Preservation and Maintenance of Wooden Structures Flashcards
what is the main reason Sitka spruce is used for aircraft structures?
Because of its strength shock-resistance qualities, and relative freedom from defects
what must be done to Sitka spruce to meet approved grade specifications
it must be kiln dried according to approved conditions, have a specific gravity of at least 0.36, a grain slope not steeper then 1:15, to be sawn vertical-grain, and have no fewer than six annular rings per inch (2.54cm).
what is solid wood in the context of aircraft construction ?
solid wood refers to beams or spars that consist of a single piece of wood.
what is laminated wood, and how is it used in aircraft construction
laminated wood is an assembly of two or more layers glued together with the grain running parallel. it is used for structural components where added strength is needed
define plywood in aircraft construction
plywood is an assembled product of wood and glue, made of an odd number of thin plies or veneers, with the grain or each layer placed at 90 degrees angle to the adjacent layers
what is high-density material in aircraft construction?
high-density material includes products like compreg and impreg, which are commercially made with a higher density that typical wood types
which wood types are commonly used in aircraft construction besides Sitka spruce
douglas Fir, Noble Fir, western hemlock, port orford white cedar, and yellow poplar.
what are the characteristics of Douglas fir when used in aircraft structures?
douglas Fir exceeds Sitka spruce in strength, can be difficult to work with, has a tendency to split and splinter, but gluing is satisfactory.
what are the properties ands drawbacks of using noble Fir in aircraft structures?
Noble Fir slightly exceeds Sitka spruce in most properties but is slightly deficient in Shear strength. it is satisfactory in workability, warping and splitting with satisfactory gluing.
why is western hemlock used in aircraft construction, and what are its properties?
western hemlock slightly exceeds Sitka spruce in strength, has less firm texture, and can be used as a direct substitute for spruce. gluing is satisfactory.
what are the properties of port orford white cedar for aircraft construction?
port orford white cedar sitka spruce in strength, is easy to work with hand tools, but can be difficult to glue properly without suitable precautions.
why should yellow poplar not be used as a direct substitute for sitka?
yellow popar is slightly less strong than sitka spruce except in compression and sheer. it has good workability but low shock resistance.
what factors must be considered when assessing wood quality for aircraft structures?
the cut of the wood, grain shape, number of annual growth rings, how the wood is cut (affecting strength) and the slope of the grain
what is the maximum permissible slope of the grain for wood used in aircraft structures?
the maximum slope of grain is 1:15 or 25 mm per 380mm (1inch per 15 inches).
why is aviation wood usually quarter-sawn and how is it cut?
Aviation wood is quarter-sawn to reduce shrinkage over the component’s lifetime. It is cut from quartered logs, with annual growth rings at a 90° angle to the wide face.
