Lightning Protection

[GordMay]

Originally Posted by David M

Given lightning can arc across miles of sky and air is a relatively poor conductor, lightning finds it quite attractive to continue its path to earth through a better conductor than air...such as your mast. It makes perfect sense to provide an excellent conductor like a copper wire to help lightning continue that path to the earth...

Exactly !

Originally Posted by David M

... The product "Strikeshield" sounds like an excellent product...it just has a misleading name. Its not a shield in any way, its more like a pathway. I think "StrikePathway" would have been a better name actually.

Which is why you're a boat Captain, not an advertising copywriter.

[Pblais]

Although cats have a higher chance of getting struck, I am still contemplating whether it is worth the expense and hassle of installing some form of grounding system be it temporary or permanent.

A direct hit to the top of the mast that makes a 1 meter hole in the deck may have had a hole half that size with better protection. It probably had some grounding in it anyway but how much grounding does it take to accept a direct hit to the top of the mast? Clearly a lot more than was there. Would jumper cables hanging in the water have carried that much energy?

The statistics were based on all claims so we don't know how large the claims were or how much the protection installed reduced each claim vs. no protection. The claims can't tell which boats were only inducted or directly hit. It does not state how severe the damages were it only says "were hit bad enough to file a claim that was attributed to lightning" probably would have included my neighbor that lost a radio but had no visible signs of damage what so ever as well as your neighbor that had the dramatic effect of the destruction of the mast. Has anyone got a letter from the insurance company dictating things you must do to retain coverage relative to lightning. What do you have restrictions on? Those are the things that cost the company the big money.

These numbers also include average grounding protection in average areas on average boats. It would be different if these boats were totally unprotected but of course you have to assume they have average protection.

The most telling number is all these claims were paid. The company paid the claims for lightning damage. We know for certain most companies do not pay 100% for claims for hurricane damage. If you are trying to decide what type of protection (really just additional insurance) to invest in I would choose the areas where the insurance companies don't pay claims because it costs them too much money.

Fire still is by a huge margin the leading cause of boat destruction. Poor wiring often includes poor grounding. In the spectrum of storm risks hurricanes count a whole lot more than lightning.

As a business, marine lightning protection isn't all that bad when doing nothing is more than 99% effective. You really can't screw up. No data to determine how effective anything really is leaves it to the advertising copywriter. BS still makes good money.

From a pure bang for the buck how much money would you spend on additional lightning protection assuming you have basic grounding on your boat now? I don't think I'll buy any jumper cables.

[colemj]

Originally Posted by Pblais

From a pure bang for the buck how much money would you spend on additional lightning protection assuming you have basic grounding on your boat now? I don't think I'll buy any jumper cables.

The problem with many multihulls is achieving basic grounding. Since they don't have large areas of lead/steel keel to bond to (or even small areas ), it makes good sense to pursue a bonding solution like Strikeshield. With the exception of rudder posts and electrically isolated saildrives, we have no metal below the waterline to bond to.

Mark

[GordMay]

Originally Posted by colemj

The problem with many multihulls is achieving basic grounding. Since they don't have large areas of lead/steel keel to bond to (or even small areas ), it makes good sense to pursue a bonding solution like Strikeshield... Mark

Good point.
Nor do multi's usually have a direct path from mast to water.

[Pblais]

The problem with many multihulls is achieving basic grounding. Since they don't have large areas of lead/steel keel to bond to (or even small areas ), it makes good sense to pursue a bonding solution like Strikeshield.

The problem with the above Multihull stats above is that Multis are a smaller class of boat in numbers and Monos are a much larger class in numbers BUT the larger numbers are made up of substantially smaller boats than Multis. To me it skews the stats because the bigger Multis on average are just bigger than the average mono.

I can understand the grounding issue and good grounding is needed for a lot of reasons beyond just lightning. I don't question the need for it at all. I just would not let the BoatUS numbers make you think Multis are that much more susceptible to lightning or more importantly that somehow on average Multis are less well grounded and so get more hits. If the skew was also shifted to Florida where 10 times as much lightning occurs you may find a higher percentage of Multis in FL than Monos. This would skew the numbers even more. While there are more Monos in FL what would be the distribution?

0.5% vs 0.2% is pretty darn small numbers. If you can boil it down to bigger boats and taller masts then all this nonsense of any difference goes pretty much out the porthole. Anything that can vaporize a carbon fiber mast can't be grounded well enough.

[ssullivan]

Originally Posted by GordMay

Good point.
Nor do multi's usually have a direct path from mast to water.

That's the one thing that irritates me when thinking about my boat in terms of lightning strikes. The "terminus" of the bolt going through the mast is a metal plate near my salon table, at about eye level. The terminus of the shrouds are two chainplates, but don't think "a metal tab down low by the water." It's more of a large triangular frame - one on each hull - at about eye level, terminating both in each stateroom and in the main salon.

Where does the current go from there? To my head, through my feet and into the water. Ouch.

I agree with Paul regarding the statistics though. They aren't exactly even close to a factual, scientific study. They are very loose and any "trends" seen could be due to almost anything, including the fact that multis often anchor in water you can wade in (close to the Earth/ground). Could be just about anything.

I am sure not completely satisfied with the paths (or lack of paths) available to lightning traveling through my mast. I was thinking of attempting an exercise to get a better path from deck-stepped mast and chainlplates to water set up.

[colemj]

I read the stats above as multi's are less likely to be hit (0.5% vs 0.6%). I think those stats are messy for the same reasons you list and think they would have been more valuable if BoatUS had been more careful with the data. Actually, I know far more people who own monos than I do multis, but among them, more multis have been hit than monos. I only present that as a non-statistical empirical observation.

I agree that the probabilities are small. Having said that, I know several people who have had lightning strikes, so the probabilities are not small enough for my instincts to ignore them. The consequences on our boat of getting hit without any path to ground was the reason I pursued a solution (I didn't even know the statistical numbers then). I'm not hoping to prevent the hit - just minimize the damage to the boat. The closest path to ground for a lightning strike on an ungrounded multi is straight through the bridgedeck as noted in the previous example. I don't agree with your estimate that providing a large conductor (1/0 copper cable clamped tightly to the mast terminated in a plate containing 144 sqin of edge) to ground around the bridgedeck would only reduce the damage to a hole half the size. The ability to vaporize a carbon mast does not have much relationship to the ability to be directed through a metal mast to ground in regards to damage mitigation.

There is also a statistical probability of losing a rudder, but I am not pursuing a solution to that (well, it would have to be both rudders in our case). Interestingly, many people do worry about this and spend time and money on a solution even though my gut feeling is that more boats get hit by lightning than loose their rudders.

Mark

[tom151]

Originally Posted by Pblais

0.5% vs 0.2% is pretty darn small numbers. If you can boil it down to bigger boats and taller masts then all this nonsense of any difference goes pretty much out the porthole. Anything that can vaporize a carbon fiber mast can't be grounded well enough.

The stats quoted earlier in this thread were stated as 'actual claims' - the implication being that there was enough damage to warrant a claim being filed.

Of interest is the extensive study of actual strike cases done at the University of Florida (SeaGrant Program) ... definitely worth a careful reading.

Of boats actually struck by lightning, fully 80% incurred no hull damage at all (not saying there wasn't other damage). Of particular note was their experience that showed boats in fresh water were uniformly hit more than twice as often as sailboats in salt water (see figure 3 at the link given above) independent of the magnitude of the damage inflicted.

If this info is factored into the other stats them it implies (to me at least) that I can cut the already small numbers in half yet again.

For myself and the safety of crew members - I would never do anything to actually help bring the current flow into the boat. On my monohulls (3) I carried heavy duty jumper cables and clipped them onto the upper shrouds above the turnbuckles, on my multihulls (4) I did the same, even removing any previously installed grounding plates. When sailing - just clipped to the leeward shroud and suffered the extra drag

[TabbyCat]

To answer a question earlier in this thread, I've never seen an insurance company ask an insured to take any special precautions against lightning. Some policies even have a lower ($250) electronics deductible that would come into play in a lightning strike claim.

I have seen insurance companies require an insured to have a Tropical Storm Plan.

The thinking is that lightning is completely unpredictable, but damage from a poorly prepared vessel in a tropical storm zone is foreseeable & could be be mitigated if the proper steps ware taken.

We have a Strikeshield on our cat. We often sail with it hanging between the hulls, dragging in the water when we see bad weather on the horizon. We don't have to slow down, the weight of the anode seems to keep it in the water.

[GordMay]

Ideally, I would bond my Catamaran (were I lucky enough to own one):
- chainplates and all significant metals to an external grounding strip (or Dr. Thomson’s “Siedarc” electrodes*) on each hull (#6AWG Cu. Cable);
- and my mast base (air terminal at top) to a “portable” ground plate via a “Strikeshield” (or other) mast terminal (also #6 AWG minimum).

* Goto: Marine Lightning Protection Inc.
Marine Lightning Protection Inc.

[sangaris]

Originally Posted by pilot

Mark,

did you ever try to have the strikeshield installed during sailing. I.e. reducing speed to minimum practical?
I could imagine, that the copper cable is bouncing around?
Had no chance to try out myself, still on job in Germany.

Regards

Ralph

Ralph, we have sailed with ours in the water 4 or 5 times over the past 3 years - the first time being on the offshore delivery trip home to Annapolis from Sarasota - no way to go around a very large storm. Have not experienced any problems with the cable being in the water - it is long & heavy enough that it tends to stay in the water well.
scott
sangaris

[pilot]

Hi, Scott,

thank you for your information!

Regards from Berlin

Ralph

[colemj]

Ralph,

We were very "fortunate" to get caught out in lightning today and was able to test the strikeshield while underway. At 7.5 kts in flat seas, the cable streams along very smoothly between the hulls with no bouncing or hitting the hulls.

Oh yeah, we didn't get hit either.

Mark

[pilot]

Hi, Mark,

good news!In all aspects.

thanks´s

Regards

ralph

[rob denney]

Originally Posted by colemj

On another forum, a denizen reports that he received a direct hit to his carbon mast on a trimaran. He had a lot of damaged electronics and melted antenna, but no damage to his mast, boat or rigging.

Mark

G'day,
Mark,
What forum, please?

Crak,
I am also in Perth. Can you tell me any details of the cat that was hit, please. I would like to know more about it.

regards,

Rob