Review of Allmand 31

Basic specs.

sail specifications
The Allmand 31 is a sailboat designed by the maritime architect Walter H. Scott together with T. R. Allmand in the early eighties. The Allmand 31 is built by the American yard Allmand Boats Inc..

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The hull is made of fibreglass. Generally, a hull made of fibreglass requires only a minimum of maintenance during the sailing season. And outside the sailing season, just bottom cleaning and perhaps anti-fouling painting once a year - a few hours of work, that's all.


The boat is equipped with 151.0 liter fresh water capacity.


The boat equipped with a masthead rig. The advantage of a masthead rig is its simplicity and the fact that a given sail area - compared with a fractional rig - can be carried lower and thus with less heeling moment.


The Allmand 31 is equipped with a fin keel. The fin keel is the most common keel and provides splendid manoeuvrability. The downside is that it has less directional stability than a long keel.

The boat can enter even shallow marinas as the draft is just about 1.16 - 1.26 meter (3.81 - 4.11 ft) dependent on the load. See immersion rate below.


Allmand 31 is typically equipped with an engine.

The fuel tank has a capacity of 95.0 liters (25 US gallons, 20 imperial gallons).

Sailing characteristics

This section covers widely used rules of thumb to describe the sailing characteristics. Please note that even though the calculations are correct, the interpretation of the results might not be valid for extreme boats.

Stability and Safety

What is Capsize Screening Formula (CSF)?

The capsize screening value for Allmand 31 is 2.03, indicating that this boat would not be accepted to participate in ocean races.

Theoretical Maximum Hull Speed

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 7.0 knots. The term "Theoretical Maximum Hull Speed" is widely used even though a boat can sail faster. The term shall be interpreted as above the theoretical speed a great additional power is necessary for a small gain in speed.

Immersion rate

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Allmand 31 is about 193 kg/cm, alternatively 1085 lbs/inch.
Meaning: if you load 193 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 1085 lbs cargo on the boat it will sink 1 inch.

Sailing statistics

This section is statistical comparison with similar boats of the same category. The basis of the following statistical computations is our unique database with more than 26,000 different boat types and 350,000 data points.

Motion Comfort Ratio

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Allmand 31 is 23.5.

Low High 50% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 50% of all similar sailboat designs. This is an average comfort value!

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Allmand 31 is 2.72.

Slim Wide 86% 0 50 100
Compared with other similar sailboats it is more spacy than 86% of all other designs. It seems that the designer has chosen a significantly more spacy hull design.

Ballast Ratio

What is a Ballast Ratio?

The ballast ratio for Allmand 31 is 39%.

Low High 38% 0 50 100
This ballast ratio shows a righting moment that is higher than 38% of all similar sailboat designs. A righting moment (ability to resist heeling) just below average.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Allmand 31 is 233 which categorizes this boat among 'light crusers & offshore racers'.

Heavy Light 62% 0 50 100
62% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.

SA/D (Sail Area Displacement ratio)

What is SA/D (Sail Area Displacement ratio)?

The SA/D for Allmand 31 with ISO 8666 reference sail is 14.9, with a 135% genua the SA/D is 17.7.

Low High 34% 0 50 100
The SA/D ratio indicates that it is faster than 34% of all similar sailboat designs in light wind.

Over- / underrigged

Low High 88% 0 50 100
The Allmand 31 has more rig than 88% of all similar sailboats, which indicates that the boat is significantly overrigged.


Bottom Paint

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 29m2 (312 ft2).
Based on this, your favourite maritime shop can tell you the quantity you need.

Note: If you use a paint roller you will need more paint than if you use a paintbrush.


Dimensions of sail for masthead rig.

mainsail specifications headsail specifications

Are your sails worn out? You might find your next sail here: Sails for Sale

If you need to renew parts of your running rig and is not quite sure of the dimensions, you may find the estimates computed below useful.

Guiding dimensions of running rig
Mainsail halyard 27.5 m(90.3 feet)10 mm(3/8 inch)
Jib/genoa halyard27.5 m(90.3 feet)10 mm(3/8 inch)
Spinnaker halyard27.5 m(90.3 feet)10 mm(3/8 inch)
Jib sheet 9.4 m(30.7 feet)12 mm(1/2 inch)
Genoa sheet9.4 m(30.7 feet)12 mm(1/2 inch)
Mainsheet 23.4 m(76.8 feet)12 mm(1/2 inch)
Spinnaker sheet20.6 m(67.6 feet)12 mm(1/2 inch)
Cunningham3.8 m(12.5 feet)10 mm(3/8 inch)
Kickingstrap7.6 m(25.0 feet)10 mm(3/8 inch)
Clew-outhaul7.6 m(25.0 feet)10 mm(3/8 inch)

Boat owner's ideas

This section is reserved boat owner's modifications, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

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