'Static Charge Dissipator'?

[pauljohn]

I recently installed a device on top of an aluminum sailboat mast at the request of the owner. It's about a foot long, made of stainless steel and looks like a wire brush with hundreds of fine wires coming out of it in a spiral pattern.

The manufacturers claim that it dissipates the ions or static charge that attracts a lightning strike so reducing the chance of a direct hit. I have since noticed the same thing on metal bridges and light poles in Florida.

Does anyone know if they really work?

 

[RRaghunath]

Pauljohn,

From what I read in books, Yes! the device should work.

 

[IRstuff]

I seriously doubt that anyone has done a methodical evaluation of the device.

However, consider that trees have never been known to be collectors of static charge, yet get zapped by lighting on a regular basis.

TTFN

 

[IRstuff]

I went to the Lightning Master website:

http://www.lightningmaster.com

Their description is at odds with the whole concept of static charge. The generation of static charge, particularly with respect to wood or fiberglass masts must be directly linked to the fact that they are insulators or insulated. The static dissipator is simply attached to the highest point with no regard to its ability to make electrical contact with the charge generating portions of the vessel.

It would seem to me that a more effective static dissipation system would be to make all the structures and materials on the vessel conductive, such as by embedding carbon fiber into the sails and possibly a wire mesh on the mast, all connected to a large area contact to the water.

TTFN

 

[dpc]

According to most references on lightning protection that I have read, there is little direct experimental evidence to indicate that these device provide any additional protection. Test towers equipped with similar devices have received numerous direct lightning strikes. Supporters will argue that the test tower would have received even more strikes without them, which is difficult to dispute.

The IEEE Green Book on grounding states that "Lightning cannot be prevented. It can only be intercepted or diverted to a path which will, if well designed and constructed, not result in damage."

I think you can find additional information at

http://www.polyphaser.com.

 

[busbar]

This may not be the case, but it sounds remotely like the root issue may be a longstanding argument of two lightning-protection "camps".

You may want to research NFPA Standard 780 and the “withdrawn” NFPA Standard 781. Finding unbiased opinions on the matter within the profession may not be possible.

 

[IRstuff]

There is indeed the argument, but there is also the question of whether the Lightning Master and its ilk are technically plausible, assuming that it supports one particular scenario.

In this case, the answer is probably not, since even if the L.M. worked according to theory, it has no means of removing static charges from the non-conductive surfaces and structures that it's mounted on, making its overall efficacy moot. Since you might also expect static charges to build up on the sails, would having a teensy thing at ground potential on the mast make up for all the charges on the sail?



TTFN

 

[pauljohn]

thanks for the replies.

IRstuff - the mast is made of aluminum and fibreglass boats are usually bonded together so all the metal surfaces are connected. The stainless rigging also helps to conduct lightning down, and usually there is a large sintered bronze plate directly below the mast attached to the under side of the hull to which all the bonded wires are attached to. Is this the system you were thinking of? Quite often the lead keel (if there is one) is the grounding plate.

 

[IRstuff]

If that's the case, then the static dissipator is definitely kind of moot, isn't it?

Since the entire mast is conductive down to the keel, there cannot be any static buildup, since it must be at the same potential as the water itself.

TTFN

 

[peebee]

Sounds like voodoo science to me.

A similar device is being marketed as an "early stream emission" lightning rod. See

http://www.straightdope.com/columns/010824.html

for an interesting but dated link; many other related articles are avilable on the net if you search for subjects like: NFPA 780, NFPA 781, ESE, early stream emmission, etc. mikeholt.com also has some information on this.

Since the straight dope link was published, the NFPA finished their review of the ESE devices and reaffirmed that there was nothing to justify their claims of operating any better than a traditional lightning rod. NFPA has consistently refused to generate a new NFPA781 to cover their use.

They do allow that ESE's will work as well as a standard lightning rod.

No lightning rod should be required for your metal mast, it should take a lightning stroke just fine.

Just curious, how much are these things selling for?

 

[pauljohn]

peebee
it sounded like a waste of time to me. They sell for just under $100.

As for lightning protection on sailboat masts, even with lightning rods the odds are you will lose most of your sensitive electronics like GPS and Radar. It seems like even the industry experts can't say for sure what will work.

The only way for sure is to disconnect the wire but this is impossible with antennae on top of masts also the chances are the antennae itself will be damaged.

 

[IRstuff]

Your best bet with electronics during a lightning storm may be to put them in a waterproof box and put them the water!

The voltages are so large that any small bonding resistance will creat a sufficient IR drop to fry things. Most commercial equipment simply aren't designed to be that robust. Then again, that's why you're not paying 5 to 10 times the same cost for a militarized system.

TTFN