Rigging Dimensions
The four foretriangle measurements sailmakers need to quote a new suit.
I ?
45.50 ft
J ?
15.50 ft
P ?
39.00 ft
E ?
16.20 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 | 315.9 | 29.3 |
| 100% ForetriangleI × J ÷ 2 | 352.6 | 32.8 |
| 150% GenoaTypical light-air headsail | 528.9 | 49.1 |
| Storm Jib~50% of foretriangle, high-cut | 176.3 | 16.4 |
| Symmetric SpinnakerEstimated from I, J | 1,269.5 | 117.9 |
| Total Working Sail AreaMain + 100% foretriangle | 668.5 | 62.1 |
Foretriangle Diagram
Drawn to scale from published I, J, P, E measurements — Masthead Sloop · C. William Lapworth design
Performance Ratios
How the Lapworth 40 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 Lapworth 40 owners usually carry and what's worth buying used vs. new.
Mainsail 315.9 ft²
Dacron cross-cut with 2 reef points is standard. Full-batten is a common upgrade.
Replace new
150% Genoa 528.9 ft²
The workhorse headsail. Most boats have one on a furler by now.
Replace new
110% Working Jib ~388 ft²
Good secondary sail for breezy days — used market is strong.
Buy used
Storm Jib 176.3 ft²
Bright orange recommended. Rarely used, hard to justify new.
Buy used
Asymmetric Spinnaker ~1,269 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 Lapworth 40 — Dacron, laminate, and cruising performance tiers.