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/122 is a 39 ′ 11 ″ / 12.2 m monohull sailboat designed by Rod Johnstone and built by J Boats and J Composites starting in 2008.
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)
J/122E (built in France) has same hull and rig with updated deck, coach roof, and interior.
Embed this page on your own website by copying and pasting this code.
- About Sailboat Guide
©2024 Sea Time Tech, LLC
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
The J122 is a 40.0ft fractional sloop designed by Johnstone and built in fiberglass by J Boats since 2008.
The J122 is a light sailboat which is a very high performer. It is stable / stiff and has a good righting capability if capsized. It is best suited as a fast cruiser. The fuel capacity is originally small. There is a short water supply range.
J122 for sale elsewhere on the web:
Main features
| Model | J122 | ||
| Length | 40 ft | ||
| Beam | 11.91 ft | ||
| Draft | 7.22 ft | ||
| Country | United states (North America) | ||
| Estimated price | $ 0 | ?? |
Login or register to personnalize this screen.
You will be able to pin external links of your choice.
See how Sailboatlab works in video
| Sail area / displ. | 22.94 | ||
| Ballast / displ. | 37.58 % | ||
| Displ. / length | 160.59 | ||
| Comfort ratio | 23.46 | ||
| Capsize | 1.94 |
| Hull type | Monohull fin keel with bulb and spade rudder | ||
| Construction | Fiberglass | ||
| Waterline length | 34.60 ft | ||
| Maximum draft | 7.22 ft | ||
| Displacement | 14900 lbs | ||
| Ballast | 5600 lbs | ||
| Hull speed | 7.88 knots |
We help you build your own hydraulic steering system - Lecomble & Schmitt
| Rigging | Fractional Sloop | ||
| Sail area (100%) | 865 sq.ft | ||
| Air draft | 0 ft | ?? | |
| Sail area fore | 413.59 sq.ft | ||
| Sail area main | 451.02 sq.ft | ||
| I | 54.42 ft | ||
| J | 15.20 ft | ||
| P | 51.34 ft | ||
| E | 17.57 ft |
| Nb engines | 1 | ||
| Total power | 40 HP | ||
| Fuel capacity | 35 gals |
Accommodations
| Water capacity | 42 gals | ||
| Headroom | 0 ft | ||
| Nb of cabins | 0 | ||
| Nb of berths | 0 | ||
| Nb heads | 0 |
Builder data
| Builder | J Boats | ||
| Designer | Johnstone | ||
| First built | 2008 | ||
| Last built | 0 | ?? | |
| Number built | 0 | ?? |
Other photos
Modal Title
The content of your modal.
Personalize your sailboat data sheet