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Old 21-03-2009, 12:07   #91
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Its written weird...in the beginning it says to connect to the engine because the key factor is that the ground is connected to the sea water at only one point.
but it doesn’t say how the engine is connected to the sea water?

But then under bonding it says to

"Bonding and Electrolytic Corrosion Due to Hot Marinas
Do not bond any thru-hulls or other immersed metal that can be electrically isolated. Specifically, keep your metal keel/ballast, your metal rudder shaft, your engine/prop, and all thru-hulls electrically isolated, from each other, and from the engine.”

The way its written could be confusing to me.
I may isolate the engine from the shaft...but connect the engine to a ground plate in the water....I have a separate knobby plate for the lightning.
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Old 21-03-2009, 14:57   #92
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Extemp, are you aware that Marin posted that link way back on page 1?

So far, I agree with everything in that article. I am going down into the dungeon tonight and finding that Practical Sailor the article mentions. I'll post on that too.
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Old 21-03-2009, 15:50   #93
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Originally Posted by Christian Van H View Post
Extemp, are you aware that Marin posted that link way back on page 1?
Nope, must have missed it (too much to cover, too little time).
Hope you'll forgive me . Good thing I didn't post it as my own .
Besides, it seemed like an article worth reading twice and the thread went to Lightning shortly after that without much comment on the article. I hope there is more comments on this article. It seams to cover everything. Properly??
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So far, I agree with everything in that article. I am going down into the dungeon tonight and finding that Practical Sailor the article mentions. I'll post on that too.
Hope you find it, I look forward to reading it.

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Old 21-03-2009, 16:23   #94
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Originally Posted by James S View Post
But then under bonding it says to

"Bonding and Electrolytic Corrosion Due to Hot Marinas
Do not bond any thru-hulls or other immersed metal that can be electrically isolated. Specifically, keep your metal keel/ballast, your metal rudder shaft, your engine/prop, and all thru-hulls electrically isolated, from each other, and from the engine.”
My suggestion would be the moment anyone starts talking about "hot marinas", ignore what they have to say. While it is always nice to have someone else to blame 99.99% of the time if one has a galvanic corrosion or electrolysis problem it is a problem or deficiency on ones own boat or is one that should have been avoided by fitting a galvanic isolator or isolating transformer if one has a shore power connection.

The decision to bond or not bond should be made with respect to whatever system approach is taken to the boat itself and not considering anything to do with the marina.
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Old 21-03-2009, 21:52   #95
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In OZ & NZ AS3004 applies.
http://www.standards.org.au/download..._and_boats.pdf
and australian standard as 3004 - Google Search
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Old 27-03-2009, 19:53   #96
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Disipation versus lighting strike; not the same?

Back after a long week, trying to catch up on this thread.

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I can report that trailing edge dissipators did not prevent lightning strikes to aircraft. Aircraft were frequently struck by lightning, which generally exited the aircraft through tail/aft fuselage surfaces.
Gord & Jedi,
I'm a little concerned here that because lighting didn't strike the actual static wick that people think it doesn't work? Its not suppose to be a lighting rod. It affects static build-up. Seems like apples an oranges. One has little to do with the other.

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Old 31-03-2009, 02:06   #97
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Exactly AND although they do help discharge static build up, they are electrically quite different from a grounded steel brush so one can't assume the brush will discharge static in the same way (if at all).
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Old 31-03-2009, 04:48   #98
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So you should be. The discussion about static wicks on aircraft is a red herring, having nothing to do with either lightning protection, nor with boats.

An aircraft, flying at very high speed, through some of the same elevations where atmospheric charge separations develop; accumulates a potentially dangerous static charge, which the static wick disperses (bleeds off).

This is the purpose they serve, which has nothing to do with lightning protection, and is in no way analogous to lightning mitigation on boats.

Boats do not build up anywhere near the static charge that aircraft do, and can derive no appreciable benefit from static wicks, or dissipaters.
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Old 31-03-2009, 05:30   #99
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Hey Gord, I also recently read in an older Practical Sailor that the charge on a boat can develop HUNDREDS of times fast than a dissipater could ever bleed off. So much for that. Hey look, I took my own thread off topic!
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Old 31-03-2009, 15:33   #100
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What Gord writes is half true: yachts don't get the static charge from friction with air molecules. But they do get a static charge when a thunder-cloud passes overhead. I had my hair standing straight up once!

So we get to Christians post: the dissipator can't bleed it off quickly enough to get rid of the charge. Very true. But keep in mind that this isn't what you need it to do. If it just gets rid of enough charge so that other objects "win" the competition for highest charge, they might form the best leader for the strike instead of you.

So, I step back to Wotname's post: a grounded pointed rod or brush is proven to dissipate an electric charge. The effect was discovered by Benjamin Franklin so not new tech at all. I still don't understand why the dissipators on planes have an electric resistance and I can't find any info on that on-line. The only info I find says they are connected to the fuselage. But that connection can have a 50- or 100kOhm resistance or none at all. I tend to believe the guys that work with/on them but don't understand the theory behind it.

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Old 31-03-2009, 15:36   #101
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Hey, I think Gord knew Benjamin Franklin personally...Gord, what did he say about this?
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Old 31-03-2009, 15:40   #102
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Gord is right, static whicks on planes have nothing to do with boat lighting. In aviation you can only miss certain number of whicks or you are grounded unless you are flying a cheapo low fare airline that wouldn't care i.e. Spirit, Jet Blue and so on.
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Old 31-03-2009, 20:07   #103
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This subject has always been a confusing one to me and all I can do here is relate an experience from the summer of 1999. My wife and I on a 33 foot sloop with a diesel, followed by a 24 foot sloop with a raised outboard were passing a traffic separation buoy about fifty yards away when it was struck by lightning. Neither boat was bonded or had lightning protection of any kind. I have no idea why the buoy was a better target than the taller masts other than it was obviously better grounded than we were. And yes it was loud,bright,frightening and very memorable. Jesse
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Old 31-03-2009, 22:32   #104
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I was caught in a frightening thunder, lightening and hail storm in - you guessed it - Storm Bay a few years ago in a 7 metre glass sloop - hail up to 2 cm. Many lightening strikes around us hitting water as far as I could see (visibility down to a few metres) but none hit the aluminium mast of the boat. Wind from many directions up to 50 knots at least. Lasted about 20 minutes. I could feel and smell the electricity! Hope to never see one of those again.
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Old 01-04-2009, 05:43   #105
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Quote:
Originally Posted by s/v Jedi View Post
<snip>

So, I step back to Wotname's post: a grounded pointed rod or brush is proven to dissipate an electric charge. The effect was discovered by Benjamin Franklin so not new tech at all. I still don't understand why the dissipators on planes have an electric resistance and I can't find any info on that on-line. The only info I find says they are connected to the fuselage. But that connection can have a 50- or 100kOhm resistance or none at all. I tend to believe the guys that work with/on them but don't understand the theory behind it.

cheers,
Nick.
Nick,
I can't lay my hands on the manufacturers data right now for static wicks but will post it when I find it - assuming this thread is still topical.

Here is how I think it works (but remember I am not a boffin, just an avionics field engineer so I might be off track).

A static build up by definition means a EMF (or a PD) is created between two points seperated by an insulating material - in this case air.

As the insulator (air) prevents current flow, the PD continues to increase until there are enough volts to ionize the air gap. At sea level, this will need to be in the order of 30+ thousand volts to ionize a small gap of some millimetres and 100's of thousand of volts if the gap is much bigger.

Once ionized, the air is no longer an insulator but becomes a rather good conductor so by Ohms law, large current flows. I.E. Big volts and low resistance equals big current.

A low resistance static wick (or brush) simply moves one end of the circuit to a new point in space, i.e. one pole of PD is now at the end of the brush instead of the end of the mast. Kirchoff's law IIRC.

However, a static wick with say 100Kohms changes the circuit substantially. Now we still have big volts, low resistance ionized air AND a high resistance wick in series so current flow is substantially decreased. Therefore EMI / RFI is reduced due to reduced current flow and the charge (PD) takes longer to discharge as the current flow is lower.

Another way to say it is: the spark is smaller.

I am sure someone could do the maths of the time constants etc of the circuit but I have a boat to rebuild .

However, just thinking aloud, I believe (but don't know) that the static charge felt on the boat during a thunderstorm should be considered as "resultant" static charge. By this I mean, the boat had nothing to do with the creation of the static charge, it was just floating in the water that has charge "impressed" on it by the movement of water and air molecules moving around in the thunderstorm clouds. Therefore trying to discharge this PD by a rod or brush on the mast seems pointless to me as the amount of charge is going to be BIG.

The static wick on the aircraft is trying to create a small controlled spark to discharge the airframe to the surrounding air rather than having a bigger uncontrolled spark discharging the airframe. I can't see how one can create a small controlled spark on the mast brush to discharge a large "resultant" charge of the surrounding water.

Lighting is just a big (very big) spark and follows all the rules of physics, the only thing is that we don't know all the physics of electrical current flow and ionization.

At the risk of further thread drift, it is impossible to create a spark with a PD of 12 or 24 volts, for those who don't believe this, PM me for the explanation or I can start another thread about this (if anyone is interested) rather than drift this thread any further . Hint, you can use 12 volts to create a very large voltage which will create a spark.
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