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Review of OVNI 31


Basic specs.

sail specifications
The OVNI 31 is a sailboat designed by the French maritime architect Philippe Briand in the mid seventies. The OVNI 31 is built by the French yard SAS Alubat Chantier Naval.

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Hull

The hull is made of aluminium. Aluminum is strong and forgiving. Where an impact on a fiberglass hull will result in major gelcoat damage and possible cracking, an aluminum hull will probably only have a scratch or a small bend. The only concern is electrolysis. Ensure that you have proper sacrificial anodes installed.


Rig

The OVNI 31 is 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.


Keel

Unknown keel type

The keel is made of iron. Many people prefer lead keel in favour of iron. The main argument is that lead is much heavier than iron and a lead keel can therefore be made smaller which again result in less wet surface, i.e. less drag. In fact iron is quite heavy, just 30% less heavy than lead, so the advantage of a lead keel is often overstated.

The boat can enter most marinas as the draft is just about 1.65 - 1.75 meter (5.41 - 5.71 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 6.8 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 OVNI 31 is about 171 kg/cm, alternatively 959 lbs/inch.
Meaning: if you load 171 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 959 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 OVNI 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 OVNI 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.


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 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.


Rig

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
Jib sheet 9.5 m(31.2 feet)12 mm(1/2 inch)
Genoa sheet9.5 m(31.2 feet)12 mm(1/2 inch)
Mainsheet 23.8 m(77.9 feet)12 mm(1/2 inch)
Spinnaker sheet20.9 m(68.6 feet)12 mm(1/2 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 OVNI 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