Great choice! Your favorites are temporarily saved for this session. Sign in to save them permanently, access them on any device, and receive relevant alerts.

  • Sailboat Guide

J/120 is a 39 ′ 11 ″ / 12.2 m monohull sailboat designed by Rod Johnstone and built by J Boats between 1999 and 2006.

Drawing of J/120

  • 2 / 7 Annapolis, MD, US 1998 J/120 $134,900 USD View
  • 3 / 7 Annapolis, MD, US 1998 J/120 $134,900 USD View
  • 4 / 7 Annapolis, MD, US 1998 J/120 $134,900 USD View
  • 5 / 7 Annapolis, MD, US 1998 J/120 $134,900 USD View
  • 6 / 7 Annapolis, MD, US 1998 J/120 $134,900 USD View
  • 7 / 7 Annapolis, MD, US 1998 J/120 $134,900 USD View

j120 sailboat length

Rig and Sails

Auxilary power, accomodations, calculations.

The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.

Classic hull speed formula:

Hull Speed = 1.34 x √LWL

Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio .311 Hull Speed = Max Speed/Length ratio x √LWL

Sail Area / Displacement Ratio

A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.

SA/D = SA ÷ (D ÷ 64) 2/3

  • SA : Sail area in square feet, derived by adding the mainsail area to 100% of the foretriangle area (the lateral area above the deck between the mast and the forestay).
  • D : Displacement in pounds.

Ballast / Displacement Ratio

A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.

Ballast / Displacement * 100

Displacement / Length Ratio

A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.

D/L = (D ÷ 2240) ÷ (0.01 x LWL)³

  • D: Displacement of the boat in pounds.
  • LWL: Waterline length in feet

Comfort Ratio

This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.

Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam 1.33 )

  • D: Displacement of the boat in pounds
  • LOA: Length overall in feet
  • Beam: Width of boat at the widest point in feet

Capsize Screening Formula

This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.

CSV = Beam ÷ ³√(D / 64)

Some were finished in France.

Embed this page on your own website by copying and pasting this code.

1998 J Boats J/120 cover photo

  • About Sailboat Guide

©2024 Sea Time Tech, LLC

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

IMAGES

  1. J120

    j120 sailboat length

  2. 1994 J Boats J/120 Sail Boat For Sale

    j120 sailboat length

  3. J Boats J/120 40 ft sailboat SAYKADOO Just Catamarans

    j120 sailboat length

  4. J-120 Upwind Sails

    j120 sailboat length

  5. J-120

    j120 sailboat length

  6. J120

    j120 sailboat length

VIDEO

  1. J-120 1998 Jboat Sailboat for sale in California By: Ian Van Tuyl

  2. 2017 Bayview One Design Regatta

  3. Bayview One Design 2013 J120 Broach and Recovery

  4. J Boats 120 FOR SALE

  5. 2019 Sailing Season J120 "with Grace"

  6. J/121 Offshore Speedster- CNC creation of sailboat hull

COMMENTS

  1. J/120

    LENGTH: Traditionally, LOA (length over all) equaled hull length. Today, many builders use LOA to include rail overhangs, bowsprits, etc. and LOD (length on deck) for hull length. That said, LOA may still mean LOD if the …

  2. Tech Specs

    J/120 Offshore Racer-Cruisesr Sailboat Technical specifications & …

  3. A Smooth & Stable Ride with Award Winning Performance

    A J/120 sailing at 7.2 knots, 38 degrees off the true wind (25 degrees apparent wind angle), makes good a velocity (VMG) of 5.7 knots straight into the wind. This is 15% faster than a boat …

  4. J/120 Sailboat Review

    The GPS agreed with the speedometer — flat out we were doing a respectable 8.6 knots on this 40-footer powered by a 38-horsepower Yanmar driving a Martec two-blade folding propeller. Optimal cruising speed would be …

  5. J/120 Used Boat Review

    Introduced with the 1995 model year, the J/120 was designed by the J/Boat team led by Rodney Johnstone. The overall length is 40 feet, or just a hair over 12 meters, which accounts for the model name. More than 200 boats …

  6. J120

    The new J/120 is an impressive 40-footer, a performance machine with cruising accommodations. Its size will appeal to sailors who want to go fast around the buoys and those …

  7. J120

    The J120 is a 40.0ft fractional sloop designed by Johnstone and built in fiberglass by J Boats between 1999 and 2006. 230 units have been built. The J120 is a light sailboat which is a high performer.