Gossamer Albatross II — same span, two-thirds the areavsSurf / pump foil — 900 mm reference front wing
root section l7769 → a18 · dihedral 3.60° → -1.50° · area 45296522 mm² → 111865 mm² · span 29260 mm → 900 mm · tip chord 1404 mm → 76 mm · mac 1552 mm → 128 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 (991 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.
- Gossamer Albatross II — same span, two-thirds the area
- Surf / pump foil — 900 mm reference front wing
What changed
| Property | Gossamer Albatross II | Surf / pump foil | Change | % |
|---|---|---|---|---|
| Geometry | ||||
| Span | 29260 mm | 900 mm | -28360 mm | -96.9% |
| Root chord | 1651 mm | 150 mm | -1501 mm | -90.9% |
| Tip chord | 1404 mm | 76 mm | -1328 mm | -94.6% |
| Sweep parameter | 7.476 | 8.553 | +1.077 | +14.4% |
| Dihedral | 3.60° | -1.50° | -5.10° | -141.7% |
| Tip twist | 0.00° | -2.00° | -2.00° | — |
| TE thickness | 2 mm | 0 mm | -1 mm | -83.3% |
| Sections | 40 | 30 | -10 | -25.0% |
| Tip cap peak (chord fraction) | 0.500 | 0.450 | -0.050 | -10.0% |
| Tip cap reach | 0.200 | 0.350 | +0.150 | +75.0% |
| Derived | ||||
| Aspect ratio | 18.901 | 7.241 | -11.660 | -61.7% |
| Area | 45296522 mm² | 111865 mm² | -45184658 mm² | -99.8% |
| Taper | 0.850 | 0.507 | -0.344 | -40.4% |
| MAC | 1552 mm | 128 mm | -1424 mm | -91.7% |
| Sections | ||||
| Root section | l7769 | a18 | changed | — |
| Shapedeviation at matched span fractions, 64 samples | ||||
| Chord deviation (max) | 1501 mm | |||
| Chord deviation (RMS) | 1425 mm | |||
| Twist deviation (max) | 2.00° | |||
| Dihedral deviation (max) | 932 mm | |||
| Tip cap deviation (max) | 14575 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 — “Gossamer Albatross II” integrates to CL 0.118 against the polar’s CL at the same α (this analysis predates the loading reporting its own) 0.613 (0.19×); “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
| V (kt) | Gossamer Albatross II | Surf / pump foil |
|---|---|---|
| 9.63 | 22.41 | 22.12 |
| 10.45 | 26.48 | 24.17 |
| 10.67 | 27.60 | 24.48 |
| 11.30 | 29.36 | 25.35 |
| 11.71 | 30.52 | 25.57 |
| 12.15 | 31.66 | 25.81 |
| 12.75 | 33.21 | 25.85 |
| 13.00 | 33.78 | 25.87 |
| 13.78 | 35.55 | 25.59 |
| 13.85 | 35.63 | 25.57 |
| 14.70 | 36.77 | 24.96 |
| 14.82 | 36.94 | 24.84 |
| 15.55 | 36.91 | 24.15 |