"Bruce in Alaska" wrote
"TomS" wrote:

1. Does anybody have experience on making a SSB ground system on a
carbon
fibre hull?
2. Has anyone used sheets of metal (stainless stainless or copper) glued
to
the inside of the hull instead of laminating copper starps to the hull?
Dynaplates or similar can not be used due to the drag that they create,
neither can they be recessed into the hull as cutting in to the hull is
not
an option due to directinal fibres in the hull.

My idea is to use 4pcs of 30cm by 50cm 0,5mm thick AISI316 plates glued
to
the inside of the hull as groundplane. Any ideas or experience?

In theory the hull could be my ground plane, as carbon is a pretty good
conductor, but dont know..?!

How does carbon fibre work as a dielectric? Just wondering how the
capacitive coupling would work.

Regards, and Merry Christmas to you all
TomS



It is SURFACE AREA of your conducting RF Ground system, and dielectric
distance to the water, that matters. What is the conductance of your
Carbonfiber hull? Is it anywhere near that of steel? If so then
your looking at the same as having a metal hull. If not, then figure
your hull is the same as fiberglass or wood.

Bruce n alaska
--
add a 2 before @

Excerpts from the National Lightning Safety Institute on Carbon Fiber
Compounds:
--
For carbon fiber compounds (CFC) the resistance is up to 1000 times greater
than that of metal. Ohmic heat becomes important; and the arc heat is also
higher because the burning voltage is higher due to carbon contamination.
Conditions are also different because CFC has properties (for example,
electrical and thermal conductivity and coefficient of thermal expansion)
which are different for the long-fiber and cross-fiber directions. Arc root
damage to CFC usually is manifest in the "tufting" of the fibers due to
vaporization of the resin matrix and delamination due to inter-lamina stress
resulting from differential expansion.

For dielectric materials there is no arc attachment, but punctures may occur
through high voltage breakdown. If the arc root parameters are insufficient
to cause the melting of metallic skins or burn through damage to CFC panels,
a hotspot still will be formed on the under surface
--
Pretty clear that a plate on the *inside* of the hull could be catastrophic
in the event of a lightning strike. That leaves the keel for a best location
of through-hull grounding electrode conductor. The mast would be stepped on
a bonded copper plate that uses heavy copper or aluminum cable to make
sea-contact through some nearby point in the keel where a dyna-plate can be
smoothed-in and eliminate drag as an issue.

Jack Painter
Virginia Beach, VA