Design and Construction
Karlsson's hull is a solid fiberglass shell with a lead fin keel. The ballast ratio of 46 percent and displacement near 7,700 pounds give the 311 a capsize screening value of 2.04 — a figure that would bar her from sanctioned ocean racing anchor yet speaks to 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 of about 921 pounds per inch means she settles predictably, and the wetted surface of roughly 301 square feet is modest, helping her accelerate.
Rig and Handling
She was offered with more than one rig, specifically a masthead sloop or a fractional sloop anchor. Under the ISO 8666 reference sail the sail-area-to-displacement ratio is 15.9, rising to 19.1 with a 135 percent genoa; a comparative review notes she carries more rig than only 42 percent of similar sailboats and is therefore slightly underrigged anchor. Theoretical hull speed is 6.9 knots and Relative Speed Performance is 50. Motion Comfort Ratio is 19.8.
Accommodations
The 10-foot beam and 30-foot-7-inch length yield a compact footprint for two, with foam-cored deck and fiberglass construction. The 53-gallon water capacity against an 11-gallon diesel tank favors anchorages over motoring.
The Verdict
The Mamba 311 offers a rare rigging choice in a lead-keeled, solid-fiberglass hull. She is slightly undercanvased by class standards and barred from ocean-race start lines by her capsize screen, but for coastal sailing she presents predictable loading and modest wetted surface.
Pros
- Lead keel with 46 percent ballast ratio for low-center-of-gravity stability
- Offered in masthead or fractional rig to suit owner preference
- Modest wetted surface and predictable 921 lb/inch immersion rate
Cons
- Slightly underrigged versus class peers
- Capsize screening of 2.04 excludes sanctioned offshore racing
- Small 11-gallon diesel capacity limits motoring range
