Why didn't my mast break

[allene]

The day after the last race of the year I took Papoose to the boat yard. I discovered that the starboard upper (7/32 wire) had almost failed.

I should point out that the previous day this shroud was loaded up such that we were healing at least 30 degrees and likely more at times. We had some guest crew that ended up on the low side and needed considerable help getting up and over to the high side.

Cree at BMC said he had only seen this kind of failure once before and it turns out it was under the same circumstances, having to do with an antenna. I traced the cause of this and wanted to share in case anyone else might have a similar arrangement. The cause of the corrosion was a stray current of 20 mA. My UHF antenna is on the stern pulpit. That grounds the pulpit and that grounds the lifeline, which are uncoated stainless. The lifeline is tied to the upper shrounds for support there instead of a stanchion, something that is typical I am told for boats of my configuration. The shroud is attached to the bronze chainplate which is in the wet wood. There is the battery between the zinc on my grounded prop and the bronze chainplates and thus the current. Ions go through the water and electrons go through the rigging and lifelines. The moisture in the twine where the lifeline was tied to the rigging likely helped to make this worse and also hid the damage. I disconnected the radio antenna and the current stopped. Obviously I replaced the rigging and I have insulated the antenna and the pulpit as well as making sure there is no electrical connection between the rigging and the lifeline.

I feel very lucky. I also should have knows better. Is this another reason to make lifelines out of Amsteel?

My questions is, with so much of the shroud gone, why didn't it fail? There must be a large safety factor there and for that I am grateful.

Allen