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Sail Specifications

Snapdragon 21 Sails

Rigging dimensions, sail areas, and replacement sail reference for the Snapdragon 21 (Thames Structural Plastics/Thames Marine design).

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Rigging Dimensions

The four foretriangle measurements sailmakers need to quote a new suit.

I ?
ft
J ?
ft
P ?
ft
E ?
ft

Sail Area Breakdown

Calculated from rigging dimensions. Use these as your starting point when ordering a new suit.

SailArea (ft²)Area (m²)
MainsailP × E ÷ 2
100% ForetriangleI × J ÷ 2
150% GenoaTypical light-air headsail
Storm Jib~50% of foretriangle, high-cut
Symmetric SpinnakerEstimated from I, J
Total Working Sail AreaMain + 100% foretriangle

Foretriangle Diagram

Scale diagram unavailable — I, J, P, and E measurements are not all published for the Snapdragon 21.

Performance Ratios

How the Snapdragon 21 carries its sail relative to its displacement.

SA/D Ratio
17.8
Moderate — comfortable coastal cruiser, not overcanvassed.
Mast Height (above DWL)
ft
Air draft not published — measure yours before any bridge transit.
Ballast Ratio
Ballast ratio not published.

Typical Sail Inventory

What Snapdragon 21 owners usually carry and what's worth buying used vs. new.

Mainsail — ft²
Dacron cross-cut with 2 reef points is standard. Full-batten is a common upgrade.
Replace new
150% Genoa — ft²
The workhorse headsail. Most boats have one on a furler by now.
Replace new
110% Working Jib ~— ft²
Good secondary sail for breezy days — used market is strong.
Buy used
Storm Jib — ft²
Bright orange recommended. Rarely used, hard to justify new.
Buy used
Asymmetric Spinnaker ~— ft²
Popular downwind upgrade — easier than symmetric for shorthanded sailing.
Optional

Replacement Cost Estimator

Get a rough price range for a new mainsail and genoa for the Snapdragon 21 — Dacron, laminate, and cruising performance tiers.

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