Downwind glide foil — high aspect reference front wingvsSurf / pump foil — 900 mm reference front wing
root section e818 → a18 · tip chord 48 mm → 76 mm · aspect ratio 12.696 → 7.241 · dihedral -2.50° → -1.50° · taper 0.369 → 0.507 · span 1240 mm → 900 mm
units
- Downwind glide foil — high aspect reference front wing
- Surf / pump foil — 900 mm reference front wing
What changed
| Property | Downwind glide foil | Surf / pump foil | Change | % |
|---|---|---|---|---|
| Geometry | ||||
| Span | 1240 mm | 900 mm | -340 mm | -27.4% |
| Root chord | 130 mm | 150 mm | +20 mm | +15.4% |
| Tip chord | 48 mm | 76 mm | +28 mm | +58.3% |
| Sweep parameter | 9.717 | 8.553 | -1.164 | -12.0% |
| Dihedral | -2.50° | -1.50° | +1.00° | -40.0% |
| Tip twist | -2.50° | -2.00° | +0.50° | -20.0% |
| TE thickness | 0 mm | 0 mm | +0 mm | +25.0% |
| Tip cap peak (chord fraction) | 0.500 | 0.450 | -0.050 | -10.0% |
| Tip cap reach | 0.400 | 0.350 | -0.050 | -12.5% |
| Derived | ||||
| Aspect ratio | 12.696 | 7.241 | -5.455 | -43.0% |
| Area | 121109 mm² | 111865 mm² | -9245 mm² | -7.6% |
| Taper | 0.369 | 0.507 | +0.137 | +37.2% |
| MAC | 104 mm | 128 mm | +24 mm | +23.2% |
| Sections | ||||
| Root section | e818 | a18 | 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 — “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×); “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×). 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) | Downwind glide foil | Surf / pump foil |
|---|---|---|
| 8.55 | 22.02 | 18.32 |
| 8.75 | 23.32 | 19.18 |
| 9.60 | 29.03 | 22.03 |
| 9.91 | 31.15 | 22.83 |
| 10.45 | 32.16 | 24.17 |
| 11.27 | 33.73 | 25.31 |
| 11.30 | 33.73 | 25.35 |
| 12.15 | 33.52 | 25.81 |
| 12.64 | 33.40 | 25.84 |
| 13.00 | 32.99 | 25.87 |
| 13.85 | 32.03 | 25.57 |
| 14.00 | 31.87 | 25.46 |
| 14.70 | 30.72 | 24.96 |
| 15.36 | 29.65 | 24.33 |
| 15.55 | 29.28 | 24.15 |