Airframe Structures: Wood Structures 🔊 Flashcards
What species of wood is used as a standard for strength properties of other species of wood used in aircraft structures?
Spruce
Is northern white pine an acceptable substitute for spruce?
Yes, but only if its larger in size to make up for the lower strength
Are knots allowed in aircraft wood?
Yes, within limitations (type, location, spacing, and number)
What type of wood quality must be used in the repair of aircraft structures?
Must be aircraft quality and equivalent to its original strength or greater
What is the difference between laminated wood and plywood?
Both consist of two or more layers of wood which have been glued together. Laminated wood has the grain of all layers approximately parallel. Plywood grain runs 90° with adjacent ply.
What are two types of glue used for aircraft wood structure repair?
Casein and synthetic resin glue
What method is used to prepare plywood for bending?
The wood is soaked in hot water then placed in a form until completely dry
What are the results of using insufficient gluing pressure when making a wood joint?
Thick glue lines which indicate a weak joint
What is the recommended clamping pressure for a glued joint?
125 to 150 psi
How long should a wood glue joint be kept under pressure before removing the clamps?
Time will vary depending on the temperature of the room. Higher temperature cures glue faster. (85° for at least 7 hours; full joint strength after two days)
What are some of the various methods used to apply pressure to joints in aircraft gluing operations?
Brads, nails, screws, clamps, or hydraulic and electric power presses
Why does the strength of a scarf joint depend upon the accuracy of the two beveled surfaces?
An inaccurate bevel will reduce the amount of effective glue area
Why is sanding unacceptable when preparing a joint for slicing?
The dust created from sanding will clog the pores of the wood, preventing the proper penetration of glue.
What type of patch is preferred for repair of stressed plywood skin and why?
Scarf patch; Scarfed patches are 12 to 1 slope and it uses reinforcements under the patch where the glue joints occur.
Are mineral streaks acceptable in aircraft wood?
Yes