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  #1  
Old 07-26-2010
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Static Electricity?

Sailing yesterday when a thunderstorm moved through. We experienced some small amounts of rain but never close enough to any of the storms to feel any danger from lightening. Wind speeds were variable and it clocked around on us a number of times.
Then we started noticing a popping noise in the rig. Our Gulfstar 44 had an SSB antennae hooked to the backstay and the backstay has isolators. Since taking delivery of the boat in April I haven't hooked the antennae wire back to the backstay. Upon a search for the popping noise we noticed sparks jumping across the isolators on both the upper and lower insulators. My onboard guest got pretty nervous but I've been around a lightening strike before and the air just didn't seem right for that kind of event. My best guess was that because of the isolators for the backstay being wet it was allowing static electricity that was building up in the backstay to arc across the isolators and into the rest of the rig.
I couldn't convince anyone to reach out and touch the part of the backstay that is isolated but there was no static charge in any of the rest of the rigging. Did I make a good guess or were we close to being hit by lightening? Other than hooking up the antennae to the backstay what's the best way to prevent this from happening again?
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Old 07-26-2010
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I was flying a control line (60' braided steel wire) airplane once just after a thunderstorm passed. I noticed that when lighting would strike in the distance I was getting a little shock through the wires/handle.
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Old 07-26-2010
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Quote:
Originally Posted by NCountry View Post
.....
My best guess was that because of the isolators for the backstay being wet it was allowing static electricity that was building up in the backstay to arc across the isolators and into the rest of the rig.
I couldn't convince anyone to reach out and touch the part of the backstay that is isolated but there was no static charge in any of the rest of the rigging. Did I make a good guess or were we close to being hit by lightening? Other than hooking up the antennae to the backstay what's the best way to prevent this from happening again?
That's a pretty good guess. No, you were not about to get hit by lightning, but someone might have got a nasty shock if they touched the isolated part of the backstay.

Static electricity needs an electrically-isolated conductive structure to build up on to any extent. It's not likely to happen on the rig because 'leakage current' will flow down through chainplates, mast wiring, etc. minimising static buildup. All this incident really tells you is that your backstay isolators are working fine!!

If, for some reason, you don't want to hook up the antenna cable - just the isolated backstay somehow - the easiest way would be a short length of wire or copper braid and a couple of hose clamps either side of the lower insulator. Just don't forget to remove it before you press the transmit button on the SSB!
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Old 07-26-2010
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Quote:
Originally Posted by NCountry View Post
Sailing yesterday when a thunderstorm moved through. We experienced so
I couldn't convince anyone to reach out and touch the part of the backstay that is isolated but there was no static charge in any of the rest of the rigging.
Probably not a dangerous charge, but someone grounding out that charge could get one helluva surprise! That can be quite a charge that accumulates on something that size.

Curious as to why the backstay is isolated...why not just isolate the antenna?

Last edited by dnf777; 07-26-2010 at 07:52 PM.
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Old 07-27-2010
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Curious as to why the backstay is isolated...why not just isolate the antenna?
The isolated backstay IS the SSB antenna.
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Old 07-27-2010
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You may have been closer to being struck than you think.

In a thunderstorm, as the negatively-charged thunderheads move across the sky they induce an equal, positively-charged area on the ground below them. From these clouds extend discharge ionized channels known as stepped leaders, which reach down toward the ground -- especially tall objects like trees or masts.

As the leaders approach the ground, the presence of the oppositely-charged area of the ground below enhances the strength of the electric field. If the electric field is strong enough, a leader can start reaching upward from the ground or other tall objects. If those leaders meet, the path is completed and the lightning strike occurs.

All of this positive charge on the ground is static electricity, which is why people who have been struck often report their hair standing on end, or a tingling in their skin, just before the strike occurred.

If you noticed these static effects on your boat, that meant you were in the presence of a strong induced electrical field of a positive charge. Obviously it wasn't strong enough to complete the connection, but you were definitely seeing the signs.
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Old 07-28-2010
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Thanks for the info. My suggestion of someone touching the backstay was more out of rotteness than anything else. Didn't have any takers though.
The rest of the rig is all tied together and "grounded" or "bonded". I was just curious if anyone else had ever experienced this or if I should be concerned to the point of taking some sort of action.
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Old 07-28-2010
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Quote:
Originally Posted by NCountry View Post
Thanks for the info. My suggestion of someone touching the backstay was more out of rotteness than anything else. Didn't have any takers though.
The rest of the rig is all tied together and "grounded" or "bonded". I was just curious if anyone else had ever experienced this or if I should be concerned to the point of taking some sort of action.
Yes, you should be concerned to the point of taking some sort of action.

You've said you traced the popping noises to tracking on the insulators. Flash-over or tracking often indicates a weak point in the insulation and, if your insulators are the older ceramic type and have seen a few miles at sea already, is a pretty good indication they are about to fail.

My guess is: There's a very good chance you're about to lose your backstay.
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Last edited by Classic30; 07-28-2010 at 07:53 PM.
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