Design and Construction
The hull is solid fiberglass, and the builder offered the 43-CC Mk I with different keel alternatives, specifically a wing keel and a fin keel. Both draw just about 4.92 to 5.22 feet depending on load, which lets the boat enter most marinas despite her 45.5-foot length. With 8,000 pounds of lead ballast and a skeg-hung rudder per the builder's specification, the underbody is a conventional fin or wing with moderate draft. The capsize screening value of 1.83 indicates that this boat could, if evaluated by that formula alone, be accepted to participate in ocean races, while the Motion Comfort Ratio of 32.1 speaks to a settled motion in a seaway for a vessel of this size.
Rig and Handling
The 43-CC Mk I is built with a cutter rig and carries more rig than 96 percent of all similar sailboats, a striking figure for a cruiser of her era. The sail-area-to-displacement ratio is 17.4 with the ISO reference sail and rises to 20.7 with a 135 percent genoa, giving her useful light-air drive without pushing into the high-performance end of the spectrum. The theoretical hull speed is 8.0 knots, and the wetted surface of about 495 square feet keeps the hydrodynamic footprint in a normal range for the length. Standing and running rigging dimensions are generous: the three halyards run 119.7 feet at 14 mm diameter, the mainsheet is 113.8 feet of 5/8-inch line, and the genoa sheets are 45.5 feet of 5/8-inch, all sized for a large foretriangle and boom. The immersion rate of about 1,680 pounds per inch means she sits heavily when loaded but resists sudden trim changes.
Accommodations
The model designation names a center-cockpit configuration. The 185-gallon water and 107-gallon diesel capacity from the builder's specification sheet show the boat was planned for extended cruising range, and the 62-horsepower diesel singles up with a 13.58-foot beam to suggest a roomy middle section rather than a stripped racer.
Refits and Ownership
The solid fiberglass hull and simple keel options argue for straightforward survey and repair compared with cored hulls. The 1984 start of production places her before the yard's late-period vinylester and improved-joint upgrades, but no production-end year is stated.
The Verdict
The Irwin 43-CC Mk I is a moderately loaded cruiser with an unusually powerful cutter rig for her type and a shoal-friendly keel option that opens marina access. Her comfort and capsize numbers suit bluewater passage aspirations, while the solid hull and conventional keels keep the structure legible to any surveyor.
Pros
- Cutter rig with more sail plan than 96 percent of similar boats
- Wing or fin keel draws under 5.25 feet, easing marina access
- Capsize screening of 1.83 and comfort ratio of 32.1 for offshore credibility
- Solid fiberglass hull simplifies inspection
Cons
- Production end year not stated
