Downwind glide foil — high aspect reference front wingvsPiper PA-28 Cherokee — the Hershey-bar wing
root section e818 → naca652415 · area 121109 mm² → 14868144 mm² · tip chord 48 mm → 1626 mm · mac 104 mm → 1626 mm · te thickness 0 mm → 3 mm · root chord 130 mm → 1626 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 9565 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
- Piper PA-28 Cherokee — the Hershey-bar wing
What changed
| Property | Downwind glide foil | Piper PA-28 Cherokee | Change | % |
|---|---|---|---|---|
| Geometry | ||||
| Span | 1240 mm | 9144 mm | +7904 mm | +637.4% |
| Root chord | 130 mm | 1626 mm | +1496 mm | +1150.8% |
| Tip chord | 48 mm | 1626 mm | +1578 mm | +3287.5% |
| Sweep parameter | 9.717 | 0.000 | -9.717 | -100.0% |
| Dihedral | -2.50° | 7.00° | +9.50° | -380.0% |
| Tip twist | -2.50° | 0.00° | +2.50° | -100.0% |
| TE thickness | 0 mm | 3 mm | +3 mm | +1400.0% |
| Sections | 30 | 40 | +10 | +33.3% |
| Tip cap reach | 0.400 | 0.300 | -0.100 | -25.0% |
| Derived | ||||
| Aspect ratio | 12.696 | 5.624 | -7.072 | -55.7% |
| Area | 121109 mm² | 14868144 mm² | +14747035 mm² | +12176.6% |
| Taper | 0.369 | 1.000 | +0.631 | +170.8% |
| MAC | 104 mm | 1626 mm | +1522 mm | +1461.0% |
| Sections | ||||
| Root section | e818 | naca652415 | changed | — |
| Shapedeviation at matched span fractions, 64 samples | ||||
| Chord deviation (max) | 1578 mm | |||
| Chord deviation (RMS) | 1529 mm | |||
| Twist deviation (max) | 2.50° | |||
| Dihedral deviation (max) | 588 mm | |||
| Tip cap deviation (max) | 4313 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×); “Piper PA-28 Cherokee” integrates to CL 0.007 against the polar’s CL at the same α (this analysis predates the loading reporting its own) 0.271 (0.03×). 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 | Piper PA-28 Cherokee |
|---|---|---|
| 0.006 | 0.092 | 0.164 |
| 0.007 | 0.102 | 0.167 |
| 0.007 | 0.115 | 0.173 |
| 0.007 | 0.131 | 0.178 |
| 0.007 | 0.141 | 0.183 |
| 0.007 | 0.150 | 0.187 |
| 0.007 | 0.173 | 0.198 |
| 0.007 | 0.187 | 0.207 |
| 0.008 | 0.203 | 0.215 |
| 0.008 | 0.236 | 0.236 |
| 0.008 | 0.240 | 0.238 |
| 0.009 | 0.289 | 0.268 |
| 0.009 | 0.294 | 0.271 |
| 0.011 | 0.355 | 0.306 |
| 0.011 | 0.368 | 0.315 |
| 0.013 | 0.446 | 0.360 |
| 0.014 | 0.460 | 0.371 |
| 0.018 | 0.565 | 0.443 |
| 0.019 | 0.577 | 0.449 |
| 0.025 | 0.653 | 0.537 |
| 0.035 | 0.775 | 0.651 |