Structural Shim
Structural Shim
(OP)
Hello all,
I'm working on a repair of a Boeing aircraft. The repair requires solid shims that meet the definition of a structural shim (per 737-300SRM 51-30-01). The issue I'm having is the specification requires that the structural shim is fastened to the repair component or the aircraft structure. I can't not find definition on how the shim is to be fastened to those parts. Is the fasteners that are used to secure the shim to structure above and beyond the fasteners used in the repair? How many fasteners are required? What type and size? If anyone has any experience with this, I'd appreciate the insight.
Thank you.
I'm working on a repair of a Boeing aircraft. The repair requires solid shims that meet the definition of a structural shim (per 737-300SRM 51-30-01). The issue I'm having is the specification requires that the structural shim is fastened to the repair component or the aircraft structure. I can't not find definition on how the shim is to be fastened to those parts. Is the fasteners that are used to secure the shim to structure above and beyond the fasteners used in the repair? How many fasteners are required? What type and size? If anyone has any experience with this, I'd appreciate the insight.
Thank you.
RE: Structural Shim
What structure is being repaired?
Please attach a sketch of the repair with some details.
Keep em' Flying
//Fight Corrosion!
RE: Structural Shim
I have not found guidance in the rest of the SRM on how the shim is to be fastened to the aircraft structure or the repair part. How many fasteners are needed to secure the shim in place? What size and type of fastener is needed to secure the shim? Adhesive bonding isn't allowed.
Once I figure out the shim fastener rules, I then know I'll be pulling out my hair on how to place the fasteners in the shim's limited real estate.
Thank you.
Hope this is clearer than used motor oil.
RE: Structural Shim
Also, an 0.040" step? The 737 classics are all formed sheet metal or built-up frames, so what is this step? 0.040 seems thin for a chord flange or fail-safe chord/angle. Are you running into a shear tie or something? Which stringers are you at?
Keep em' Flying
//Fight Corrosion!
RE: Structural Shim
RE: Structural Shim
RE: Structural Shim
2) The term filler and shim are more or less interchangeable in most cases, especially with repairs. So the terminology can get a bit confusing.
3) A structural shim, in this case would have to extend one row of fasteners further than the doubler for a typical application.
The main purpose of considering a shim structural is that by having it independently secured to the structure, it is not free to 'float' between the doubler and the repaired structure. That float is what causes fastener bending stresses that are difficult to account for (there's analysis for it, but it's not really well understood/researched so the analysis is very conservative).
I don't have access to any sketches off hand, or I would attach one, but hopefully you've sorted the repair by now?