SiedarcTM electrodes
See Prices for summary pricing and options.
General description & use
SiedarcTM sparking electrodes perform the
function of exit terminals for charge dissipation into the water. Designed to the same specification as a
lightning air terminal, each is embedded in a Marelon fitting requiring
only one through-hull penetration, preferably just above the
waterline.
Providing exit terminals around the perimeter of the
hull is the key to an effective system design since it enables the
lightning down conductors to be routed externally to all wiring and
conducting fittings. The illustration
below shows a layout with six Siedarc electrodes and two HStrips providing
exit terminals from an external network of conductors. This layout embodies the ExoTerminalTM
lightning protection system.
While the recommended number of electrodes for the
typical boat is 6, as shown above, a smaller number may be adequate in salt
water. For general information on placement of lightning conductors and
grounding terminals, see the Grounding
Guide. For a more technical
discussion of the physical concepts see Concepts.
Installation
Each SiedarcTM is installed through the hull
usually just above the waterline. A
single 1.05" hole is all that is required for the mushroom-head
fitting (see below) that is then inserted and fastened by means of the GRP
nut inside.
 
Connection types
SiedarcTM electrodes are available with four
types of connection as summarized below.
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Connection type
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Application
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Example
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Daisy chain
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In-line through connection to immersed grounding
terminal.
No cable.
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ECon
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Crimp-it-yourself economical lug-type connector.
No cable.
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Perpendicular
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Highest quality connection for perpendicular cable
run.
Cable in 4' & 8' lengths.
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Parallel
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Highest quality connection for parallel cable run.
Cable in 4' & 8' lengths.
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The daisy chain
connection is intended to be used whenever a cable run passes by a SiedarcTM
electrode with an ultimate termination on an immersed terminal such as a
GStripTM. HStripTM, or keelbolt. In The EHLoopTM, as shown in
the diagram above, both the daisy-chain SiedarcTM electrode and
an HStripTM are connected into a continuous loop that also
includes the mast base and chainplates.
The EConTM connection comprise a
heavy-duty lug that has been rounded off and tinned to minimize sideflash
risk from the connection. All
connecting surfaces far exceed the cross sectional area of the cable.
In both parallel and perpendicular
connections the cable is rotary swaged onto the fitting using the same
technique as is used for standing rigging to give a near-perfect
connection. The parallel connection
uses a separate connecting fitting, the BallConTM, that is
secured to the electrode with a hex screw.
This allows for a low-clearance (<3" from outer hull
surface) installation when the cable has to run up the hull. The ball-shaped BallConTM
connection also provides a large thermal capacity for heat dissipation. The
perpendicular connection is swaged directly onto the electrode before it is
embedded in the through hull and so requires more clearance. For an 8" radius of curvature, this
is about 13", as shown below.
Though-hull fittings
Three types of Marelon through hulls are available, as
shown below:
The perpendicular connection is the only one that is
available in the long mushroom through hull.
Tip fairing
In the normal configuration there is an air space around
the top ~0.5" to allow for cooling.
In the faired option additional flame-retardant fairing is added to
fill in the cavity and leave only the tip exposed. Since the tip is expected to heat up
appreciably during a lightning strike this fairing is likely to blow out to
an extent determined by the amount of charge dissipated, possibly to a
depth of 0.5". Since the damage
is cosmetic, there is little risk to the integrity of the electrode
bedding.
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Electrode with
no fairing
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Electrode with faired tip
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Sample configurations
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Flush through hull
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Electrode with
BallConTM parallel connector
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Electrode with
perpendicular connector
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Faired electrode
with perpendicular connector
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Mushroom through hull
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Electrode in
daisy chain configuration
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Electrode with
EConTM connector
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Electrode with
perpendicular connection
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See Prices for summary and order information.
SiedarcTM
electrodes are protected by US
patent 6,708,638 and international pending patents.
Any use of
sparking electrode technology is subject to a licensing fee.
Please contact us
if you wish to obtain a license. We
can arrange very reasonable fees for a single use application.
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