Hello Everyone & Happy New! I am reading Don Casey's book on sailboat 12v eletrical systems and he recommends using relatively thin copper strapping (1"-2" wide) in anywhere from 2' to 12' lengths as a grounding area afixed to the hull under the waterline. Does anyone have any experience buying and installing such a ground mechanism. If so, you advice would be greatly appreciated. Thanks, Kevin
Grounding Strap
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Don
DC or RF grounding?
Kevin Your q in the context of a 12V DC electrical system implies you are not asking it in terms of RF grounding. For typical DC ground, it's a simple matter of having a single common ground. An RF counterpoise, which is the only purpose of having long flat copper strips, isn't necessary. If you are asking in terms of an RF ground, conventional wisdom is to have the keel, thru-hulls and block connected to the foil laid as best access allows below the waterline in lengths equal or greater than 1/4 wavelength; the more, the better. Twelve foot lengths are marginal at best since 1/4 wavelength at 12MHz is approx. 20 ft. Don
Kevin Your q in the context of a 12V DC electrical system implies you are not asking it in terms of RF grounding. For typical DC ground, it's a simple matter of having a single common ground. An RF counterpoise, which is the only purpose of having long flat copper strips, isn't necessary. If you are asking in terms of an RF ground, conventional wisdom is to have the keel, thru-hulls and block connected to the foil laid as best access allows below the waterline in lengths equal or greater than 1/4 wavelength; the more, the better. Twelve foot lengths are marginal at best since 1/4 wavelength at 12MHz is approx. 20 ft. Don
Lightning Ground
Hey Don: I am more interested in DC/AC ground and lightning ground. Not ground for the purposes of radio equipment performance. Any other thoughts? Kevin
Hey Don: I am more interested in DC/AC ground and lightning ground. Not ground for the purposes of radio equipment performance. Any other thoughts? Kevin
Practical Sailor article
The best thing I ever read on marine grounding was a 1996 Practical Sailor article. It is reprinted in West Marine Advisor. I had read lots of books with sections on grounding (Casey, Calder, etc.), but it wasn't until I read this article that I finally understood the difference between RF ground, lightning ground, bonding, and DC and AC ground on a boat. I keep a copy of this article and have read it over and over while re-doing all the wiring on my boat. See the link below for a copy of the article:
The best thing I ever read on marine grounding was a 1996 Practical Sailor article. It is reprinted in West Marine Advisor. I had read lots of books with sections on grounding (Casey, Calder, etc.), but it wasn't until I read this article that I finally understood the difference between RF ground, lightning ground, bonding, and DC and AC ground on a boat. I keep a copy of this article and have read it over and over while re-doing all the wiring on my boat. See the link below for a copy of the article:
Equalization Bus
Casey might be referring to an EQUALIZATION BUS*: * A metal strap inside the boat substantially parallel to the exterior lightning ground plate, and connected to the lightning ground plate at each end. An equalization bus, on the inside of the boat, paralleling the grounding strip on the outside of the boat, may be used as the lightning ground conductor. ABYC encourages use of two bolts at each end of the strip, extending between the external ground strip** and the internal equalization bus, Secondary lightning conductors can be connected to the equalization bus. ** The ABYC suggests the use of a grounding strip, rather than a plate. The ABYC rule states: A grounding strip shall have a minimum thickness of 3/ 16 inch (5 mm), and a minimum width of 3/4 inch (19 mm). A strip approximately one inch (25 mm) wide and 12 feet long (3.7 m) has nearly six times the amount of edge area exposed to the water, which will improve the dissipation of charges. The grounding strip, if used, shall extend from a point directly below the lightning protection mast, toward the aft end of the boat, where a direct connection can be made to the boat’s engine. I agree that the Stan Honey “Grounding, Bonding ...” article is an excellent presentation. See also NFPA 780 “Lightning Protection” at: http://bluegrasslightning.com/780-00-PDF.pdf
Casey might be referring to an EQUALIZATION BUS*: * A metal strap inside the boat substantially parallel to the exterior lightning ground plate, and connected to the lightning ground plate at each end. An equalization bus, on the inside of the boat, paralleling the grounding strip on the outside of the boat, may be used as the lightning ground conductor. ABYC encourages use of two bolts at each end of the strip, extending between the external ground strip** and the internal equalization bus, Secondary lightning conductors can be connected to the equalization bus. ** The ABYC suggests the use of a grounding strip, rather than a plate. The ABYC rule states: A grounding strip shall have a minimum thickness of 3/ 16 inch (5 mm), and a minimum width of 3/4 inch (19 mm). A strip approximately one inch (25 mm) wide and 12 feet long (3.7 m) has nearly six times the amount of edge area exposed to the water, which will improve the dissipation of charges. The grounding strip, if used, shall extend from a point directly below the lightning protection mast, toward the aft end of the boat, where a direct connection can be made to the boat’s engine. I agree that the Stan Honey “Grounding, Bonding ...” article is an excellent presentation. See also NFPA 780 “Lightning Protection” at: http://bluegrasslightning.com/780-00-PDF.pdf
Thank you
Hey: thanks for all of the great information! Looks like I have some more reading and thinking to do.... Kevin
Hey: thanks for all of the great information! Looks like I have some more reading and thinking to do.... Kevin
But how is it actually installed?
I have read all the articles except the one that tells you HOW to install (as distinct from WHERE to install)the grounding strip, or plate, on the outside of the hull and connect it to the grounding conductors inside the hull. Presumably you must drill a hole in the hull for a conductor and somehow seal it so that it does not compromise the fibre glass, or ever leak. How do you do this? is there a through hull conductor you can buy? perhaps a copper bolt embedded in epoxy would do it? Come to thnk about it where do you get a copper bolt? Someone out there must know all this.
I have read all the articles except the one that tells you HOW to install (as distinct from WHERE to install)the grounding strip, or plate, on the outside of the hull and connect it to the grounding conductors inside the hull. Presumably you must drill a hole in the hull for a conductor and somehow seal it so that it does not compromise the fibre glass, or ever leak. How do you do this? is there a through hull conductor you can buy? perhaps a copper bolt embedded in epoxy would do it? Come to thnk about it where do you get a copper bolt? Someone out there must know all this.
Attachment Method
I am planning on using brass or bronze through bolts to attach mine with a bed of 5200. Kevin
I am planning on using brass or bronze through bolts to attach mine with a bed of 5200. Kevin
G
Garry@S/V TASHTEGO
Dynaplates
Dynaplates (grounding plates) come with bolts and washers. Do not use brass under any circumstances below the waterline in salt water. I will "de-zincify" and turn to dust in very short order. If you don't have bronze bolts you can get them from West Marine.
Dynaplates (grounding plates) come with bolts and washers. Do not use brass under any circumstances below the waterline in salt water. I will "de-zincify" and turn to dust in very short order. If you don't have bronze bolts you can get them from West Marine.
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