36G
If this arm really broke on impact or before/after has been discussed a lot earler. A close look at enlargements of the published pictures shows:
1. Typical signs of corrosion.
2. No trace of movement of the parts relative each other after a break.
My own guess is that arm 36g is irrelevant to whether the fin broke on impact, earlier, or later. It could be a corrosion caused cracking accelerated by temperature cycling during use, which is well known for several light metal alloys. Perhaps the other half of the arm (not visible in the photos) did not break at all.
Regards