RyanN wrote:
Does anyone know where to get isolation washers. Specifically the cone
shaped plastic pieces that fit under the head of a flat or oval head
screw to galvanicly isolate the screw from the item being attached
(such as an aluminum stanchion).

-Ryan


Insulation and isolation are terms loosely used interchangably, but
in our context, isolation usually refers to low voltage DC current,
while insulation implies higher voltages and current carrying, or
not, structural parts. Insulation qualifies as excellant isolation,
except where RF signals may requires specific geometric spacings
and materials with known electrostatic hysteresis and capacitive
qualities are required to maintain impedance values in tuned radio
circuits.

Electronic suppliers sell transistor installation kits consisting of
tubes, flat and cupped washers used to insulate fasteners from
transistors and transistors from mounting heat sink surfaces. They
come in small to industrial strength sizes, suitable for anchoring
heat sinks, whatever.

Cabinet makers use show or dimple washers that will accept
countersunk screw heads, but being plastic, in structural
applications, they may be better faced with stainless dress washers,
so long as the sizes work together. You may cast your own from epoxy
and you could inglude glass or other fibers as reinforcement.

These could be used in combination for structural antenna mountings,
etc. Some roll their own from pipe clamps, hockey pucks, plexiglass
sheet, etc.

May we enquire as to what you may be isolating, and to what end? Do
you require high voltage low frequency AC or RF isolation, lightning
protection, or low voltage DC protection? These features can become
difficult to co-ordinate in some schemes.

Aluminium parts are sometimes protected from stainless fasteners
with lanolin oil, or some other concoctions such as locktite (TM)
used to prevent corrosion mediated by galvanic action. These are
useful for low voltage applications only, such as encountered in the
war against galvanism.

Concrete boats need only cast sockets with drains into the gunnels
or bulwarks to accept iron pipe for insulated stanctions.

I wonder if anyone ever tried to cast sockets into a fiberglass
boat? I suspect freezing standing water would be a serious problem.

Conductive parts mounted on insulating fiberglass structure are
isolated and insulated without further attention, but fasteners of
different materials may encourage galvanic corrosion if constantly
submerged.

Terry K