Review of GK 34 Grand Prix

Basic specs.

The GK 34 Grand Prix is a sailboat designed by the French maritime architect Edward George Dubois. The GK 34 Grand Prix is built by the British yard Westerly Marine.

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Hull

The deck is made of fibreglass.

Interior

Floor plan of GK 34 Grand Prix. Grand Prix version of the floor plan.

The boat is equipped with 3 cabins, 6+2 berths, a galley and 114 liters (30 US gallons, 25 imperial gallons) fresh water capacity.

Rig

The GK 34 Grand Prix is built 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 GK 34 Grand Prix is built 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.

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 only enter major marinas as the draft is about 2.00 - 2.10 meter (6.56 - 6.86 ft) dependent on the load. See immersion rate below.

Engine

The fuel tank has a capacity of 57 liters (15 US gallons, 12 imperial gallons).

GK 34 Grand Prix may be equipped with an inboard Bukh DV20ME diesel engine at 20 hp (14 kW). Calculated max speed is about 6.0 knots

The transmission is a shaft drive. A shaft drive will in the long run require less maintenance than other types of drive e.g. a sail drive.

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 34 Grand Prix is 2.21, 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 7.0 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 GK 34 Grand Prix is about 193 kg/cm, alternatively 1084 lbs/inch.
Meaning: if you load 193 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 1084 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 34 Grand Prix is 17.4.

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 GK 34 Grand Prix is 2.99.

Compared with other similar sailboats it is more spacy than 69% of all other designs. It seems that the designer has chosen a slightly more spacy hull design.

Ballast Ratio

What is a Ballast Ratio?

The ballast ratio for GK 34 Grand Prix is 55%.

This ballast ratio shows a righting moment that is higher than 97% 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 34 Grand Prix is 177 which categorizes this boat among 'light racers'.

82% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.

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 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.

Rig

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**
Usage	Length		Diameter
Jib sheet	10.3 m	(33.7 feet)	12 mm	(1/2 inch)
Genoa sheet	10.3 m	(33.7 feet)	12 mm	(1/2 inch)
Mainsheet	25.6 m	(84.2 feet)	12 mm	(1/2 inch)
Spinnaker sheet	22.6 m	(74.1 feet)	12 mm	(1/2 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 GK 34 Grand Prix 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

[Ref 1]: ISO 8666 Small craft — Principal data.
[Ref 3]: ISO 12215-5 Small craft — Hull construction and scantlings.