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outbound 01-19-2013 09:45 AM

lightning advice
 
Building boat. Although it has a high aspect,bulbed fin keel the keel is fully encapsulated in glass. Going to spent summers in New England ( low strike area) and USVI area winters (high strike area). Don't care about electronics so much ( insurance, boat already set up to ABYC rules to decrease side flashes) but do care about sinking. So far interested in Ewan's system form Marine Lightning but too many holes in the boat, major expense, and some fittings are marelon which I don't trust. Other is a grounding plate from Ward's in Florida. Everything solid bronze. Both give the "adequate" area by ABYC but Ewan's has more "edge" being a long (12') strip. Builder is putting heavy wire from shrouds/chainplates and mast to central point during construction.
? Any body have experince with either system or suggestion for another vendor.
? Has anybody had issues with electrolysis. Tying aluminum ( mast), stainless ( riggging )and bronze/copper ( grounding) together. Told can't zinc system as grounding plate/ strip must be left bare or will foul if zinc'd system.
?anybody use a knife switch or other device to leave grounding plate disconnected except when in "at risk" situation.
Any help or thoughts greatly appreciated.
thanks

BELLATRIX1965 01-19-2013 10:42 AM

Re: lightning advice
 
Some fellow sailors in our harbor have tied the rig together with heavy gauge ground wires, then permanently fastened them to a heavy wire (1/0 or more) that has at least a foot of insulation stripped on the bottom end, and hung that wire over the stern into the drink. Probably not ABYC certified, but seems logical and practical (OK - cheap!). Regarding your systems - I doubt very much that there should be ANY "knife switch" in the circuit - a lightning strike will fry just about any switch, then you have nothing. Curious to see what others come up with. . . . ?

kd3pc 01-19-2013 11:39 AM

Re: lightning advice
 
you may want to do some further research, there is a lot here and other sites. Some is rubbish (ie wrapping a chain around the mast and dropping the other end overboard) and some has merit, although lightning AKA mother nature will show you those shortcomings. Some of the radio communication and tower manufacturer sites will provide some more realistic mitigation thoughts.

Unless you are having the builder take the absolute shortest path from the mast and plates, via at least a 1/0 copper cable, to the keel with NO mechanical connections....lightning will find the shortest path, or jump to ground.

The idea of "attaching" (anything mechanical) the stuff to a cable and dropping the end in the water is absurd if you think lightning will follow the path YOU deem. Not going to happen. Even cadwelds and welded connections will blow apart when a strike occurs.

Your best bet is to avoid the strike, good insurance and luck. You are creating a boat that will have zinc/bonding/ground issues. Stick with ABYC.

As to electolysis, even a poorly designed ground plate or improperly installed and grounded can cause issues tough to find. Read up on ground loops, potential to ground, measuring leakage, etc.

YMMV

Vasco 01-19-2013 12:27 PM

Re: lightning advice
 
Agree 100% with kd3pc. After a direct strike while sailing I spent a lot of time researching the subject. I have come to the conclusion the only thing one can do is avoid electrical storms completely (impractical) or prayer (should have thought of this one before being hit). Fifteen years after the strike I am still extremely scared of lightning although, funnily enough, I gave it very little thought before being struck. As for hanging stuff over the side, that's ludicrous.

chef2sail 01-19-2013 01:41 PM

Re: lightning advice
 
Quote:

Originally Posted by Vasco (Post 978031)
Agree 100% with kd3pc. After a direct strike while sailing I spent a lot of time researching the subject. I have come to the conclusion the only thing one can do is avoid electrical storms completely (impractical) or prayer (should have thought of this one before being hit). Fifteen years after the strike I am still extremely scared of lightning although, funnily enough, I gave it very little thought before being struck. As for hanging stuff over the side, that's ludicrous.

Any thoughts of directing 2 million volts is really ludicrous. It will find its shortest way out when it finds it way in wether a direct hoit, or a side swipe. The best thing to do is ro rey and give it some easy pathways like a plate on the humm directly wired with 1 gauges wire, but the truth be told as ataed above is to keep the thru hulls safe, have good insurance, and try to mitigate as much as possible the area you are in when the storm occurs.

We were side struck this sumer in Back Creek on a morring Annapolis surrounded by over 900 masts, By no means were we the tallest or isolated.
In our strike the lightening was traced to have it the water tower on the land 200 yards from us, comethrough the water, up the prop shaft and dyna plate and entered the electrical panel through the ground to the engine. It fused the engine panel ( engine was not affected), blew up most of the elctroinics ( even though many were off and disconnected), was very discriminating ( took out the white LED while leavung the eds alone on the same fixtures), left the radar and radar pole on the stern unscathed whhile getting the chartplotter. It exited the boat up the mast and jumped masts to the boat morred next to as as wa seen by the person on that boat. Yes we had a diffuser on top of the mast which ws blown off along with the windex.

preventable.....impossible...cone of protection...in your dreams...following prrescribed path....had its own mind and direction.

Dave

outbound 01-19-2013 02:51 PM

Re: lightning advice
 
from what research I've done seems diffusers are not likely to be effective. ?still wondering if anybody has placed either the Ward ground plate or the Marine Lightning system on their boat and at their experience was with it.

noelex77 01-19-2013 04:02 PM

Re: lightning advice
 
Grounding systems do help minimise the damage from a lightning strike. They are especially effective in reducing in catastrophic damage that sinks boats.
There is no risk of electrolysis problems despite the dissimilar metals. The metals are not immersed in an electrolyte. The only exception is a localised reaction around the aluminium / copper connection is if gets wet. So try and keep it dry.

Breaking the connection to the underwater plate will not make any difference to the risk of corrosion, but will reduce, or disable the lightning protection, so this is a bad idea.

Frogwatch 01-19-2013 05:00 PM

Re: lightning advice
 
Having routinely worked with multi-million volt potentials, I disagree with some advice given here. One can minimize the probability of the strike going thru certain paths by offering a much better path and eliminating paths that you do not desire.
Most effective would be a very good lightning ground.

Frogwatch 01-19-2013 05:02 PM

Re: lightning advice
 
For long term use, I'd use silver epoxy to seal the connection to the mast against corrosion.

chef2sail 01-19-2013 06:27 PM

Re: lightning advice
 
Quote:

Originally Posted by noelex77 (Post 978113)
Grounding systems do help minimise the damage from a lightning strike. They are especially effective in reducing in catastrophic damage that sinks boats.
There is no risk of electrolysis problems despite the dissimilar metals. The metals are not immersed in an electrolyte. The only exception is a localised reaction around the aluminium / copper connection is if gets wet. So try and keep it dry.

Breaking the connection to the underwater plate will not make any difference to the risk of corrosion, but will reduce, or disable the lightning protection, so this is a bad idea.

Can you give me some actual data. Tests? not just hypothesis or ligic, actual real workd tests?


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