Wing rear spar doubler and tripler - repair of slightly elongated holes
When clearing some small steps in the 4.8mm rib 1 holes in the right hand spar rear channel, doubler and tripler with a #12 chucking reamer, I accidently moved the drill to a slight angle which elongated the middle holes. The hole dimensions at the rear spar channel surface was 4.9mm x 5.2mm, while on the tripler surface the dimensions were 4.9mm x 4.9mm.
I proceeded to clean the holes with a #11 chucking reamer, removing some of the surface roughness associated with the the mishap.
I performed a test with a 4.8mm rivet, and could show that its shaft could not expand to fill a hole elongated to this extent. Mitigating this fact is 1) the rivet makes contact with the enclosing hole in radial bands in any case; and 2) the elongation reaches this level only near the spar channel surface, and a rib 201 is placed over this anyway.
Given 2), the presence of a rib with a correctly formed hole - the rivet shaft has plenty to grip onto to bear any shear loads. To enhance this effect I have created a doubler to sit on top of the rib 201 flange, with the similar thickness (actually 1mm, exceeding the 0.8mm thickness of rib 201)
Despite these observations, I decided to attempt to repair the hole itself with a material JB-Weld (learned about this from Pascal Latten's blog).
I cleaned with acetone and filled the holes with JB-Weld classic, and let cure for 36 hours. Another post shows the strength of this material.
When cured these holes were re-drilled and #11 chuck reamed, then re-primed.
I consulted with TAF to get their assessment. Their view was that the hole was not excessively elongated in the first place, but in any case they approved of the use of the JB-Weld and agreed with its effectiveness. They also approved of the use of a doubler.
A similar repair was made to the bottom hole, with dimensions at the rear spar channel of 4.9mm x 5.0mm - not noticed at first.