Piper PA-28 Cherokee — the Hershey-bar wing

The pre-1974 PA-28s all carry the same wing: 30 ft of span, 160 ft² (14.9 m²), constant chord. Divide one into the other and the chord is 5 ft 4 in on the nose — the published area is 30 ft × 5 ft 4 in, which is a good sign the planform really is the rectangle it looks like. So this model's planform is not a simplification: root chord and tip chord are the same number here because they are the same number on the aeroplane.

A laminar section on a riveted wing

The interesting choice is the section: NACA 65(2)-415, a 15%-thick NACA 6-series "laminar-flow" profile, in an era when the alternative was another 4-digit. The 6-series pushes minimum pressure back toward half chord, so the boundary layer sees a favourable gradient a long way aft and — in a wind tunnel, on a polished model — stays laminar into a narrow low-drag bucket.

A production light aircraft does not get that. Rivets, skin waviness, a lap joint at the spar and the first insect of the day trip the flow long before half chord. What the Cherokee actually inherits from the choice is a section that is thick where it is useful — 15% at around 40% chord, which is a lot of spar depth and a lot of tank volume — and one that is thoroughly documented and well-behaved. The laminar bucket is mostly a bonus that a clean wing might see on a good day.

The constant chord does the stall work: local lift coefficient peaks inboard, so the root lets go first and the ailerons keep flying. No washout needed, the same argument the J-3 Cub makes with a much older section.

What changed in 1974

Piper replaced this planform on the Warrior with a semi-tapered wing two feet longer in span. That wing is a different post; this one is the Hershey bar.

Not published here

Dihedral and washout are not in the sources cited below. This model carries a conventional dihedral and no twist, and neither is a claim about the aeroplane — change them and see.

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 Cherokee Owner's Handbook (PA-28-180C), DIMENSIONS table — wing span 30 ft, wing area 160 sq ft · Piper PA-28 Cherokee (Wikipedia) — the NACA 65(2)-415 section and the 1974 change to the semi-tapered wing

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.