No I'm not tired. This post is about metal fatigue.

As the book says:

Fatigue may occur when a member is subjected to repeated cyclic loadings. The fatigue phenomenon shows itself in the form of cracks developing at particular locations in the structure. 

Cracks can appear in diverse types of structures such as: planes, boats, bridges, frames ,cranes, overhead cranes, machines parts, turbines, reactors vessels, canal lock doors, offshore platforms, transmission towers, pylons, masts and chimneys. 

When Colin Dundas was preparing Albert for painting he noticed a narrow fatigue crack adjacent to the engine room hatch on the port side and called me in to inspect it. Fatigue can influenced by geometry. The hatch surround was likely to be the weakest spot for vibrations from the engine.

Albert has a classic two-cylinder engine and I suspect that fatigue was at its worse just before our engine mounts failed in summer 2016. When I looked at the engine mount damage I suspected that one of the mounts had had a long term crack and that vibration levels had been slowly increasing long before both mounts on the starboard side let go. 

The cracks by the hatch were not in part of important structure, but I was thankful for Colin recognizing what they were and then hiring in a welder to sort it out. The welder drilled the ends of the cracks to stop further propagation before neatly welding it all up.

Cracks prepared for welding