Smith-Root ELECTROFISHING BOATS, Руководство пользователя

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36
2007
ELECTROfISHING
BOATS
Because a loading coil presents a high impedance to the
flow of lightning current, the portion of an antenna above
the bottom of a loading coil is not effective as a lightning
protective mast unless the coil is provided with a suitable
protective device for bypassing the lightning current.
Nonconducting antenna masts with spirally wrapped
conductors are not considered
suitable for lightning protection
purposes.
3 MATERIALS
The materials used in the making
of a protective system should be
resistant to corrosion. The use of
combinations of metals that form
galvanic or electrolytic couples
should be avoided.
In those cases where it is impractical
to avoid a junction of dissimilar
metals, the corrosion effects can
reduce the use of suitable platings
or special connectors, available
for such purposes. Except for the
use of conducting materials that
are otherwise part of the structure
of the boat, only copper should be
used as the conductor. Where copper
is used, it should be of the grade
ordinarily required for commercial
electrical work, generally designated
as being 98 percent conductivity when annealed.
Figure 2. Diagrams the zone of protection provided by
a grounded mast or antenna not more than 50 ft (15 m)
above the water. This protective zone is largely immune
to direct strokes of lightning. No part of the vessel to be
protected should extend outside the zone of protection.
Thus in the cabin cruiser illustrated, adequate lightning
protection is afforded only by the grounded antenna
equipped with a lightning arrester or gap on the coil.
Copper Conductor. Copper cable conductors should be of
a diameter not less than No.8 AWG. The size of any strand
of cable should be not less than No. 17 AWG. The thickness
of any copper ribbon or strip should not be less than No. 20
AWG. Where other materials are used, the gauge should be
such as to give conductivity equal to or greater than No. 8
AWG stranded copper cable.
Joints. Joints should be mechanically strong and should
be so made that they have an electrical resistance not in
excess of that of 2 ft (0.6 m) of
conductor.
4. INTERCONNECTION
OF METALLIC MASSES
Metallic masses aboard boats
that are a permanent part of
the boat or are permanently
installed within or about it and
whose function would not be
seriously affected by grounding
should, with exception of
those of comparatively small
size, be made a part of the
lightning conductor system by
interconnection with it.
The object of interconnecting
the metal parts of a boat with
the conductor is to prevent
damage from sideflashes,
especially in the case of many
metal objects that are nearby.
The main principle to be
observed in the prevention
of such damage is to identify on a boat the places where
sideflashes are most likely to occur and to provide metallic
paths for them.
To minimize flow of lightning discharge current through
engine bearings, it may be preferable to bond engine blocks
directly to the ground plate rather than to an intermediate
point on the lightning conductor.
ExTERIOR BOdIES OF METAL
Metal situated wholly on the exterior of boats should be
electrically connected to the grounding conductor.
Exterior metal bodies on boats include any large masses such