lightning

[frankbarbehenn]

I read that there are conflicting views about how to deal with lightning: to protect and ground to water or not. It seems to me that there must have been some real physics research on this question since it is so important for sailors. Does anyone know where to look for a real scientific answer???

[GordMay]

Some excellent on-line resources on ‘Lightning & Boats’ - Goto:
http://CruisersForum.com - Power Equipment & Electricity - Lightning Information
http://cruisersforum.com/showthread.php?s=&postid=10366#post10366
including:
“Lightning And Sailboats” - by Ewen M Thomson, Univ. Fla. 1992. Sea Grant Publication
[size]The best basic lightning primer for boaters[/size]
http://www.thomson.ece.ufl.edu/lightning/
and more
HTH,
Gord May

[tondelayo29]

I just read a great article this morning but it is far to large (20,000 characters) to post here.... It is from
Bruce A. Kaiser
President
Lightning Master Corporation
09/26/90

[sailphoto]

Lightning scares the bejeebes out of me and I have spent many nights anchored out among other boats hoping that if lightning strikes it would find the radio tower across the harbor or a taller mast ( without any ill will towards others) on a grounded boat around me more attractive than my own. When I first bought my boat which is a 1980 Dockrell 27 cutter and read the survey it revealed that my little ship is not grounded and this prompted me to do a little research on the matter. What I found out after exhausting the resources on the web is the following: In rough numbers a boat that is grounded is twice as likely to be hit by lightning than one that isn't. On the flip side, a boat that isn't grounded and is hit by lighning is twice as likely to catastrophic damage i.e. have a hole blown in the hull and sink and/or kill the crew. None of the sites I visited gave me any absolute statistics except for the ones selling products which in my sceptical way always assume are skewed. It seems also that grounding a boat doesn't provide absolute protection to the crew, especially on smaller boats where you cannot physically get away from the path the lightning wants to take to the ground, down the mast and out through the grounding cable and line.
I don't really love any of these odds. What I have done to date is not ground my boat and to further reduce the likelyhood of being struck I have installed a stainless brush at the mast top designed to "bleed off" negative ions thereby reducing the potential of the boat. Experts disagree as to the effectiveness of this system. As I write this though I am again wondering if I shouldn't ground my boat. The following link discusses the brush system in greater detail http://www.oceanpix.co.uk/Seamanship...g-at-sea-2.htm

[sailingdog]

Sailphoto-

If I understand the theory behind the lightning dissipators, then the boat needs to be grounded for them to work. Adding one to a boat that is not properly grounded does nothing. The brush can not bleed off the massive static charge potential if it is not ground.

[Cruisingdad]

Photo, et all,

I believe SD is right. Not going to help a lot with the dissipator if the boat is not grounded.

My personal opinion (AND IT IS A PERSONAL OPINION): If you are primarily coastal and do NOT need a SSB, do NOT ground.

If you either want an SSB or are going to be doing a fair amount of offshore: Ground the crap out of the boat and put a dissipator on top.

Either way, you take your chances... but you also take your chances everytime you hop in your car and get on the highway. Do your best, then don't let it consume you (no pun intended).

[sailingdog]

I'd second CruisingDad's recommendation to not ground if primarily coastal or inland, and ground well if going offshore or need an SSB. BTW, why would you have an SSB if you're not going offshore???

BTW, I'll take my chances with sailing...far fewer idiots out on the ocean than on the local streets.

[sailphoto]

Originally Posted by sailingdog

Sailphoto-

If I understand the theory behind the lightning dissipators, then the boat needs to be grounded for them to work. Adding one to a boat that is not properly grounded does nothing. The brush can not bleed off the massive static charge potential if it is not ground.

The problem with using an ionic dissipator on a grounded boat is that you then are trying to disipate the negative charge of the entire ocean through this little stainless steel brush. It just isn't going to be able to do it.

[Cruisingdad]

Photo,

Buy a bigger brush... HAHA!! Just kidding.

[sailingdog]

Originally Posted by sailphoto

The problem with using an ionic dissipator on a grounded boat is that you then are trying to disipate the negative charge of the entire ocean through this little stainless steel brush. It just isn't going to be able to do it.

Actually, the idea is that you're reducing the charge local to the boat, just a slight amount...and thereby reducing the potential of a lightning strike in that specific location. You aren't trying to dissipate the entire negative charge...that would be almost impossible, given how large the forces involved are.