A DIY Class 40 Racer

by Laurie McGowan



WB No. 252, Sept/Oct 2016: The racing strategy for Class 40 boats involves running downwind, and PROTON’s freestanding cat-ketch rig, using carbon-fiber masts and wishbone booms, is designed to make the most of it, including stable wing-on-wing sailing.

Steering is via dual rudders operated by a single tiller working through an Ackermann arm linkage.

When heeled, PROTON’s center of flotation shifts forward, and its waterline aft terminates just below the transom, avoiding drag. The hull, when heeled, has minimal wetted surface.


  • LOA: 39.99′ (12.19m)
  • Measurement LWL: 35.75′
  • Sailing LWL: 40′ (12.19m)
  • Beam: 14.76′ (4.50m)
  • Draft: 9.84′ (3.0m)
  • Mast height: 62.34′ (19m)
  • Minimum lightship displacement: 9,920 lbs (4,500 kg)
  • Estimated loaded displacement:
    • (without water ballast): 11,420 lbs (5180 kg)
    • Water ballast: 1,695 lbs per side (750 liters, or 769 kg)
  • Fixed ballast: 3,968 lbs (1,800 kg)
  • Sail area, upwind: 1,238 sq ft (115 m2)
  • Sail area, with spinnakers: 2,852 sq ft (265 m2)
  • D/L ratio (sailing, no water ballast): 80
  • SA/D ratio: 39

Laurie McGowan is a boat designer in Nova Scotia with a diverse on- and below-water work history; he specializes in energy-efficient commercial and pleasure boats. More of his work may be found at

Do you have a boat concept you’d like to see Laurie McGowan develop on these pages? If so, send it to Sketchbook, WoodenBoat Publications, P.O. Box 78, Brooklin, ME 04616, or email it to Your letter should be no longer than 500 words.

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