copper pipe for freestanding wooden mast grounding?

  • 02 Mar 2019 16:57
    Reply # 7195259 on 7192629
    Deleted user
    Anonymous 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

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

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

    I'd about reached the same conclusion after reading the PDF I posted David, fascinating read that, it explains in layman's terms exactly what happens when lightning strikes a mast.  Now that I'm a bit better informed I'll probably do as the experts recommend and a bit more besides.

    Thanks for the links David, very helpful, and now I'm even more worried, according to the stats on strikes by boat type a catamaran is about 12 times more likely to be struck by lightning than a sail only monohull and sustain about twice as much damage!

    and I'm working on a proa which is essentially an asymmetrical catamaran, I guess sometimes ignorance really is bliss. 

    On the upside, there will be very little metal or electrical on my boat, just the woodstove and stovepipe, and handheld devices that'll be stored in a waterproof plastic case when not in use, and either a windmill or solar panel and a charging station for cordless tool batteries which I'll use to power LED lighting.

    Because it's a telescoping mast and they tend to get a lot of rain running down the top section into the bottom section that needs somewhere to go, I already have a drain hole through the bottom of the boat drawn for the mast step so it'll be easy to put a cable out the bottom.
    And on the Proa I'm designing the mast step will be outside of the water line in the flare of the hull so it'll be even easier to ground.

    I must have been writing my last post when you posted Arne, I like your idea, so much that I'm giving serious consideration to standing rigging, something that I really wanted to avoid, a couple stays with copper cable clamped to them leading to the ends of the ama would protect the cockpit area between the hulls and lead the charge away from the boat. A stay to the bow with the wood stove would protect that a bit as well.

    here's a link to a Sidearc System which takes your idea a couple steps further, lots of great info there both on what happens during direct strikes and near misses.

    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

    1 file
    Last modified: 02 Mar 2019 17:00 | Deleted user
  • 02 Mar 2019 09:56
    Reply # 7194859 on 7192629
    Anonymous member (Administrator)

    Tanks, Bill,

    that PDF was an interesting read. It strengthen my attitude to rigging the lightning conductor from the mast top, in a straight line to the water, outside the rail  -   that is  -  unless the boat is made of some metal. Metal boats seem to be a good idea in Florida...

    Arne


  • 02 Mar 2019 09:27
    Reply # 7194842 on 7192629

    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

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

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

  • 01 Mar 2019 23:34
    Reply # 7194423 on 7192629
    Deleted user

    Thanks Len and Erik, I'm going down to victoria next week, the library there ought to have one or the other if not both texts.

    this PDF on sailboats and lightning in florida is pretty interesting.


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

    B
    ill F

  • 01 Mar 2019 22:48
    Reply # 7194352 on 7192629
    Anonymous member (Administrator)

    In my area (Stavanger) I haven’t heard of any who has had their boats destroyed by lightning, but several have had electronics knocked out. However, in my job as an engineer, maintaining all sorts of radio beacons, proper protection from lightning strikes and overvoltage on incoming lines, was essential.

    Protection against direct hit..
    One rule for lightning conductors was to avoid sharp bends, or the lightning may ‘jump off’. Sometimes, when the antenna wire and the lightning conductor was the same, a clever sharp bend and spark gap were fitted to encourage the lightning to jump to a grounded wire, instead of destroying our transmitter or receiver.

    We had a few direct hits in my time, but my guess is that the tall antennas we needed was much of the reason  -  and of course, many of our sites were sitting on hilltops. If I were (I am not) to fit a lightning conductor to any boat, I would not bring the conductor inside, but rather clamp it (a thick, insulated copper wire) to one of the shrouds or stays. In normal weather, during sailing, I would just let a 3m long tail of it rest along the rail, but when at the mooring, or in bad weather, I would throw the tail over board. No danger of knocking holes in the boat with this ‘outside’ setup . (This can even be arranged on an un-stayed JR)

    Protections against indirect hits (much more frequent).
    A strike that hits near the boat (or goes through the l-conductor), may induce a spike of several thousand volts in the 12-volt wiring. The fuse box will not protect against this but will rather act as a distribution hub, and the result may be lots of fried electronics. If I were to have a boat full of electronics, I would terminate the outlets of the fuse-box in sockets. The electronics could then be unplugged, when not in use, and much damage could be avoided.
    And then there are over-voltage protectors, etc, etc...

    Luckily, all I have of electronics on board is my trusty old Garmin 72  -  handheld....

    Arne


  • 01 Mar 2019 22:06
    Reply # 7194316 on 7192629
    Bill wrote:

    Just wondering if copper pipe would work for mast grounding?

    I'm designing a two piece telescoping mast and am playing with the idea of having a 1/2"/13mm copper pipe in the lower section and a 3/4 / 19mm copper pipe in the upper section so they can telescope when the mast sections do.
    I can't see any way of making a cable work which just leaves tacking copper flashing to the inside of the lower mast section and outside of the upper mast section and hope they're make enough contact to carry the load at the moment the lightning hits.


    From looking at the design of radio towers,  AM radio towers (remember AM radio?) are often insulated from the ground and the transmitter output is fed across the insulator with one side powering the tower and the other the ground plane (a circle of long wires spread out across the field the tower is in). The voltage difference across this gap may well be 15000v (for a 50k transmitter) and direct grounding is not possible. Instead they have a conductor from the top and bottom with ball ends, and a gap between them. (from the NAB engineering handbook) In the radio amateurs handbook, I have seen something similar except the gap has pointed ends (1k watt is a lot less than 50kw). All that to say, I don't think direct contact is strictly needed to work. Even a half inch gap will not stop a high voltage static charge from jumping from one to the other.

    I understand that because you are making a telescoping mast, the connection is a concern. The problem with both ideas you have is that you end up with wide surfaces next to each other which will raise the voltage and heat at the point where it arcs from one conductor to the other. While that would still work, it may also weld the two parts of your mast together :)  this is probably not what you intend. A sharp interface would be best from at least one side. I would suggest a copper strap on the outside of the top part that runs at least as low as the top of your bury. Another copper strap on the outside of the lower part that bends over the top of the rim of the lower mast that comes to a point as close to the top bar as is practical (it doesn't have to touch).


    One thing to watch. this will not protect the wiring of any lamp or other electronics at the top of the mast... though to be honest, I am not sure what would... there are ways to protect lamps on top of masts however that is beyond the scope of this message. Electronics? wireless with their own solar panel all on top of the pole is the best you can do (and still might fail).

    Certainly see if your local library has a copy of the Radio Amateurs Handbook if you wish to study this some more.

  • 01 Mar 2019 21:48
    Reply # 7194305 on 7192629
    Deleted user

    I know what you mean David, I had never even heard of grounding the mast before I read the practical junk rig, If I had an aluminum mast and/or standing rigging I wouldn't worry about it.

    I'd like to sail far enough north to go for a walk on the ice in the middle of august at least once, and I may do the northwest passage at some point as well, I understand lightning is pretty common up there.

    I couldn't find anything else here and on other sites every technical discussions tends to turn into bickering pretty fast, due to back pain I have a very low tolerance for other peoples childishness D) , the only thing I'm inclined to post on Sailing Anarchy is the joke where a boy tells his mom he wants to be a sailor when he grows up and she tells him he can't do both.

    I don't plan on running any wires to the masthead, on those rare occasions when I'm motoring at night I'll just run a lantern up the spare halyard


    I'm with Asmat, thanks for posting the thread, I'll definitely have a look. I used to volunteer for firefighting up in the interior of British Columbia, mostly for the chopper rides :) I've seen what lightning will do to a tree, I can imagine what it might do to a lightly built wooden boat, there are enough things to worry about in a storm that I'd like to remove lightning from the list if I can do so in a way that fits my SOR.

    I suppose the easiest way to deal with the problem would be carry a 50' chunk of 1/2" copper cable and run one end up the mast on the spare halyard and toss the other end overboard if it looks lighteningy out, heck, I suppose it'd make a passable anchor rode in a pinch as well :) .
    Or I could just run copper down the bottom section and lower the upper section when it's stormy, that's kind of the plan anyways, the upper section would mostly be for light air which is a problem here.

    Bill F

  • 01 Mar 2019 20:10
    Reply # 7194141 on 7192629

    Bonsoir

    Lightning protection on small vessels is defined the ISO 10134:2003 document.

    Usually the protection provided by the boat builders doesn't last long ; it corrodes fast.

    For French speeking members, there is an interresting thread on C. Coudert Voilelec website (a good reference) :

    https://www.voilelec.com/pages/quille.php

    He suggests a wide (20cm) sheet of stainlessstell plate betwenn the keel bolt and the mast.

    Eric

    Last modified: 01 Mar 2019 20:14 | Anonymous member
  • 01 Mar 2019 19:53
    Reply # 7194103 on 7192629

    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.

  • 01 Mar 2019 10:56
    Reply # 7193141 on 7192629

    Members thoughts on mast lightning conductors would be interesting, although there's probably a thread on that topic already in existence somewhere.....

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

                                                              Site contents © the Junk Rig Association and/or individual authors

Powered by Wild Apricot Membership Software