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Sailboat specifications and datasheets

J/121

The J/121 is a 40’ monohull sailboat designed by Alan Johnstone. She was built by J/Boats (United States) and made of sandwich Core-Cell / fiberglass / polyester (composite infusion). The production started in 2017 .
J/Boats J/121 J/Boats J/121 sailplanJ/Boats J/121 layoutJ/Boats J/121 layoutJ/Boats J/121 sailingJ/Boats J/121 sailingJ/Boats J/121 sailingJ/Boats J/121 sailingJ/Boats J/121 sailingJ/Boats J/121 accommodationsJ/Boats J/121 accommodationsJ/Boats J/121 accommodationsJ/Boats J/121 detail
J/121's   Main Features
Model J/121
Type of hull Monohull
Category Offshore cruiser-racer sailboat
Shipyard
Designer Alan Johnstone
Construction Hull and deck:
sandwich Core-Cell / fiberglass / polyester (composite infusion)
First built hull 2017
Last built hull Discontinued
Appendages Keel :
L-shaped keel (with bulb)
Helm 2 wheels
Rudder 1 spade rudder
Cockpit Open aft cockpit
Unsinkable No
Trailerable No
Standard public price ex. VAT (indicative only) N/A
J/121's   Main dimensions
Hull length 40’
Waterline length 35’ 10”
Beam (width) 12’ 4”
Draft 7’ 1”
Light displacement 11464 lbs
Ballast type Cast iron fin with lead bulb
Water ballast Lateral water ballasts
Water ballast capacity 2 x 100.4 gal
J/121's   Rig and sails
Upwind sail area 969 sq.ft
Downwind sail area 2153 sq.ft
Rigging type Sloop Marconi 7/8
Rotating spars No
Mast position Keel stepped mast
Spars Mast and boom in Carbon fiber
Standing rigging Single-strand (ROD) discontinuous
Number of levels of spreaders 2
Spreaders angle Swept-back
J/121's   Performances
Upwind sail area to displacementiThe 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 23 it indicates a fast sailboat.
29.99
Downwind sail area to displacementiThe 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 23 it indicates a fast sailboat.
66.63
Displacement-Length ratio (DLR)iThe Displacement Length ratio is a figure that points out the boat's weight compared to its waterline length. 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.
114
Hull speediAs 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.
8.01 knots
J/121's   Auxiliary engine
Engine(s) 1
Engine type Inboard engine
Engine 29 HP
Fuel type Diesel
Fuel tank capacity 26.4 gal
J/121's   Accommodation
Cabin(s) (min/max) 1 / 2
Berth(s) (min/max) 2 / 8
Head(s) 1
Fresh water tank capacity 26.4 gal
Holding tank capacity 11.9 gal

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