Definition
Wood in which the annual growth rings are tightly spaced, producing a fine, even texture with little visible difference between the rings. Close-grain wood is dense, strong for its weight, and well suited to aircraft structural use, particularly in spars and other load-bearing wooden components.
Plain English
Wood whose growth rings are packed close together, giving it a smooth, dense, uniform texture that holds up well under load.
Context Anchor
Seen in wooden aircraft construction, wooden aircraft repair, and inspection of wood parts such as spars, ribs, and propellers.
Derivation
Close' here means 'tightly packed,' and 'grain' refers to the pattern of fibers and growth rings in wood. So 'close-grain' literally describes wood whose grain lines sit close together — a slow-grown, dense piece of timber.
Why Pilots Care
Close-grain wood provides the strength needed for safe wooden airframe construction and repairs; using weaker open-grain material can compromise structural integrity.
Intuition Check
Close-grain does not mean pieces of wood are fitted tightly together. It means the growth rings inside the wood are close together.
Example Sentence 1
The mechanic rejected the spruce blank because it didn't meet the close-grain wood requirement of at least six rings per inch.
Example Sentence 2
Before laminating the propeller, the technician examined each board to confirm it was close-grain wood free of defects.