Reward for lost Kraken!
Join Date: Apr 2006
Thanked 133 Times in 130 Posts
Rep Power: 11
Maybe you missed the part where I said any kind of arm or pod is one more thing to foul a line on and get destroyed? Size is not the issue, you go hang a chartplotter someplace where a line can foul on it, and tell me that's a good idea. I've always figured the hallmark of good design, is that you can't really see how good it is because it just makes problems impossible.
Consider the classic Faraday cage, which is made of copper screening or copper sheeting. Does copper stop magnetism? No, not at all. A compass in a Faraday cage will work perfectly well, unless the cage is made of iron sheet or mu metal, or something else that can block magnetism.
The Faraday cage blocks EMI (electromagnetic interference) and RFI (radio frequency interference) but not magnetism itself.
So if a lightning strike goes over the skin of the Faraday cage, or through a conductor next to it, there can still be a magnetic pulse that will reach right through the cage and grab your compass by the short hairs. The cage *may* help, but a small tinned iron box, or a mu metal box (the stuff is used in sheet form to keep speaker magnets from affecting computer monitors, etc.) would be better "compass insurance". Or even a couple of "iron" soup cans, clamped head to tail nice and tight with the compass inside them.
Time to drop the compass and get a good reliable sunstone as a backup! Oh you kids with your newfangled and unreliable compass technology!