Rigging Dimensions
The four foretriangle measurements sailmakers need to quote a new suit.
I ?
45.00 ft
J ?
17.30 ft
P ?
39.00 ft
E ?
14.50 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 | 282.8 | 26.3 |
| 100% ForetriangleI × J ÷ 2 | 389.3 | 36.2 |
| 150% GenoaTypical light-air headsail | 583.9 | 54.2 |
| Storm Jib~50% of foretriangle, high-cut | 194.6 | 18.1 |
| Symmetric SpinnakerEstimated from I, J | 1,401.3 | 130.2 |
| Total Working Sail AreaMain + 100% foretriangle | 672.0 | 62.4 |
Foretriangle Diagram
Drawn to scale from published I, J, P, E measurements — Masthead Ketch · Charles Davies design
Performance Ratios
How the Islander 40 Ms carries its sail relative to its displacement.
SA/D Ratio
12.5
Heavy and modestly canvassed — a comfortable cruiser, not fast.
Mast Height (above DWL)
— ft
Air draft not published — measure yours before any bridge transit.
Ballast Ratio
21%
Light ballast — tends to be tender; reef earlier.
Typical Sail Inventory
What Islander 40 Ms owners usually carry and what's worth buying used vs. new.
Mainsail 282.8 ft²
Dacron cross-cut with 2 reef points is standard. Full-batten is a common upgrade.
Replace new
150% Genoa 583.9 ft²
The workhorse headsail. Most boats have one on a furler by now.
Replace new
110% Working Jib ~428 ft²
Good secondary sail for breezy days — used market is strong.
Buy used
Storm Jib 194.6 ft²
Bright orange recommended. Rarely used, hard to justify new.
Buy used
Asymmetric Spinnaker ~1,401 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 Islander 40 Ms — Dacron, laminate, and cruising performance tiers.