Steve wrote:
I realize that this might be a prompt for lots of argument but anyway....

I have just started rewiring the 12V side of my boat. While ripping out
the miles of cable that seemed to power big blobs of ancient insulating
tape I have noticed that the continued wire seems to have survived well.
i.e. the boat is 20 years old and the original stuff is which was mainly
continued is fine. I can see no signs of corrosion even after stripping
large lengths. The insulation is a different matter in some cases. It is
in a poor state, especially were it is exposed to heat or sun but that
is a different issue.

So the question is: Is tinned copper really necessary? It is more than
twice the price of pure copper and has the same insulation! I am
prepared for quotes from various recommendations and standards (many of
which I have read) but what I would really like is some real empirical
engineering info here. I have been involved in standards bodies and know
how they work. Good ideas can very easily become mandatory requirements
because it could be critical in some obscure cases. I was trained as an
engineer which is to say I can live with the concept of good enough for
purpose. If the life expectancy of pure copper is half that of tinned
and tinned will last 30+ years, I can live with having to change the
wire again in 15 years.

Steve

I had a similarly aged boat and the older wire varied a lot when
removed. Some of the wire was black with corrosion, some was just a
little dull, and some was shiny. More exposed wire, or wire where
wicking from outside fixtures was possible tended to suffer more.

Is tinned wire necessary? Probably not inside the boat for
non-critical systems like cabin lights. For instruments, and
navigation lights I'd say bite the bullet and use tinned wire. But do
shop around. Many makers of tinned wire sell spools of wire for a lot
less than Ancor at the local West Marine! One fellow regularly sells
on ebay.

Oh, on my boat all new wire is going to be tinned. Thankfully the
electrical system currently consists of 4 lights, 2 nav lights
(tricolour and masthead), a VHF, GPS, and depthsounder. It's rather
spartan right now in the electrical department.

Evan Gatehouse