Mast Earth Bonding ???

[Prashanti]

Hi there,

Now I understand that these are probably two of the deepest and most complex of subjects, Earthing and Lightning.... But I felt that I had to at least try and do something.... I have just bonded the foot of the mast of my FP Belize to the body of the windlass... I am hoping that this will give me an Earth bond to the water via the anchor chain and gypsy. Now talking in idiots terms... Have I done the right thing?? Or have I now just attracted more headaches??

Thanks,

[callmecrazy]

what about when the boat is not anchored?

my mast was bonded to the keel bolts. I don't know if that is the proper way to do it, but it was recommended in 2 separate surveys before they Previous Owner finally got it done.

[colemj]

The bond to the water through windlass and chain will be weak and intermittent. The chain-chain interfaces are small contact areas and usually partially insulated with rust. The bond through the chain gypsy most likely goes through a layer of grease and small ball bearing surfaces (if not teflon isolators). The one thing you have surely done is connected your DC electrical system directly to your mast through the negative lead of the motor to the DC (-) bus, so you can expect significant electronics/electrical damage if you take a hit. On the other hand, this link probably already exists if you have a vhf antenna on the masthead.

Mark

[Prashanti]

Thanks for the input guys. I was thinking that the bonding through the chain and gypsy would be very poor and of high resistance but lightning seems to know no insulators. When underway I have 3m of 3/8 chain inside a sleeve that I planed to put into the gypsy and drop through the anchor well into the water. If there is a problem with having the windlass bonded to the mast I could always shackle it to one of the shrouds and drop over the side, might make a mess of the boat though...

[jeremiason]

Prashanti

There are several other threads on lightning and arrestors... The one thing about these discussions is, like anchors, everyone has an opinion.

The true question to be answered is: "Are there firsrt hand accounts of boats that were struck by Lightning that had an arresting system on board; and if so what happened?"

Everytime I ask this question there are mulitple replies about how someone read something or heard from some else that bonding was good... There are no studies that prove arrestors or bonding will work and most definetly it will not protect your electronics, only possibly save the boat from holing. Although that dosn't seem to happen very frequently during lightning strikes.

Back to your question, I met a boat earlier this year that was struck by lightning while anchored...

Althought not bonded to the anchor chain, it appears the lightning went to ground along the anchor chain... The chain was melted onto itself and broke loose causing the boat to drift onto shore... The boat was subsequently re-floated. The owner dicovered in addition to his anchor chain, all his electronics were fried.

[Prashanti]

Thanks Jeremiason, you're right there is just too much energy there for us mortals to predict or protect ourselves from. I am tempted just to do away with it and just ride fate...

[zeehag]

neighbor here in mexico was hit and his chain was fused by the lightning hit.
another neighbor here had his wifi antenna collect lightning to bring it inside boat. 2 weeks ago.
on another dock, a catamaran just received a hit and blew out ALL his electronics very spectacularly--so much so it was seen as a phosphorescent green glow for 10 miles. was 3 days ago. he was protected.

i dont know who if anyone was hit in puerto vallarta.

i will remain unprotected so those with protection dont have any competition for the excess energy. so far, my thinking has saved me from this event of being hit by lightning.

seems we have more dangerous lightning here than in fla--and our air currents are vertical not horizontal as are florida's-- we have hits with each storm, and we have storms daily.

i have a feline on board to deflect the static charge away from boat.
and crocs, which attract nothing. good luck and be safe out there.

[Cotemar]

Prashanti,

I think your setup will get you more hits than your want.

[colemj]

Originally Posted by jeremiason

The true question to be answered is: "Are there firsrt hand accounts of boats that were struck by Lightning that had an arresting system on board; and if so what happened?"

Everytime I ask this question there are mulitple replies about how someone read something or heard from some else that bonding was good... There are no studies that prove arrestors or bonding will work and most definetly it will not protect your electronics, only possibly save the boat from holing. Although that dosn't seem to happen very frequently during lightning strikes.

I don't know of any lightning prevention or arresting system - only systems that take the strike as directly as possible to ground to prevent as much damage as possible.

We have a Strike Shield system on board, which consists of a 4/0 cable permanently attached to the mast, terminated in an electrode with 48" of sharp edge length and led directly overboard into the water in a fairly straight line. We were hit by lightning and lost most of the electronics but no damage to the boat's structure.

A friend of ours with the same boat as us was hit without any bonding of mast to ground (he was off the boat and did not have his Strike Shield system deployed). He had numerous holes blown through his hull as the lightning found its way off the boat.

We were recently anchored near a boat containing the system designed by the FL professor. They took a direct hit and lost some of their electronics (~35%) and had no structure damage.

We were anchored next to a boat painted bright orange that was not hit by lightning, thereby proving zeehag's theory that random, unrelated and uncorrelated things prevent one from being hit by lightning as long as they haven't yet been hit by lightning.

Mark

[Adelie]

Originally Posted by Prashanti

Hi there,

Now I understand that these are probably two of the deepest and most complex of subjects, Earthing and Lightning.... But I felt that I had to at least try and do something.... I have just bonded the foot of the mast of my FP Belize to the body of the windlass... I am hoping that this will give me an Earth bond to the water via the anchor chain and gypsy. Now talking in idiots terms... Have I done the right thing?? Or have I now just attracted more headaches??

Thanks,

You have not done the right thing. You MAY have attracted more headaches.

Chain is a poor conductor because the contact point between each pair of links is very small. Given the fact that the chain will have a large cross section the fact that it is steel will not be that big a deal. The fact that there is the galvanizing in the current path may be an issue too, but I don't know how important.

[sabray]

Originally Posted by colemj

I don't know of any lightning prevention or arresting system - only systems that take the strike as directly as possible to ground to prevent as much damage as possible.

We have a Strike Shield system on board, which consists of a 4/0 cable permanently attached to the mast, terminated in an electrode with 48" of sharp edge length and led directly overboard into the water in a fairly straight line. We were hit by lightning and lost most of the electronics but no damage to the boat's structure.

A friend of ours with the same boat as us was hit without any bonding of mast to ground (he was off the boat and did not have his Strike Shield system deployed). He had numerous holes blown through his hull as the lightning found its way off the boat.

We were recently anchored near a boat containing the system designed by the FL professor. They took a direct hit and lost some of their electronics (~35%) and had no structure damage.

We were anchored next to a boat painted bright orange that was not hit by lightning, thereby proving zeehag's theory that random, unrelated and uncorrelated things prevent one from being hit by lightning as long as they haven't yet been hit by lightning.

Mark

Best response. Thanks. Direct path exposed edged plate/ strip excellent. . Bonding back to the windless opens the path to all ground. Keep the lightening path separate. We're talking best practice. Not absolute not experience but best practice/ science available. Large surface with edge exposed connected to mast. yes I chuck a cable attached to a stay over even though I have a mast with direct path bonding to a big surface ground.

[Mike Banks]

If you have a glass or timber hull I would fit a through hull to a proper lightning plate--preferably copper unless your hull is aluminium, in which case use aluminium plate insulated from the rest of the hull by tuffnel fasteners. I have a heavy cable passing through the pipe fastened to the through-hull and going up to the base of the mast directly above it. Around this plastic stand pipe up to above the water line is another box which also contains a shower sump--so even if the stand pipe is burned away the boat will not sink.

I would never connect anything to an anchor windlass and I would use double solenoids to switch it on and off--so it is completely isolated from the ship's electrical system when not in use. If you do not do this the galvanizing on your anchor and chain will not last very long. Failing this--use a manual heavy current two pole manual switch to disconnect the battery negative and positive leads when the anchor is not being raised.

Only a comparatively light discharge can be taken to earth by lightning protection--but having it discharges the air in close proximity to the collector--thereby raising its dielectric strength and reducing the likelihood of ionization. Once air becomes ionized--it becomes a much better conductor of electrons--and in the presence of a high earth potential may allow a discharge.

Putting your electric instruments in a mu-metal box will help preserve them from a proximal discharge and its associated magnetic pulse--the one which induces the current that fries their little insides--.

The edge of four feet on the earth plate is a measure of surface area--not just the edge. DO NOT PAINT the earth plate--or put antifouling on it.

[DotDun]

I agree with most that grounding via the windlass and chain isn't going to provide much protection.

I have a Strike Shield and keep it deployed. This won't protect against getting hit, but like others say, it'll help get the lightning off the boat hopefully without hull damage.

A friend buying a new cat asked me about Strike Shield and upon investigation they appear to be out of business.

I've been investigating Marine Lightning and I'm intrigued with their new bridge deck electrode. (Catamarans) bottom of the page. I've traded a few emails with Ewen Thompson and what he is saying makes sense. Mount this unit via a thru hull directly below the mast, the rod is 2-12" above the water. The thru hull is sealed with a cable direct to the mast and the electrode can lifted if needed. The part that is hard to comprehend is their Siedarc electrode technology, which he backs up with scientific testing. Since lightning protection is an art and not an exact science, I'll admit that Ewen and team have the pedigree to backup the claim of expertise.

[jeremiason]

Since we have been in Central America, we know of four boats that have been directly struck by lightning and one boat who received an indirect strike after a nearby boat was struck direcly.

All of the boats with direct strikes had their electronics fried... The near miss boat's ICOM 802 SSB circuit board melted, but they found no other damages.

Also, none of these fiberglass boats had hull damage or any type of lightning arresting gear or bonding.

There is an interesting article in Seaworhy Magaine (BoatUS) dicussing lightning and the randomness of the strikes.

A statistic I found interesting is that a multihull (9.1 in 1000) is more likely to be struck by lightning than a monohull sailboat (4.5 in 1000). The only conclusion I can reach from that data would be the Cats have twice as much surface area as the monohulls.
BoatUS.com - Seaworthy Magazine

The BoatUS study, which based on insurance claims in Florida, also indicates that your boat has less than a 1% chance of being struck by lightning.

Finally, the last thought is those of you doing bonding... Lightning bolts generate up to several million volts or about 10 kiloamperes per bolt.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/lightning2.html#c5

Do you think the bonding wires you are using will accomodate that massive current flow of a direct strike?

[colemj]

Originally Posted by jeremiason

Finally, the last thought is those of you doing bonding... Lightning bolts generate up to several million volts or about 10 kiloamperes per bolt.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/lightning2.html#c5

Do you think the bonding wires you are using will accomodate that massive current flow of a direct strike?

I think it will conduct more of it than no bonding wires.

Our 4/0 cable has a fusing (melting) current of 173 kiloamperes for 32msec, which is about the time for a lightning bolt, and 31 kiloamperes for 1 second in case it lasts longer. Voltage is irrelevant in choosing a wire for leading the strike to ground.

So for a strike of 10 kiloamperes, an 8 AWG wire will suffice. However, one would have to be really cheap to not go with a larger wire for such short distances.

Mark