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Hydro 28
Designer: David Thomas  ·  Builder: Seaglass (Uk)  ·  First built: 1978
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About the Hydro 28

Designed by David Thomas and built by Seaglass in the UK starting in 1978, the Hydro 28 represents British yacht design philosophy of the late 1970s. This 28-footer features a moderate displacement hull with a fin keel and transom-hung rudder configuration, paired with a fractional sloop rig that provides versatile sailing characteristics. With her 5,401-pound displacement and traditional fiberglass construction, the Hydro 28 strikes a balance between performance and stability that makes her well-suited for coastal cruising and club racing. The boat's 10.01-foot beam provides comfortable interior volume while maintaining reasonable sailing performance, with a hull speed of 6.53 knots. Her comfort ratio of 15.52 indicates a relatively stiff, quick motion that experienced sailors will appreciate, while the capsize screening formula of 2.29 suggests good stability for coastal and near-shore sailing. The moderate draft of 5.58 feet allows access to most harbors while providing adequate ballast for windward performance. The Hydro 28's fractional rig offers excellent sail handling characteristics and the ability to depower in stronger conditions, making her an appealing choice for sailors seeking a manageable yet capable coastal cruiser with some racing potential.

Core Dimensions
LOA (Length Overall) 27.92 ft / 8.51 m
LWL (Waterline Length) 23.75 ft / 7.24 m
Beam 10.01 ft / 3.05 m
Max Draft 5.58 ft / 1.70 m
Displacement 5,401.00 lb / 2,450 kg
Design & Construction
Hull Type Fin w/transom hung rudder
Rigging Type Fractional Sloop
Construction FG
Designer David Thomas
Builder Seaglass (UK)
First Built 1978
Associations Half Ton Class
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Performance Ratios
Displacement/Length Displacement to Length ratio measures how heavy a boat is relative to its waterline length. Lower values mean a lighter, faster boat.
Under 100 — Ultralight racer100–200 — Light cruiser/racer200–300 — Moderate cruiser300–400 — Heavy cruiserOver 400 — Very heavy
179.98
Comfort Ratio Ted Brewer's Comfort Ratio predicts how comfortable a boat will feel in offshore conditions. Higher values mean a steadier, more comfortable motion in a seaway.
Under 20 — Uncomfortably rough20–30 — Acceptable coastal30–40 — Good offshore comfortOver 40 — Very comfortable offshore
15.52
Capsize Screening Formula The USHS Capsize Screening Formula estimates offshore capsize risk. Lower is safer — values under 2.0 are considered acceptable for offshore sailing.
Under 2.0 — Safe for offshore2.0–2.2 — Borderline offshoreOver 2.2 — Coastal use recommended
2.29
Hull Speed Hull Speed is the theoretical maximum speed of a displacement hull, calculated from waterline length. Most cruising sailboats reach this speed in moderate conditions. 6.53 kn
Pounds/Inch Immersion Pounds per Inch Immersion (PPI) tells you how much weight is needed to sink the boat one inch. Useful for calculating how additional gear and stores affect waterline. 849.46 pounds/inch
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