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Review of Sun Fast 31


Basic specs.

sail specifications
The Sun Fast 31 is a sailboat designed by the French maritime architect Daniel Andrieu. The Sun Fast 31 is built by the French yard Jeanneau.

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Hull

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.


Rig

The Sun Fast 31 is equipped with a fractional rig. A fractional rig has smaller headsails which make tacking easier, which is an advantage for cruisers and racers, of course. The downside is that having the wind from behind often requires a gennaker or a spinnaker for optimal speed.


Keel

The Sun Fast 31 has been built with different keel alternatives.

Deep keel

One option is a deep keel. A deep keel provide a better healing moment than a shallow keel.

The keel is made of lead. Compared with iron, lead has the advantage of being 44% heavier, which allows a smaller keel and hence less water resistance and higher speed.

The boat can enter most marinas as the draft is just about 1.75 - 1.85 meter (5.74 - 6.04 ft) dependent on the load. See immersion rate below.

Shallow keel

Another option is a shallow keel. A shallow keel allow to sail both coastal and inland waters.

The keel is also made of lead.

The boat can enter even shallow marinas as the draft is just about 1.45 - 1.55 meter (4.76 - 5.06 ft) dependent on the load. See immersion rate below.

Unknown keel type

The keel is also made of lead.

Sun Fast 31 can enter most marinas as the draft is just about 1.51 - 1.61 meter (4.95 - 5.25 ft) dependent on the load. See immersion rate below.


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.

Theoretical Maximum Hull Speed

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 6.7 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 Sun Fast 31 is about 163 kg/cm, alternatively 915 lbs/inch.
Meaning: if you load 163 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 915 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.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Sun Fast 31 is 2.90.

Slim Wide 73% 0 50 100
Compared with other similar sailboats it is more spacy than 73% of all other designs. It seems that the designer has chosen a slightly more spacy hull design.


Ballast Ratio

What is a Ballast Ratio?

The ballast ratio for Sun Fast 31 is 34%.

Low High 15% 0 50 100
This ballast ratio shows a righting moment that is higher than 15% of all similar sailboat designs. A righting moment (ability to resist heeling) significantly below average.


Over- / underrigged

Low High 85% 0 50 100
The Sun Fast 31 has more rig than 85% of all similar sailboats, which indicates that the boat is significantly overrigged.


Maintenance

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 28m2 (301 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.


Rig

Dimensions of sail for fractional 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
UsageLengthDiameter
Mainsail halyard 29.3 m(96.1 feet)10 mm(3/8 inch)
Jib/genoa halyard29.3 m(96.1 feet)10 mm(3/8 inch)
Spinnaker halyard29.3 m(96.1 feet)10 mm(3/8 inch)
Jib sheet 9.2 m(30.2 feet)12 mm(1/2 inch)
Genoa sheet9.2 m(30.2 feet)12 mm(1/2 inch)
Mainsheet 23.0 m(75.5 feet)12 mm(1/2 inch)
Spinnaker sheet20.2 m(66.4 feet)12 mm(1/2 inch)
Cunningham3.7 m(12.1 feet)10 mm(3/8 inch)
Kickingstrap7.4 m(24.3 feet)10 mm(3/8 inch)
Clew-outhaul7.4 m(24.3 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.

Do you have changes/improvements you would like to share? Upload a photo and describe what you have done.



Finally

We are always looking for new photos. If you can contribute with photos for Sun Fast 31 it would be a great help.

If you have any comments to the review, improvement suggestions, or the like, feel free to contact us. Criticism helps us to improve.



References