J/70

Sailboat specifications

The J/70 is a 22’8” (6.93m) one design sailboat designed by Alan Johnstone (United States). She is built since 2012 by J/Boats (United States). She has been awarded "2013 - European Yacht of the Year: Special Yacht".

J/70's main features

Model

J/70

Hull type

Monohull

Category

One design sailboat

Sailboat builder

J/Boats

Sailboat designer

Alan Johnstone

Country

United States

Construction

GRP (glass reinforced polyester):
Sandwich fiberglass polyester

First built hull

2012

Last built hull

Still in production

Award(s)

2013: European Yacht of the Year: Special Yacht

Appendages

Lifting keel : fin with bulb, lifting

Helm

Single tiller

Rudder

Single transom hung rudder

Unsinkable

Trailerable

Yes

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

Standard public price ex. VAT (indicative only)

About

35 400 €

(2020)

J/70's main dimensions

Hull length: 22’ 8”6.93 m
Waterline length: 20’ 6”6.24 m
Beam (width): 7’ 5”2.25 m
Draft: 4’ 10”1.45 m
Draft when appendages up: 3’0.9 m
Mast height from D_WL: 32’ 10”10 m
Light displacement (M_LC): 1753 lb795 kg
Ballast weight: 639 lb290 kg
Ballast type: Lead

J/70's rig and sails

Upwind sail area: 284 ft²26.38 m²
Downwind sail area: 657 ft²61.07 m²
Mainsail area: 173 ft²16.07 m²
Jib area: 111 ft²10.31 m²
Asymmetric spinnaker area: 484 ft²45 m²
I iFore triangle height (from mast foot to fore stay top attachment): 26’ 10”8.16 m
J iFore triangle base (from mast foot to bottom of forestay): 7’ 8”2.34 m
P iMainsail hoist measurement (from tack to head): 26’ 1”7.97 m
E iMainsail foot measurement (from tack to clew): 9’ 5”2.88 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: Carbon fiber spars
Standing rigging: 1x19 strand wire continuous

J/70'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.: 331 ft²/T30.74 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.: 766 ft²/T71.16 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.: 93
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.: 36 %
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.: 6.06 knots