Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 25-07-2016, 06:03   #1
Registered User
 
Davidhoy's Avatar

Join Date: Jul 2016
Location: Fort Lauderdale
Boat: Morgan 462
Posts: 537
Chart table faraday cage?

My recent lightning strike has gotten me thinking about future protection of portable electronics like EPIRBs, handheld GPS/VHFs, laptops, etc. I've seen threads discussing putting these items inside your oven, but this seems like something you can do if a thunderstorm is imminent and you're on the boat, but what if you're not there. So what to do to protect your gear in a convenient way, even when you're not onboard?

I like to keep stuff like this either in the chart table or in drawers/storage nearby. So how about lining the inside of some of these spaces with fine copper mesh to form a faraday cage inside which your equipment will be better protected? Is it feasible to have a reasonably good faraday cage with material like this? Would it need to be grounded to the boat's bonding system? Would copper mesh be the best material for this?

The PO of my boat had removed the nav station to add more storage and counter space across from the galley - might be OK for coastal cruising, but a blue water boat needs a nav station so I intend to rip out what he did and build a new chart table, etc in its place. As I design and build this it would be great to include lightning protection. Of course nothing can fully protect your equipment from lightning, but does this idea have any merit at all?

Regards,
David
__________________

__________________
Davidhoy is offline   Reply With Quote
Old 25-07-2016, 06:14   #2
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 3,788
Re: Chart table faraday cage?

Which handheld items were damaged during your lightning strike? What were they doing when damaged?

A Faraday cage is just an enclosure of metal. It does not have to be grounded to anything to perform its function. But it has to be fully closed on all sides. If it has an opening then the opening has to have some kind of good low resistance metal/metal seal when closed.
__________________

__________________
transmitterdan is offline   Reply With Quote
Old 25-07-2016, 06:22   #3
Registered User
 
Davidhoy's Avatar

Join Date: Jul 2016
Location: Fort Lauderdale
Boat: Morgan 462
Posts: 537
Re: Chart table faraday cage?

Quote:
Originally Posted by transmitterdan View Post
Which handheld items were damaged during your lightning strike? What were they doing when damaged?

A Faraday cage is just an enclosure of metal. It does not have to be grounded to anything to perform its function. But it has to be fully closed on all sides. If it has an opening then the opening has to have some kind of good low resistance metal/metal seal when closed.
Actually I had no handheld equipment onboard during the strike, as I'd literally just bought the boat. A lot of the built-in electronics and other electrics are damaged, and I just got off the phone with the insurance company to start the claims process. I was more thinking proactively about *future* protection, and building that in to the new nav station I'm going to install in the next year or two.
__________________
Davidhoy is offline   Reply With Quote
Old 25-07-2016, 06:32   #4
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 3,788
Re: Chart table faraday cage?

I have never actually talked to anyone experiencing failure of handheld equipment due to a lightning strike. So I was curious that you might be the first.

One obvious answer is to get a metal box with a lid that fastens with screws (no hinges). Thin steel is a good choice of material. The screws should be about 4 inches (10 cm) apart. When leaving the boat put all the handheld stuff in the box and put the screws in the lid.

A fancier box can be made if the lid seals with electrical contact strips sometimes called finger stock. This eliminates the need for lots of screws.

In my experience failure of powered off handheld equipment due to lightning is mostly the stuff of Internet legends.
__________________
transmitterdan is offline   Reply With Quote
Old 25-07-2016, 06:38   #5
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: nondum cognita
Boat: sunk by irma
Posts: 3,419
Re: Chart table faraday cage?

Microwave ovens will work. A regular oven will not because the window and the gap at the door. Try non conductive grounding or anti static bags like what delicate computer parts are shipped in.

They are made from a metalized plastic and have a zip lock closure and are made specifically to protect electronics. I found ones on eBay that I can fit my laptop in.
__________________
Delancey is offline   Reply With Quote
Old 25-07-2016, 06:50   #6
Senior Cruiser
 
mikereed100's Avatar

Cruisers Forum Supporter

Join Date: Dec 2005
Location: Santa Barbara
Boat: 46' custom cat
Posts: 1,529
Images: 2
Re: Chart table faraday cage?

We keep our satphone in an old cookie tin at the nav station. The portable GPS and handheld VHF have their own tin. We also have a large ammo box where the laptops, instrument displays, tablets, phones etc. go when there is lightning about. When we left our boat in Borneo for a few months we removed all electronics, including the radome, and stored them ashore.
__________________
Mike

www.sailblogs.com/member/rumdoxy

Come to the dark side. We have cookies.
mikereed100 is offline   Reply With Quote
Old 25-07-2016, 06:50   #7
Registered User
 
Davidhoy's Avatar

Join Date: Jul 2016
Location: Fort Lauderdale
Boat: Morgan 462
Posts: 537
Re: Chart table faraday cage?

Quote:
Originally Posted by Delancey View Post
Microwave ovens will work. A regular oven will not because the window and the gap at the door. Try non conductive grounding or anti static bags like what delicate computer parts are shipped in.

They are made from a metalized plastic and have a zip lock closure and are made specifically to protect electronics. I found ones on eBay that I can fit my laptop in.
Trying to avoid things like ovens and microwaves, and build the protection in to the nav station itself, if possible. The anti-static bags are a good idea in addition to the faraday cage as they would provide extra electrical protection, and also protection against moisture with the aid of some silica gel packets.
__________________
Davidhoy is offline   Reply With Quote
Old 25-07-2016, 08:41   #8
Registered User
 
redhead's Avatar

Join Date: Mar 2011
Location: PNW 48.59'45N 122.45'50W
Boat: Ian Ross design ketch 63'
Posts: 731
Images: 5
Re: Chart table faraday cage?

Quote:
Originally Posted by Delancey View Post
Microwave ovens will work. A regular oven will not because the window and the gap at the door. Try non conductive grounding or anti static bags like what delicate computer parts are shipped in.

They are made from a metalized plastic and have a zip lock closure and are made specifically to protect electronics. I found ones on eBay that I can fit my laptop in.
When I read this I questioned our plan to use our Dickinson diesel stove as a cage. It has no window and the oven handle actually locks down forming a seal. Does that meet the requirement as you know them? Hoping not to rethink this. Sorry for kidnapping the thread.
__________________
redhead is offline   Reply With Quote
Old 25-07-2016, 08:53   #9
Registered User

Join Date: Feb 2016
Posts: 10
Re: Chart table faraday cage?

The likelihood of a hand-held item being affected by a lightening strike is slim to none unless it is in your hand and being used at the time of the strike. The lightening will typically strike the highest point of the boat and the current travels down cables, wires, rigging etcetera to reach the ground provided by the water you are floating on. This applies an enormous voltage to the conductors, and anything attached to the conductors therefore is at risk of being damaged because radios, plotters et. al, are all connected to the ground circuit in the boat. That's why your electronics get fried.

It's also why so often lightening strike on a sailboat punches a hole in the hull as the current goes down the rigging and flashes down the wet hull to the ocean.

So if something isn't connected to the boat wiring, which hand-held gear typically isn't, then the likelihood of damage is virtually nonexistent. This is the same as you being safer inside the boat during a lightening event than on the deck!
__________________
rodgoult is offline   Reply With Quote
Old 25-07-2016, 09:48   #10
Senior Cruiser
 
FSMike's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Bahamas/Florida
Boat: Solaris Sunstar 36' catamaran
Posts: 2,654
Images: 5
Re: Chart table faraday cage?

Quote:
Originally Posted by rodgoult View Post
-----
So if something isn't connected to the boat wiring, which hand-held gear typically isn't, then the likelihood of damage is virtually nonexistent. This is the same as you being safer inside the boat during a lightening event than on the deck!
Then there's the idea that lightning is basically unpredictable. A friend was standing in his galley near the companionway when his boat was struck by lightning. The lightning jumped from his vhf to his shoulder, then exited from his ankle to the foot pump lever. He wasn't touching anything at the time, with the exception of his feet on the cabin sole.

He was fine, except for two fifty cent sized patches of burned skin.
Lightning is strange stuff.
__________________
Sail Fast Live Slow
FSMike is offline   Reply With Quote
Old 25-07-2016, 10:00   #11
cruiser

Join Date: May 2010
Location: SF Bay Area; Former Annapolis and MA Liveaboard.
Boat: Looking and saving for my next...mid-atlantic coast
Posts: 6,197
Re: Chart table faraday cage?

https://weather.com/health/news/catc...rikes-20140114
__________________
SaltyMonkey is offline   Reply With Quote
Old 25-07-2016, 11:11   #12
Registered User
 
buzzstar's Avatar

Join Date: Apr 2012
Posts: 1,215
Re: Chart table faraday cage?

Now I am somewhat more confused than usual, or at least uncertain: Will a Faraday Cage protect a wired device located inside the cage? I'd always thought a Faraday Cage was effective against loose electrical charges (EMP, lighting, etc. looking for a route) but not that which was carried by wire into the Faraday Cage. Can someone with both actual and theoretical knowledge please answer, rather than those folks like me speculating based upon experience, intuition, and /or partial information.
__________________
Brian, sometimes called "Old California"
Still learning after all these years
buzzstar is offline   Reply With Quote
Old 25-07-2016, 11:11   #13
Registered User

Join Date: Jan 2010
Location: St Michaels, MD
Boat: Cal 46-3, 46' ketch
Posts: 184
Re: Chart table faraday cage?

Just the science of it suggests you'll need to surround your protectables with a solid or mess conductive surround... and all those surfaces need to be soldered or bonded together. In practice I suppose just the top cover could be hinged at the back to allow easier in/ out access of your electronics. If it's not easy you'll not use it! If you hinge it just make sure there is a flexible wire grounding the lid to the 'box' so your not relying on an iffy metal hinge for grounding/ bonding. I have a bigger sailboat/ more bigger stuff than would fit in a drawer... done mounted to bulkhead. My 'what if' plan is that I have small handheld radios, GPS,... in a 'bread box' just in case. In 40 yrs of sailing in Chesapeake Bay and Caribbean... both with their fair share of lightning, never had a strike.


Sent from my iPhone using Cruisers Sailing Forum
__________________
W3GAC is offline   Reply With Quote
Old 25-07-2016, 11:21   #14
Registered User

Join Date: Feb 2011
Posts: 2,105
Re: Chart table faraday cage?

Quote:
Originally Posted by rodgoult View Post
The likelihood of a hand-held item being affected by a lightening strike is slim to none unless it is in your hand and being used at the time of the strike. The lightening will typically strike the highest point of the boat and the current travels down cables, wires, rigging etcetera to reach the ground provided by the water you are floating on. This applies an enormous voltage to the conductors, and anything attached to the conductors therefore is at risk of being damaged because radios, plotters et. al, are all connected to the ground circuit in the boat. That's why your electronics get fried.

It's also why so often lightening strike on a sailboat punches a hole in the hull as the current goes down the rigging and flashes down the wet hull to the ocean.

So if something isn't connected to the boat wiring, which hand-held gear typically isn't, then the likelihood of damage is virtually nonexistent. This is the same as you being safer inside the boat during a lightening event than on the deck!
You might want to update your ideas. Grounded or not grounded, a lightening strike can destroy anything in the boat. The "cone" of protection is more myth than reality. Grounding does allow lightening a quick path to earth, but its no guarantee. But better that option than having it blast through the hull. Whether an appliance is grounded or not has little bearing on the massive electrical disturbance caused by lightening once inside a boat. Even our epirb, sealed in a plastic tube, got fried.
__________________
reed1v is offline   Reply With Quote
Old 25-07-2016, 11:22   #15
Moderator
 
Adelie's Avatar

Join Date: Feb 2010
Location: La Ciudad de la Misión Didacus de Alcalá en Alta California, Virreinato de Nueva España
Boat: Cal 20
Posts: 4,237
Re: Chart table faraday cage?

Quote:
Originally Posted by rodgoult View Post
The likelihood of a hand-held item being affected by a lightening strike is slim to none unless it is in your hand and being used at the time of the strike. The lightening will typically strike the highest point of the boat and the current travels down cables, wires, rigging etcetera to reach the ground provided by the water you are floating on. This applies an enormous voltage to the conductors, and anything attached to the conductors therefore is at risk of being damaged because radios, plotters et. al, are all connected to the ground circuit in the boat. That's why your electronics get fried.

It's also why so often lightening strike on a sailboat punches a hole in the hull as the current goes down the rigging and flashes down the wet hull to the ocean.

So if something isn't connected to the boat wiring, which hand-held gear typically isn't, then the likelihood of damage is virtually nonexistent. This is the same as you being safer inside the boat during a lightening event than on the deck!
Wrong.

The magnetic fields from a lightning strike are so high and ramp up so quickly they can induce currents in in the wiring of items not attached to the electrical system of the boat in anyway.

Not being attached improves the items' odds and probably decreases the severity of the damage but in no way garuntees protection.



A house is but a boat so poorly built and so firmly run aground you would never try to refloat it.
__________________

__________________
A house is but a boat so poorly built and so firmly run aground no one would think to try and refloat it.
SailboatData
Adelie is online now   Reply With Quote
Reply

Thread Tools
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
Faraday cage for hand held GPS DoubleWhisky Marine Electronics 46 18-07-2015 08:28
'granny' cage for a mast radar D&D Marine Electronics 16 25-05-2013 15:33
Faraday Cage belizesailor Electrical: Batteries, Generators & Solar 22 29-07-2012 10:26
Building an Effective Faraday Cage to Protect Against Lightning Strikes teneicm Marine Electronics 58 25-01-2012 18:50
Faraday Cage Principle - Do Steel / Aluminium Hulls Qualify ? Jaden44 Electrical: Batteries, Generators & Solar 26 16-10-2010 01:38


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 22:50.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.