copper pipe for freestanding wooden mast grounding?

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  • 04 Mar 2019 18:34
    Reply # 7198810 on 7192629
    Deleted user

    I operate on the principle "The gods help those who help themselves"

    If I put in a lightning protection system all it'll cost me is a tiny bit of money/weight/time when compared to the total cost of the boat and I'll have piece of mind when ThunderBird, the local God of lightning decides a bit of target practice is in order :) seems like a bargain to me.

    after reading Davids thoughts on using an aluminum rod I may just go thataway.
    I've been following the "tree or metal for masts"  thread and I'm considering a wooden bottom section lined with 16 ounce copper sheeting and an aluminum upper section.
    the other alternative would be to use all wood and just line the bottom section and lower the upper if it looks lighteningy out.  Any time the wind is over ~force 4-5 the upper section will be lowered anyways.
    I think that would be the simplest solution all around, but, have you ever looked at an aluminum mast and thought to yourself, "They sure did a beautiful job on that"?
    I realize that with a fair amount of time/money/cancerous chemicals/work, an aluminum mast can be made to look really good, but wood starts off that way.

    Light wind and patches of dead air/ holes are a real problem here amongst the islands, especially in the first two to three miles from the boat launch I use and being able to quickly increase/decrease my sail area and aspect ratio by half by simply pulling on the halyard seems like the best way to deal with the problem, as an added bonus the mast should be super strong while still being able to flex when the upper section is lowered, two thumbs up for one less thing to worry about :)

    I've considered a few other options, head sails, stay sails, top sails, and more masts, a telescoping mast seems like the best option to me, it does everything the other options do as well as increasing aspect ratio, and without changing either the fore and aft balance/ center of effort of the boat
    To use staysails/headsails I'd have to use stays wich add in extra cost, extra weight, extra maintenance, and worst of all, extra but-ugliness.
    More masts means more weight in the very worst place on a proa, in the bows, more lines, and more work, and that's a four letter word. :)


    I hope that's a wooden pole Annie, the thought of a concrete or alloy pole exploding like that makes it even scarier.

    The problem with a wooden mast is that it doesn't conduct at all when it's dry, but if it gets wet it conducts just well enough to accumulate a positive charge at the masthead, which in turn can attract a lightning strike. Even if it doesn't the woodstove and it's steel chimney pipe probably will, I'm planning on grounding it as well.

    Bill F


  • 04 Mar 2019 13:31
    Reply # 7198260 on 7195723
    Anonymous wrote:

    I couldn't tell from the video what the pole was made of: could anyone else see?  It did look a bit like wood, but all the other poles around seemed to be metal.  Scary, anyway!


    It certainly looks like wood in the way it explodes into pieces!
  • 04 Mar 2019 13:27
    Reply # 7198259 on 7194103
    Anonymous wrote:

    Tony,

    Have a look at the May - Oct 2015 thread, 'Thunderstruck'. I take lightning protection very seriously, having experienced some pretty impressive thunderstorms at sea. Few things scare me more.


    Thanks Asmat - have done!
  • 04 Mar 2019 10:27
    Reply # 7197386 on 7192629

    A further thought on this:

    Aluminium has a conductivity two thirds that of copper, but weighs and costs one third as much (that's why, with a steel core for strength, it's used for overhead high voltage power lines).

    A #4 copper wire, 21 sq mm cross section or equivalent to a 5mm dia copper rod, is specified for the vertical component of a lightning protection system. A 6mm dia aluminium rod, used as both the air terminal and the upper part of a sliding conductor, would have the same conductivity and would weigh and cost much less. The lower part would still be a tube, just large enough to give an easy sliding fit.

  • 03 Mar 2019 08:05
    Reply # 7195976 on 7195732
    Annie wrote:
    David wrote:

    ... I have always chosen to leave this one to the Gods, and worry about things I have more control over.

    What sang-froid - and what a sensible attitude.  I do take it that a libation of gin is made at the same time?
    I too adhere to the Que Sera Sera school of thought. Unless I move to Florida, which would be about as likely as suffering a lightning strike in the high temperate latitudes, I won't worry about it.

    A long time ago, I was in the middle of a storm in the English Channel, with lightning causing the water to sizzle as it struck close by (or was that my imagination?), and with me rehearsing my abandon ship procedures.

    More recently, there was a major thunderstorm ahead of us as we approached the Tuamotus, and we hove to at first, and then turned and ran away from it for a while. We heard later that a yacht had had a terrible time underneath it.

    Those are the only two instances during a long sailing career that lightning could have been a big issue.

  • 03 Mar 2019 00:25
    Reply # 7195732 on 7195563
    David wrote:

    ... I have always chosen to leave this one to the Gods, and worry about things I have more control over.

    What sang-froid - and what a sensible attitude.  I do take it that a libation of gin is made at the same time?
  • 03 Mar 2019 00:18
    Reply # 7195723 on 7194423
    Bill wrote:


    This video pretty much mirrors my imagination of what a lightning strike would do to my mast.

    B
    ill F

    I couldn't tell from the video what the pole was made of: could anyone else see?  It did look a bit like wood, but all the other poles around seemed to be metal.  Scary, anyway!

    Rob Prince and I were talking about lightning conductors a couple of days ago.  Trees, I gather, are destroyed because the sudden heat boils the sap and causes them to explode.  In theory, this wouldn't happen with a wooden mast. 

    We put lightning conductors on Badger, (as per PJR) which were extremely reassuring until I read about the lightning taking the shortest route to earth - in this case water.  As the lightning conductor from the foremast led back to the keel, and as the chain locker was only inches away, It occurred to me that the shortest route for the lightning would be via the chain.  Hmm.

    Supposedly, the true object of the exercise is to use your 'lightning rod' to discourage the lightning strike in the first place.  I have to say that for me, the whole thing is an act of faith, particularly because there seems to be such a variety of views and, it has to be said, and even great variety of solutions!

    I have had several friends whose boats were struck by lightning and the worst that happened was the destruction of their electronics and possible engine damage (though to be fair, on a sophisticated boat, this is a pretty bad worse!)  These boats all had rigging. I don't know of any boat with a free-standing mast being struck, so it's guessing games again.   Being in the middle of a serious lightning storm is terrifying and all you can do is hope it goes away!

  • 02 Mar 2019 21:34
    Reply # 7195563 on 7192629

    I have always been aware of the risk of lightning strike, particularly during one summer spent in the Gold Coast of Australia on one of my yachts where we witnessed some spectacular lightning strikes during the summer rain storms. However it is one of those things where the actual chances of it happening are statistically so small, and there seem to be so many opinions on how to provide lightning protection, that I have always chosen to leave this one to the Gods, and worry about things I have more control over.

     

    Last modified: 02 Mar 2019 21:46 | Anonymous member
  • 02 Mar 2019 21:06
    Reply # 7195541 on 7194842
    David Tyler wrote:

    A little bit of reading about what the professionals do in the field of marine lightning protection tells me that it's a very complex subject, and unskilled amateurs are just as likely to make things worse as make them better.

    http://www.marinelightning.com/index.html

    Yikes! A little bit of reading about what the professionals do, scares me. In the above article, their reasoning for using their "SiedarcTM electrodes" Does not make sense. In fact, it would suggest the opposite to me. Pure (distilled) water does not conduct electricity, it is the impurities in the water that make water conductive. This is why their sparks jump to the edges of the tank with fresh water but not with salt water. A large spark right next to the hull is likely to do damage. I don't know the specifics of the test but I wonder if the hull piece was wet... or if there was even a hull piece beside the electrode. The slight glow of the electrode in the water means that there was a better connection to the water ground plane which means less heat and less hull damage. Also, with a wet hull, the power would take the shorter path to the wet hull rather than the surface of the water. Depending on the conductivity of that water, there could be a hot spot on the hull.

    This link is the one that will possibly be of most interest to us:

    http://www.marinelightning.com/science.htm#Cruising_sailboats

    I still need to read that one.

    Copper bottom boats would seem to be a winner here. Not only do they do the very best job of keeping growth off the bottom but they also provide probably the very best ground connection for a static electricity system. Price is the big problem here.

    The idea behind "Lightening rods" or perhaps how they tend to work in practice, Is that they should prevent lightening from happening in the area because they continually bleed charge from the atmosphere to ground. So spark gaps should be small, just enough to prevent electrodes from welding together. Solid conductor from top to bottom still seems the very best.

  • 02 Mar 2019 17:17
    Reply # 7195285 on 7195259
    Anonymous member (Administrator)

    Bill wrote:

    One question though, since you've probably forgotten more about electricity than I'll ever know, why an insulated wire? As I understand it, (Not very well) insulating a wire raises it's resistance, considering that the average lightning bolt is around a billion volts and from 10,000-200,000 ampres, wouldn't that just vaporize the insulation?

    Well, time to stop planning and start doing :)

    Speaking of which, just started on an aerojunk rig.


    Bill F


    The reason for the insulation is simply to avoid any corrosion problem between dissimilar metals. If the l-conductor is of the right gauge, it will not get very hot, since the current burst only lasts for a split second. My reason for trying to avoid 'spliced' or jointed pieces of l-conductors, is that these joints may easily develop high resistance over time. A high-resistans spot on any l-conductor will surely become terribly hot, leading to molten metal flying around  (in a direct hit...). If that molten metal was supposed to keep the mast upright, then...

    Arne

    Last modified: 02 Mar 2019 17:21 | Anonymous member (Administrator)
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