Review of First 31.7
Basic specs.
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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 6 berths.
The First 31.7 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.
The First 31.7 has been built with different keel alternatives.
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 only enter major marinas as the draft is about 1.90 - 2.00 meter (6.23 - 6.53 ft) dependent on the load. See immersion rate below.
Shallow keel
The First 31.7 is equipped with a shallow keel. A shallow keel allow to sail both coastal and inland waters.
This keel is also made of iron.
First 31.7 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 boat 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.
The First 31.7 has been equipped with different engine alternatives.
Alternative 1:
The boat may be equipped with an inboard Yanmar diesel engine at 21 hp (15 kW). Calculated max speed is about 6.5 knots
Alternative 2:
First 31.7 may be equipped with an inboard Volvo Penta MD2020 diesel engine at 18 hp (13 kW). Calculated max speed is about 6.0 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.
What is Capsize Screening Formula (CSF)?
The capsize screening value for First 31.7 is 2.13, indicating that this boat would not be accepted to participate in ocean races.
First 31.7 holds a CE certification:
The boat is by European Union certified as Class A. OCEAN:What is Theoretical Maximum Hull Speed?
The theoretical maximal speed of a displacement boat of this length is 7.2 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.
The immersion rate is defined as the weight required to sink the boat a certain level.
The immersion rate for First 31.7 is about 190 kg/cm, alternatively 1066 lbs/inch.
Meaning: if you load 190 kg cargo on the boat then it will sink 1 cm.
Alternatively, if you load 1066 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.
What is Motion Comfort Ratio (MCR)?
The Motion Comfort Ratio for First 31.7 is 17.8.
What is L/B (Length Beam Ratio)?
The l/b ratio for First 31.7 is 2.94.
The ballast ratio for First 31.7 is 29%.
What is Displacement Length Ratio?
The DL-ratio for First 31.7 is 147 which categorizes this boat among 'ultra light racers'.
What is SA/D (Sail Area Displacement ratio)?
The SA/D for First 31.7 with ISO 8666 reference sail is 18.0, with a 135% genua the SA/D is 21.0.
Maintenance
When buying anti-fouling bottom paint, it's nice to know how much to buy.
The surface of the wet bottom is about 34m2 (365 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 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.
| Usage | Length | Diameter | ||
| Mainsail halyard | 28.3 m | (92.8 feet) | 10 mm | (3/8 inch) |
| Jib/genoa halyard | 28.3 m | (92.8 feet) | 10 mm | (3/8 inch) |
| Spinnaker halyard | 28.3 m | (92.8 feet) | 10 mm | (3/8 inch) |
| Jib sheet | 9.5 m | (31.2 feet) | 12 mm | (1/2 inch) |
| Genoa sheet | 9.5 m | (31.2 feet) | 12 mm | (1/2 inch) |
| Mainsheet | 23.8 m | (77.9 feet) | 12 mm | (1/2 inch) |
| Spinnaker sheet | 20.9 m | (68.6 feet) | 12 mm | (1/2 inch) |
| Cunningham | 3.9 m | (12.8 feet) | 10 mm | (3/8 inch) |
| Kickingstrap | 7.8 m | (25.6 feet) | 10 mm | (3/8 inch) |
| Clew-outhaul | 7.8 m | (25.6 feet) | 10 mm | (3/8 inch) |
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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