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Review of X-79


X-79
X-79 anno 1985.


Basic specs.

sail specifications
The X-79 is a sailboat designed by the maritime architect Niels Jeppesen in the late seventies. Several hundred boats have been produced. The X-79 is built by the Danish yard X-Yachts A/S.

Looking for a new boat? Find a X-79 or similar boat for sale

Hull

Both the hull and the deck 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.

Both the hull and the deck 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.


Interior

The boat is equipped with one cabin, 4 - 6 berths, a galley, 17.0 liter fresh water capacity and toilet facility.

Note: the boat has also been sold to be self-made/-interiored, which means that the quality of each boat may vary.


Rig

The X-79 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

The X-79 has been built with different keel alternatives.

Fin keel

One option is 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 iron. Many people prefer lead keel in favour of iron. The main argument is that lead is much heavier than iron and a lead keel can therefore be made smaller which again result in less wet surface, i.e. less drag. In fact iron is quite heavy, just 30% less heavy than lead, so the advantage of a lead keel is often overstated. As the surface of a fin type keel is just a fraction of the total wet surface, the difference between an iron keel and a lead keel can in reality be ignored for cruising yachts.

X-79 can enter even shallow marinas as the draft is just about 1.33 - 1.43 meter (4.36 - 4.66 ft) dependent on the load. See immersion rate below.

Fin keel

Another option is 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.

This keel is also made of iron.

The boat can enter even shallow marinas as the draft is just about 1.35 - 1.45 meter (4.43 - 4.73 ft) dependent on the load. See immersion rate below.


Engine

An outboard motor is often used on this boat. In that case the boat will typically require a power of 3 - 4 hp, alternatively 71 - 85 lbs thrust if you prefer an electrical motor. Electric outboards are becoming popular for sailboat owners who want clean instant power with less noise and no exhaust fumes.


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 X-79 is 2.48, 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 6.1 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 X-79 is about 123 kg/cm, alternatively 691 lbs/inch.
Meaning: if you load 123 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 691 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 X-79 is 12.1.

Low High 12% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 12% 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 X-79 is 2.76.

Slim Wide 82% 0 50 100
Compared with other similar sailboats it is more spacy than 82% 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 X-79 is 50%.

Low High 88% 0 50 100
This ballast ratio shows a righting moment that is higher than 88% of all similar sailboat designs. A righting moment (ability to resist heeling) significantly above average.


D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for X-79 is 170 which categorizes this boat among 'light racers'.

Heavy Light 79% 0 50 100
79% 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 X-79 with ISO 8666 reference sail is 21.8, with a 135% genua the SA/D is 24.8.

Low High 96% 0 50 100
The SA/D ratio indicates that it is faster than 96% of all similar sailboat designs in light wind.


Over- / underrigged

Low High 100% 0 50 100
The X-79 has more rig than 100% of all similar sailboats, which indicates that the boat is significantly overrigged.


RSP (Relative Speed Performance)

What is Relative Speed Performance?

The Relative Speed Performance for X-79 is 99

Slow Fast 99% 0 50 100
The relative speed performance is 99 which means that a it is faster than 99% of all similar sailboat designs.


Maintenance

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 20m2 (215 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 genoa specifications spinnaker 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 26.3 m(86.3 feet)8 mm(5/16 inch)
Jib/genoa halyard26.3 m(86.3 feet)8 mm(5/16 inch)
Spinnaker halyard26.3 m(86.3 feet)8 mm(5/16 inch)
Jib sheet 7.9 m(26.0 feet)10 mm(3/8 inch)
Genoa sheet7.9 m(26.0 feet)10 mm(3/8 inch)
Mainsheet 19.9 m(65.1 feet)10 mm(3/8 inch)
Spinnaker sheet17.5 m(57.3 feet)10 mm(3/8 inch)
Cunningham3.5 m(11.5 feet)8 mm(5/16 inch)
Kickingstrap7.0 m(23.0 feet)8 mm(5/16 inch)
Clew-outhaul7.0 m(23.0 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 X-79 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