Review of J/105
Basic specs.
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The hull is made of fibreglass. Generally, a hull made of fibreglass requires only a minimum of maintenance during the sailing season.
The boat is equipped with a galley, 20.0 liter fresh water capacity and toilet facility.
The J/105 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.
The J/105 has been built with different keel alternatives.
Unknown keel type
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 most marinas as the draft is just about 1.67 - 1.77 meter (5.48 - 5.78 ft) dependent on the load. See immersion rate below.
Fin keel
The J/105 is equipped with a fin keel. The fin keel is the most common keel and provides splendid manoeuvrability. The downside is that it has less directional stability than a long keel.
J/105 can only enter major marinas as the draft is about 1.98 - 2.08 meter (6.50 - 6.80 ft) dependent on the load. See immersion rate below.
The J/105 has been equipped with different engine alternatives.
Alternative 1:
The boat may be equipped with an inboard Yanmar 2GM20F diesel engine at 20 hp (14 kW). Calculated max speed is about 6.5 knots
Alternative 2:
The boat may be equipped with an inboard Yanmar diesel engine at 18 hp (13 kW). Calculated max speed is about 6.2 knots
The fuel tank has a capacity of 46.0 liters (12 US gallons, 10 imperial gallons).
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.
What is Capsize Screening Formula (CSF)?
The capsize screening value for J/105 is 2.22, indicating that this boat would not be accepted to participate in ocean races.
What is Theoretical Maximum Hull Speed?
The theoretical maximal speed of a displacement boat of this length is 7.3 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.
The immersion rate is defined as the weight required to sink the boat a certain level.
The immersion rate for J/105 is about 201 kg/cm, alternatively 1129 lbs/inch.
Meaning: if you load 201 kg cargo on the boat then it will sink 1 cm.
Alternatively, if you load 1129 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.
What is Motion Comfort Ratio (MCR)?
The Motion Comfort Ratio for J/105 is 15.8.
What is L/B (Length Beam Ratio)?
The l/b ratio for J/105 is 3.14.
The ballast ratio for J/105 is 44%.
What is Displacement Length Ratio?
The DL-ratio for J/105 is 134 which categorizes this boat among 'ultra light racers'.
What is SA/D (Sail Area Displacement ratio)?
The SA/D for J/105 with ISO 8666 reference sail is 23.6, with a 135% genua the SA/D is 27.5.
Maintenance
When buying anti-fouling bottom paint, it's nice to know how much to buy.
The surface of the wet bottom is about 34m2 (365 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.
Dimensions of sail for fractional rig.
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.
| Usage | Length | Diameter | ||
| Mainsail halyard | 32.9 m | (108.0 feet) | 12 mm | (1/2 inch) |
| Jib/genoa halyard | 32.9 m | (108.0 feet) | 12 mm | (1/2 inch) |
| Spinnaker halyard | 32.9 m | (108.0 feet) | 12 mm | (1/2 inch) |
| Jib sheet | 10.5 m | (34.5 feet) | 14 mm | (0.55 inch) |
| Genoa sheet | 10.5 m | (34.5 feet) | 14 mm | (0.55 inch) |
| Mainsheet | 26.3 m | (86.2 feet) | 14 mm | (0.55 inch) |
| Spinnaker sheet | 23.1 m | (75.9 feet) | 14 mm | (0.55 inch) |
| Cunningham | 4.5 m | (14.6 feet) | 12 mm | (1/2 inch) |
| Kickingstrap | 8.9 m | (29.2 feet) | 12 mm | (1/2 inch) |
| Clew-outhaul | 8.9 m | (29.2 feet) | 12 mm | (1/2 inch) |
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