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Review of GK 29


Basic specs.

sail specifications
The GK 29 is a sailboat designed by the British maritime architect Jack Laurent Giles. The GK 29 is built by the British yard Westerly Marine.

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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.


Rig

The GK 29 is equipped with a masthead rig. The advantage of a masthead rig is its simplicity and the fact that a given sail area - compared with a fractional rig - can be carried lower and thus with less heeling moment.


Keel

Fin keel

The GK 29 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 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.

The boat can enter most marinas as the draft is just about 1.60 - 1.70 meter (5.25 - 5.55 ft) dependent on the load. See immersion rate below.


Engine

The boat may be equipped with a Petter diesel engine.


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 GK 29 is 2.07, 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 6.8 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 GK 29 is about 165 kg/cm, alternatively 927 lbs/inch.
Meaning: if you load 165 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 927 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 GK 29 is 20.8.

Low High 38% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 38% of all similar sailboat designs. This comfort value is just below average.


L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for GK 29 is 2.80.

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 GK 29 is 50%.

Low High 92% 0 50 100
This ballast ratio shows a righting moment that is higher than 92% 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 GK 29 is 217 which categorizes this boat among 'light crusers & offshore racers'.

Heavy Light 69% 0 50 100
69% 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 GK 29 with ISO 8666 reference sail is 14.6, with a 135% genua the SA/D is 17.5.

Low High 34% 0 50 100
The SA/D ratio indicates that it is faster than 34% of all similar sailboat designs in light wind.


Over- / underrigged

Low High 54% 0 50 100
The GK 29 has more rig than 54% of all similar sailboats, which indicates that the boat is slightly overrigged.


RSP (Relative Speed Performance)

What is Relative Speed Performance?

The Relative Speed Performance for GK 29 is 79

Slow Fast 79% 0 50 100
The relative speed performance is 79 which means that a it is faster than 79% 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 28m2 (301 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 masthead 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 25.4 m(83.5 feet)8 mm(5/16 inch)
Jib/genoa halyard25.4 m(83.5 feet)8 mm(5/16 inch)
Spinnaker halyard25.4 m(83.5 feet)8 mm(5/16 inch)
Jib sheet 8.9 m(29.1 feet)10 mm(3/8 inch)
Genoa sheet8.9 m(29.1 feet)10 mm(3/8 inch)
Mainsheet 22.2 m(72.8 feet)10 mm(3/8 inch)
Spinnaker sheet19.5 m(64.1 feet)10 mm(3/8 inch)
Cunningham3.0 m(10.0 feet)8 mm(5/16 inch)
Kickingstrap6.1 m(20.0 feet)8 mm(5/16 inch)
Clew-outhaul6.1 m(20.0 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.

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Finally

We are always looking for new photos. If you can contribute with photos for GK 29 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