12v EMP

nfg2u

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Feb 13, 2016
92
Hunter Legend 35.5 Fort Pierce
I was chatting with a powerboat owner the other day after a big T-storm that knocked power out at the marina for about 12 hours....he laughed about not being worried about his boat being struck by lightening....he has a Hunter 33 on one side, and a Hunter 40 on the other! He figures he is in a safe spot.

Greg
My boat dock neighbor is a 24 PowerCat power boat. My first lighting strike took out all my electronics, fridge, cleaned everything off the top of my mast and left my nav panel LEDs on the floor. It also took most all of his electronics. He lost his both his engine ECUs and some of his Garmin units. Both of us were down for months.
 
Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
Capta: Excellent point about dock ground limitation. That's why I have tried to get these Skippers to understand that the water is your best ground. As for the guy worried about chain not connected enough: it does not have to be as its mass located link by link is the best current path a sailor can provide. It is also why I wrap the chain to the mast and not shrouds as they are too small. Max current carry is what you want and chain link to link passage won't affect its flow with thousands of volts as its impetus. If lightning can blast great distances through air to your mast why the hell do these guys think it will have problems passing through the links of chain! Shunting to ground before lightning enters your interior is also a desired consideration and this method provides that. The size of the anchor is also not a primary as it is submerged. Once the current reaches the water it has the grounding mass it needs. Chief, EE
 

DArcy

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Feb 11, 2017
1,690
Islander Freeport 36 Ottawa
My concern with chain would be that given its shape the amount of cross sectional area you're actually providing to carry the current is very small. The contact surface between chain and mast, or between individual links is not nearly enough to carry the tens of thousands of amps of a strike.
You could separate the links of the chain by an 1/8" and it would still be effective. Radomes often use segmented lightning diverters to re-direct lightning strikes away from the antennas under them. These segmented diverters are small metal dots separated by 1/8 to 1/4 inch but they effectively conduct lightning strikes.

I'm not familiar with any add on 12V EMP devices. It seems that unless you had one of these on each device you are trying to protect it wouldn't be very effective since you can get some pretty big induced voltages across wire bundles. Direct lightning strikes would likely fry it (which may protect your equipment if installed between the strike and the equipment) but indirect effects are much broader and harder to defend against at the system level; the individual equipment needs to have protection. It's unfortunate that marine electronics don't have the same requirements as avionics equipment. We design equipment for up to 1600 V on interconnect wiring to protect against indirect lightning effects.
 
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Likes: Chief RA

walt

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Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
Just my opinion and this is more of a trailer sailor thing where you pretty much always have an ungrounded mast. . A length of 4 gauge wire makes a much better conductor compared to chain and is probably lighter to carry on the boat. Wrap the wire around the mast to form a spark gap, drape the wire so that it goes near the side stays (to also form a spark gap). The ends of the wire only need to get near the water surface. Some sort of underwater ground plate only works in salt water anyhow but the end of the wire near the water surface has some chance of re-sparking and dissipating the charge on the water surface in fresh or salt water. Even if the wire were to extend below the water surface, it would like still re-spark and jump to the water surface.

The 12 volt transorb voltage clamps have to go on every wire that comes into an electronic box you are trying to protect. The OP found some device that works on the communication lines and these will be the most sensitive. But every wire can pick up the magnetic field from the lightning strike - even if the lighting strike did not hit your boat.

This is all about dealing with a strike. Trying to avoid a strike.. good luck might be your best bet.
 
Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
Walt: 4 gauge wire isn't even close to how large a wire must be to be more effective than anchor chain! This is right back to the assumption a ground system at the dock would work. Read Capta's post again. Chief