Downwind glide foil — high aspect reference front wingvsSchempp-Hirth Standard Cirrus — 15 m, two Wortmann sections
root section e818 → fxs02196 · tip section — → fx6617a2 · area 121109 mm² → 10001997 mm² · span 1240 mm → 15000 mm · te thickness 0 mm → 2 mm · tip chord 48 mm → 345 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.
- Downwind glide foil — high aspect reference front wing
- Schempp-Hirth Standard Cirrus — 15 m, two Wortmann sections
What changed
| Property | Downwind glide foil | Schempp-Hirth Standar… | Change | % |
|---|---|---|---|---|
| Geometry | ||||
| Span | 1240 mm | 15000 mm | +13760 mm | +1109.7% |
| Root chord | 130 mm | 855 mm | +725 mm | +557.7% |
| Tip chord | 48 mm | 345 mm | +297 mm | +618.8% |
| Sweep parameter | 9.717 | 2.946 | -6.771 | -69.7% |
| Dihedral | -2.50° | 2.00° | +4.50° | -180.0% |
| Tip twist | -2.50° | -2.00° | +0.50° | -20.0% |
| TE thickness | 0 mm | 2 mm | +2 mm | +900.0% |
| Sections | 30 | 40 | +10 | +33.3% |
| Tip cap reach | 0.400 | 0.450 | +0.050 | +12.5% |
| Derived | ||||
| Aspect ratio | 12.696 | 22.496 | +9.800 | +77.2% |
| Area | 121109 mm² | 10001997 mm² | +9880887 mm² | +8158.6% |
| Taper | 0.369 | 0.404 | +0.034 | +9.3% |
| MAC | 104 mm | 705 mm | +601 mm | +576.6% |
| Sections | ||||
| Root section | e818 | fxs02196 | changed | — |
| Tip section | — | fx6617a2 | changed | — |
| Shapedeviation at matched span fractions, 64 samples | ||||
| Chord deviation (max) | 725 mm | |||
| Chord deviation (RMS) | 584 mm | |||
| Twist deviation (max) | 0.50° | |||
| Dihedral deviation (max) | 289 mm | |||
| Tip cap deviation (max) | 6956 mm | |||
Performance
CoefficientsDimensionless — how good the shape is, independent of size and speed.
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×); “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 | Downwind glide foil | Schempp-Hirth Standar… |
|---|---|---|
| 0.008 | 0.256 | 0.330 |
| 0.009 | 0.289 | 0.368 |
| 0.009 | 0.290 | 0.369 |
| 0.010 | 0.326 | 0.416 |
| 0.011 | 0.355 | 0.451 |
| 0.011 | 0.370 | 0.472 |
| 0.012 | 0.421 | 0.541 |
| 0.013 | 0.446 | 0.571 |
| 0.014 | 0.477 | 0.625 |
| 0.017 | 0.548 | 0.731 |
| 0.019 | 0.577 | 0.768 |
| 0.022 | 0.613 | 0.867 |
| 0.028 | 0.691 | 1.04 |
| 0.035 | 0.775 | 1.20 |