The Oyster 39 Sailboat
Specs & Key Performance Indicators

The Oyster 39, a centre-cockpit ketch, was designed by Donald Pye and built in the UK by Oyster Marine Ltd.

An Oyster 39 cruising ketchAn Oyster 39

Published Specification for the Oyster 39

Underwater Profile: Fin keel with skeg-hung rudder

Hull Material: GRP (Fibreglass)

Length Overall: 40'8" (12.4m)

Waterline Length: 33'4" (10.2m)

Beam: 12'11" (3.9m)

Draft: 5'8" (1.7m)

Rig Type: Ketch

Displacement: 19,498 lb (8,844 kg)

Designer: Donald Pye

Builder: Oyster Marine Ltd (UK)

Year First Built: 1978

Year Last Built: 1984

Number Built: 43


Published Design Ratios for the Oyster 39

1. Sail Area/Displacement Ratio: Not available

  • 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: 40.1

  • 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: 28.2

  • 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 Oyster 39

1. The Sail Area/Displacement Ratio of the Oyster 39 is not published; hence we are unable to comment on this aspect of the yacht's performance.

2. A Ballast/Displacement Ratio of 40.1 means that the Oyster 39 should stand up well to her canvas in a blow, helping her to power through the waves.

3. A Displacement/Length Ratio of 235, tells us the Oyster 39 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 28.2 suggests that crew comfort of a Oyster 39 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 1.9 tells us that a Oyster 39 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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