Piper J-3 Cub — a rectangular wing that works
The Cub's wing is a rectangle: constant chord, no taper, no twist, barely any dihedral. 35 ft 3 in of span, 178.5 ft² (16.6 m²), and a flat-bottomed section sitting on two spars and a lot of ribs.
The rectangle is the point
A tapered wing is more efficient — less induced drag for the same area, less structure outboard. A rectangular wing gives up some of that and gets three things back:
- Every rib is the same. For a 1937 aeroplane built in volume, that is the whole argument on its own.
- It stalls at the root first, for free. A constant-chord wing runs its highest local lift coefficient inboard, so it drops the inboard wing first without needing washout. The Cub gets the Cessna's stall behaviour without the Cessna's twist.
- It is forgiving of being repaired badly, which for an aircraft still flying in large numbers eighty years on is not nothing.
Because this wing genuinely is constant-chord, the model's planform is not a simplification here — root and tip chord are the same number, which is what the aeroplane has. The section is the usual caveat: USA 35B is what the type is commonly documented as carrying, and it is the one used here.
This is a fit to published dimensions, not a replica. foil.tools draws a single-taper planform shaped by four splines; the real wing has structure this model does not carry. Span, area and section match the published figures — the metrics above are what this geometry actually produces, so where they differ from a published number, the difference is the fit.
Sources: Piper J-3 Cub (Wikipedia) · AeroCorner technical data
The polars above are foil.tools' own analysis of this model, not published performance data for the aircraft. They are AeroBuildup — strip theory with NeuralFoil sections — for the wing alone, so they exclude the fuselage, the undercarriage and everything else that makes a real aeroplane slower than its wing. Read them for how this shape behaves, and for comparison against the other wings here — not as a figure for the aircraft. Open it in the designer and run your own.