J/105 Standard

Sailboat specifications

The J/105 is a 34’5” (10.5m) racer-cruiser sailboat designed by Rod Johnstone (United States). She was built since 1991 (and now discontinued) by J/Boats (United States).

The J/105 is as well listed, on Boat-Specs.com, in Shoal draft version (see all the versions compared).

J/105's main features

Model: J/105
Version: Standard
Hull type: Monohull
Category: Racer-cruiser sailboat
Sailboat builder: J/Boats
Sailboat designer: Rod Johnstone
Country: United States
Construction: GRP (glass reinforced polyester):
Sandwich fiberglass polyester
First built hull: 1991
Last built hull: Discontinued
Appendages: Keel : L-shaped keel (with bulb)
Helm: Single helm wheel
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 €

J/105's main dimensions

Hull length: 34’ 5”10.5 m
Waterline length: 29’ 6”8.99 m
Beam (width): 11’3.35 m
Draft: 6’ 6”1.98 m
Mast height from D_WL: 50’ 4”15.34 m
Light displacement (M_LC): 7749 lb3515 kg
Ballast weight: 3417 lb1550 kg
Ballast type: Lead
French customs tonnage: 8.81 Tx

J/105's rig and sails

Upwind sail area: 577 ft²53.6 m²
Downwind sail area: 1305 ft²121.2 m²
Mainsail area: 304 ft²28.2 m²
Solent area: 273 ft²25.4 m²
Asymmetric spinnaker area: 1001 ft²93 m²
I iFore triangle height (from mast foot to fore stay top attachment): 40’ 7”12.37 m
J iFore triangle base (from mast foot to bottom of forestay): 13’ 6”4.12 m
P iMainsail hoist measurement (from tack to head): 41’ 6”12.65 m
E iMainsail foot measurement (from tack to clew): 14’ 7”4.45 m
Rigging type: Sloop Marconi fractional
Mast configuration: Keel stepped mast
Rotating spars: No
Number of levels of spreaders: 2
Spreaders angle: Swept-back
Spars construction: Aluminum spars
Standing rigging: Single-strand (ROD)

J/105'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.: 250 ft²/T23.19 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.: 564 ft²/T52.43 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.: 137
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.: 44 %
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.: 7.28 knots