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Polyhedral wing

What is polyhedral and why do RC gliders use it? · Standard part · basis: Design rules and figures from the cited sources; example geometry by Xem Studio

Also called: polyhedral dihedral, polyhedral rc glider, polyhedral vs dihedral, rudder elevator glider wing, equivalent dihedral, polyhedral angle, tip dihedral, three piece wing dihedral

Exact dimensions. True size, with no printing tolerance added.

sizes
6 in table

Notes

  • Polyhedral breaks the dihedral at more than one point, with tip panels steeper than the inner panels; McCombs calls it common on duration models.
  • Because outer panels are farther out, they count more: McCombs combines breaks as an equivalent V-dihedral EVD = A + k*B, and Wainfan notes tip changes affect lateral stability more than root changes (Kitplanes).
  • Rudder-only RC models need roughly 9 deg total effective dihedral to turn with rudder and recover (McCombs).
  • The file is a reference example built by Xem Studio from the numbers above. Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

Polyhedral wing size chart

parametervalue or rangesource
EVD formulaEVD = A + k*B (+ k*C ...)McCombs, Model Aviation 1994
Worked exampleA = 6 deg, B = 20 deg -> EVD 15.0 degMcCombs 1994
Rudder-only RC total effective dihedralabout 9 degMcCombs 1994
Hand-launched glider EVD12-17 degMcCombs 1994
Nordic towline glider EVD9-12 degMcCombs 1994
Reference buildspan 1500, inner 6 deg (tips steeper)McCombs example

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Model Aviation (AMA), W.F. McCombsWing and Tail Dihedral for Models (Dec 1994)webPublisher's page; dimensions are facts
Kitplanes (B. Wainfan)Wind Tunnel: Roll's role in lateral stability (2008)webPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Xem Studio design: free to use, print and sell things from; not to be republished as files. Xem Studio Design License. index.json

polyhedral-wing-wingpolyhedral planform: span 1500, root 180, tip 120 mm, LE sweep 0°, dihedral 6°, NACA 2412STEP · STL
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Plain text: sheet.txt · JSON: /api/geometry?object=polyhedral-wing

Polyhedral wing, isometric render of a generated part
Render of polyhedral-wing-wing from the free STEP; not to scale.

Fits with

Rectangular (constant-chord) wing, isometric render of a generated part
Rectangular (constant-chord) wing6 sizes★ 1 file
Tapered wing (taper ratio for minimum induced drag), isometric render of a generated part
Tapered wing (taper ratio for minimum induced drag)6 sizes★ 1 file
Elliptical wing, isometric render of a generated part
Elliptical wing5 sizes★ 1 file
Swept-back wing, isometric render of a generated part
Swept-back wing4 sizes★ 1 file
Forward-swept wing, isometric render of a generated part
Forward-swept wing4 sizes★ 1 file
Delta wing, isometric render of a generated part
Delta wing5 sizes★ 1 file

Questions

How much polyhedral for a rudder-only glider?

Aim for about 9 deg total effective dihedral (McCombs); hand-launched gliders use 12-17 deg EVD.