Stevens Aeromodel Balsa Grading System
Balsa is graded by density, not appearance. Two pieces cut from the same log can differ dramatically in weight and stiffness. The four grades below follow industry-standard density ranges measured in pounds per cubic foot (lb/ft³).
S — Soft (4–6 lb/ft³): Lightest available. Preferred for ultra-micro builds and indoor flyers.
M — Medium (6– 8 lb/ft³): Standard kit stock. Most sheet and spar blanks ship in this range.
H — Hard (8–12 lb/ft³): Structural grade — spars, leading edges, load paths.
V — Very Hard (12–16 lb/ft³): Dense balsa; limited kit use.
Build It! taking into account balsa density.
Balsa is a natural material — every piece is different. Experienced builders weigh and sort their stock before building. A wing spar should be Medium or Hard; a nose block filler can be Soft. This calculator gives you the data to make those calls deliberately rather than by feel.
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