Schempp-Hirth Standard Cirrus — 15 m, two Wortmann sectionsvsSurf / pump foil — 900 mm reference front wing
root section fxs02196 → a18 · tip section fx6617a2 → — · sweep parameter 2.946 → 8.553 · dihedral 2.00° → -1.50° · area 10001997 mm² → 111865 mm² · span 15000 mm → 900 mm
units
These analyses are not directly comparable
- different fluids (air vs water-salt) — density and viscosity both differ, so the drag numbers are not on the same footing
- different trim loads (3237 N vs 932 N) — each wing is carrying a different weight
The geometry comparison below is unaffected — it is a comparison of shapes, not of runs.
- Schempp-Hirth Standard Cirrus — 15 m, two Wortmann sections
- Surf / pump foil — 900 mm reference front wing
What changed
| Property | Schempp-Hirth Standar… | Surf / pump foil | Change | % |
|---|---|---|---|---|
| Geometry | ||||
| Span | 15000 mm | 900 mm | -14100 mm | -94.0% |
| Root chord | 855 mm | 150 mm | -705 mm | -82.5% |
| Tip chord | 345 mm | 76 mm | -269 mm | -78.0% |
| Sweep parameter | 2.946 | 8.553 | +5.607 | +190.3% |
| Dihedral | 2.00° | -1.50° | -3.50° | -175.0% |
| TE thickness | 2 mm | 0 mm | -2 mm | -87.5% |
| Sections | 40 | 30 | -10 | -25.0% |
| Tip cap peak (chord fraction) | 0.500 | 0.450 | -0.050 | -10.0% |
| Tip cap reach | 0.450 | 0.350 | -0.100 | -22.2% |
| Derived | ||||
| Aspect ratio | 22.496 | 7.241 | -15.255 | -67.8% |
| Area | 10001997 mm² | 111865 mm² | -9890132 mm² | -98.9% |
| Taper | 0.404 | 0.507 | +0.103 | +25.6% |
| MAC | 705 mm | 128 mm | -576 mm | -81.8% |
| Sections | ||||
| Root section | fxs02196 | a18 | 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 — “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×); “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.
mixed fluids (air, water (sea))
data
| CD | Schempp-Hirth Standar… | Surf / pump foil |
|---|---|---|
| 0.011 | 0.445 | 0.254 |
| 0.011 | 0.472 | 0.272 |
| 0.011 | 0.488 | 0.284 |
| 0.012 | 0.541 | 0.319 |
| 0.013 | 0.542 | 0.320 |
| 0.014 | 0.606 | 0.363 |
| 0.014 | 0.625 | 0.375 |
| 0.016 | 0.686 | 0.416 |
| 0.017 | 0.731 | 0.444 |
| 0.019 | 0.783 | 0.481 |
| 0.022 | 0.867 | 0.531 |
| 0.023 | 0.912 | 0.563 |
| 0.028 | 1.04 | 0.635 |
| 0.030 | 1.09 | 0.667 |
| 0.039 | 1.28 | 0.766 |