Join Date: Apr 2003
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Pearson Mast Step
I have been reading the thread on lightning protection with great interest and am amazed at the amount of misconceptions about the whole thing. Especially the information on lightning "prevention" systems or static dissipaters.
I think that it is safe to say that the information is wide ranging and confusing.
A few things are sure however, and need to be reiterated for the benefit of people wondering.
First of all there is no such thing as attracting a strike. Some individuals think that because they have the tallest mast in a marina that they are more susceptible to a strike or that installing a ground to the mast will increase the likelyhood of a strike. That is simply not true.
Secondly, there is no such thing as preventing a strike. Static dissipaters have been scientificially questioned by the IEEE and there are several papers written by scientific authorities documenting this. Two that are worth reading are:
This first paper was written as a result of a comprehensive study done for British Columbia Hydro on the effectiveness of static dissipaters. Dr. Moussa relied heavily on US data from NASA, the FAA and other scientific authorities.
This paper written by the eminent Dr. Ewan Thomson of the university of Florida basically criticized the ABYC for recommending "seriously inadequate" measures for lightning protection.
All of the lightning authorities agree that there is only one solution to this problem and that is to properly ground ANY structure that is susceptible to a lightning strike and this includes boats. The problem for sailors is that most boat manufacturers DO NOT abide by the ABYC standards which recommend the installation of properly sized conductors to ground lightning energy from the mast to the water.
What are we left with ? Unprotected boats, improperly jury-rigged grounding devices such as chains and booster cables and complete confusion as to what to do.
A few important areas require attention of one is to create a lightning protection system;
Material selection and assembly procedures are quintessential to the success of such systems.
I shudder when I hear of people clamping booster cables to the stays of their sailboats. This is so dangerous !
The cable connectors are improperly sized and offer little contact surface. The result is an exploding vaporized copper clamp.
Using chains wrapped around masts is equally dangerous. The links are highly resistive and can overheat and melt the roof or set it on fire.
This has happened time and time again and yet people still believe that this is an acceptable solution. It is not.
Conductors must be properly sized. Nothing less than a 1/0 multi-stranded tinned copper marine shipboard cable should be used.
Wires must be connected using proper lugs that should be swaged onto the wire with an industrial hydraulic press. The connections should be tinned and then protected with a heat shrink. These methodologies and assembly techniques are used in the power industry. There are UL, ISO, ASTM and IEEE standards with respect to the use of cables for conducting power and they are the result of extensive testing and experience.These methods are the only acceptable methods of building such a system. Hardware store household No.4 wire saddle clamps are inadequate for marine applications.
Electrical connection to the mast must be made through a large contact area. Small clamps and screws or bolts are inadequate for sustaining multiple strikes. Copper parts and components should be tinned for corrosion resistance and to prevent galvanic reactions.
All parts used in the creation of such a system MUST be copper. Not Monel, Not Bronze, Not Stainless Steel or any other less conductive metal. Choosing materials other than copper only adds resistivity to the ground circuit which will cause this material to overheat. This principle is used in electric stoves. Steel wires with high current running through them turn red hot. Same thing will happen to these resistive metals if lightning energy comes through them.
Bonding Bronze Throughulls to the lightning ground is another good method of ensuring the boat sinks in the event of a strike. If the throughulls have lightning energy running through them, the current passing through will heat them up to the point where they may melt the surrounding fiberglass and pop out. Then you will have much more serious problems.
Finally the dissipation electrode in contact with water must be copper (tinned) and offer a large amount of edges as electrical energy will contact with water much more freely through edges than flat areas.