The Oyster 575 Sailboat
Specs & Key Performance Indicators

The Oyster 575, a centre-cockpit cutter, was designed by Rob Humphreys and built in the UK by Oyster Marine Ltd.

An Oyster 575 sailboat at anchorAn Oyster 575

Published Specification for the Oyster 575

Underwater Profile: Fin keel and spade rudder

Hull Material: GRP (Fibreglass)

Length Overall: 58'8" (17.9m)

Waterline Length: 51'6" (15.7m)

Beam: 16'5" (5.0m)

Draft: 8'10" (2.7m)*

Rig Type: Cutter

Displacement: 58,422lb (26,500kg)

Designer: Rob Humphreys

Builder: Oyster Marine (UK)

Year First Built: 2010

* A shoal draft and a centreboard version are also available.

Published Design Ratios for the Oyster 575

1. Sail Area/Displacement Ratio: 22.4

  • 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: 30.6

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

3. Displacement/Length Ratio: 191

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

4. Comfort Ratio: 40.5

  • 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 Oyster 575

1. A Sail Area/Displacement Ratio of 22.4 suggests that, in the right hands, the Oyster 575 will have enough performance to leave most other sailboats of similar waterline length well astern. 

2. A Ballast/Displacement Ratio of 30.6 would usually mean that the Oyster 575 would have a tendency to heel uncomfortably in a gust, and need to be reefed early to keep her sailing upright in a moderate breeze.

However, as she has much of her ballast concentrated in a bulb at the foot of her keel, she's likely to be considerably stiffer than her published Ballast/Displacement Ratio might suggest.

3. A Displacement/Length Ratio of 191, tells us the Oyster 575 is a light-to-moderate displacement sailboat. If she's loaded with too much heavy cruising gear her performance will suffer to a degree.

4. Ted Brewer's Comfort Ratio of 40.5 suggests that crew comfort of an Oyster 575 in a seaway is similar to what you would associate with the motion of a heavy bluewater cruising boat. Pitching and rolling will be well damped - your cup of coffee on the salon table stands a reasonable chance of staying there in most conditions.

5. The Capsize Screening Formula (CSF) of 1.7 tells us that an Oyster 575 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 Oyster range include:


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