate is about 921 pounds per inch, so she settles predictably as weight comes aboard. Wetted surface is roughly 301 square feet, a modest figure that helps her accelerate.
Rig and Handling
The Mamba 311 was offered with more than one rig: specifically, a masthead sloop or a fractional sloop. Under the ISO 8666 reference sail, the sail-area-to-displacement ratio is 15.9. With a 135 percent genoa, it rises to 19.1.
A comparative review notes that she carries more rig than only 42 percent of similar sailboats and is therefore slightly underrigged. Theoretical hull speed is 6.9 knots, Relative Speed Performance is 50, and the Motion Comfort Ratio is 19.8.
Accommodations and Capacities
The 30-foot-7-inch length and 10-foot beam create a compact footprint for two. Tankage consists of 53 gallons of water and 11 gallons of diesel, a balance that favors time at anchor over extended motoring.
Verdict
The Mamba 311 offers a rare choice of rigs in a lead-keeled boat with a solid-fiberglass hull. She is slightly undercanvased by class standards, and her capsize screening value bars her from sanctioned ocean-race start lines. For coastal sailing, however, she offers predictable loading and modest wetted surface.
Pros
- Lead keel and 46 percent ballast ratio provide low-center-of-gravity stability
- Choice of masthead or fractional rig to suit owner preference
- Modest wetted surface
- Predictable immersion rate of 921 pounds per inch
Cons
- Slightly underrigged compared with class peers
- Capsize screening value of 2.04 excludes her from sanctioned offshore racing
- Small 11-gallon diesel capacity limits motoring range
