Design and Construction
Primrose’s hull carries a length-to-beam ratio of 3.35 and a displacement of 6,500 pounds, of which 3,040 pounds is iron ballast — a 47 percent ballast ratio that, with a capsize screening value of 1.98, places her firmly in the cruiser-racer band rather than the offshore expedition class. The hull itself is solid fiberglass, as is the deck, and the wetted surface runs about 269 square feet. A displacement-length ratio of 210 earns her the “moderate racer” categorization, while a Motion Comfort Ratio of 19.7 suggests a tolerable but not especially soft motion in a seaway. The theoretical hull speed for a displacement hull of this waterline is 6.6 knots, though the calculated maximum speed is closer to 4.5 knots in practice.
Rig and Handling
The Sirocco 31 is built with a masthead rig and a sail-area-to-displacement ratio of 14.46, a figure that indicates modest light-air drive rather than sparkling acceleration. Her running rig follows period masthead convention: jib and genoa sheets of 31 feet at half-inch diameter, a 77.5-foot mainsheet of the same diameter, and 68.2-foot spinnaker sheets. With a skeg-hung rudder and fin keel she is built to pivot reasonably about her own length, and the shallow-ish draft dependent on load means she is forgiving of crowded anchorages. The immersion rate of 774 pounds per inch means she sits sensibly to her ballast and does not squat dramatically under cruising stores.
Accommodations
The class record provides no interior arrangement, berth count, or tankage for this design. What can be said from the outside in is that her 9.25-foot beam and 24-foot waterline give a hull volume typical of a 31-foot cruiser-racer of the era, but the specific layout must be judged hull by hull.
Known Issues
The Sirocco 31 shows no structural defects, osmotic blistering, or rigging failures in service. For a 1970s fiberglass production boat this absence of flagged problems is itself noteworthy.
Refits and Ownership
No class-wide refit campaigns or recurring maintenance regimes are specific to the Sirocco 31. Ownership context is limited to her Spanish construction and straightforward fiberglass-solid build, which implies the usual period maintenance of a solid-glass hull rather than core-saturation worries.
The Verdict
The Sirocco 31 is a Primrose-designed, Ballina Marine–built fiberglass sloop that sits comfortably in the moderate-racer category without pretending to offshore-racer credentials. Her numbers describe a predictable, marina-friendly cruiser with a sensible ballast ratio and a forgiving draft, let down only by the lack of a published accommodation plan or tankage detail.
Pros
- Designed by Angus S. Primrose, a recognized British naval architect
- Solid fiberglass hull and deck with iron ballast at a 47 percent ratio
- Load-dependent draft near 5.5 feet eases marina access
- No class-wide structural or rigging defects in service
Cons
- Modest light-air drive from a 14.46 sail-area-to-displacement ratio
- No published accommodation plan or tankage detail
- Calculated top speed of 4.5 knots below theoretical hull speed
