The Westerly 33 Sailboat
Specs & Key Performance Indicators

The Westerly 33, a bilge-keeled masthead sloop, was designed by Laurent Giles and built in the UK by Westerly Yachts Ltd.

The Westerly 33 sailing in light windsThe Multi-Option Westerly 33

Published Specification for the Westerly 33

Underwater Profile: Bilge keels with Skeg-hung Rudder (Fin Keel version was also produced)

Hull Material: GRP (Fibreglass)

Length Overall: 33'3" (10.1m)

Waterline Length: 28'5" (8.7m)

Beam: 11'2" (3.4m)

Draft: 5'5" (1.7m)

Rig Type: Masthead Sloop (Ketch version was also produced)

Displacement: 14,341lb (6,505kg)

Designer: Laurent Giles

Builder: Westerly Yachts Ltd (UK)

Year First Built: 1975

Year Last Built: 1977

Number Built: 235

Owners AssociationWesterly Owners' Association


Published Design Ratios for the Westerly 33

1. Sail Area/Displacement Ratio: 14.3

  • 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: 42.2

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

3. Displacement/Length Ratio: 277

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

4. Comfort Ratio: 29.9

  • 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: 1.8

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

read more about these all-revealing numbers...


Summary Analysis of the Design Ratios for the Westerly 33

1. A Sail Area/Displacement Ratio of just 14.3 suggests that the Westerly 33 will need a stiff breeze to get her going. In light conditions, unless you've got plenty of time on your hands, motor-sailing may be the way to go.

2. A Ballast/Displacement Ratio of 42.2 means that the Westerly 33 will stand up well to her canvas in a blow, helping her to power through the waves.

3. A Displacement/Length Ratio of 277, tells us the Westerly 33 is a heavy displacement cruising boat. You can load her down with all your cruising gear and equipment and it will hardly affect her waterline. Not an ideal choice for coastal sailing, but she'll come into her own on an offshore passage in testing conditions.

4. Ted Brewer's Comfort Ratio of 29.9 suggests that crew comfort of a Westerly 33 in a seaway is similar to what you would associate with the motion of a coastal cruiser with moderate stability, which is not encouraging news for anyone prone to seasickness. 

5. The Capsize Screening Formula (CSF) of 1.8 tells us that a Westerly 33 would be a safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0. 

Other sailboats in the Westerly range include:


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