Dart 15 Forums

Nick wrote:

Hi during the Martello long distance race at pevensey a lightening squall came through, being a chicken I went straight to the nearest beach and moved away from the mast .Legend at the club is that you can not be zapped on a boat as the lightening goes straight down the mast and into the water people reckon that they have been unable to find any stories of anyone being killed in this manner. does any one know anything about sailing in thunderstorms?

Bob replied:

Hi Nick
Yes, it is most unnerving sailing in a thunderstorm. The evidence is that sailors are very seldom (if ever)get killed in a thunderstorm. The fatalality rate for golfers high but it is very difficult to find records of any sailors getting killed by a lightening strike.
So sailing is much better for your health than golfing!

Frank replied:

How about staying close to a boat with a longer mast.

AndrewHannah replied:

Some years ago, I overheard someone say there is less chance of being killed by lightening, than for winning the football pools. This must be reassuring to some, like me, who have never played the pools.

Nevertheless, lightening still frightens me. Often it is associated with very strong gusts of wind.

Andrew.

steve willis replied:

Whatever the odds an average lightning strike is about 500,000 volts and tens of thousands of amps.

After 35 years in the electricity distribution business I have had to deal with the aftermath a number of times - including a 350mm diameter electricity network wood pole that exploded into firewood and a house that had every socket and switch blown out of the wall plaster. My own house was nearly destroyed in the 1940s by a direct strike and the burnt timbers can still be found under the upstairs floor (I live on a hill).

Suffice it to say that the strike would go straight down the mast to the sea (it does not go round corners very well)but the mast would be very likely to explode in your face as it melts because it is hollow and the pressure build up inside would be tremendous. Do not go there!!!!

In the south east a typical major lightning storm will achieve around 2000-3000 ground strikes across Kent, Surrey and Sussex (the electricity companies have PC based satellite imaging of ground strikes that plot onto a map on the screen so they can direct staff for emergencies to the worst hit areas).

If you are caught on the water in a lightning storm and cannot get back to shore you would probably be best to get the sail down and lower yourself into the water at the stern (not by the front beam!!)but that is potentially risky because high wind squalls are likely and you don't want to get separated from the boat.

Me, I would stay ashore indoors and away from the boat park.

George Stephen replied:

I understand that a lightning strike would also go down the shrouds and forestay/bridle wires, with disastrous consequences for all three and for the hull level fittings, and for the hulls in those areas. The likely insurance claim would be for a write off of the whole boat.

If caught on the water in a serious electric storm with strikes in close vicinity (rely on time from lightning to thunder to estimate distance), I'd capsize through 180 degrees...... and right the cat when the danger seemed to be over.

(My theory is limited to that gained working in an Electrical Research Dept many years ago, including being involved with gear that could generate voltage that could spark over several feet (more than most people are tall). A long way short of a lightning strike, but I recall reading about what was then known about lightning and boats, including pre-strike indications such as St Elmo's fire - glowing light around the rigging....)

While I have sailed my cat when an electrical storm developed - but with no strikes in close vicinity (counting from flash to thunder to estimate distance) - it was unnerving, and I was glad to sail back and park my boat temporarily until the storm moved away.

Steve Willis's advice of keeping clear of the boat park, let alone not sailing, is safest. If there aren't many recorded incidents of small boats being hit by lightning, it is probably because their sailors usually follow this sensible course of action.

George

Bob replied:

Hi Steve,
I'm sure that your statistics are correct for on shore strikes, but can you provide ANY statistics for boats struck by lightning and any consequential casualties? Some time ago it was discussed at the Grafham Sailing Committee in order that we could give our race officers guidance on what should be done when a race is in progress when a thunder storm struck. Quite a search was conducted and no data on casualties at sea was found. The RYA was contacted but did not have any specific advice for sailing clubs. Everyone is cautious, but I think the evidence (or lack of it) suggests lightning strikes of boats at sea are not as serious as on land. If anyone can find good statistics I would be interested in seeing them.

Bob replied:

Just for the hell of it I tried Googleing "Lightning at Sea" and got lots of articles - mostly from the USA. They quote quite a lot of casualty data. It is worse on fresh water than on sea water due to the reduced conductivity & worse on open motorboats than on sailboats due to the lack of the conducting mast. On sailboats where the bottom of the mast has no conductor to the water it increases the risk and they talk of systems to earth the base of the mast to reduce the risk. So it seems that avoiding being on the water in a Thunderstorm is the best idea. I have copied below one of the summaries fyi
Cheers
Bob

Personal Safety
Consider the worst case scenario for a lightning strike to a sailboat - a small boat in fresh water. If the boat has been provided with a well-built protection system it is still an exceedingly hazardous situation. If lightning protection does not exist, the situation is life threatening. In both cases, the areas to avoid are close to the waterline and close to large metal fitting. In the unprotected boat, an additional -danger zone is beneath the mast or boom. Even in the unprotected boat, it is unwise to get in the water, as electrocution is highly probable if lightning strikes nearby. In fact, there is no safe place on an unprotected small sailboat, and in a protected boat only places of relative safety. There is, however, one place that is more hazardous than a small unprotected sailboat, that is a small unprotected boat without a mast. Every year there are multiple deaths of boaters in open boats caused by lightning strikes, but very few reports of sailors in sailboats killed by lightning.
The above general rules also apply to larger sailboats. These are generally safer, if protected, since it is possible to get away from the waterline and large metal objects, and yet still stay dry inside the cabin. As far as unharnessed electricity is concerned, a dry human body is much less attractive than a wet one.

Conclusions
Lightning protection on a sailboat means diverting the lightning current into the water without its causing any hull damage, personal injury, or electronics damage. This involves providing a continuous, mainly vertical, conducting path from above any vulnerable masthead transducers to grounding conductors immersed in the water (the grounding system) and a network of mainly horizontal interconnected conductors attached to large metal fittings, including the grounding system (the bonding system). Transient suppressors are needed on each piece of electronics equipment, and wiring should all be twisted pair for protection of electronics.

Robin (Gurnard) replied:

This is very interesting.

I have to admit, I am very cautious of thunder storms when sailing or thinking of going sailing.

I remember once being caught out during the build up of a summer evening storm. The worse part was the wind dying to nothing as the storm built. Paddling like mad.

Could only get ashore once the storm got closer and the wind built a bit.

There are now some good storm tracking web sites that are worth a look. http://www.isleofwightweather.co.uk/live_storm_data.htm. It covers the UK and northern France

Dartful Codger replied:

Somebody seems to have stirred up the glowing embers of a St.Elmo's Fire here.
All very interesting if not dramatic news, where the over-riding message would seem to be :
Submit Class rule amendment to allow wooden masts, and just for added safety, up-rate shrouds/ forestay to at least 6mm dia !
Oh - and re-locate, re-locate, re-locate to anywhere other than Kent !!
Could be the theme for the next magazine, as all news is good news ! Anybody got a pikchur of sum lite ning ?
Keep it up guys - it's good to talk.

nick replied:

Thanks I knew I could rely on a gold mine of infomation from this site. My house was hit 3 years ago so I am wary of the stuff. On this occasion we were caught out also we had hail comming in on 35+ knots of wind which hurt!! so I wasnt too worried about running away .but we can now have a few hours in the bar on this thread cheers

spud1616 replied:

i was sailing my laser at southampton in a traveler event and it started to thunder and lightening
i admit i was scared sh..less and couldnt wait to get off the water
after reading the above
i suggest keep an eye on the forcast and if in doubt dont go out!!

john replied:

if you were caught a long way out and couldn't get back in time would George's suggestion (turn the cat upside down) work?