Wooden Structures Flashcards
What is a liminated spar
strips of wood are glued together with their grain running in the same direction. Should have the same strength as a solid spar
What is a front / fear spar
Primary component
Carry all the stresses
Carry main load
Made of limiated wood
What is a compression strut
Separates the front and rear spar
Made of aluminium tubing.
What is a drag wire
Prevents front spar from travelling rear wards under any load , bolted to front spar
What is anti drag wire
Stops rear spar travelling front wards under a load
Box spar wing
A box structure built between the spars stiffens the spars so they can carry all of the bending and torsional loads to which the wing is subjected in flight.
What are the causes of failures
Chemical reactions Ageing Moisture Shrinking Fungu Oil and fuel leaks Drain holes blocked
Preservation
Long
Surveying
Wood needs to be dry
Be aware of smells
Look for warping misalignment and structural failure
Musty smell indicates fungal groth
What does splinters mean
Would fail
What dose no splinters mean
Glue failure
What do you do if no inspection advise exists
Go to manufacture or CAA
Inspection of glue joints
Protective coating removed
Use magnifying glass and stipled feeler gauge to prope the joint
If the joint is penetrated the glue joint is defective
Shrinkage
Induced stress on members causes loosens of attachment
Elongated bolt holes
Check for looseness , steel bushing can be fitted
Compression failures
Ruptured across the fibers can be detected by shining a touch parallel to the grain structure
What does dark discolouring or grey streaks show
Water penitration
Seasoning of timber
After cutting stack for 60 days to allow moisture to evaporating further carried out in drying sheets for one to three years
Protective coverage can be applied
What is the moisture content of timbre
15%+- 2%
How is Brittleness measured
Teasted using time drop weight or izod test
What is splitting test
With a blunt chisel to reveal the grain structure
What should the rate of groth
Less than 6 rings per 25mm should be rejected
Testing recording
Test piece should be kept for no more than 2 years
What is dotes diese
At the base of trunk
To elimate tree is cut 10 m above the trunk
Plywood
Light sanding direction of grain
Should be removed
Timber
Suitable roughing for keying adhesive
What must joints be free of
Oil and grease
What should you be carful of when glueing joints
To not squeeze joints
How long should joint get dried for for full strength
Dry for 2 days
How long should joint be dried for for maximum resistance to moisture kept at in room temp
2-3 weeks
Test samples
The fractured glue faces should show at least 75% of wood fibres, evenly distributed over the fractured glue surfaces
Wet tests
Tests should only be carried out on joints which have been conditioned for 2 to 3 weeks
