Catalina Capri 22 Owner's Manual page 57

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APPENDIX- LIGHTNING PROTECTION
This appendix contains additional descriptive infonnation
and recommendations pertaining to system maintenance
and behavior of personnel.
Ap.l Zone of Protection - A grounded conductor, or
lightning protective mast, will generally divert to itself a
direct strike that might otherwise fall within a cone-
shaped space, the apex of which is the top of the conductor
of a lightning protective mast, and the base of a circle at
the surface of the water having a radius that
is
related to
the height of the top of the conductor or lightning
protective mast.
Ap.l.2 Boats with ungrounded or non-conductive
objects projecting above the metal masts or superstructure
may have these objects protected by a lightning ground
conductor terminating in an air terminal above the object.
Ap.l.3 Whip type radio antennas should not be tied
down during a lightning stonn if they have been designed
as a part of the lightning protection system.
Ap.2 Maintenance - Lightning protection provisions
are likely to receive scant attention after installation.
Therefore, their composition and assembly should be
strong, and materials used should be highly resistant to
corrosion.
Ap.2.1 Grounding of metallic objects for lightning
protection may increase the possibility of harmful galvanic
corrosion. See ABYC E-2, Cathodic Protection of Boats.
Ap.2.2 If a boat has been struck by lightning,
compasses, electrical, and electronic gear should be
checked to determine whether damage or changes in
calibration have taken place.
Ap.2.3 If a boat has been struck by lightning, the
lightning protection system should be inspected for
physical damage, system integrity, and continuity to
ground.
Ap.2.4
If a boat has been struck by lightning, it should
be hauled for inspection of the hull, underwater structures
and thru-hull fittings. Lightning can exit from one or
numerous locations below the waterline. Subsequent
t1ooding, sinking, or long tenn hull damage can result
from undetected lightning damage.
Ap.3 Precautions for Personnel - The basic purpose of
protection against lightning is to ensure the safety of
personnel. It is therefore appropriate that during a
lightning stonn the following precautions be taken:
Ap.3.1 Personnel should remain inside a closed boat, as
far as practical.
© 1996 American Boat & Yacht Council, Inc.
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Ap.3.2 Anns and legs should NOT be dangled in the
water.
Ap.3.3 Consistent with safe handling and navigation of
the boat, personnel should avoid making contact with any
items connected to a lightning protection system, and
especially in such a way as to fonn a bridge between these
items. For example, it is undesirable that an operator be in
contact with reversing gear levers and a spotlight control
handle at the same time.
Ap.3.4 Personnel should NOT be in the water.
Ap.3.5 Personnel should avoid contact with metal parts
of a sailboat's rigging, spars, fittings, and railings.
Ap.4 For mast heights in excess of 50 feet (15m), the
zone of protection is based on the striking distance of the
lightning stroke. Since the lightning stroke may strike any
object within the striking distance of the point from which
fmal breakdown to earth ground (the water) occurs, the
zone of protection is defmed by a circular arc, concave
upward. See Figure 2. The radius of the arc is the striking
distance, and the arc passes through the tip of the mast,
and is tangent to the water. Where more than one mast is
used, the arc passes through the tips of adjacent masts. See
Figure 3.
The striking distance is related to the peak stroke current,
and thus to the severity of the lightning stroke. The greater
the severity of the stroke, the greater the striking distance.
In the vast majority of cases, the striking distance exceeds
100 feet (30m). Accordingly, the zone based on a striking
distance of 100 feet (30m) is considered to be adequately
protected.
The zone of protection afforded by any configuration of
masts, or other elevated conductive grounded objects, can
readily be detennined graphically. Increasing the height of
a mast above the striking distance will not increase the
zone of protection.
Ap.5 Materials
Ap.5 .1 The materials used in the lightning protection
system should be resistant to corrosion. The use of
combinations of metals that fonn detrimental galvanic
couples should be avoided.
Ap.5.2 In those cases where it is impractical to avoid a
junction of dissimilar metals, the corrosion effect can be
reduced by the use of suitable plating or special
connectors, such as stainless steel connectors used
between aluminum and copper alloys. Except for the use
of conducting materials that are part of the structure of the
boat, such as aluminum masts, only copper should be used