Design and Construction
The Rainbow 42 has a solid-fibreglass hull and deck. Her waterline length is 36.4 feet, with a beam of 12.3 feet. She carries 3,108 pounds of lead ballast in a fin keel with bulb, for a ballast ratio of 37 percent.
Draft varies from 7.64 to 7.94 feet depending on load—deep enough that she can only enter major marinas. The bottom has about 548 square feet of wetted surface, while the immersion rate is roughly 1,561 pounds per inch. She therefore responds quickly to added load as well as to sail trim.
Her displacement-length ratio is 79, placing her among the “ultra light racers” of her era. A length-to-beam ratio of 3.39 and a motion comfort ratio of 12.0 to 12.6 describe a lively, responsive hull rather than a slow, voluminous passage-maker.
The capsize screening value is 2.38. Under that metric, she wouldn’t have been accepted for ocean racing—a reminder that the design was intended for coastal and performance cruising rather than to meet bluewater minima.
Rig, Performance, and Handling
The Rainbow 42’s defining feature on paper is her fractional sloop rig. By one assessment, she carries more rig than 100 percent of similar sailboats, indicating that the boat is significantly overrigged.
Mainsail and jib area totals 808 square feet. The sail-area-to-displacement ratio is 30.4 with the ISO reference sail, rising to 34.9 with a 135 percent genoa. Paired with the ultralight displacement, that powerful sail plan produces a Relative Speed Performance figure of 97 and a theoretical displacement-hull maximum of 8.1 knots.
The running rig is generously sized. Main, jib, and spinnaker halyards are each 133.4 feet long and half an inch in diameter. The jib sheets, genoa sheets, and mainsheet use 14 mm line; the mainsheet alone is 104.2 feet long.
A buyer or crew should expect a boat that accelerates in modest breeze and rewards disciplined sail handling, rather than a sluggish, forgiving hull.
Accommodations and Comfort
The available authority material gives no descriptive details about the interior arrangement, berth count, or joinerwork, and the builder’s background adds no further information.
What can be said with confidence is that the boat’s 42-foot length and 12.3-foot beam provide a contemporary cruising footprint. The 37 percent ballast ratio, with 3,108 pounds of lead in a bulb fin, suggests a stiff platform once heeled. A motion comfort ratio in the low teens reinforces that she is built to move with the sea rather than smother it.
Cruising Limitations
The main design-level caveat is draft. At 7.64 to 7.94 feet depending on load, the Rainbow 42 was historically restricted to major marinas and excluded from many shallow anchorages and smaller harbours.
That limitation comes from the bulb-fin configuration rather than from a defect, but it shaped where the fleet could reasonably cruise.
Refit and Ownership Notes
The published rig dimensions provide a useful baseline for re-rigging and line replacement. Halyards are 133.4 feet long by half an inch in diameter. Sheets use 14 mm line, with the mainsheet measuring 104.2 feet. Control lines, including the cunningham and kicking strap, are 36 feet long.
Owners maintaining the original overdriven rig should plan their line inventories around those figures rather than around typical assumptions for a 40-foot boat.
The Verdict
The Rainbow 42 is a Harter-designed, Farsø-built performance cruiser that trades volume and ocean-race acceptance for lively light-air speed and a responsive, ultralight hull. She’s a specialist’s boat: quick, stiff, and demanding of a crew that prefers sail power to motoring. Her deep draft is likely to dictate her cruising range more than any accommodation limit.
Pros
- Ultralight displacement, with a DL ratio of 79
- Overdriven rig with strong speed potential
- Lead-ballasted bulb fin and a 37 percent ballast ratio
- Generous, well-documented running-rig dimensions that simplify maintenance planning
Cons
- Deep draft of 7.64–7.94 feet limits access to marinas, anchorages, and harbours
- Capsize screening value of 2.38 excludes acceptance for ocean racing under that metric
