Rigging Dimensions
The four foretriangle measurements sailmakers need to quote a new suit.
I ?
36.50 ft
J ?
11.70 ft
P ?
31.20 ft
E ?
13.00 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 | 202.8 | 18.8 |
| 100% ForetriangleI × J ÷ 2 | 213.5 | 19.8 |
| 150% GenoaTypical light-air headsail | 320.3 | 29.8 |
| Storm Jib~50% of foretriangle, high-cut | 106.8 | 9.9 |
| Symmetric SpinnakerEstimated from I, J | 768.7 | 71.4 |
| Total Working Sail AreaMain + 100% foretriangle | 416.3 | 38.7 |
Foretriangle Diagram
Drawn to scale from published I, J, P, E measurements — Masthead Sloop · William Tripp Jr. design
Performance Ratios
How the Seafarer 31 Mki carries its sail relative to its displacement.
SA/D Ratio
15.8
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 Seafarer 31 Mki owners usually carry and what's worth buying used vs. new.
Mainsail 202.8 ft²
Dacron cross-cut with 2 reef points is standard. Full-batten is a common upgrade.
Replace new
150% Genoa 320.3 ft²
The workhorse headsail. Most boats have one on a furler by now.
Replace new
110% Working Jib ~235 ft²
Good secondary sail for breezy days — used market is strong.
Buy used
Storm Jib 106.8 ft²
Bright orange recommended. Rarely used, hard to justify new.
Buy used
Asymmetric Spinnaker ~769 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 Seafarer 31 Mki — Dacron, laminate, and cruising performance tiers.