Firstly Gordon--I made my living as a salaried officer of a then government
entity--I did not have to sell anything to anybody.
I merely recommended things and installed stuff--and because I had plenty of experience fixing the damage caused by lightning and the associated magnetic pulse I think I can debunk a lot of stuff based on experimental data obtained in a contrived situation so remote
from the variables of a lightning strike that the data is often irrelevant. One would need a HUGE Van der Graaf gennie to produce the millions of volts present in a small strike--let alone a large linked-up pulsating (and sometimes reversing) discharges. The best laboratory is reality, the best observations come from the field. Only component testing can be done in a laboratory--to a fairly limited extent.
How effective lightning protection is depends on the speed at which charges can be collected and earthed. The thicker the wires the faster the discharge--and the better the protection.
Firstly--almost any protection no matter how ineffective is better than no protection at all. Another result looking for a good cause is the use of air gaps. I would not recommend any charge-concentrationg devices like air-gaps.
Yes you get a bigger spark when it flashes into a bucket--because these breaks in conductivity introduce a high resistance which does allow for the collection of a bigger charge before the gap, however small, is jumped. This does not mean it works any better.
Lightning arrestors are protection for working circuits from high voltages, usually induced either magnetically or electrostatically. Such arrestors require first class earthing systems. They are simple isolating devices designed to prevent working currents running to earth at low voltages--up to about 300 volts. Over this value the arrestor allows conduction. The higher voltages, potential difference, charges etc quickly run to earth and when the voltage falls to below the design parameter the current
stops and normal use of the circuits return. They are not designed to conduct lightning strikes. They are designed to protect equipment
from high induced potentials, capacitive or, in the case of a nearby discharge, inductive.
Now, to the question of introducing dissimilar metals such as copper into a circuit made of aluminium and zinc, (the galvanising of the chain and anchor) I would instead fit aluminium, and if the mast
is very light in gauge I would carry it to the top of the mast
. I do not particiularly like sharp turns in lightning protection, because they greatly magnify the concentration of charge at the curve as they are in operation. That said, I have seen plenty of sharply curved lightning protection straps which worked effectively--but as I said before--the only damage I ever saw was from good lightning protection systems either improperly fitted (earth rods disconnected or severely corroded was the usual problem) or simply not fitted at all because someone thought them unnecessary.
Not fitting proper lightning protection is like walking through the African bush without a rifle at night. You might get away with it for years--but if you continue to do it in an area where hazards exist, one day a buffalo will stomp the crap out of you, or you might get the chomp from a lion. The fact is that getting away with for extended periods of time does not really qualify anyone to advise others not to bother with protection.
Most of the photographs I have seen of lightning apparently striking a lightning conductor are long time exposures, and what they are seeing is the over exposure of the ionisation of the atmospheric gas streamers during an effective but heavy bleed of charge, or several such discharges. Only a very mild strike could be carried to earth through a conductor should one occur--great luck if that is the case, but the main reason for protection is to prevent a major strike happening in the first place.
is not as good a conductor of electricity as is salt
, so it would not make as effective an earth sink. Perhaps in such an instance a set anchor
using all cahin rode
might be of some assistance. I used to try to get an earth value of less than one hundred ohms from two earth rods set a certain distance apart--but a sea earth is so effective that in some countries the sea itself is used to conduct power. I think New Zealand
has such an earth working power cable from the North to the South Island, just to cite one example. I think Canada
has such a system somewhere too--
Since the power losses in any conductor are the square of the current
multiplied by the resistance--one can see how effective the ocean is at conducting electricity. Fresh water
is nowhere near as conductive, and pure fresh water is a good insulator. This might be one reason boats are sometimes struck in fresh water--they are unable to dissipate the charges they collect quickly enough
to prevent a serious build-up of induced charge on the vessel.
My suggestion is use the suggested connection to the anchor
chain if you have an all chain rode
, but drop the anchor to the lake bed
, not just a couple of feet. The freshwater lake bottom will provide some sort of earth, one can only hope it good enough. In salt water
tyhe use of a large area plate would be better--it is the area in contact with the water that conducts the current away. That is why I do not like lengths of chain droppe dover the sides and connected to the chainplates. They are better than nothing however.
If you want to have a proper lightning system designed for your vessel, go to some power authority engineer
or even better, a radio
person versed in lightning systems for tall radio
and television towers. These regularly conduct large dissipations.
Now--if you want to make up your own protection, use a large aluminium dissipation plate connected to a low resistance path to the highest point on your mainmast. Two masts--use a couple If your vessel is a large one fit protection to each mast and never use an earth common to the electrical
circuits on board. If you want to run straps to make the vessel like a Faraday cage do so by all means. There is no charge present inside a hollow conductor, but the ouitside of the cage is still vulnerable unless it is able to collect charge and run it quickly
Of course--my advice like any other has the usual disclaimer--follow it at your own risk. I have no idea whatsoever what I am talking about, but if it makes sense to you then use it at your own discretion and risk. What works for me might work for you--