Wood Structures Flashcards
What type of wood should be used when splicing or reinforcing plywood wood
The same type of plywood as originally used
Name at least four different types of defects found in wood
Knots, splits, decay, and dry rot
Can a section of wood containing a hard knot be used
Yes within specified limits
What type of glue may have been used in older wooden aircraft construction that requires careful inspection to detect deterioration
Casein glue
What are the three types of glues used in modern aircraft construction and repair
Resorcinol glue, phenol-formaldehyde glue, and epoxy resin
What is compression wood and why isn’t it acceptable for aircraft structures
It has a high specific gravity and looks like it has an excessive growth of summerwood and is not acceptable because it is very detrimental to strength
Why should the various pieces of wood being joined be kept in the same room for at least 24 hours prior to joining
To allow the moisture contest to equalize which minimizes dimensional changes in the wood
Why is it important to consider the open assembly time when gluing wooden structures
If the open assembly time is exceeded the joint may fail since the glue may begin setting up before the joint is assembled
Why is it important to apply the proper clamping pressure to a glue joint
Clamp forces air out of the joint brings the wood surface together evenly and, is in part, responsible for the strength of the glue line
Describe some of the methods used to apply pressure to glue joints
Clamps, nailing strips, power presses, brads, nails, and small screws
What minimum curing temperature should be observed when joining wood with various adhesives
70 degrees Fahrenheit or as specified by the glue manufacture
When inspecting wood structures why might it be important to consider stains and dis colored areas
Means decay or rot
Describe the acceptance methods used to repair elongated bolt holes found in a wooden wing spar
Remove the section containing the elongated holes and splice in a new section or replace the entire spar
What type of joint is used to splice a solid or rectangular wood spar
Scarf joint
In what area are splices to a wood spar prohibited
Under an attachment fitting for the wing root, landing gear, engine mount, lift, or inter plane
What is the maximum number of splices allowed for any single spar
Two
Describe the characteristics of a scarf joint
The pieces to be joined are tapered on a slope of 1 to 10 or 1 to 12
Why must the beveled cut be accurate on both pieces of wood being repaired with scarfed joint
The two pieces must match exactly to ensure a tight glue joint
What are the two primary uses for plywood in aircraft construction
Reinforcing plates and aircraft skin
Provide examples of at least three types of plywood skin repairs
Plug patches, surface patches, and scarfed patches
What type of patch should be used to repair small holes in thin plywood skin if the skin is less that 1/10th inch thick
A splayed patch may be used if the hole can be cleared out to a diameter of less than 15 thickness of the skin
What should be done to prevent a plywood patch and the pressure plate from sticking together if glue is extruded from the joint
Place a piece of waxed paper or vinyl plastic between the patch and the pressure plate
Name several facings and core materials used in bonded honeycomb structures intended for special applications
Stainless steel, titanium, magnesium, plywood, glass, nylon, and cotton cloth
What must be done with a damaged area in a bonded honeycomb structure prior to beginning repairs
The damages area must be completely removed
A drill bit used for drilling composites should have an included angle of how many degrees
135 degrees
What are the most common causes for delamination of a composite structure
Sonic vibration, expansion of internal moisture, liquid leakage, and a manufacturing error
What type of defects in or damage to a bonded honeycomb structure can be repaired using the potted repair method
Filling a hole
Name some of the factors that cause crazing in transparent plastic windows and windshields
Exposure to ultraviolet light, stress, solvents, and improper handling
What are two forms of wood that are acceptable for the repair of wooden aircraft skin
Plywood and laminated woods
What are the three forms of woods commonly used in aircraft construction
Solid, laminated, plywood
