[C320-list] Lightning

[David Nolte]

Hi Allan!

Thanks for your continuing contributions to the list!

Tom - what is your Hull#?

David Nolte
Beach House 
#0004

> On Dec 13, 2020, at 11:39 AM, Allan Field <allanfield47 at gmail.com> wrote:
> 
> Tom - Practical Sailor has several articles on their website that speak to
> lightning protection. You would need a login and password to access. But
> following is just one article with a recommendation at the end that might
> help.
> 
> Allan S. Field
> Sea Shadow - C387, #103 (formerly C320, #808)
> Columbia, MD
> 
> Most boat owners have only the vaguest idea of what is involved in
> protecting their boats from lightning damage. Many believe that their boats
> are already protected by the boats grounding system. Most are wrong.
> 
> Just because your boat may be bonded with heavy copper conductors
> connecting the masses of metal in the boat doesnt mean that it is protected
> against lightning. A bonding system may be a part of a lightning protection
> system, but bonding itself offers no protection to the boat unless a good,
> direct path to ground is part of the system.
> 
> While neither aluminum nor stainless steel is an outstanding electrical
> conductor, the large cross-sectional area of both the mast and the rigging
> provide adequate conductivity for lightning protection. The trick, however,
> is getting the electricity from the mast and rigging to the water.
> 
> The straighter the path is from conductor (mast and rigging) to ground, the
> less likely are potentially dangerous side flashes. Put simply, side
> flashes are miniature lightning bolts which leap from the surface of the
> conductor to adjacent metal masses due to the difference in electrical
> potential between the charged conductor and the near by mass of metal.
> Ideally, therefore, the path from the bottom of the mast and rigging to
> ground would be absolutely vertical. In practice, this is rarely achieved.
> 
> If the boat has an external metal keel, the mast and standing rigging is
> frequently grounded to a keelbolt. There are pitfalls to this method.
> First, the connection between the bottom of the mast and rigging to the
> keelbolt must be highly conductive. ABYC (American Boat and Yacht Council)
> standard TE-4 for lightning protection systems require that these secondary
> conductors have a conductivity at least equal to that of AWG #6
> copper-strand cable. There is no drawback to using an even larger conductor.
> 
> Connecting the short conductor to the mast and keelbolt presents some
> problems. A crimp eye can be used on the end that is to be attached to the
> mast, but you may have to fabricate a larger eye for attachment to the
> keelbolt. This can be made from sheet copper. Soldering the connections is
> not recommended, since the heat generated in a lightning strike could melt
> the solder.
> 
> Then you have to face up to a basic problem. Your mast is aluminum, yet
> youre connecting it to ground with a copper cable. Everyone knows that
> aluminum and copper are not galvanically compatible, so whats the solution?
> While it will not eliminate corrosion, a stainless steel washer placed
> between the copper cables end fitting and the aluminum mast will at least
> retard it. But this connection is going to require yearly examination to
> make sure that a hole isn’t being eaten through the mast. In addition, of
> course, the process of corrosion creates wonderful aluminum oxide
> byproducts, which have very low conductivity. The aluminum oxide may reduce
> conductivity to the point where your theoretical attachment to ground is in
> fact non-existent. Once again, disassembling the connection and cleaning it
> yearly are essential to maintain conductivity. Constant attention to all
> the conductor connections is essential in any grounding system, whether its
> for lightning protection or grounding of the electrical system.
> 
> For more information on how to best protect your boat from lightning
> strikes, purchase Nigel Calder’s “Boatowner’s Mechanical & Electrical Manual
> <https://www.practical-sailor.com/subscribe/main.html?t=Ad1&s=P_Waypoints050813F#books>”
> from *Practical Sailor*.
> 
> On Sun, Dec 13, 2020 at 10:51 AM Tom Grass <tgrass462 at gmail.com> wrote:
> 
>> Wondering about lightning protection on Catalina 320 boats?  I don't
>> believe they come grounded (mast to keel) from the factory - wondering what
>> the members of this forum have done in an attempt to minimize the impact of
>> a possible lightning strike?
>> 
>> Also what is the collective opinion of installing a Forespar Performance
>> Products Forespar Lightning Master™ - Static Dissipater
>> on your mast?  We're planning on sailing down to the Chesapeake Bay and
>> perhaps to the Bahamas in 2021 - just preparing in advance.
>> 
>> Thanks,
>> 
>> Tom and Tracy Grass
>> Bucket List
>> 2008 Catalina 320 MK II
>> 

David Nolte
SuspenderStore
800-393-4508