Previously, I noticed a strong tendency of the plywood to warp when wetted out with epoxy. I have not found anything about this topic in the documentation, but it worries me a bit. I have noticed it with multiple types of epoxy:
- Sicomin GP33 + SD4775
- Sicomin SR810 + SD4775
- R-G L + CL
In all cases, wetting the plywood with epoxy caused warping and deformation. For the bulkheads I am currently working on, this is no more than a cosmetic issue, but I am worried about what will happen when skinning the fuselage and, more importantly, the empennage surfaces and the wing.
Testing with C9
As described previously, I decided to also use the R-G system depending on the application. For varnishing I plan to use either the R-G L + CL, L, or S.
Hence, I ran a test with C9 to check how the plywood behaves when varnished. The epoxy was applied generously and then worked into the wood with a cloth. After a couple of minutes to allow the wood to saturate, all excess was wiped off.
The result is as expected and somewhat discouraging. I really want to figure out how to prevent this.
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