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10-11-2020, 23:24
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#16
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Registered User
Join Date: Mar 2005
Location: Beijing
Posts: 718
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Re: Lightning Protection for Electronics
Would be so easy on a keel stepped monohull. On a seawind for example the mast is stepped on a FRP bulkhead very close to the Gas/Petrol locker.
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11-11-2020, 00:29
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#17
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Registered User
Join Date: Dec 2019
Posts: 169
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Re: Lightning Protection for Electronics
Put everything electric in the oven it acts as a Faraday cage.
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11-11-2020, 05:16
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#18
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,087
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Re: Lightning Protection for Electronics
I cannot think of anyone’s more qualified to advise you (on this), than Dr. Ewen Thomson.
Has he offered any specific advice (details) on Surge Suppression Devices?
FWIW: Thomson’s ‘Lightning & Sailboats’ was published in 1990. He, and the science & technology have advanced “a little”, since then.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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11-11-2020, 05:36
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#19
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Registered User
Join Date: Nov 2018
Location: Panama
Boat: Norseman 447
Posts: 1,625
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Re: Lightning Protection for Electronics
For those who blithely equate "oven" with Faraday cage, you might want to actually look at your oven. Mine has a silicone gasket around the opening. Thus the door isn’t really electrically connected to the body of the stove. Perhaps coincidentally through the hinge mechanism, but certainly not well enough to be an effective Faraday cage.
Even with microwave ovens, the door joint is designed to block/conduct the specific frequency used by the oven. It may or may not be effective at other frequencies.
Attempting to remedy this by grounding the door with straps or wires won’t work either. The gaps around the door are perfectly capable of passing RF energy of the right frequency. Google "choke joint" to see why.
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11-11-2020, 08:00
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#20
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Registered User
Join Date: Jan 2014
Posts: 1,829
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Re: Lightning Protection for Electronics
Quote:
Originally Posted by Bycrick
For those who blithely equate "oven" with Faraday cage, you might want to actually look at your oven. Mine has a silicone gasket around the opening. Thus the door isn’t really electrically connected to the body of the stove. Perhaps coincidentally through the hinge mechanism, but certainly not well enough to be an effective Faraday cage.
Even with microwave ovens, the door joint is designed to block/conduct the specific frequency used by the oven. It may or may not be effective at other frequencies. ...
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Exactly.
I read a book written by a EE PhD that was talking about EMP. ANY gaps in the container can let in EMP. Even the gaps in the wire mesh built into the microwave can let in EMP. It just depends. Sometimes the microwave will work but there will be times when it won't.
Even a metal ammo can has problems because they have a gasket and said gasket can let in EMP.
What does work is plain old aluminum foil. Wrap devices that need to be protected in a couple of layers of aluminum foil and they are good to go. Or put them in a box and wrap the box.
The book had a photo of a closet that was totally wrapped and sealed with aluminum foil, including the door and gaps. That may be taking things a bit too far. Well, that is what the wife said.
The building I normally work in has lightning rods all over the roofs. Some of the building used to have very expensive manufacturing equipment that could not go down. There are dozens of locomotive sized generators, direct connections to the high voltage transmissions lines, and UPS systems for buildings. I don't know if we have ever been hit by lightning, but I have heard some very big booms, and we have never had damage.
Later,
Dan
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11-11-2020, 08:23
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#21
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Moderator
Join Date: Jan 2010
Location: Minnesota
Boat: Tartan 3800
Posts: 4,759
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Re: Lightning Protection for Electronics
Quote:
Originally Posted by stull61
To complete our design, we need to find some well-designed marine 12V Surge Protection Devices that are rated for lightning. I’m interested to see what other owners have actually installed on their yachts and their experience with fitting these SPDs.
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Polyphaser are the best. I don't have lightning protection on my boat but use the polyphasers on antenna connections coming into my house. They are widely used in the cellular and LMR industries.
They have a variety of products for DC power, also, same underlying technology.
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11-11-2020, 10:16
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#22
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Registered User
Join Date: Oct 2007
Posts: 387
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Re: Lightning Protection for Electronics
I was delivering a friends 45ft. catamaran from Nassau to New York and we were struck twice, different days, during that passage.
It had a lightning dissipator at the top of the mast, with the shrouds on both sides grounded to underwater plates.
The strikes destroyed all electonics, breaker panels, inverter, refrigeration, all LED lights, bilge pumps, etc. The engine that the electrical system was grounded to was incapacitated, though later repaired.
When I got home to my own 38ft. catamaran I installed a dedicated underwater grounding plate connected to the mast with dedicated cable, the shrouds were already connected to an underwater grounding plate with a Forespar Lightning Master at the top of the mast. The lightning wants a path to earth and the large aluminium mast is obviously a much better conductor than SS shrouds.
I still cringe every time I am near lightning.
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11-11-2020, 10:21
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#23
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Registered User
Join Date: Jan 2005
Location: On board
Boat: Van de Stadt 50'
Posts: 1,405
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Re: Lightning Protection for Electronics
Consider an Antenna Patch Bay for every antenna, with jumper connectors.
Consider double pole circuit breakers on all electronics
Consider a big microwave oven as a faraday cage.
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11-11-2020, 11:42
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#24
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Registered User
Join Date: May 2008
Location: daytona beach florida
Boat: csy 37
Posts: 2,976
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Re: Lightning Protection for Electronics
we were hit by lightning. struck the masthead antenna (it disappeared) came down the mast (i watched it from the cockpit) and went through the boat and out god knows where.
first thing i checked were the bronze thruhulls - all seven of them. i'm not bonded. they were all fine. after making sure we were not taking on water anywhere i checked for other damage.
lost some interior and navigation lights, but not all. seemed to be random. all my electrics that were directly wired to the battery bank (not through the breaker panel) were undamaged. they included the cpt autopilot, the adler barbour fridge, and the 600w inverter. they all had appropriate sized fuses on the positive side, none of whcih were blown.
then to the electronics. i dpn't have a lot of hard wired electronics - vhf, depth, and navtex. all went through the breaker panel and all had additional fuses on the positive wire. none of the three were working. i checked the fuses on the vhf and depth and neither of them were blown.
then i checked the navtex. and had what i consider a 'eureka' experience. it also had a fuse on the positive side that was not blown; AND it had a fuse on the negative side, that was blown! i replaced that fuse and up it ccame!
i did not wire in that negative side fuse - it came that way from furuno.
so my advice is, obvioiusly, fuse both sides of anything you want to protect. cheap and easy. and indicative to me that the lightning strike came in from the ground side.
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11-11-2020, 13:58
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#25
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Registered User
Join Date: Jun 2016
Location: Brisbane Australia
Boat: Schionning Waterline 1480
Posts: 1,987
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Re: Lightning Protection for Electronics
If you ground your mast to the water aren't you increasing the likelihood of being hit with an unquantifiable possible decrease damage ?
__________________
Regards
Dave
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11-11-2020, 14:07
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#26
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Registered User
Join Date: Feb 2006
Posts: 2,767
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Re: Lightning Protection for Electronics
Quote:
Originally Posted by stull61
I am currently looking at protecting my new FP Saba 50 Catamaran from lightning as much as I practically can. I have Ewen Thompson PhD ( Marine Lightning Protection Inc.), an expert on Marine Lightning, designing a protective rib cage around the sensitive interior of the boat. We want to augment this with some Surge Protective Devices (SPDs) to further protect the sensitive electronics on board from the effects of a lightning strike.
My reasons for undertaking this project is:
• Lightning can kill you and sink the boat, two things that would ruin my day.
• I can count up 10 friends that have been hit by lightning and have incurred significant delays (some lost a whole year of cruising), whilst they put their boat back together.
• I’ve had several close calls in the Med, Atlantic Portugal and the Caribbean. It a truly frightening experience to be surrounded by lightning. I particularly don’t like scaring the Admiral.
• Insurance companies are increasingly looking to up their lightning excesses, as the world experiences increased lightning (the journal Science reported that we could expect to see a 12% increase in lightning activity for every 1 degree of warming). Pantaenius have already indicated that their lightning excess is 30%, unless an endorsed lightning protection system is installed. I can see other insurance companies following suit.
To complete our design, we need to find some well-designed marine 12V Surge Protection Devices that are rated for lightning. I’m interested to see what other owners have actually installed on their yachts and their experience with fitting these SPDs.
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Just what is an "endorsed" lightning protection system????? Tell us.
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11-11-2020, 14:15
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#27
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Registered User
Join Date: Jun 2013
Location: Up Qld Coast, near Yeppoon.
Boat: Passport 41, Custom Perry in steel.
Posts: 624
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Re: Lightning Protection for Electronics
Re SV Gilana, Double pole switch would be nice but hard to do in a existing install.
However I am of the opinion that disconnecting mast electronics by pulling nmea plug, also the power injector. Having a 7 pin trailer plug would be good for other Mast lighting. Having ability to disconnect other Large negative conductors may also be useful but unsure if this should then be fitted to earth plate/hull.
These lightening protection thingohs, do they divert lightening power to earth plate? On positive conductor do they open the circuit, then connect to earth plate?.
I believe big air gaps is way to go, but I was shocked to find that my mast is insulated from hull (Well 50 ohms), maybe insulated mat on deck step and SK75 Dyneema shrouds.
Would like a picture please of any devise that would be useful for antennae disconnect.
__________________
Oceanrider.
"The floggings will continue until morale improves"
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11-11-2020, 14:40
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#28
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Registered User
Join Date: Jan 2014
Location: Panama City FL
Boat: Island Packet 32 Keel/CB
Posts: 995
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Re: Lightning Protection for Electronics
Quote:
Originally Posted by Oceanride007
Would like to see a picture... be useful for antennae disconnect.
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https://www.cruisersforum.com/forums...cture32360.jpg
VHF antenna coax in the middle (disconnected and grounded in this position), shunted with a gas discharge tube in operating position (two VHF radios), less than $100 US. Radio inputs grounded in off position. Using them for years. No direct strikes but close enough to throw you out of the bed.
Frankly
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11-11-2020, 15:25
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#29
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Registered User
Join Date: Jun 2013
Location: Up Qld Coast, near Yeppoon.
Boat: Passport 41, Custom Perry in steel.
Posts: 624
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Re: Lightning Protection for Electronics
^^^^ Thanks
__________________
Oceanrider.
"The floggings will continue until morale improves"
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11-11-2020, 15:46
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#30
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Registered User
Join Date: Nov 2018
Location: Panama
Boat: Norseman 447
Posts: 1,625
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Re: Lightning Protection for Electronics
There were several studies leading to a conclusion that even a perfect Faraday cage would not keep all energy out. The hypothesis was that currents flowing on the outside of the cage could induce current flow on the inside, thus .....
You’re also supposed to have good, low resistance connections on the surface of the cage. I’ll bet wrapping something in foil leaves a little to be desired.
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