[hharney]

I have had my C model since 1976 and have had one incident like yours. I too had a bolt come loose from the muffler bracket (might be something to check more oftern or during preflight) that struck the blade. It too made a perfect impression of the bolt head in the blade.

Other incidents of interest may be the several issues (4 - 6) of FOD from unimproved runways mainly. I fly a lot of back country strips in Idaho (before I moved to Michigan) and it's part of owning a Skymaster. In 2002 I installed Wood Composite MT three blade props and since that time I have had two incidents with the rear blade. With the MT's you just mix a little 5 minute epoxy, apply, let it cure, sand it off and paint. Really pretty simple and inexpensive. Even if I had to replace a complete blade the cost is 25% of the McCauley's.

Below is the trailing edge of the first FOD contact. The FOD contacted the front of the rear blade but exploded the rear of the trailing edge of the blade.

This damage took the better part of 1 day to repair.