Sun Fast 31 Performance / Lead keel

Sailboat specifications

The Sun Fast 31 is a 30’ (9.15m) cruiser-racer sailboat designed by Andrieu Yacht Design (France). She was built between 1990 and 1993 by Jeanneau (France) with 130 hulls completed. The Performance / Lead keel version displays a deep lead fin offering high righting moment and low drag.

The Sun Fast 31 is as well listed, on Boat-Specs.com, in Deep draft and Shoal draft version (see all the versions compared).

Sun Fast 31's main features

Model: Sun Fast 31
Version: Performance / Lead keel
Hull type: Monohull
Category: Cruiser-racer sailboat
Sailboat builder: Jeanneau
Sailboat designer: Andrieu Yacht Design
Sailboat range: Sun Fast
Country: France
Construction: GRP (glass reinforced polyester):
- Hull: Single skin fiberglass polyester
- Deck: Sandwich balsa fiberglass polyester
Number of hulls built: 130
First built hull: 1990
Last built hull: 1993
Appendages: Keel : fin without bulb
Helm: Single tiller
Rudder: Single spade rudder
Unsinkable: No
Trailerable: No
Former French navigation category: 2
Standard public price ex. VAT (indicative only): N/A €

Sun Fast 31's main dimensions

Overall length: 30’ 6”9.3 m
Hull length: 30’9.15 m
Waterline length: 25’ 4”7.7 m
Beam (width): 10’ 7”3.23 m
Waterline beam (width): 8’ 5”2.56 m
Draft: 5’ 8”1.75 m
Fore freeboard: 3’ 10”1.17 m
Mid-ship freeboard: 33’ 10”10.3 m
Light displacement (M_LC): 6834 lb3100 kg
Ballast weight: 2601 lb1180 kg
Ballast type: Lead
French customs tonnage: 8.12 Tx

Sun Fast 31's rig and sails

Upwind sail area: 546 ft²50.7 m²
Downwind sail area: 887 ft²82.4 m²
Mainsail area: 255 ft²23.7 m²
Genoa area: 291 ft²27 m²
Symmetric spinnaker area: 632 ft²58.7 m²
I iFore triangle height (from mast foot to fore stay top attachment): 36’ 1”11 m
J iFore triangle base (from mast foot to bottom of forestay): 10’ 6”3.2 m
P iMainsail hoist measurement (from tack to head): 36’ 8”11.2 m
E iMainsail foot measurement (from tack to clew): 12’ 1”3.7 m
Rigging type: Sloop Marconi 7/8
Mast configuration: Deck stepped mast
Rotating spars: No
Number of levels of spreaders: 2
Spreaders angle: Swept-back
Spars construction: Aluminum spars
Standing rigging: 1x19 strand wire discontinuous

Sun Fast 31'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.: 18.0
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.: 257 ft²/T23.85 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.: 417 ft²/T38.76 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.: 192
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.: 38 %
Wetted area: 209 ft²19.43 m²
Righting moment @ 1° iThe righting moment is a moment (torque) that tends to restore a boat to its previous position after heeling. Its value corresponds to the torque needed to heel the boat for this angle. Higher the righting moment is for an angle, greater is the stability.: 449 lb.ft62 kg.m
Maximum transverse section: 11 ft²1.03 m²
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.: 6.74 knots