The Westerly Vulcan 34 Sailboat
Specs & Key Performance Indicators

The Westerly Vulcan 34, a sloop-rigged motor-sailor was designed by Jack Laurent Giles and built in the UK by Westerly Marine Ltd.

Published Specification for the Westerly Vulcan 34

Underwater Profile: Twin keels & skeg-hung rudder

Hull Material: GRP (Fibreglass)

Length Overall: 34'0" (10.4m)

Waterline Length: 28'5" (8.7m)

Beam: 11'9" (3.6m)

Draft: 4'3" (1.3m)

Rig Type: Masthead sloop

Displacement: 15,602lb (7,077kg)

Designer: Jack Laurent Giles

Builder: Westerly Marine Ltd. (UK)

Year First Built: 1980

Year Last Built: 1984

Number Built: 42


Published Design Ratios for the Westerly Vulcan 34

1. Sail Area/Displacement Ratio: 14.7

  • 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: 44.7

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

3. Displacement/Length Ratio: 303

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

4. Comfort Ratio: 30.1

  • 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: 1.9

  • 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 Westerly Vulcan 34

1. A Sail Area/Displacement Ratio of 14.7 suggests that the Westerly Vulcan 34 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 44.7 means that the Westerly Vulcan 34 will stand up well to her canvas in a blow, helping her to power through the waves.

3. A Displacement/Length Ratio of 303, tells us the Westerly Vulcan 34 is clearly 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 30.1 suggests that crew comfort of a Westerly Vulcan 34 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 1.9 indicates that a Westerly Vulcan 34 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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