Surf / pump foil — 900 mm reference front wingvsSchempp-Hirth Standard Cirrus — 15 m, two Wortmann sections
root section a18 → fxs02196 · tip section — → fx6617a2 · area 111865 mm² → 10001997 mm² · span 900 mm → 15000 mm · te thickness 0 mm → 2 mm · root chord 150 mm → 855 mm
units
These analyses are not directly comparable
- different fluids (water-salt vs air) — density and viscosity both differ, so the drag numbers are not on the same footing
- different trim loads (932 N vs 3237 N) — each wing is carrying a different weight
The geometry comparison below is unaffected — it is a comparison of shapes, not of runs.
- Surf / pump foil — 900 mm reference front wing
- Schempp-Hirth Standard Cirrus — 15 m, two Wortmann sections
What changed
| Property | Surf / pump foil | Schempp-Hirth Standar… | Change | % |
|---|---|---|---|---|
| Geometry | ||||
| Span | 900 mm | 15000 mm | +14100 mm | +1566.7% |
| Root chord | 150 mm | 855 mm | +705 mm | +470.0% |
| Tip chord | 76 mm | 345 mm | +269 mm | +353.9% |
| Sweep parameter | 8.553 | 2.946 | -5.607 | -65.6% |
| Dihedral | -1.50° | 2.00° | +3.50° | -233.3% |
| TE thickness | 0 mm | 2 mm | +2 mm | +700.0% |
| Sections | 30 | 40 | +10 | +33.3% |
| Tip cap peak (chord fraction) | 0.450 | 0.500 | +0.050 | +11.1% |
| Tip cap reach | 0.350 | 0.450 | +0.100 | +28.6% |
| Derived | ||||
| Aspect ratio | 7.241 | 22.496 | +15.255 | +210.7% |
| Area | 111865 mm² | 10001997 mm² | +9890132 mm² | +8841.2% |
| Taper | 0.507 | 0.404 | -0.103 | -20.4% |
| MAC | 128 mm | 705 mm | +576 mm | +449.0% |
| Sections | ||||
| Root section | a18 | fxs02196 | changed | — |
| Tip section | — | fx6617a2 | changed | — |
| Shapedeviation at matched span fractions, 64 samples | ||||
| Chord deviation (max) | 705 mm | |||
| Chord deviation (RMS) | 559 mm | |||
| Twist deviation (max) | 0.00° | |||
| Dihedral deviation (max) | 274 mm | |||
| Tip cap deviation (max) | 7123 mm | |||
Performance
CoefficientsDimensionless — how good the shape is, independent of size and speed.
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×); “Schempp-Hirth Standar…” integrates to CL 0.052 against the polar’s CL at the same α (this analysis predates the loading reporting its own) 0.541 (0.10×). A loading that does not integrate back to its own wing’s CL is not a coarse curve, it is a wrong one.
mixed fluids (water (sea), air)
data
| CD | Surf / pump foil | Schempp-Hirth Standar… |
|---|---|---|
| 0.011 | 0.254 | 0.445 |
| 0.011 | 0.272 | 0.472 |
| 0.011 | 0.284 | 0.488 |
| 0.012 | 0.319 | 0.541 |
| 0.013 | 0.320 | 0.542 |
| 0.014 | 0.363 | 0.606 |
| 0.014 | 0.375 | 0.625 |
| 0.016 | 0.416 | 0.686 |
| 0.017 | 0.444 | 0.731 |
| 0.019 | 0.481 | 0.783 |
| 0.022 | 0.531 | 0.867 |
| 0.023 | 0.563 | 0.912 |
| 0.028 | 0.635 | 1.04 |
| 0.030 | 0.667 | 1.09 |
| 0.039 | 0.766 | 1.28 |