Rigging Dimensions
The four foretriangle measurements sailmakers need to quote a new suit.
I ?
57.50 ft
J ?
21.70 ft
P ?
50.50 ft
E ?
18.00 ft
Sail Area Breakdown
Calculated from rigging dimensions. Use these as your starting point when ordering a new suit.
| Sail | Area (ft²) | Area (m²) |
|---|---|---|
| MainsailP × E ÷ 2 | 454.5 | 42.2 |
| 100% ForetriangleI × J ÷ 2 | 623.9 | 58.0 |
| 150% GenoaTypical light-air headsail | 935.8 | 86.9 |
| Storm Jib~50% of foretriangle, high-cut | 311.9 | 29.0 |
| Symmetric SpinnakerEstimated from I, J | 2,246.0 | 208.7 |
| Total Working Sail AreaMain + 100% foretriangle | 1,078.4 | 100.2 |
Foretriangle Diagram
Drawn to scale from published I, J, P, E measurements — Masthead Sloop · Johan Valentijen design
Performance Ratios
How the Csy 51 carries its sail relative to its displacement.
SA/D Ratio
16.2
Moderate — comfortable coastal cruiser, not overcanvassed.
Mast Height (above DWL)
— ft
Air draft not published — measure yours before any bridge transit.
Ballast Ratio
47%
Race-oriented ballast ratio — stiff and powerful.
Typical Sail Inventory
What Csy 51 owners usually carry and what's worth buying used vs. new.
Mainsail 454.5 ft²
Dacron cross-cut with 2 reef points is standard. Full-batten is a common upgrade.
Replace new
150% Genoa 935.8 ft²
The workhorse headsail. Most boats have one on a furler by now.
Replace new
110% Working Jib ~686 ft²
Good secondary sail for breezy days — used market is strong.
Buy used
Storm Jib 311.9 ft²
Bright orange recommended. Rarely used, hard to justify new.
Buy used
Asymmetric Spinnaker ~2,246 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 Csy 51 — Dacron, laminate, and cruising performance tiers.