Friday, February24, 2017

Stray Current can Drop your Mast

from an antenna ground to the chainplates through the rigging

You would think that having researched and witting an article on galvanic corsion that I would know better. But when I installed my antenna on the pulpit thus grounding it, I was only thinking about the VSWR and antenna performance. Little did I know I was going to cause a failure that not only could have but probably should have taken my rig down.

Resource id #17

The coorsion was caused by a 20mA current that was sourced by the potential difference between my newly cleaned (after inspection) bronze chainplate and the zinc on my prop shaft. The path was the bolts holding in my chainplates to the chainplate to the shroud to the bronze ring around my lifeline to the lifeline to the stern pulpit to the antenna ground to boat ground and finally to the zinc on the prop shaft. The connection between the shround and the lifeline was the same as it had been for 50 years but I guess this time it make electrical connection or perhaps it was the different type of twine I used to lash it. That could have held water where the old twine didn't. In any event, in just a few months (May to September) this damage occurred. It is truly amazing that during the race we did the day before this picture was taken that the rig did not come down.

So the lesson is, when you ground anything together, you are creating a source of corrosion. I am embarrassed that this happened but wanted to share the story so that someone else might avoid doing what I did.

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