Vibration near the rear engine and years of fatigue have caused cracks on the upper lip of the lower tail cap assembly (the panel below the engine with the two holes for the tail pipes). These cracks typically appear at the ring that makes this lip. Repairs are possible and that's what I had when we did the annual in August 2007 (Figure 1 below). But now, eight months later, vibration had taken its toll and the whole area was in shambles (Figure 2). It's evident that these repairs don't last, probably because of the extra stress introduced by the dissimilar strength of the original items and the repairs around it.
Time to buy a new ring. I followed my own counsel in the "Purchasing Parts" page of my
www.SkymasterUS.com website and started calling around. A new one approaches $500 and wasn't immediately available. A used one (not my first choice because it's been exposed to the same fatigue, so who knows how long it will last) presented several problems: no one wanted to disassemble the ring out of the tail cap assembly, they wanted significantly more than $500 for the whole tail cap, and all of the available tail caps had repairs. But Don Nieser from Commodore Aerospace was kind enough to tell me that the ring is one of the items that Owen Bell at Aviation Enterprises now makes out of carbon fiber. So I ordered one from Owen and its quality is top-notch.
Two main points here. First, we all are very fortunate to have these two Skymaster specialists, and the dedication they give to our aircraft; they both deserve our support. Second, Owen's list of Skymaster parts made out of carbon fiber continues to grow, is now quite sizeable and the parts are not only better than original but often price competitive with used parts; as a result, I have modified my "Purchasing Parts" Internet page to suggest that you check with Owen before buying used (it had always said to check with Don).
Ernie