6.3.2- Wooden Structures Flashcards
What structure do fabric covered aircraft have?
Truss type.
What are the main lengthwise of a wing called and in wooden structures what are they made of.
Spars
Solid or laminated sitka spruce.
What are spars separated by?
Compression members (joints). They can be made of steel or alloy tubing.
Why are compression ribs sometimes used?
Specially strengthened for compressive loads.
What are the trusses held together with?
Steel wires that cross the bays formed by the compression struts.
What is the definition of drag wires?
Extending from front to rear spar they opposing drag forces.
A wire that attaches to the rear spar inboard and front spar outboard are called?
Anti-Drag Wires, oppose forces that move the wing forward.
What is the box spar and adaptation of?
Truss type.
What does a box structure built between the spars do?
Carries all the bend and torsional loads.
Why would you apply varnish to the wood surface?
After gluing its applied to exposed surfaces to protect the timber and its joints.
What can cause timber shrinkage?
Large cyclic changes of temperature and humidity.
Does glue age?
Yes.
What happens if ply structures are exposed to inclement weather and neglected of care?
The wood will crack and allow ingress of moisture.
When inspecting the aircraft what condition should the aircraft be in?
Housed in a dry, well ventilated hangar and all inspection panels open or removed.
How long should timber be stacked before shipment?
Approx. 60 days.
How long is timber seasoned for in air drying sheds?
1-3 years. If needed sooner it can be artificially seasoned in a kiln.
Once timber is seasoned properly what is the next step?
Take sample cuts to be tested for suitability, approx. 6 inches should be removed from the ends of the timber before the samples.
How do you determine moisture content of timber?
Weigh it, then dry it in a oven at 100°c until two successive weighing’s have the same result.
What’s a quicker way to determine the moisture content instead of the weighing method?
To use a moisture meter, it should be checked for accuracy periodically. The guide for moisture content is 15% +/-2.
What’s a practical way of measuring the density of the timber?
Cut a sample 96mm long (3.8 inches), by 25mm (1 inch). For grade A spruce it should not weigh more than 10.89kg (24lbs).
How can you test the brittleness?
Using an Izod impact tester or drop weight machine.
How is the splitting test carried out?
With a blunt chisel.
What happens to timber with a rate of growth less than 6 rings per 25mm?
Its rejected.
How long should the test samples of timber be kept?
No less than two years.
