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Review of J/24


J/24
J/24. J 24 One Design


Basic specs.

sail specifications
The J/24 also known as J 24 One Design or J 24 One Design is a sailboat designed by the maritime architect Rodney S. Johnstone in the late seventies. Several thousand boats have been produced. The J/24 is built by the American yard J Boats Tillotson Pearson.

Looking for a new boat? Find a J/24 or similar boat for sale

Hull

The hull is made of fibreglass. Generally, a hull made of fibreglass requires only a minimum of maintenance during the sailing season. And outside the sailing season, just bottom cleaning and perhaps anti-fouling painting once a year - a few hours of work, that's all.

The hull is a sandwich construction which improves the indoor climate. Especially when the water is colder than the air in the cabin, then the double hull insulates against cold water and reduce the condense water in the cabin. The core material in the sandwich construction is balsa.


Interior

The interior is like most other boats made of teak. Teak has the advantage of being naturally very oily and therefore water-repellent, which is suitable on boats.
The boat is equipped with 2 berths and a galley.


Rig
Rig
Rig of J/24.

The J/24 is equipped with a fractional rig. A fractional rig has smaller headsails which make tacking easier, which is an advantage for cruisers and racers, of course. The downside is that having the wind from behind often requires a gennaker or a spinnaker for optimal speed.


Keel

Fin keel

The J/24 is equipped with a fin keel. A boat with a fin keel is more manoeuvrable but has less directional stability than a similar boat with a full keel.

The keel is made of lead. Compared with iron, lead has the advantage of being 44% heavier, which allows a smaller keel and hence less water resistance and higher speed.

The boat can enter even shallow marinas as the draft is just about 1.22 - 1.32 meter (4.00 - 4.30 ft) dependent on the load. See immersion rate below.


Sailing characteristics

This section covers widely used rules of thumb to describe the sailing characteristics. Please note that even though the calculations are correct, the interpretation of the results might not be valid for extreme boats.

Stability and Safety

What is Capsize Screening Formula (CSF)?

The capsize screening value for J/24 is 2.45, indicating that this boat would not be accepted to participate in ocean races.


Theoretical Maximum Hull Speed

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 6.0 knots. The term "Theoretical Maximum Hull Speed" is widely used even though a boat can sail faster. The term shall be interpreted as above the theoretical speed a great additional power is necessary for a small gain in speed.


Immersion rate

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for J/24 is about 111 kg/cm, alternatively 622 lbs/inch.
Meaning: if you load 111 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 622 lbs cargo on the boat it will sink 1 inch.


Sailing statistics

This section is statistical comparison with similar boats of the same category. The basis of the following statistical computations is our unique database with more than 26,000 different boat types and 350,000 data points.

Motion Comfort Ratio

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for J/24 is 10.2 - 12.2.

Low High 21% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 21% of all similar sailboat designs. This is a comfort value significantly below average.


L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for J/24 is 2.69.

Slim Wide 79% 0 50 100
Compared with other similar sailboats it is more spacy than 79% of all other designs. It seems that the designer has chosen a significantly more spacy hull design.


Ballast Ratio

What is a Ballast Ratio?

The ballast ratio for J/24 is 31%.

Low High 18% 0 50 100
This ballast ratio shows a righting moment that is higher than 18% of all similar sailboat designs. A righting moment (ability to resist heeling) significantly below average.


D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for J/24 is 158 which categorizes this boat among 'light racers'.

Heavy Light 76% 0 50 100
76% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.


SA/D (Sail Area Displacement ratio)

What is SA/D (Sail Area Displacement ratio)?

The SA/D for J/24 with ISO 8666 reference sail is 19.7, with a 135% genua the SA/D is 22.9.

Low High 73% 0 50 100
The SA/D ratio indicates that it is faster than 73% of all similar sailboat designs in light wind.


Over- / underrigged

Low High 100% 0 50 100
The J/24 has more rig than 100% of all similar sailboats, which indicates that the boat is significantly overrigged.


Maintenance

Hull / Deck

As balsa wood is used as sandwich core material special care must be taken in relation to work that require penetration of the sandwich construction in order to to prevent water to get in contact with the balsa wood. Otherwise the balsa wood will eventually rotten and be expensive/impossible to repair.

Bottom Paint

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 18m2 (193 ft2).
Based on this, your favourite maritime shop can tell you the quantity you need.

Note: If you use a paint roller you will need more paint than if you use a paintbrush.


Rig

Dimensions of sail for fractional rig.

mainsail specifications headsail specifications

Are your sails worn out? You might find your next sail here: Sails for Sale



If you need to renew parts of your running rig and is not quite sure of the dimensions, you may find the estimates computed below useful.



Guiding dimensions of running rig
UsageLengthDiameter
Mainsail halyard 22.6 m(74.2 feet)8 mm(5/16 inch)
Jib/genoa halyard22.6 m(74.2 feet)8 mm(5/16 inch)
Spinnaker halyard22.6 m(74.2 feet)8 mm(5/16 inch)
Jib sheet 7.3 m(24.0 feet)10 mm(3/8 inch)
Genoa sheet7.3 m(24.0 feet)10 mm(3/8 inch)
Mainsheet 18.3 m(60.0 feet)10 mm(3/8 inch)
Spinnaker sheet16.1 m(52.8 feet)10 mm(3/8 inch)
Cunningham3.0 m(9.7 feet)8 mm(5/16 inch)
Kickingstrap5.9 m(19.5 feet)8 mm(5/16 inch)
Clew-outhaul5.9 m(19.5 feet)8 mm(5/16 inch)

Boat owner's ideas

This section is reserved boat owner's modifications, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

Do you have changes/improvements you would like to share? Upload a photo and describe what you have done.



Finally

We are always looking for new photos. If you can contribute with photos for J/24 it would be a great help.

If you have any comments to the review, improvement suggestions, or the like, feel free to contact us. Criticism helps us to improve.



References