Lightning Protection

[shaula]

I have an old Westerly with copper braid earth straps from the chainplates to one of the keel bolts. The braid is falling apart and so I am considering replacing like for like but I am aware there is much discussion on what is a suitable method of lightning protection. The copper braids pass through foam lining material and wooden bunk bases on their way to the keel so I would think this creates a fire risk. Is my current means of earthing still considered suitable, what is the minimum cross sectional area of any replacement tapes? Any future replacement needs to be a moderate cost or I am inclined to disconnect whats there and hope for the best. What lightning protection is given to your average new production yacht these days?

 

[AntarcticPilot]

None!

 

[Graham376]

According to a physics prof friend, bonding is more likely to attract a strike but may cause less damage in the unlikely event you have one. Unbonded, we've had lightening strikes within maybe 75 metres of the boat, to land and water but no boats on moorings were struck.

 

[William_H]

The need for lightning protection is of course a matter of personal concern and prevalence of lightning in your area. ie parts of USA seem to be very prone while here in west Oz it is seldom seen. However IMHO it is a bad idea to earth the chain plates. This would conduct current from the mast top to the water though quite significant resistance of the stainless steel. This will overheat the wire so it loses its temper if not fuse it completely. Far better is to earth the bottom of the mast. The mast being ali will conduct a huge current without much damage. Your then concerns are high current in the earthing straps and cast iron keel. If that is what you have. ol'will

 

[William_H]

I would question this assertion. A lightning strike starts with a low current leader from the ground (sea or mast). This low current high voltage can sneak through quite high resistance. It is very unlikely that your ali mast could be seen as well insulated from the sea. ie leakage from chain plates to sea via salt and moisture or from the bottom of the mast via support or bilge water. In other words if it;s nearby it may well see you boat as a closest target. ol'will

 

[coopec]

I have taken a 40mm X 5mm copper strap from the mast step direct to a SS earthing strip (1.5 meter X 25 mm x 5m). That earthing strip is also earthed to the engine. In addition I have X3 slightly shorter SS earthing strips for the chain plates using 4(?) AWG copper cable.

When I get around to it I plan to earth all the stanchions and winches but I think that has something to do with "stray electrical currents"?

That might be considered an overkill but I've read yachts on the average will be hit by lightning X2 in their lifetime (but the article was alluding to lightning in southern US of A- Florida, Mexico and Carribean)