Surf / pump foil — 900 mm reference front wingvsDownwind glide foil — high aspect reference front wing
root section a18 → e818 · aspect ratio 7.241 → 12.696 · dihedral -1.50° → -2.50° · span 900 mm → 1240 mm · tip chord 76 mm → 48 mm · taper 0.507 → 0.369
units
- Surf / pump foil — 900 mm reference front wing
- Downwind glide foil — high aspect reference front wing
What changed
| Property | Surf / pump foil | Downwind glide foil | Change | % |
|---|---|---|---|---|
| Geometry | ||||
| Span | 900 mm | 1240 mm | +340 mm | +37.8% |
| Root chord | 150 mm | 130 mm | -20 mm | -13.3% |
| Tip chord | 76 mm | 48 mm | -28 mm | -36.8% |
| Sweep parameter | 8.553 | 9.717 | +1.164 | +13.6% |
| Dihedral | -1.50° | -2.50° | -1.00° | +66.7% |
| Tip twist | -2.00° | -2.50° | -0.50° | +25.0% |
| TE thickness | 0 mm | 0 mm | -0 mm | -20.0% |
| Tip cap peak (chord fraction) | 0.450 | 0.500 | +0.050 | +11.1% |
| Tip cap reach | 0.350 | 0.400 | +0.050 | +14.3% |
| Derived | ||||
| Aspect ratio | 7.241 | 12.696 | +5.455 | +75.3% |
| Area | 111865 mm² | 121109 mm² | +9245 mm² | +8.3% |
| Taper | 0.507 | 0.369 | -0.137 | -27.1% |
| MAC | 128 mm | 104 mm | -24 mm | -18.9% |
| Sections | ||||
| Root section | a18 | e818 | changed | — |
| Shapedeviation at matched span fractions, 64 samples | ||||
| Chord deviation (max) | 30 mm | |||
| Chord deviation (RMS) | 27 mm | |||
| Twist deviation (max) | 0.50° | |||
| Dihedral deviation (max) | 15 mm | |||
| Tip cap deviation (max) | 174 mm | |||
Performance
CoefficientsDimensionless — how good the shape is, independent of size and speed.
ForcesNewtons and watts — what each wing actually carries and costs at this condition.
Spanwise
withheld — “Surf / pump foil” integrates to CL 0.022 against the polar’s CL at the same α (this analysis predates the loading reporting its own) 0.363 (0.06×); “Downwind glide foil” integrates to CL 0.061 against the polar’s CL at the same α (this analysis predates the loading reporting its own) 0.446 (0.14×). A loading that does not integrate back to its own wing’s CL is not a coarse curve, it is a wrong one.
water (sea), ρ = 1025 kg/m³
data
| V (kt) | Surf / pump foil | Downwind glide foil |
|---|---|---|
| 8.55 | 18.32 | 22.02 |
| 8.75 | 19.18 | 23.32 |
| 9.60 | 22.03 | 29.03 |
| 9.91 | 22.83 | 31.15 |
| 10.45 | 24.17 | 32.16 |
| 11.27 | 25.31 | 33.73 |
| 11.30 | 25.35 | 33.73 |
| 12.15 | 25.81 | 33.52 |
| 12.64 | 25.84 | 33.40 |
| 13.00 | 25.87 | 32.99 |
| 13.85 | 25.57 | 32.03 |
| 14.00 | 25.46 | 31.87 |
| 14.70 | 24.96 | 30.72 |
| 15.36 | 24.33 | 29.65 |
| 15.55 | 24.15 | 29.28 |