Review of Finnflyer 31

Basic specs.

The Finnflyer 31 is a sailboat designed by the maritime architect Eivind Still in the early eighties. The Finnflyer 31 is built by the Finnish yard Polar Yacht Oy.

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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.
The hull is a double hull which improves the indoor climate. Especially when the water is colder than the air in the cabin, then the double hull insulates against cold water and reduce the condense water in the cabin.

Interior

The interior is like most other boats made of teak. Teak has the advantage of being naturally very oily and therefore water-repellent, which is suitable on boats.
The boat is equipped with 6 berths, a galley, 100.0 liter fresh water capacity and toilet facility.

Rig

The Finnflyer 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

Unknown keel type

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.

Engine

Finnflyer 31 may be equipped with an inboard Yanmar diesel engine at 18 hp (13 kW). Calculated max speed is about 5.6 knots

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 Finnflyer 31 is 2.13, 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 6.6 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 Finnflyer 31 is about 160 kg/cm, alternatively 900 lbs/inch.
Meaning: if you load 160 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 900 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 Finnflyer 31 is 19.5.

Comparing this ratio with similar sailboats show that it is more comfortable than 27% of all similar sailboat designs. This comfort value is just below average.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Finnflyer 31 is 2.94.

Compared with other similar sailboats it is more spacy than 69% 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 Finnflyer 31 is 31%.

This ballast ratio shows a righting moment that is higher than 8% of all similar sailboat designs. A righting moment (ability to resist heeling) significantly below average.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Finnflyer 31 is 231 which categorizes this boat among 'light crusers & offshore racers'.

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 Finnflyer 31 with ISO 8666 reference sail is 16.9, with a 135% genua the SA/D is 19.3.

The SA/D ratio indicates that it is faster than 58% of all similar sailboat designs in light wind.

Over- / underrigged

The Finnflyer 31 has more rig than 92% of all similar sailboats, which indicates that the boat is significantly overrigged.

RSP (Relative Speed Performance)

What is Relative Speed Performance?

The Relative Speed Performance for Finnflyer 31 is 69

The relative speed performance is 69 which means that a it is faster than 69% of all similar sailboat designs.

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.

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**
Usage	Length		Diameter
Mainsail halyard	29.6 m	(96.9 feet)	10 mm	(3/8 inch)
Jib/genoa halyard	29.6 m	(96.9 feet)	10 mm	(3/8 inch)
Spinnaker halyard	29.6 m	(96.9 feet)	10 mm	(3/8 inch)
Jib sheet	9.4 m	(30.8 feet)	12 mm	(1/2 inch)
Genoa sheet	9.4 m	(30.8 feet)	12 mm	(1/2 inch)
Mainsheet	23.5 m	(77.1 feet)	12 mm	(1/2 inch)
Spinnaker sheet	20.7 m	(67.8 feet)	12 mm	(1/2 inch)
Cunningham	4.0 m	(13.1 feet)	10 mm	(3/8 inch)
Kickingstrap	8.0 m	(26.2 feet)	10 mm	(3/8 inch)
Clew-outhaul	8.0 m	(26.2 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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Finally

We are always looking for new photos. If you can contribute with photos for Finnflyer 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

[Ref 1]: ISO 8666 Small craft — Principal data.
[Ref 3]: ISO 12215-5 Small craft — Hull construction and scantlings.