J/24

Sailboat specifications

The J/24 is a 24’ (7.32m) one design sailboat designed by Rod Johnstone (United States). She was built since 1977 (and now discontinued) by J/Boats (United States).

J/24's main features

Model: J/24
Hull type: Monohull
Category: Coastal one design sailboat
Sailboat builder: J/Boats
Sailboat designer: Rod Johnstone
Country: United States
Construction: GRP (glass reinforced polyester):
Sandwich fiberglass polyester
Number of hulls built: About 5300
First built hull: 1977
Last built hull: Discontinued
Appendages: Keel : fin without bulb
Helm: Single tiller
Rudder: Single transom hung rudder
Unsinkable: No
Trailerable: Yes
Standard public price ex. VAT (indicative only): N/A €

J/24's main dimensions

Hull length: 24’7.32 m
Waterline length: 20’6.1 m
Beam (width): 8’ 11”2.7 m
Draft: 3’ 11”1.2 m
Light displacement (M_LC): 3086 lb1400 kg
Ballast weight: 948 lb430 kg
Ballast type: Lead
French customs tonnage: 3.00 Tx

J/24's rig and sails

Upwind sail area: 347 ft²32.2 m²
Downwind sail area: 562 ft²52.2 m²
Mainsail area: 153 ft²14.2 m²
Genoa area: 194 ft²18 m²
Symmetric spinnaker area: 409 ft²38 m²
I iFore triangle height (from mast foot to fore stay top attachment): 26’ 2”8 m
J iFore triangle base (from mast foot to bottom of forestay): 9’ 6”2.9 m
P iMainsail hoist measurement (from tack to head): 28’8.53 m
E iMainsail foot measurement (from tack to clew): 9’ 8”2.97 m
Rigging type: Sloop Marconi fractional
Mast configuration: Deck stepped mast
Rotating spars: No
Number of levels of spreaders: 1
Spreaders angle: Swept-back
Spars construction: Aluminum spars
Standing rigging: 1x19 strand wire continuous

J/24's performances

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.: 277 ft²/T25.73 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.: 449 ft²/T41.71 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.: 175
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.: 31 %
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.: 5.99 knots