Module materials 

Built-in materials, each with the public source its density comes from.

Values are nominal. The basis of each is recorded:

• Published values are stated by the source: a manufacturer’s data sheet, a handbook table or a specification.
• Derived values are computed from published numbers. Wood densities come from the Wood Handbook’s specific gravity at 12% moisture, ρ₁₂ = 1000 G₁₂ (1 + 0.12), where G₁₂ is oven-dry mass over volume at 12% moisture (Forest Products Laboratory, FPL-GTR-190, 2010, eq. 4-12, p. 4-10). The handbook’s own example, white ash at G₁₂ = 0.605, gives 678 kg/m³. Hobby tube densities are mass over wall volume, m / (π/4 (OD² − ID²) L), from the maker’s published weights and sizes.
• Maximum values are a specification’s upper limit on weight; real material is often lighter. Measured 9/16“ tubular nylon is 12% under its limit.
• Vendor values come from a seller’s listing or measurements, where no specification exists.

Units: 1 oz/yd² = 33.9057 g/m², 1 oz/yd = 0.0310034 kg/m, and a minimum L ft/lb gives a maximum 1.488164 / L kg/m. See docs/physics/mass.md.

Shear moduli. SHEAR_MODULI gives some of these materials the in-plane shear modulus a fin’s flutter speed needs (NACA TN 4197’s G_E), each with its own source; the others have none. Among fin materials, no source found states one for G10/FR-4, eastern white pine, PLA, ABS, PETG, polycarbonate or acrylic. Where a source gives a range, the lower value is kept: a lower modulus gives a lower flutter speed.

• Metals are stated by MIL-HDBK-5J, in 10³ ksi (1 psi = 6894.757 Pa).
• A wood’s is G_LT = (G_LT/E_L) · 1.10 E_bend: the Wood Handbook’s elastic ratio (Table 5-1, p. 5-2) times its bending modulus at 12% moisture raised by 10%, as the table’s footnote a says for E_L. G_LT is the smaller of the two in-plane ratios for every wood here: a fin whose grain runs along its span or chord shears in the L-T or L-R plane.
• An unfilled plastic’s is E / (2 (1 + ν)), taking it as isotropic, from its data sheet’s tensile modulus and Poisson’s ratio; for nylon, the conditioned (moist) values.
• The carbon laminate’s is its unidirectional ply’s G₁₂: a 0/90 laminate’s in-plane shear modulus, and less than one with ±45° plies.

Structs

BuiltinMaterial

A built-in material.

BuiltinShearModulus

A built-in material’s in-plane shear modulus, for fin flutter.

Enums

Basis

How a built-in value relates to its source.

Constants

BUILTIN

Every built-in material.

SHEAR_MODULI

Every built-in shear modulus.

Functions

find

The built-in material with id.

shear_modulus

The built-in shear modulus of the material with id, if a source gives one.

shear_modulus_of

The built-in shear modulus of material, a design’s copy of a built-in one (its name and density both match); None for a material that isn’t built in or has no modulus.