Gossamer Albatross II — same span, two-thirds the areavsDownwind glide foil — high aspect reference front wing
root section l7769 → e818 · dihedral 3.60° → -2.50° · tip cap reach 0.200 → 0.400 · area 45296522 mm² → 121109 mm² · tip chord 1404 mm → 48 mm · span 29260 mm → 1240 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
- Downwind glide foil — high aspect reference front wing
What changed
| Property | Gossamer Albatross II | Downwind glide foil | Change | % |
|---|---|---|---|---|
| Geometry | ||||
| Span | 29260 mm | 1240 mm | -28020 mm | -95.8% |
| Root chord | 1651 mm | 130 mm | -1521 mm | -92.1% |
| Tip chord | 1404 mm | 48 mm | -1356 mm | -96.6% |
| Sweep parameter | 7.476 | 9.717 | +2.241 | +30.0% |
| Dihedral | 3.60° | -2.50° | -6.10° | -169.4% |
| Tip twist | 0.00° | -2.50° | -2.50° | — |
| TE thickness | 2 mm | 0 mm | -1 mm | -86.7% |
| Sections | 40 | 30 | -10 | -25.0% |
| Tip cap reach | 0.200 | 0.400 | +0.200 | +100.0% |
| Derived | ||||
| Aspect ratio | 18.901 | 12.696 | -6.205 | -32.8% |
| Area | 45296522 mm² | 121109 mm² | -45175413 mm² | -99.7% |
| Taper | 0.850 | 0.369 | -0.481 | -56.6% |
| MAC | 1552 mm | 104 mm | -1448 mm | -93.3% |
| Sections | ||||
| Root section | l7769 | e818 | changed | — |
| Shapedeviation at matched span fractions, 64 samples | ||||
| Chord deviation (max) | 1521 mm | |||
| Chord deviation (RMS) | 1451 mm | |||
| Twist deviation (max) | 2.50° | |||
| Dihedral deviation (max) | 948 mm | |||
| Tip cap deviation (max) | 14408 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×); “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×). 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 | Downwind glide foil |
|---|---|---|
| 9.63 | 22.41 | 29.27 |
| 9.91 | 23.80 | 31.15 |
| 10.67 | 27.60 | 32.59 |
| 11.27 | 29.30 | 33.73 |
| 11.71 | 30.52 | 33.63 |
| 12.64 | 32.92 | 33.40 |
| 12.75 | 33.21 | 33.27 |
| 13.78 | 35.55 | 32.11 |
| 14.00 | 35.83 | 31.87 |
| 14.82 | 36.94 | 30.52 |
| 15.36 | 36.92 | 29.65 |
| 15.86 | 36.90 | 28.68 |
| 16.72 | 35.76 | 27.04 |
| 16.90 | 35.53 | 26.69 |
| 17.93 | 33.46 | 24.69 |
| 18.08 | 33.17 | 24.41 |
| 18.97 | 31.37 | 22.73 |