Designer
Sparkman & Stephens
Builder
South Hants Engineering
Association
Half Ton Class
# Built
?
Hull
Monohull
Keel
Fin
Rudder
Skeg
Construction
FG
Also Known As
S&S design #1899

Dimensions

Length Overall
30 3 / 9.2 m
Waterline Length
22 2 / 6.8 m
Beam
8 9 / 2.7 m
Draft
5 4 / 1.7 m
Displacement
7,800 lb / 3,538 kg
Ballast
3,400 lb / 1,542 kg (Iron)
Drawing of She 31
  • 1 / 3
  • 2 / 3
  • 3 / 3

Rig and Sails

Type
Sloop
Reported Sail Area
410′² / 38.1 m²
Total Sail Area
?
Mainsail
Sail Area
?
P
?
E
?
Air Draft
?
Foresail
Sail Area
?
I
?
J
?
Forestay Length
?

Auxilary Power

Make
Beta
Model
?
HP
20
Fuel Type
Diesel
Fuel Capacity
42 gal / 158 l

Accomodations

Water Capacity
18 gal / 70 l
Holding Tank Capacity
?
Headroom
?
Cabins
?

Calculations

Hull Speed
6.5 kn
Classic: 6.31 kn

Hull Speed

The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.

Formula

Classic hull speed formula:

Hull Speed = 1.34 x √LWL

A more accurate formula devised by Dave Gerr in The Propeller Handbook replaces the Speed/Length ratio constant of 1.34 with a calculation based on the Displacement/Length ratio.

Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio.311
Hull Speed = Max Speed/Length ratio x √LWL

6.47 knots
Classic formula: 6.31 knots
Sail Area/Displacement
16.7
16-20: good performance

Sail Area / Displacement Ratio

A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.

Formula

SA/D = SA ÷ (D ÷ 64)2/3

  • SA: Sail area in square feet, derived by adding the mainsail area to 100% of the foretriangle area (the lateral area above the deck between the mast and the forestay).
  • D: Displacement in pounds.
16.68
<16: under powered
16-20: good performance
>20: high performance
Ballast/Displacement
43.6
>40: stiffer, more powerful

Ballast / Displacement Ratio

A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.

Formula

Ballast / Displacement * 100

43.58
<40: less stiff, less powerful
>40: stiffer, more powerful
Displacement/Length
319.2
275-350: heavy

Displacement / Length Ratio

A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.

Formula

D/L = (D ÷ 2240) ÷ (0.01 x LWL)³

  • D: Displacement of the boat in pounds.
  • LWL: Waterline length in feet
319.19
<100: ultralight
100-200: light
200-300: moderate
300-400: heavy
>400: very heavy
Comfort Ratio
26.7
20-30: coastal cruiser

Comfort Ratio

This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.

Formula

Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam1.33)

  • D: Displacement of the boat in pounds
  • LWL: Waterline length in feet
  • LOA: Length overall in feet
  • Beam: Width of boat at the widest point in feet
26.74
<20: lightweight racing boat
20-30: coastal cruiser
30-40: moderate bluewater cruising boat
40-50: heavy bluewater boat
>50: extremely heavy bluewater boat
Capsize Screening
1.8
<2.0: better suited for ocean passages

Capsize Screening Formula

This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.

Formula

CSV = Beam ÷ ³√(D / 64)

  • Beam: Width of boat at the widest point in feet
  • D: Displacement of the boat in pounds
1.78
<2: better suited for ocean passages
>2: better suited for coastal cruising

Notes

From BlueWaterBoats:

Penned as Sparkman and Stephens design #1899 by Olin Stephens, the SHE 31 introduced in 1969 has enjoyed popularity in the UK and Europe. Though originally intended as a half ton IOR racing thoroughbred, this boat often nicknamed a “baby Swan”, has gone on to be adapted for cruising in a myriad of derivative models. Known for her speed, close winded performance, and absolutely beautiful lines this racer/cruiser is often compared the Contessa 32.

The unusual SHE name comes from the initials of South Hants Engineering, a UK light engineering firm founded in 1947 that branched out with a marine division. Headed up by two brothers, Derek and Simon Fitzgerald armed with an enthusiasm for sailing, the SHE line of yachts flourished from the late sixties to the mid seventies producing solely Sparkman and Stephens designs from the cramped SHE 27, the SHE 31 which was the most popular, the SHE 32, and the SHE 36 which was without a doubt the best boat in the line up.

The division ultimately succumbed to the financial climate of the late seventies and competition from cheaper, faster and roomier French imports. The company continues today as SH Enterprises but no longer produces boats.

The SHE 31 moulds were bought by Laird Adams Engineering who developed the design with increased headroom and a new, more practical interior. These boats sold under the name Delta 94. Also there were a few examples that were home-built by enthusiastic amateurs.

The design, optimised for racing, was the beneficiary of Olin’s latest thinking in the same era of the legendary S&S 34 and Swan 36 both introduced 2 years earlier in 1967. He was a master of designing yachts to take maximum advantage of IOR rules for ocean racing.

Typical of these designs the SHE 31 has pinched bow and tail sections and a tumblehome amidships, reminiscent of much larger yachts. Her sharp bow profile gives her a good bite on tacks, and a swept back fin keel carefully faired into the hull with 3400 lbs of lead in results in a balanced feeling and stability in nearly all sea conditions. Notable is the skeg rudder pushed far aft and the propellor on a P bracket forward allowing better reversing.

There is accommodation for five but belowdecks it’s reasonably cramped with very little headroom, especially in the forecabin. The interior finish was restrained, modern and perhaps a little austere and betraying the use of ply.

Variants

Many variants were produced, we’ll summarise these below.

SHE 9.5 Traveller
South Hants Engineering responded to public demand for a cruising model by producing the 9.5 Traveller, a version with more lavish accommodations;. It had a new deck, coachroof providing better cruising accommodations, higher topsides and increased headroom. Most owners will refer to their Traveller simply as a SHE. They are relatively rare.

Performance was still good and many examples will have been raced hard and spent long lives on exposed moorings rather than snug in marinas. Despite this, most have stood up well to the action, reflecting the high quality of build.

Delta 94/95
This particular boat caused quite a stir when she was unveiled to the yachting world at Southampton Boat Show in 1977. Produced by Laird Adams Engineering in the late senventies, the Delta 94 (also called the Delta 95) is a later version with the same hull, but with slightly more freeboard to produce more interior headroom, and a revised interior layout. Only 17 of them were produced.

IW 31
Simultaneously with the South Hamp Engineering yachts, Swedish builder I.W. Varvet on the island of Orust, an island which traces its roots back to the time of Viking ships, produced a large number of yachts. Over 350 boats were produced starting around 1968 in three revisions.

MK I (1968 – 1972): Small stern, ‘dinette’ layout.
MK II (1972 – 1980): Larger stern, new deck, revised wood trim.
MK III (1980 – 1985): Aluminium toe rail (instead of Teak), glass hatch, revised hardware.

Other Notes
Please note the SHE 31B produced by South Hants Engineering from 1970 onwards was an altogether different design – being Sparkman and Stephens design #2042 which was also designated for 1/2 ton IOR racing. It was further developed into the SHE 32 – a more luxurious and roomier yacht intended for cruising.

Links, References and Further Reading

» Sailing Today Used Boat Test
» Sparkman and Stephens Blog, SHE 31 / IW 31
» Sparkman and Stephens Blog, IW 31 / IW 31

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