First 31.7 Deep draft

Sailboat specifications

The First 31.7 is a 31’2” (9.5m) cruiser-racer sailboat designed by Finot Conq Architectes (France). She was built between 1997 and 2010 by Bénéteau (France). The Deep draft version offers a deeper L-shaped keel bringing extra performance especially upwind.

The First 31.7 is as well listed, on Boat-Specs.com, in Shoal draft version (see all the versions compared).

First 31.7's main features

Model: First 31.7
Version: Deep draft
Hull type: Monohull
Category: Cruiser-racer sailboat
Sailboat builder: Bénéteau
Sailboat designer: Finot Conq Architectes
Sailboat range: First
Country: France
Construction: GRP (glass reinforced polyester):
- Hull: Single skin fiberglass polyester
- Deck: Sandwich balsa fiberglass polyester
Number of hulls built: About 1500
First built hull: 1997
Last built hull: 2010
Appendages: Keel : L-shaped keel (with bulb)
Helm: Single tiller
Rudder: Single spade rudder
Unsinkable: No
Trailerable: No
EC design category iThe CE design category indicates the ability to cope with certain weather conditions (the sailboat is designed for these conditions) A: Wind < force 9, Waves < 10m B: Wind < force 8, Waves < 8m C: Wind < force 6, Waves < 4m D: Wind < force 4, Waves < 0,5m: A
Standard public price ex. VAT (indicative only): N/A €

First 31.7's main dimensions

Overall length: 31’ 6”9.61 m
Hull length: 31’ 2”9.5 m
Waterline length: 28’ 11”8.8 m
Beam (width): 10’ 7”3.23 m
Draft: 6’ 2”1.9 m
Mast height from D_WL: 45’ 7”13.9 m
Light displacement (M_LC): 8267 lb3750 kg
Ballast weight: 2260 lb1025 kg
Ballast type: Cast iron
French customs tonnage: 9.36 Tx

First 31.7's rig and sails

Upwind sail area: 565 ft²52.5 m²
Downwind sail area: 1011 ft²93.96 m²
Mainsail area: 254 ft²23.6 m²
Genoa area: 311 ft²28.9 m²
Solent area: 226 ft²21 m²
Jib area: 205 ft²19 m²
Symmetric spinnaker area: 757 ft²70.36 m²
I iFore triangle height (from mast foot to fore stay top attachment): 38’ 11”11.87 m
J iFore triangle base (from mast foot to bottom of forestay): 11’ 4”3.44 m
P iMainsail hoist measurement (from tack to head): 35’ 5”10.8 m
E iMainsail foot measurement (from tack to clew): 12’ 10”3.9 m
Rigging type: Sloop Marconi 9/10
Mast configuration: Keel stepped mast
Rotating spars: No
Number of levels of spreaders: 2
Spreaders angle: Swept-back
Spars construction: Aluminum spars
Standing rigging: 1x19 strand wire

First 31.7's performances

HN (French rating) iHN or "Handicap Nationale" is an empirical rating system used in France allowing various monohulls, of different sizes and designs, to race each other fairly. It is particularly suitable for cruiser and cruiser-racer. Therefore, by comparing these values, we can have an indication of the relative speed of 2 boats.: 21.0
Upwind sail area to displacement iThe ratio sail area to displacement is obtained by dividing the sail area by the boat's displaced volume to the power two-thirds. The ratio sail area to displacement can be used to compare the relative sail plan of different sailboats no matter what their size. Upwind: under 18 the ratio indicates a cruise oriented sailboat with limited performances especially in light wind, while over 25 it indicates a fast sailboat.: 234 ft²/T21.75 m²/T
Downwind sail area to displacement iThe ratio sail area to displacement is obtained by dividing the sail area by the boat's displaced volume to the power two-thirds. The ratio sail area to displacement can be used to compare the relative sail plan of different sailboats no matter what their size.: 419 ft²/T38.93 m²/T
Displacement-length ratio (DLR) iThe Displacement Length Ratio (DLR) is a figure that points out the boat's weight compared to its waterline length. The DLR is obtained by dividing the boat's displacement in tons by the cube of one one-hundredth of the waterline length (in feet). The DLR can be used to compare the relative mass of different sailboats no matter what their length: a DLR less than 180 is indicative of a really light sailboat (race boat made for planning), while a DLR greater than 300 is indicative of a heavy cruising sailboat.: 156
Ballast ratio iThe Ballast ratio is an indicator of stability; it is obtained by dividing the boat's displacement by the mass of the ballast. Since the stability depends also of the hull shapes and the position of the center of gravity, only the boats with similar ballast arrangements and hull shapes should be compared. The higher the ballast ratio is, the greater is the stability.: 27 %
Critical hull speed iAs a ship moves in the water, it creates standing waves that oppose its movement. This effect increases dramatically the resistance when the boat reaches a speed-length ratio (speed-length ratio is the ratio between the speed in knots and the square root of the waterline length in feet) of about 1.2 (corresponding to a Froude Number of 0.35) . This very sharp rise in resistance, between speed-length ratio of 1.2 to 1.5, is insurmountable for heavy sailboats and so becomes an apparent barrier. This leads to the concept of "hull speed". The hull speed is obtained by multiplying the square root of the waterline length (in feet) by 1.34.: 7.20 knots