Swan 47 Keel and centerboard

Sailboat specifications

The Swan 47 is a 47’10” (14.57m) cruiser-racer sailboat designed by Sparkman & Stephens (United States). She was built between 1974 and 1979 by Nautor's Swan (Finland). The Keel and centerboard version features a centerboard inside of a short fin-keel allowing shoal draft while maintaining upwind capabilities.

The Swan 47 has also been marketed as NYYC 48 and she is as well listed, on Boat-Specs.com, in Fin keel version (see all the versions compared).

Swan 47's main features

Model: Swan 47
Version: Keel and centerboard
Hull type: Monohull
Category: Offshore cruiser-racer sailboat
Sailboat builder: Nautor's Swan
Sailboat designer: Sparkman & Stephens
Country: Finland
Construction: GRP (glass reinforced polyester):
- Hull: Single skin fiberglass polyester
- Deck: Sandwich fiberglass polyester
Number of hulls built: About 70
First built hull: 1974
Last built hull: 1979
Appendages: Centerboard : pivoting centerboard in the keel
Helm: Single helm wheel
Rudder: Single rudder on skeg
Unsinkable: No
Trailerable: No
Standard public price ex. VAT (indicative only): N/A €

Swan 47's main dimensions

Hull length: 47’ 10”14.57 m
Waterline length: 36’ 4”11.05 m
Beam (width): 13’ 8”4.19 m
Draft: 9’ 6”2.9 m
Draft when appendages up: 5’ 11”1.8 m
Mast height from D_WL: 66’ 10”20.35 m
Light displacement (M_LC): 34172 lb15500 kg
Ballast weight: 17196 lb7800 kg
Ballast type: Lead

Swan 47's rig and sails

Upwind sail area: 1366 ft²126.9 m²
Downwind sail area: 2652 ft²246.4 m²
Mainsail area: 446 ft²41.4 m²
Genoa area: 920 ft²85.5 m²
Symmetric spinnaker area: 2207 ft²205 m²
I iFore triangle height (from mast foot to fore stay top attachment): 62’18.9 m
J iFore triangle base (from mast foot to bottom of forestay): 19’ 10”6.04 m
P iMainsail hoist measurement (from tack to head): 55’ 8”16.98 m
E iMainsail foot measurement (from tack to clew): 16’4.88 m
Rigging type: Sloop Marconi masthead
Mast configuration: Keel stepped mast
Rotating spars: No
Number of levels of spreaders: 2
Spreaders angle: 0 °
Spars construction: Aluminum spars
Standing rigging: Single-strand (ROD) discontinuous

Swan 47's performances

IOR rating iIOR, or International Offshore Rule, was a measurement rule system used internationally for ocean racing. It allows boats of different sizes and designs to race each other fairly. Therefore, by comparing these values, we can have an indication of the relative speed of 2 boats.: 34.5
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.: 220 ft²/T20.41 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.: 427 ft²/T39.64 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.: 325
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.: 50 %
Wetted area: 506 ft²47 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.: 8.07 knots