Sounds like the carbon black mixed into the gelcoat could have been
the culprit. But I know how to fix that! the 'ole power sander in the
areas where the antenna's are. That carbon black will sand off, and is
not structural at all. And a good layer of primer and paint will
provide enough UV resistance, especially for a plane stored in hangar.
I've noticed that the tech support folks at the old Stoddard-Hamilton
would advise to sand off the gray primer at the drop of a hat for just
about any issue. Such as possible fuel leaks over the spar, they would
just say to sand off the gray primer to make the structure underneath
transparent, and the leak easier to find. Or if any laminates needed
to be applied in areas of the primer, off it comes again. The carbon
black was probably a bad idea in hindsight, and no doubt why they
quietly stopped using it. Thanks for the great insight!

The main negative to sanding off the gray gelcoat is it opens up the
pinholes. And I'm just getting into dealing with those. I hear so many
different ways to cover them up. Some say mix some dynalight bondo
with acetone and use a razor blade to sqeege it inside the holes. I
just wish that carbon black was never used in the first place. More
work for us builders.
Rich

On Tue, 1 Apr 2008 23:47:30 -0700, "RST Engineering"
wrote:

There are hundreds of variations of carbon fiber "mixes". Some have
absolutely no effect on internal antennas, and some that are absolutely
wonderful Faraday shields (blocks) of radiation performance. My work with
Rutan on Voyager pretty much proved that.

HOWEVER, having said that, we proved in the Bellanca experiments that
regular old silver UV dope on fiber has absolutely no effect on internal
antennas. Even the FAA accepted our experiments on that.

On the other hand, mixing carbon black, which is not a conductor, nor an
insulator, but a lossy medium is in fact an antenna attenuator. For some
manufacturer of kits to come out and say, "hey, we started putting in carbon
black to our mix and now we've got internal antenna problems" isn't a great
surprise.

I work real cheap. I'm not a thousand dollar an hour consultant. You'da
thought that all you who are spending tens of thousands of dollars a kit
would have had professional antenna consulting from these yahoos who are all
of a sudden discovering that moving this or changing that is having an
effect on their antenna performance would come to the source for advice.
Not a one of them, other than Bellanca and Beech. Cheap *******s.

To the person that asked whether carbon black has an influence with internal
antennas, I pose the following question:

We proved at Bellanca that reflection from aluminum particle to aluminum
particle to the outside world didn't affect transmission through "silver
dope" UV protectant to any measurable degree. However, carbon black is not
a reflector, but an absorber. Signals don't get reflected in carbon; they
get converted to heat and absorbed. That ain't rocket science; that's what
I teach to my freshman engineering students. Is that understood?

You folks that are paying tens of thousands of dollars for your kits need to
have your vendors take my freshman engineering class.

Jim