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- Sailboat Guide
Gloucester 18
Gloucester 18 is a 18 ′ 0 ″ / 5.5 m monohull sailboat designed by J.R. (Rod) Macalpine-Downie and Dick Gibbs and built by Lockley Newport Boats starting in 1985.
Rig and Sails
Auxilary power, accomodations, calculations.
The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.
Classic hull speed formula:
Hull Speed = 1.34 x √LWL
Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio .311 Hull Speed = Max Speed/Length ratio x √LWL
Sail Area / Displacement Ratio
A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.
SA/D = SA ÷ (D ÷ 64) 2/3
- SA : Sail area in square feet, derived by adding the mainsail area to 100% of the foretriangle area (the lateral area above the deck between the mast and the forestay).
- D : Displacement in pounds.
Ballast / Displacement Ratio
A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.
Ballast / Displacement * 100
Displacement / Length Ratio
A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.
D/L = (D ÷ 2240) ÷ (0.01 x LWL)³
- D: Displacement of the boat in pounds.
- LWL: Waterline length in feet
Comfort Ratio
This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.
Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam 1.33 )
- D: Displacement of the boat in pounds
- LOA: Length overall in feet
- Beam: Width of boat at the widest point in feet
Capsize Screening Formula
This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.
CSV = Beam ÷ ³√(D / 64)
Same as the BUCCANEER 18. When Gloucester Yachts purchased the molds for the BUCCANEER 18 in the mid 1980’s, they renamed it the GLOUCESTER 18.
BUCCANEER 18 PRODUCTION HISTORY: Chrysler Corporation - 1968 thru 1980, hull #1 thru approx. #4050. (Just over 4000 boats built). Texas Marine International (TMI) - 1981 thru 1982, hull approx. #4051 thru approx. #4750. (Around 700 boats built). Wellcraft Marine Corporation, Starwind Division - 1982 thru 1984, hull approx. #4751 thru approx. #5000. (Approx. 250 boats built). Gloucester Yachts - 1985 thru 1986, hull #5001 thru #5059. (59 boats built). Cardinal Yachts - 1987 thru present, hull #5060 thru #5065, #5100 thru #5106 and #5200 thru #5214. (28 boats built).
Nickels Boatworks is current builder. (2008)
Not the same as another GLOUCESTER 18 (aka WHITECAP), designed by Harry Sindle, and also built by Gloucester Yachts.
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Buccaneer 18
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Review of Gloucester 18 (Macalpine-Downie)
Basic specs..
The boat 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 genaker or a spinnaker for optimal speed.
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.
The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Gloucester 18 (Macalpine-Downie) is about 62 kg/cm, alternatively 348 lbs/inch. Meaning: if you load 62 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 348 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 L/B (Length Beam Ratio)?
Maintenance
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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