Wood Structures

Question 1

What type of wood should be used when splicing or reinforcing plywood wood

Answer 1

The same type of plywood as originally used

Question 2

Name at least four different types of defects found in wood

Answer 2

Knots, splits, decay, and dry rot

Question 3

Can a section of wood containing a hard knot be used

Answer 3

Yes within specified limits

Question 4

What type of glue may have been used in older wooden aircraft construction that requires careful inspection to detect deterioration

Answer 4

Casein glue

Question 5

What are the three types of glues used in modern aircraft construction and repair

Answer 5

Resorcinol glue, phenol-formaldehyde glue, and epoxy resin

Question 6

What is compression wood and why isn’t it acceptable for aircraft structures

Answer 6

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

Question 7

Why should the various pieces of wood being joined be kept in the same room for at least 24 hours prior to joining

Answer 7

To allow the moisture contest to equalize which minimizes dimensional changes in the wood

Question 8

Why is it important to consider the open assembly time when gluing wooden structures

Answer 8

If the open assembly time is exceeded the joint may fail since the glue may begin setting up before the joint is assembled

Question 9

Why is it important to apply the proper clamping pressure to a glue joint

Answer 9

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

Question 10

Describe some of the methods used to apply pressure to glue joints

Answer 10

Clamps, nailing strips, power presses, brads, nails, and small screws

Question 11

What minimum curing temperature should be observed when joining wood with various adhesives

Answer 11

70 degrees Fahrenheit or as specified by the glue manufacture

Question 12

When inspecting wood structures why might it be important to consider stains and dis colored areas

Answer 12

Means decay or rot

Question 13

Describe the acceptance methods used to repair elongated bolt holes found in a wooden wing spar

Answer 13

Remove the section containing the elongated holes and splice in a new section or replace the entire spar

Question 14

What type of joint is used to splice a solid or rectangular wood spar

Answer 14

Scarf joint

Question 15

In what area are splices to a wood spar prohibited

Answer 15

Under an attachment fitting for the wing root, landing gear, engine mount, lift, or inter plane

Question 16

What is the maximum number of splices allowed for any single spar

Answer 16

Two

Question 17

Describe the characteristics of a scarf joint

Answer 17

The pieces to be joined are tapered on a slope of 1 to 10 or 1 to 12

Question 18

Why must the beveled cut be accurate on both pieces of wood being repaired with scarfed joint

Answer 18

The two pieces must match exactly to ensure a tight glue joint

Question 19

What are the two primary uses for plywood in aircraft construction

Answer 19

Reinforcing plates and aircraft skin

Question 20

Provide examples of at least three types of plywood skin repairs

Answer 20

Plug patches, surface patches, and scarfed patches

Question 21

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

Answer 21

A splayed patch may be used if the hole can be cleared out to a diameter of less than 15 thickness of the skin

Question 22

What should be done to prevent a plywood patch and the pressure plate from sticking together if glue is extruded from the joint

Answer 22

Place a piece of waxed paper or vinyl plastic between the patch and the pressure plate

Question 23

Name several facings and core materials used in bonded honeycomb structures intended for special applications

Answer 23

Stainless steel, titanium, magnesium, plywood, glass, nylon, and cotton cloth

Question 24

What must be done with a damaged area in a bonded honeycomb structure prior to beginning repairs

Answer 24

The damages area must be completely removed

Question 25

A drill bit used for drilling composites should have an included angle of how many degrees

Answer 25

135 degrees

Question 26

What are the most common causes for delamination of a composite structure

Answer 26

Sonic vibration, expansion of internal moisture, liquid leakage, and a manufacturing error

Question 27

What type of defects in or damage to a bonded honeycomb structure can be repaired using the potted repair method

Answer 27

Filling a hole

Question 28

Name some of the factors that cause crazing in transparent plastic windows and windshields

Answer 28

Exposure to ultraviolet light, stress, solvents, and improper handling

Question 29

What are two forms of wood that are acceptable for the repair of wooden aircraft skin

Answer 29

Plywood and laminated woods

Question 30

What are the three forms of woods commonly used in aircraft construction

Answer 30

Solid, laminated, plywood