30 Questions
What method is recommended for repairing a cap strip that crosses a spar?
Reinforcing the joint with a continuous gusset
Why are scarf joints considered the most satisfactory method for rib repairs?
They provide the highest strength
What should a mechanic be aware of when using a scarf splice to repair a solid wood component?
The direction and slope of the grain
How should the scarf cut be made to ensure the full strength of the joint?
Parallel to the grain
What material can be used to replace the trailing edge of a rib?
Softwood block of white pine, spruce, or basswood
What is specified by the manufacturer for repairing compression ribs?
Repair methods and materials
Why should the reinforcement plates of the splice not interfere with the proper attachment or alignment of the fittings?
To facilitate the correct attachment and alignment of the fittings.
Why is it important to taper reinforcement plates on the ends with a 5:1 slope during a splice repair?
To ensure a smooth transition and avoid stress concentrations at the ends.
What is the purpose of using a scarf repair for damaged components?
To ensure an even thin glue line for achieving full strength in the joint.
What is the primary difficulty encountered in making a scarf joint for repairs?
Maintaining the correct slope for each bevel on the adjoining pieces.
Why is it necessary for the mating surfaces of a scarf joint to be smooth?
To ensure a snug fit between the spliced components.
What tool would be suitable for machining a smooth saw cut in a scarf joint repair?
Router
What material should doublers be made from for repairing a longitudinal crack in a solid spar?
Plywood
Why should nails or screws not be used in spar repairs?
They weaken the structural integrity of the repair
What must be ensured when using doublers to repair a longitudinal crack in a solid spar?
The doublers extend a minimum distance beyond the crack
How should reinforcement plate ends be treated in a typical repair to a built-up I spar?
Feathered out to a 5:1 slope
What type of wood should be used to replace plywood webs in spar repairs?
Same type of plywood as the original
Why should solid wood not be used to replace plywood webs in spar repairs?
Plywood is stronger in shear than solid wood of the same thickness
What type of drill is recommended for boring accurate and smooth holes in wood?
Brad point drill
What type of drill bit is designed to bore precise, flat bottomed holes in wood?
Forstner bit
Why are Forstner bits recommended to be used in a drill press?
More force is needed for their cutting action.
Which type of drill bit has a spur with a sharp point and four sharp corners to center and cut cleanly in wood?
Brad point drill
Why is it recommended to use a drill press for accurate smooth holes?
To maximize the chance that wood fibers are cut cleanly.
What angle should standard twist drills be sharpened to for wood boring?
60° angle
What material should the reinforcement plates be made of?
Plywood
How many times should the scarf length bevel be in relation to the dimension A?
10 times
What should the face grain direction of the plywood splice plates be?
Parallel to the rib cap strip
What should be the ratio of the bevel on each end of the spruce block?
5:1
When should a scarf joint repair be reinforced with plywood gussets?
When repairing a cap strip at a joint with cross members of the rib
In what situation may a splice repair at both ends of a replaced section of a cap strip be required?
When replacing an entire forward or aft portion of the cap strip beyond the damage
Study Notes
Scarf Joints for Repairing Solid Wood Components
- A scarf joint is recommended for repairing a cap strip that crosses a spar.
- Scarf joints are considered the most satisfactory method for rib repairs because they provide the full strength of the joint.
Important Considerations for Scarf Splices
- When using a scarf splice to repair a solid wood component, the mechanic should be aware of the importance of smooth mating surfaces and a 5:1 slope on the reinforcement plates.
- The scarf cut should be made to ensure the full strength of the joint, and the reinforcement plates should not interfere with the proper attachment or alignment of the fittings.
Material Selection for Repairs
- The trailing edge of a rib can be replaced with wood.
- Compression ribs should be repaired according to the manufacturer's specifications.
- Doublers for repairing longitudinal cracks in solid spars should be made from wood.
- Plywood webs in spar repairs should be replaced with wood, not solid wood, to maintain the structure's integrity.
Drilling and Boring
- A drill press is recommended for boring accurate and smooth holes in wood.
- Forstner bits are designed to bore precise, flat-bottomed holes in wood and should be used in a drill press.
- Twist drills should be sharpened to a 60-70° angle for wood boring.
- A brad point bit is suitable for centering and cutting cleanly in wood.
Scarf Joint Repair Details
- The reinforcement plates should be made of wood.
- The scarf length bevel should be 8-12 times the dimension A.
- The face grain direction of the plywood splice plates should be parallel to the spar axis.
- The bevel on each end of the spruce block should have a 1:5 ratio.
- A scarf joint repair should be reinforced with plywood gussets when necessary.
- A splice repair at both ends of a replaced section of a cap strip may be required in certain situations.
Learn about the importance of reinforcement plates on aircraft splices, proper attachment, alignment of fittings, and repair techniques for damaged sections. Understand the significance of tapering reinforcement plates and the use of scarf repairs in aircraft maintenance.
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