The Shearwater 45 Sailboat
Specs & Key Performance Indicators

The Shearwater 45, an aft-cockpit cutter, was designed by Dudley Dix and built in South Africa by Acheson Yachts.

'Maggy May', a Shearwater 45 long-distance cruising boat on a mooring ball in Jolly Harbour, AntiguaA Shearwater 45

Published Specification for the Shearwater 45

Underwater Profile: Fin keel & spade rudder

Hull Material: GRP (Fibreglass)

Length Overall: 51'5" (15.7m)

Waterline Length: 37'5" (11.4m)

Beam: 13'1" (4.0m)

Draft: 6'3" (1.9m)

Rig Type: Cutter

Displacement: 27,550lb (12,497kg)

Designer: Dudley Dix

Builder: Acheson Yachts (South Africa)

Year First Built: 1990

Published Design Ratios for the Shearwater 45

1. Sail Area/Displacement Ratio: 20.2

  • Less than 16 would be considered under-powered;
  • 16 to 20 would indicate reasonably good performance;
  • Over 20 suggests relatively high performance.

2. Ballast/Displacement Ratio: 38.0

  • Under 40: less stiff, less powerful
  • Over 40: stiffer, more powerful

3. Displacement/Length Ratio: 235

  • Under 100: Ultralight
  • 100 to 200: Light
  • 200 to 275: Moderate
  • 275 to 350: Heavy
  • Over 350: Ultraheavy

4. Comfort Ratio: 33.3

  • Under 20 indicates a lightweight racing boat
  • 20 to 30 indicates a coastal cruiser
  • 30 to 40 indicates a moderate offshore cruising boat
  • 40 to 50 indicates a heavy offshore boat
  • Over 50 indicates an extremely heavy offshore boat

5. Capsize Screening Formula: 1.7

  • Under 2.0 (the lower the better): Better suited for ocean passages
  • Over 2.0: Less suited for ocean passages

read more about these Key Performance Indicators...

Summary Analysis of the Design Ratios for the Shearwater 45

1. A Sail Area/Displacement Ratio of 20.2 suggests that, in the right hands, the Shearwater 45 will have enough performance to leave most other sailboats of similar waterline length well astern. 

2. A Ballast/Displacement Ratio of 38.2 means that a sailboat like the Shearwater 45 (which doesn't have its ballast concentrated in a bulb at the foot of a deep keel), is likely to benefit from being reefed early to keep her sailing upright in a moderate breeze.

3. A Displacement/Length Ratio of 235, tells us the Shearwater 45 is a moderate displacement cruiser, which means she'll carry all your cruising gear without it having a dramatic effect on her performance. Most of today's sailboats intended for offshore cruising fall into this displacement category.

4. Ted Brewer's Comfort Ratio of 33.3 suggests that crew comfort of a Shearwater 45 in a seaway is similar to what you would associate with the motion of a moderate bluewater cruising boat - a predictable and acceptable motion for most seasoned sailors.

5. The Capsize Screening Formula (CSF) of 1.7 tells us that a Shearwater 45 would be a safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0. 

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