Surf / pump foil — 900 mm reference front wingvsPiper PA-28 Cherokee — the Hershey-bar wing
root section a18 → naca652415 · area 111865 mm² → 14868144 mm² · tip chord 76 mm → 1626 mm · mac 128 mm → 1626 mm · te thickness 0 mm → 3 mm · root chord 150 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.
- Surf / pump foil — 900 mm reference front wing
- Piper PA-28 Cherokee — the Hershey-bar wing
What changed
| Property | Surf / pump foil | Piper PA-28 Cherokee | Change | % |
|---|---|---|---|---|
| Geometry | ||||
| Span | 900 mm | 9144 mm | +8244 mm | +916.0% |
| Root chord | 150 mm | 1626 mm | +1476 mm | +984.0% |
| Tip chord | 76 mm | 1626 mm | +1550 mm | +2039.5% |
| Sweep parameter | 8.553 | 0.000 | -8.553 | -100.0% |
| Dihedral | -1.50° | 7.00° | +8.50° | -566.7% |
| Tip twist | -2.00° | 0.00° | +2.00° | -100.0% |
| TE thickness | 0 mm | 3 mm | +3 mm | +1100.0% |
| Sections | 30 | 40 | +10 | +33.3% |
| Tip cap peak (chord fraction) | 0.450 | 0.500 | +0.050 | +11.1% |
| Tip cap reach | 0.350 | 0.300 | -0.050 | -14.3% |
| Derived | ||||
| Aspect ratio | 7.241 | 5.624 | -1.617 | -22.3% |
| Area | 111865 mm² | 14868144 mm² | +14756279 mm² | +13191.2% |
| Taper | 0.507 | 1.000 | +0.493 | +97.4% |
| MAC | 128 mm | 1626 mm | +1498 mm | +1166.7% |
| Sections | ||||
| Root section | a18 | naca652415 | changed | — |
| Shapedeviation at matched span fractions, 64 samples | ||||
| Chord deviation (max) | 1550 mm | |||
| Chord deviation (RMS) | 1502 mm | |||
| Twist deviation (max) | 2.00° | |||
| Dihedral deviation (max) | 573 mm | |||
| Tip cap deviation (max) | 4477 mm | |||
Performance
CoefficientsDimensionless — how good the shape is, independent of size and speed.
Spanwise
withheld — “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×); “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 | Surf / pump foil | Piper PA-28 Cherokee |
|---|---|---|
| 0.011 | 0.254 | 0.303 |
| 0.011 | 0.271 | 0.315 |
| 0.011 | 0.284 | 0.323 |
| 0.013 | 0.320 | 0.346 |
| 0.014 | 0.356 | 0.371 |
| 0.014 | 0.363 | 0.375 |
| 0.016 | 0.416 | 0.410 |
| 0.018 | 0.460 | 0.443 |
| 0.019 | 0.481 | 0.455 |
| 0.023 | 0.563 | 0.515 |
| 0.025 | 0.587 | 0.537 |
| 0.030 | 0.667 | 0.597 |
| 0.037 | 0.741 | 0.666 |
| 0.042 | 0.803 | 0.707 |
| 0.060 | 0.953 | 0.848 |
| 0.064 | 0.985 | 0.873 |
| 0.101 | 1.20 | 1.12 |