The Seastream 43 Sailboat
Specs & Key Performance Indicators

The Seastream 43, a heavy displacement pilothouse cutter, was designed by Ian Anderson and built in the UK by Seastream Yachts Ltd.

A Seastream 42 sailboat anchored in Tyrrel Bay, Carriacou, West IndiesA Seastream 43

Published Specification for the Seastream 43

Underwater Profile: Fin keel & skeg-hung rudder

Hull Material: GRP (Fibreglass)

Length Overall: 43'8" (13.3m)

Waterline Length: 35'5" (10.8m)

Beam: 14'2" (4.3m)

Draft: 6'3" (1.9m)

Rig Type: Cutter

Displacement: 31,526lb (14,300kg)

Designer: Ian Anderson

Builder: Seastream Yachts Ltd (UK)

Year First Built: 1981

Number Built: 35

Published Design Ratios for the Seastream 43

1. Sail Area/Displacement Ratio: Not published

  • 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: 35.7

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

3. Displacement/Length Ratio: 316

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

4. Comfort Ratio: 37.9

  • 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 Key Performance Indicators...

Summary Analysis of the Design Ratios for the Seastream 43

1. In the absence of a published Sail Area/Displacement Ratio we are unable to make a performance assessment for the Seastream 43.

2. A Ballast/Displacement Ratio of 35.7 means that a sailboat like the Seastream 43 (which doesn't have a stiffness-enhancing bulb keel), is likely to benefit from being reefed early to keep her sailing upright in a moderate breeze.

3. A Displacement/Length Ratio of 316, tells us the Seastream 43 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 37.9 suggests that crew comfort of a Seastream 43 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 1.8 indicates that a Seastream 43 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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