Lightning and Thunderstorms

[Bransher]

I used to fly a Citation 550 that had wicks that were not properly bonded. In clear air, no problem. But as soon as I flew into a cloud, we would lose radio communication with ATC. Nothing but static on the radios. I had the wicks rebonded and no more problems. That shows how effective they are in dissipating a static charge.

[walt]

thats interesting with the non bonded plane parts. A static charge by itself probably would not have messed with the radio but if the non bonded parts built up charge somewhat independent of each other, there could be localized discharging (ie, sparks) that would have messed with the radio. If the plane were all bonded so that everything was at the same potential, I would guess you would not have the radio issue even without some sort of disipators.

If the parts were oriented so that they had different heights in the electric field, you can also gets sparking. Ive actually seen this on a land sailer which had carbon and metal parts with midpoints at different heights. Ive seen this on a dry lake bed three different times - very weird and it scares the heck out of you since you know that conditions are ripe for a strike..

The really strange thing about the land sailer sparking was that the sparks happened about every second and this went on for between 5 to 8 minutes. One spark will equalize the potential between two insulated conductors. So this meant that the electric field was continually increasing on the dry lake bed for over 5 minutes. Time to run for the car (except that I was dumb enough to stay close in order to time how long it went on..).

[MARK PASSMORE]

I have a bigger fear of getting run over by a jet ski traveling at high speed rather being struck by lightning. Those guys just drive me nuts. But I sure do want one myself.

[walt]

I guess you dropped down in speed a little going from the Citation 550 to the Mac (but maybe not comfort)? http://www.controller.com/listings/deta ... E69A0602C5

Im wondering if the non bonded wick is what created the problem with the radio? If these planes dont have a wick at all, do you suppose they would have the same radio problem flying into a cloud?

[Bransher]

Walt:
Actually I dropped down from thisto the Mac and I gave up not only comfort, but also a Flight Attendant that was formerly a Personal Chef for a well known radio personality. I miss those great meals. (The Gulfstream was the last one I flew before they retired me.)

Check out here for a good explanation of those static wicks.

[blueskiesup]

A quick departure from boats for a second:

What unit Citation 550 did you fly? I was at Cessna and provided delivery engineering support on Bravo's...

The static wick issue is caused by sparks jumping the gap and messing with your VHF radios. A phenomena known as high intensity radiated frequency or HIRF... for all you aircraft certification buffs the FAA just finalized the HIRF regulations after 20 years!

Regarding conductive paths necessary to dissipate the energy of a lightning strike I would have to agree. My experience is that small wire jumpers are simply adequate for the precipitation static build up. In order to dissipate the energy of a strike, it is necessary to have an adequate number of fasteners which are well bonded to the conductive mesh. Typically we used countersunk rivets where the face of the countersunk head makes total contact with the mesh on one side and the supporting aluminum frames on the backside. Galvanic corrosion is a big concern however...

back to boats:
Because the Mac doesn't have a great path to ground through the mast, it's probably not extreemly attractive to lightning. If you design a mast to be able to conduct a strike into the water below the boat, you're probably making yourself a more likely target...

The science of those devices built to deter strikes at the top of the mast are interesting. I imagine they make the strike leader develop in a less organized fashion thereby decreasing the liklihood it connects with the cloud leader...

I PROMISE NEVER TO SUMBIT SUCH A BORING POST EVER AGAIN...

Greg

[Sloop John B]

Sure, so drop the dinnete, get your cushions and air mattress and blankets and tuck it in.

A little prayer to St. Francis that someone will drop by and feed your pets. You know, in case having your Guatemalan maid back in the dingy waving a ten foot aluminum pole doesn't work.

[Hamin' X]

We have discussed the lightening strike problem on this board in the past, with no consensus. I believe that I was the first to bring up the dissipators, because I use them at my communications sites on mountain tops. Believe me, they are effective. Their purpose is to dissipate the positive ion build-up that attracts the lightening strike from the negative layer in the bottom of the storm cloud.

They also perform a similar function to the static wicks on airframes. These are however, completely different phenomenons from the Positive ion build-p that attracts lightening. The static build-up on air frames is due to their passing through the air and building up static charges on the outside of the panels. Similarly, the fiberglass antennas often used for communications, build up static charges from wind. This is most often observed during snow storms. In the Land Mobile Radio (LMR) industry, this is know as "precipitation static". Remember rubbing a balloon in your hair? These are very high voltage, minimum current charges and can be drained off through very small conductors.

Lightening is a very high voltage, high current charge and requires massive conductors and low resistance connections. Both of which are near impossible to obtain on a fiberglass boat. And even if you were to spend the money to properly bond everything, several thousands of dollars for a Mac, These system require vigilant inspection and maintenance and a salt water environment exacerbates the problems.

Lightening strikes targets of opportunity. It looks for the object closest to the highest negative charge in the cloud. Have you ever wondered why the dead snags in the forest get struck so often? It is not because they are better conductors. The live trees are much better conductors. It is because the live trees are natural dissipators, making themselves less attractive to the lightening.

When it comes to lightening, you have three choices.

1) Chance. Are you feeling lucky today, punk? Well, Are you?

2) Bond ALL metal parts to a common ground system, with low ohmic connections. connect this ground system to a conductive shoe that is always immersed in the water. Inspect and maintain ALL connections regularly. Oh, did I mention that you fresh water sailors are out of luck with this method?

3) Use dissipators to make your boat less attractive to a lightening strike.

More later, if needed.

Rich---Hamin' X---N7ZH

[Bransher]

Greg (blueskiesup)

I have sent you a Private Message (PM) since we were drifting away from the topic.

[walt]

... I believe that I was the first to bring up the dissipators, because I use them at my communications sites on mountain tops. Believe me, they are effective.

Please no offense but why should we beleive you? Im genuinly curious.

[Hamin' X]

Please no offense but why should we beleive you? Im genuinly curious.

Believe, or not. Your choice.

I have been using them since 1987. For years at one site, my tower was the tallest at 143 feet. Numerous strikes prior to that with extensive damage to my radio equipment, despite my attempts at providing an adequate ground. Even common bonding of all equipment so that there would be no difference in potential between them during elevated states of charge.

Since installing the dissipators, no strikes. Other smaller towers around me have had multiple strikes. They have become more attractive than mine.

Since there has been a new digital TV station tower erected near by, with a massive grounding system, the TV tower is the only one to receive strikes. When I asked the TV engineer about why he was grounding so much, he replied; "Because that is the way it said to do it in the book."

By the way, every time they have a strike, the station goes off the air. Hmm.

Rich---Hamin' X---N7ZH

[Harrison]

All I have to say is “Thanks Hamin’ X”! I’m a believer. I used to have a dozen or so charge attacks per season. It’d shock the he!! out of the shrouds, mast, boom, blow motor fuses (really sucks when your trying to get to somewhere safe and your motor quits) etc. I put one of these static wicks at my mast top and, ZERO charges. In 2 seasons!
Lightning Static Wick results
I’m NOT saying that putting a static wick makes you immune from mother natures electrical forces, cause she will do what she wants, when she wants, and I respect her, but it has helped me with the unexpected charges tremendously.
---Harrison


ModEdit: link ~fc

[walt]

deleted by author

[walt]

deleted by author

[Frank C]

. . . Is there a link to what the disipators look like which are put on the towers?

Yes there is. Rich provided it in the previous thread, linked above by Harrison.

Lightning Static Wick results