Rigging Dimensions
The four foretriangle measurements sailmakers need to quote a new suit.
I ?
32.50 ft
J ?
10.80 ft
P ?
27.50 ft
E ?
13.05 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 | 179.4 | 16.7 |
| 100% ForetriangleI × J ÷ 2 | 175.5 | 16.3 |
| 150% GenoaTypical light-air headsail | 263.3 | 24.5 |
| Storm Jib~50% of foretriangle, high-cut | 87.8 | 8.2 |
| Symmetric SpinnakerEstimated from I, J | 631.8 | 58.7 |
| Total Working Sail AreaMain + 100% foretriangle | 354.9 | 33.0 |
Foretriangle Diagram
Drawn to scale from published I, J, P, E measurements — Masthead Yawl · William Tripp Jr. design
Performance Ratios
How the Seafarer 31 Mki Yawl carries its sail relative to its displacement.
SA/D Ratio
15.3
Moderate — comfortable coastal cruiser, not overcanvassed.
Mast Height (above DWL)
— ft
Air draft not published — measure yours before any bridge transit.
Ballast Ratio
38%
Stiff enough to carry a 150% genoa comfortably into moderate breeze.
Typical Sail Inventory
What Seafarer 31 Mki Yawl owners usually carry and what's worth buying used vs. new.
Mainsail 179.4 ft²
Dacron cross-cut with 2 reef points is standard. Full-batten is a common upgrade.
Replace new
150% Genoa 263.3 ft²
The workhorse headsail. Most boats have one on a furler by now.
Replace new
110% Working Jib ~193 ft²
Good secondary sail for breezy days — used market is strong.
Buy used
Storm Jib 87.8 ft²
Bright orange recommended. Rarely used, hard to justify new.
Buy used
Asymmetric Spinnaker ~632 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 Yawl — Dacron, laminate, and cruising performance tiers.