The Slipper 42 Sailboat
Specs & Key Performance Indicators

The Slipper 42, a centre-cockpit ketch, was designed by Robin Chadworth-Musters & Alan Gurney and built in the UK by Tyler Boat Company Ltd.

A Slipper 42 Ketch

Published Specification for the Slipper 42

Underwater Profile: Fin keel with skeg-hung rudder;

Hull Material: GRP (Fiberglass);

Length Overall: 42'0" (12.8m);

Waterline Length: 30'4" (9.2m);

Beam: 12'3" (3.7m);

Draft: 6'0" (1.8m);

Rig Type: Masthead ketch;

Displacement: 16,500lb (7,484kg);

Designer: Robin Chadworth-Musters & Alan Gurney;

Builder: Tyler Boat Co. Ltd. (UK);

Year First Built: 1978;

Year Last Built: 1979;

Number Built: 13

Published Design Ratios for the Slipper 42

1. Sail Area/Displacement Ratio: 15.9

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: 43.4

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

3. Displacement/Length Ratio: 264

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

4. Comfort Ratio: 26.8

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

Summary Analysis of the Design Ratios for the Slipper 42

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1. A Sail Area/Displacement Ratio of 15.9 suggests that the Slipper 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 43.4 means that the Slipper 42 will stand up well to her canvas in a blow, helping her to power through the waves.

4. Ted Brewer's Comfort Ratio of 26.8 suggests that crew comfort of a Slipper 42 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 Slipper 42 would be a safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0.

Sailboat-Cruising.com says...

About the Boat:

The Slipper 42 sailboat is a moderate displacement sailboat which is slightly underpowered, but is very stable/stiff and has a good righting capability if capsized. The fuel capacity is good however and she has a good water supply range.

The Slipper 42 started life as the Rancher 41, for which Tyler Boat Works acquired the molds. They raised the topsides about a foot and discarded the bolt-on keel and spade rudder in favor of internal ballast and a skeg rudder. This converted a racing hull into a cruising boat.

The Slipper 42 has two dedicated sleeping cabins with double berths.

About the Designers:

Robin Chadworth-Musters is a yacht designer who has designed several sailboats. One of his sailboats is the Slipper 42 shown here, which he designed in collaboration with Alan Gurney.

Alan Gurney was a British sailboat designer who designed boats the old fashioned way with drafting pencil on velum, using splines and ducks (weights), a planimeter, and a seaman’s eye. He thought like the water through which he had sailed, in England, transatlantic, the USA, both polar regions and much of what lay in between. He was tasked to design a suitable replacement for the famous Herreshoff design Ticonderoga, and produced one of the greatest designs of the past 50 years called Windward Passage.

Here is a list of some of his sailboat designs:

Islander 36 (1971)
O’Day 27 (1972)
Carib 41 (1970)
Carib 41 TM (1970)
Whitney 41 (1972)
Nantucket 33 (1967)
Islander 41 (Gurney) (1972)
Competition 1000 (1973)
Rancher 41

About the Builder:

Tyler Boat Company was founded by John Tyler in the 1960s. The company was known for building fiberglass yachts and sailboats. Tyler's primary business was in the manufacture of pre-fabricated buildings for the housing of livestock. Here is a list of some of the sailboats built by Tyler Boat Company:

Tyler Deb 33: A 33-foot sailboat designed by Angus Primrose. It has a long fin keel and a skeg-hung rudder. The boat has a displacement of 11,000lbs and a beam of 10'6".

Tyler Custom 62 cutter: A 62-foot sailboat designed by Robert Perry. It has a long fin keel and a skeg-hung rudder. The boat has a displacement of 60,000lbs and a beam of 16'6".

Tyler S42: A 42-foot sailboat designed by Ron Holland. It has a long fin keel and a skeg-hung rudder. The boat has a displacement of 22,000lbs and a beam of 12'6".

Tyler Victory 40 Ketch: A 40-foot sailboat designed by Angus Primrose. It has a long fin keel and a skeg-hung rudder. The boat has a displacement of 22,000 lbs and a beam of 12'6".

This additional info was drafted by sailboat-cruising.com using GPT-4 (OpenAI’s large-scale language-generation model) as a research assistant to develop source material, and believes it to be accurate to the best of their knowledge.