Looking for input on getting caught in a lightning storm. What level of protection is there on a sailboat(CD30}. The boat is grounded. ???
Zipwhittle@aol.com
Lightning
Moderator: Jim Walsh
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John R.
Re: Lightning
Check the long list of past "lightning" posts in the archive that many of us have made on the subject. Type "lightning" into the archive search box.
ken wrote: Looking for input on getting caught in a lightning storm. What level of protection is there on a sailboat(CD30}. The boat is grounded. ???
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Murray Glue
Re: Lightning
In Singapore, where I race frequently in lightning storms, we have a high strike rate on yachts. A couple of observations we have noted though:
1.0: Lightning seems to hit the water more often than the masts even where there are 10 or 20 yachts around the area. The moving boats are less likely to get zapped than moored or stationary boats.
2.0: Moored boats or boats at the marina are often hit, and regardless of whether they have grounding straps in the water or lightning domes on the masthead, they invariable lose the more sensitive electronics. One 42 ft yacht lost all the instrumentation recently and a Swan 68 had a surge in the negative side of her 24 volt system and lost some, but not all of her electronics. Interesting that this was in the negative rail of the DC system and not in the positive rail.
3.0: In the tropics I used to set up navigation beacons using 100ft towers for the antenna support. These were hit often too, regardless of the addition of expensive lightning domes and large copper grounding straps to earth. The use of in-line coaxial lightning arrestors did not usually save the electronics from damage.
I havent been on board when yacht has been hit, but recently saw the mast of a vessel hit, and the masthead gear was neatly vaporised, including the anemometer stalk and VHF antennas.
It adds a new dimension to tropical sailing!!
Murray Glue
CD30 Dayspring
Nelson
New Zealand
murray@offshoretechnical.com
1.0: Lightning seems to hit the water more often than the masts even where there are 10 or 20 yachts around the area. The moving boats are less likely to get zapped than moored or stationary boats.
2.0: Moored boats or boats at the marina are often hit, and regardless of whether they have grounding straps in the water or lightning domes on the masthead, they invariable lose the more sensitive electronics. One 42 ft yacht lost all the instrumentation recently and a Swan 68 had a surge in the negative side of her 24 volt system and lost some, but not all of her electronics. Interesting that this was in the negative rail of the DC system and not in the positive rail.
3.0: In the tropics I used to set up navigation beacons using 100ft towers for the antenna support. These were hit often too, regardless of the addition of expensive lightning domes and large copper grounding straps to earth. The use of in-line coaxial lightning arrestors did not usually save the electronics from damage.
I havent been on board when yacht has been hit, but recently saw the mast of a vessel hit, and the masthead gear was neatly vaporised, including the anemometer stalk and VHF antennas.
It adds a new dimension to tropical sailing!!
Murray Glue
CD30 Dayspring
Nelson
New Zealand
murray@offshoretechnical.com
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Larry DeMers
Re: Lightning
Ken,
Lots has been written, and theorized over..for decades. There are several working theories in vogue right now, and some recent information is available online. I included a url below. This source was provided (I believe) by JohnR. sometime a while back and I found it fairly thorough, although I don't necessarily agree totally. Good starter for some serious thinking...;^)
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30 Lake Superior
Lightning and Boats
Ewen M. Thomson
Lightning and Boats by Ewen M. Thomson </a>
demers@sgi.com
Lots has been written, and theorized over..for decades. There are several working theories in vogue right now, and some recent information is available online. I included a url below. This source was provided (I believe) by JohnR. sometime a while back and I found it fairly thorough, although I don't necessarily agree totally. Good starter for some serious thinking...;^)
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30 Lake Superior
Ewen M. Thomsonken wrote: Looking for input on getting caught in a lightning storm. What level of protection is there on a sailboat(CD30}. The boat is grounded. ???
Lightning and Boats
Ewen M. Thomson
Lightning and Boats by Ewen M. Thomson </a>
demers@sgi.com
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John Nuttall
Copper Core Or Liquid Sodium Masts solve this problem....
......yes folks the solution is already at hand.
The folks from "Down Under" have already figured this one out. So much for Yankee Ingenuity.
The solution can be found at the attached link....
John
The folks from "Down Under" have already figured this one out. So much for Yankee Ingenuity.
The solution can be found at the attached link....
John
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Joel
Re: Lightning
This month's SAIL magazine's feature article is on the issues and, from my read, the disagreements regarding lightning. Some believe that grounding the mast to the keel will allow the lightning to discharge harmlessly; others believe that it mkes the boat a more attractive target.
Joel
Pokey II
'73 Ty #549 (still for sale)
Bayside, NY
bondy_joelNOSPAM@hotmail.com
Joel
Pokey II
'73 Ty #549 (still for sale)
Bayside, NY
bondy_joelNOSPAM@hotmail.com
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Larry DeMers
Re: Lightning
My experience and reading has led me to believe this:
A well grounded mast, with the properly sized ground conductor going *straight* to the grounding connection on the boat, will safely conduct the charge to ground as well as you can do it. Despite the ground however, the EMP generated by the strike will likely damage electronic circuits, batteries, and any parallel metal conductor to the ground which will have induced into it a very large voltage spike, which is likely to cause problems in the boats equipment. By grounding the mast, you provide a pathway for the lightning, and you get most of the charge out of the boat safely. There still can be flashovers to other metal fixtures and objects nearby (which is why they should also be included in the bonding, via a separate wire pathway), and this itself can cause holes in the hull ( I have seen them).
Grounding the mast in theory at least, raises the ground level up higher in altitude, than the surrounding ground, which makes it more likely to get struck. But once struck, the charge is directed away from the boats interior asap. Now this is not a 100% solution, as the currents we are talking about are tremendous.
The other side is where the mast is not grounded. In this scenario, you escape troubles (in theory) by *blending* in with the surrounding ground (water). Lightning now does not see you as well as before, making a strike less likely. But if a strike does happen, you have provided no pathway for the charge to get to ground peacefully. It has to find it's own way, and that will do the damage to the boat. (Saw this happen two years ago). Typically, the lightning will exit at the water level, or slightly above it. Expect 200-300 holes from pencil sized to fist sized, some could be underwater too. Expect that besides the EMP pulse likely damaging all electronics, the boat itself is compromised such that it could sink. There is a greater chance of a flashover hitting you too,when the mast is ungrounded.
So the true dilemma here is that this argument will never be solved. Both are right and both carry risks, although I see less risks with the properly grounded mast.
Cape Dory used 8AWG solid wire for the bonding effort. New ABYC specs call for 4AWG solid wire. This should be led directly to the ground contact on the hull. Additional bonding wires from surrounding metal objects should then also be routed to this same grounding contact, but with separate wires from the mast ground wire. That is to keep the charge going straight as possible, without meandering all over the boat while on the way to ground, and so, flashing off to nearby objects.
Good Sailing,
Larry DeMers
DeLaMer
Cape Dory 30 Lake Superior
demers@sgi.com
A well grounded mast, with the properly sized ground conductor going *straight* to the grounding connection on the boat, will safely conduct the charge to ground as well as you can do it. Despite the ground however, the EMP generated by the strike will likely damage electronic circuits, batteries, and any parallel metal conductor to the ground which will have induced into it a very large voltage spike, which is likely to cause problems in the boats equipment. By grounding the mast, you provide a pathway for the lightning, and you get most of the charge out of the boat safely. There still can be flashovers to other metal fixtures and objects nearby (which is why they should also be included in the bonding, via a separate wire pathway), and this itself can cause holes in the hull ( I have seen them).
Grounding the mast in theory at least, raises the ground level up higher in altitude, than the surrounding ground, which makes it more likely to get struck. But once struck, the charge is directed away from the boats interior asap. Now this is not a 100% solution, as the currents we are talking about are tremendous.
The other side is where the mast is not grounded. In this scenario, you escape troubles (in theory) by *blending* in with the surrounding ground (water). Lightning now does not see you as well as before, making a strike less likely. But if a strike does happen, you have provided no pathway for the charge to get to ground peacefully. It has to find it's own way, and that will do the damage to the boat. (Saw this happen two years ago). Typically, the lightning will exit at the water level, or slightly above it. Expect 200-300 holes from pencil sized to fist sized, some could be underwater too. Expect that besides the EMP pulse likely damaging all electronics, the boat itself is compromised such that it could sink. There is a greater chance of a flashover hitting you too,when the mast is ungrounded.
So the true dilemma here is that this argument will never be solved. Both are right and both carry risks, although I see less risks with the properly grounded mast.
Cape Dory used 8AWG solid wire for the bonding effort. New ABYC specs call for 4AWG solid wire. This should be led directly to the ground contact on the hull. Additional bonding wires from surrounding metal objects should then also be routed to this same grounding contact, but with separate wires from the mast ground wire. That is to keep the charge going straight as possible, without meandering all over the boat while on the way to ground, and so, flashing off to nearby objects.
Good Sailing,
Larry DeMers
DeLaMer
Cape Dory 30 Lake Superior
Joel wrote: This month's SAIL magazine's feature article is on the issues and, from my read, the disagreements regarding lightning. Some believe that grounding the mast to the keel will allow the lightning to discharge harmlessly; others believe that it mkes the boat a more attractive target.
Joel
Pokey II
'73 Ty #549 (still for sale)
Bayside, NY
demers@sgi.com