Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 27-04-2021, 12:00   #16
Registered User

Join Date: Mar 2020
Posts: 22
Re: So my boat lacks a lightning ground.

Well, well, well. I see there is a smorgasbord of responses on this topic that has little scientific on the answer about how to coral a lightning strike on a boat. ABYC use to have a section in their regulations about lightning suppression (like some how we two legged pedaling animals have any control what lighting does). ABYC with great wisdom removed that section. When I got my ABYC certification in electrical the trainer said that one day while he was inside his sailboat sitting, a lightning strike happened on the boat two slips from his. The lightning migrated over to his boat and he saw round balls of energy bouncing around inside his boat and exit out the side of his boat. That experience made him understand how temporary life is and that experience prompted him to take a good look at his life and he decided it was time to make some changes. Lightening will do as it pleases regardless of what you do to re-direct it or suppress it.
RigBig is offline   Reply With Quote
Old 27-04-2021, 12:21   #17
Registered User

Join Date: Nov 2018
Posts: 703
Re: So my boat lacks a lightning ground.

This is a case where you probably shouldn’t listen to anyone's advice. Everyone has an opinion, and almost nobody can back it up by a science. Even having years of experience in what to do in buildings (a previous poster) or broadcast antennas (me) has little application to fiberglass sailboats. Thus anecdotal evidence is no more than bar stories.

My boat is a 45’ fiberglass sailboat. 69’ mast, stepped on an encapsulated keel. No evidence of any bonding or grounding. There was a factory-installed bonding system which was so poorly done as to be completely ineffective. It was removed as I got access to the various wires.

I have been struck by lightning twice, once in Costa Rica and again in Panama. Both times completely destroyed the VHF antenna, so they weren’t just close strikes. The only consistent damages between the two strikes was the VHF antenna, and the wind indicator MHU. For example, one strike wrecked the VHF radio, one didn’t. Same with radar, loudhailer, autopilot, MFDs, depth sounder. Sometimes yes, sometimes no. The only mechanical damage ever found was the hydraulic seal in the back stay tensioning cylinder which was charred.

A study I read a number of years ago was based on the number of insurance claims and the amounts paid out. There was no significant difference in the number of boats damaged between boats that tried to do everything for lightning protection and boats that did nothing. Of the boats that were struck, there wasn’t a significant difference in the amount of damage between boats that tried to protect things and those who didn’t.

My takeaway is to do whatever makes you feel comfortable because you’ll never be able to prove what you did was right, nor can anybody prove that you were wrong.

Sufficient rum and a good insurance policy will provide enough freedom of mind to worry about other things.
Bycrick is offline   Reply With Quote
Old 27-04-2021, 14:03   #18
Registered User

Join Date: Sep 2019
Posts: 51
Re: So my boat lacks a lightning ground.

I don’t have any recommendations for your boat. However, if your interested in general knowledge regarding lightning strikes, there was a podcast about a year ago that had some interesting information. I found it really interesting, but probably not for everyone.

The “On the Wind” podcast from 4/28/2020. I copied the description below.

“#290. Jeff Thayer is a physicist, and back in the Space Shuttle days, studied and designed lightning defense systems for NASA to protect the Shuttle and other NASA rockets while they sat, vulnerable, tall metal objects on the launchpad in otherwise flat Florida. Jeff is also an avid sailor, and couldn't help but get in touch when he heard Andy talking about lightning on the podcast. Guest host August Sandberg dives deep with Jeff on the physics of lightning at sea in this very interesting and technical discussion.”
Chris31415 is offline   Reply With Quote
Old 27-04-2021, 14:26   #19
Registered User

Join Date: Oct 2019
Location: Kennebunk ME
Boat: Owner built 60’ Aluminum Expedition Yacht.
Posts: 706
Re: So my boat lacks a lightning ground.

Has anyone seen a fiberglass boat wherein lightning exited through a depth transducer causing the vessel to sink. The vessel had no bonding wires nor any “lightning “ protection system.
I’ve seen lightning jump to a metal object such as a strut, seacock or similar but never to a transducer.
I didn’t think it was possible given the wire size. All plastic transducer.
Thank you.
Mark and crew.
Manateeman is online now   Reply With Quote
Old 27-04-2021, 14:56   #20
Registered User

Join Date: Jan 2014
Location: Panama City FL
Boat: Island Packet 32 Keel/CB
Posts: 780
Re: So my boat lacks a lightning ground.

Quote:
Originally Posted by Bycrick View Post
has little application to fiberglass sailboats. Thus anecdotal evidence is no more than bar stories.

Quite the contrary. In many respects a sailboat is an easier nut to crack than a building. Comes factory equipped with an almost perfect air terminal (lightning rod) and floats in a conductive medium (assuming sea water).

My clients spent considerable money and electrical contractors went to great effort to establish low resistance earth grounds here in Florida's sandy soils.

While the physics of strike attachment is not quite as settled as say gravity, once that strike is attached the physical laws of electricity flow (quite well understood) are pretty well followed. Provide it a low impedance path to where it is ultimately heading almost guaranteed to work. Fail to provide that path and the strike will find its own way, maybe not to your liking.


Frankly
Frankly is online now   Reply With Quote
Old 27-04-2021, 15:03   #21
Registered User

Join Date: Jan 2016
Location: San Diego, CA
Boat: Beneteau 40.7
Posts: 286
Re: So my boat lacks a lightning ground.

Although it sure should not be this way, make sure your DC return for mast mounted lights is not using the mast itself. If it is this needs to be addressed first by isolating the return lines from the mast and running a separate insulated (black) wire to DC low at/near your batteries.
thunderhoof is offline   Reply With Quote
Old 27-04-2021, 15:06   #22
Registered User

Join Date: Nov 2018
Posts: 703
Re: So my boat lacks a lightning ground.

I don’t think the small wire size would matter. If the lightning "decides" to go down the tiny transducer wires, they’d immediately vaporize. But that vapor could easily provide a plasma path for the arc to continue. But I’ve never actually seen a boat that was sunk by lightning. I’ve worked on my own boat twice and helped six other people fix lightning victims. Not a big survey. Sometimes lots of electrical damage, even to batteries and engine components. But never any real physical damage to components of the boat itself. YMMV.
Bycrick is offline   Reply With Quote
Old 27-04-2021, 15:31   #23
Registered User

Join Date: Jul 2020
Location: Virginia, USA
Boat: Tayana 37
Posts: 151
Re: So my boat lacks a lightning ground.

Quote:
Originally Posted by thunderhoof View Post
Although it sure should not be this way, make sure your DC return for mast mounted lights is not using the mast itself. If it is this needs to be addressed first by isolating the return lines from the mast and running a separate insulated (black) wire to DC low at/near your batteries.
Ah hadn't considered that. Looks like I will be tracing some wiring and taking some readings this weekend.
Statistical is online now   Reply With Quote
Old 27-04-2021, 16:06   #24
Registered User

Join Date: Dec 2009
Location: Australia
Boat: building Roberts Mauritius 43ft
Posts: 2,667
Re: So my boat lacks a lightning ground.

Quote:
Originally Posted by Statistical View Post
it is encapsulated so I will need an external plate. Nigel Calder makes the same warning as you. Looks like the consensus is 1 sq ft solid copper plate as a lightning ground thru bolted and connected to the mast by heavy gauge wire. Should be isolated from the DC system.

It doesn't seem particularly hard (famous last words on a boat) and will give me peace of mind.

Maybe someone has mentioned this previously (I haven't read all the posts) so sorry in advance if they have.

I have read many times that a strip is more effective as an earth than a grounding plate.

"The external grounding plate should be located so that it can never be out of direct contact with the water, and should be made of either copper, bronze or Monel (a predominantly nickel and copper alloy). A long strip is more effective at dissipating the electrical flow than a square plate of the same area".

https://www.clubmarine.com.au/explor...htning-strikes

https://www.pbo.co.uk/expert-advice/...-strikes-67072
coopec43 is offline   Reply With Quote
Old 27-04-2021, 16:09   #25
Registered User

Join Date: Nov 2018
Posts: 703
Re: So my boat lacks a lightning ground.

Frankly — I apologize if you took that as a dig. It wasn’t intended. I used to help build radio towers many years ago. I learned a lot about how to try to protect from lightning, which wasn’t "if" but rather "how often." We had a ground system with 120 #8 radials and maybe a ton of copper strap all silver-soldered together. I’m never going to have that kind of ground on my sailboat, and a small plate in the water isn’t equivalent. Maybe doing "something" is better than doing nothing, but I don’t have any real proof yet. That’s why I keep paying for my insurance.
Bycrick is offline   Reply With Quote
Old 27-04-2021, 16:16   #26
Registered User

Join Date: Nov 2018
Posts: 703
Re: So my boat lacks a lightning ground.

Supposedly, the lightning dissipates off the edge of the "plate." That would imply that a long, narrow strip would work better than a square plate. One theory also said to round off the corners to reduce the voltage gradients at the corners. I have no proof of any of this.

The famous lightning stuff supplier has said that air-terminals above the waterline dissipate better than submerged plates. His system appears to have a lot of engineering behind it, but I’d have to tear the whole boat apart to install it.
Bycrick is offline   Reply With Quote
Old 27-04-2021, 16:33   #27
Registered User

Join Date: Apr 2021
Location: Perth WA
Posts: 37
Re: So my boat lacks a lightning ground.

Quote:
Originally Posted by Bycrick View Post
I don’t think the small wire size would matter. If the lightning "decides" to go down the tiny transducer wires, they’d immediately vaporize. But that vapor could easily provide a plasma path for the arc to continue. But I’ve never actually seen a boat that was sunk by lightning. I’ve worked on my own boat twice and helped six other people fix lightning victims. Not a big survey. Sometimes lots of electrical damage, even to batteries and engine components. But never any real physical damage to components of the boat itself. YMMV.
I gather that Bob and Sheila Wise's Loose Moose 2 (Bolger AS38) was lost to a lightning strike, although I don't know the details of exactly how. I've always assumed a fire rather than direct physical damage.
PatB is offline   Reply With Quote
Old 27-04-2021, 16:38   #28
Registered User

Join Date: Jan 2014
Location: Panama City FL
Boat: Island Packet 32 Keel/CB
Posts: 780
Re: So my boat lacks a lightning ground.

The voltage gradient producing the lightning discharge is between the cloud and surface (ocean or earth). I suspect that is Dr Thompson thinking with his electrodes just above the waterline. 3 or 4 ft down might not be optimum but just one of them practical tradeoffs. If you are installing while the craft is under construction more options available.


I am comfortable enough with my setup that I live in Florida uninsured (boats and house). Yes my house also has a lightning mitigation system installed. YMMV.


Frankly
Frankly is online now   Reply With Quote
Old 27-04-2021, 16:47   #29
Registered User

Join Date: Jun 2016
Location: Jensen Beach, Fl
Boat: O'Day 34
Posts: 311
Re: So my boat lacks a lightning ground.

Things boat was struck by lightning <50’ away from a boat I was working on at the base of the mast.
Attached Thumbnails
Click image for larger version

Name:	8A7A78F1-32B4-4417-BA66-061BDF69E207.jpg
Views:	62
Size:	430.4 KB
ID:	237409  
Quadrille in JB is offline   Reply With Quote
Old 27-04-2021, 16:48   #30
Registered User

Join Date: Jun 2012
Location: Port Aransas, Texas
Boat: 2019 Seawind 1160 Lite
Posts: 1,881
Re: So my boat lacks a lightning ground.

Quote:
Originally Posted by OS2Dude View Post
That said, our boat has no lightening mitigation in place. When we first got our boat, I researched lightening protection quite a bit. Half said it will attract lightening, half said (as above) that it can only mitigate the effects and the last half swore by the latest fad.
Same here. But my understanding is grounding increases the chance of being hit by lightening, but system would reduce damage in case of a strike.
sailjumanji is offline   Reply With Quote
Reply

Tags
boat, lightning

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Activecaptain on Android Cell lacks much detail Capn Jimbo Marine Electronics 0 25-08-2018 17:10
Prospective boat lacks a few systems jimp1234 Monohull Sailboats 28 08-01-2017 08:53
Mounting Lightning Ground Strip? Beausoleil Electrical: Batteries, Generators & Solar 2 28-09-2012 12:21
DIY Copper Lightning Ground Plate - How Thick ? sv.Crake Construction, Maintenance & Refit 4 13-07-2011 14:46
No Keel Bolts - How to Ground for Lightning ? sabray Construction, Maintenance & Refit 19 25-08-2010 11:12

Advertise Here


All times are GMT -7. The time now is 18:48.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.