The Formosa 42 Sailboat
(aka the Slocum 43)
Specs & Key Performance Indicators

The Formosa 42, an aft cockpit cutter, was designed by Stan Huntingford and built in Taiwan by Formosa Boat Building Co. Ltd.

A Formosa 42 sailboat on a mooring ballA Formosa 42, also known as the Slocum 43

Published Specification for the Formosa 42

Underwater Profile: Fin keel & skeg-hung rudder

Hull Material: GRP (Fibreglass)

Length Overall: 42'6" (12.9m)

Waterline Length: 35'10" (10.9m)

Beam: 12'11" (3.9m)

Draft: 6'4" (1.9m)

Rig Type: Cutter

Displacement: 28,104lb (12,748kg)

Designer: Stan Huntingford

Builder: Formosa Boat Building Company Ltd. (Taiwan)

Year First Built: 1981

Year Last Built: 1990

Number Built: 60

Published Design Ratios for the Formosa 42

1. Sail Area/Displacement Ratio: 14.1

  • 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: 32.0

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

3. Displacement/Length Ratio: 273

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

4. Comfort Ratio: 38.0

  • 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 Formosa 42

1. A Sail Area/Displacement Ratio of just 14.1 suggests that the Formosa 42 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 32.0 means that a sailboat like the Formosa 42 (which doesn't have a stiffness-enhancing bulb keel), is likely to bene

fit from being reefed early to keep her sailing upright in a moderate breeze.

3. A Displacement/Length Ratio of 273, tells us the Formosa 42 is a moderate-to-heavy displacement cruiser, which means she'll carry all your cruising gear without it having a dramatic effect on her performance. 

4. Ted Brewer's Comfort Ratio of 38.0 suggests that crew comfort of a Formosa 42 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 indicates that a Formosa 42 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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