Lightning -- to ground or not to ground, that is the qn

[GordMay]

Originally Posted by aberglas

...
I am grounding my mast with a thick cable connected to a chain in the water. ...

ABYC TE-4 says, in part:

“LIGHTNING GROUNDING TERMINAL
A lightning grounding terminal for a boat should consist of a metal surface (copper, copper alloys, stainless steel, aluminum or lead) which is in contact with the water, having a thickness of at least 3/16 inch (5 mm), and an area of at least 1 square foot (0.1m²). It should be located as nearly as possible directly below the lightning protective mast in order to minimize any horizontal runs in the primary (main) conductor...

... The spark initiation necessary to dissipate a lightning stroke is more likely to occur at sharp edges and corners than from flat surfaces. The edges of the external ground plate or grounding strip need to be sharp, exposed, and not caulked or faired into the adjoining area.
Any through hull stud connecting a lightning conductor to a grounding terminal shall have conductivity not less than that of the primary (main) conductor ...”

Welded steel link chain makes a lousy lightning ground terminal,

[s/v Jedi]

For different metals, you can insert a small piece of aluminum in between them, to act as a sacrificial part.

[aberglas]

I actually have some Tef-Gel anti-corrosion paste. I measured a sample and it does not conduct electricity. But following your post I tried it on the bolt and mast, and the electrical connection is fine. It says "dielectric gel", but the ohm meter is just DC. So magic.


Cable goes from a bit up the mast over the side and into the sea. Not vertical, but electricity does not have momentum, hopefully the charge will follow the easy path down the copper cable.


We will see. Actually, hopefully we will never see and hopefully this is a complete waste of effort!

[dannc]

Originally Posted by TeddyDiver

That's about what I'll do. Grounding stays to water with deployable copper cable. Maybe a rod on the mast top.. Wooden masts thou

From the TE-4 document that Jedi, posted,

If the mast is composed of non-metallic material, the associated lightning or grounding conductor should be essentially straight, be securely fastened to the mast, extend at least six inches (150mm) above the mast, terminate
in an air terminal, and be led as directly as practicable to the grounding connection. See Figure 4. An outrigger that serves as a lightning protective mast should have conductivity equivalent to or less than the resistance of a primary conductor.

I would suggest reading the TE-4 document in detail

Furthermore, Professional Boat Builder magazine just had a two part series on lightning protection in the April/May issue 202 and June/July issue 203 that would be helpful to read.

Later,
Dan

[s/v Jedi]

Originally Posted by aberglas

I actually have some Tef-Gel anti-corrosion paste. I measured a sample and it does not conduct electricity. But following your post I tried it on the bolt and mast, and the electrical connection is fine. It says "dielectric gel", but the ohm meter is just DC. So magic.

Cable goes from a bit up the mast over the side and into the sea. Not vertical, but electricity does not have momentum, hopefully the charge will follow the easy path down the copper cable.

We will see. Actually, hopefully we will never see and hopefully this is a complete waste of effort!

Tef gel and dielectric grease are different products. I don’t know if dielectric grease will prevent corrosion but I know it will allow good electrical contact. Similarly, I don’t know if Tef gel will allow good electric contact, but it will prevent corrosion… mostly.

Also, no, lightning does not follow the easy path, hoping that is futile, it simply won’t. It will follow the shorter path and you can only hope to contain it when you accept that shortest path because you can’t make it divert to another path of your wish.

Please read the document I posted above: -vertical- conductors.

[GordMay]

Tef-Gel does not electrically insulate hardware. The PTFE (40%) is ultra fine powder, that will extrude out of the contact area, and into the voids of the surrounding areas.
Tef-Ge, applied between electrical contacts and connectors, does not increase the resistance of the connections, even at hundreds of amps.

[s/v Jedi]

Originally Posted by GordMay

Tef-Gel does not electrically insulate hardware. The PTFE (40%) is ultra fine powder, that will extrude out of the contact area, and into the voids of the surrounding areas.
Tef-Ge, applied between electrical contacts and connectors, does not increase the resistance of the connections, even at hundreds of amps.

Hmmmmm…. so when it is extruded out, how does it prevent corrosion? Just by making it air tight?

[GordMay]

Originally Posted by s/v Jedi

Hmmmmm…. so when it is extruded out, how does it prevent corrosion? Just by making it air tight?

Tef-Gel paste contains 40% PTFE powder and 0% volatile solvents, no silicones or petroleum solvents to evaporate, which would leave voids for electrolytes to be drawn into creating a galvanic cell. When both surfaces are coated and mated with Tef-Gel there are no voids for electrolytes (saltwater) to be drawn in by capillary action over extended periods of time.
See ➥ https://www.tefgel.com/contain.php?param=tefgel_infor
And ➥ https://www.tefgel.com.au/technical-information/

[s/v Jedi]

Originally Posted by GordMay

Tef-Gel paste contains 40% PTFE powder and 0% volatile solvents, no silicones or petroleum solvents to evaporate, which would leave voids for electrolytes to be drawn into creating a galvanic cell. When both surfaces are coated and mated with Tef-Gel there are no voids for electrolytes (saltwater) to be drawn in by capillary action over extended periods of time.
See ➥ https://www.tefgel.com/contain.php?param=tefgel_infor
And ➥ https://www.tefgel.com.au/technical-information/

Interesting, sounds exactly like what dielectric grease does…

[sinnerman]

I am not any expert on this, but the question is what you would be trying to protect with a lightning grounding system.

By providing a ground connection (through the hull) for the forestay, backstay(s) and side shrouds, you are creating a path for a lighting strike to follow to ground. The grounded standing rigging will provide a "cone of protection" shielding anything inside this pyramid/cone from injury/damage.

So in this case a grounding system is advisable.

The electronics, on the other hand (IMHO) will still be susceptible to the strike, as the magnetic field created by the discharge will induce voltage spikes into the ships wiring.

I had a lighting strike years ago in my neighborhood where the lightning hit an electrical telephone pole down the street. Even with the protection I had in my home office (UPS, power strips with everything being properly grounded etc.) the "spike" fried my phones and fax machine.

cheers....

[s/v Jedi]

Originally Posted by sinnerman

I am not any expert on this, but the question is what you would be trying to protect with a lightning grounding system.

By providing a ground connection (through the hull) for the forestay, backstay(s) and side shrouds, you are creating a path for a lighting strike to follow to ground. The grounded standing rigging will provide a "cone of protection" shielding anything inside this pyramid/cone from injury/damage.

So in this case a grounding system is advisable.

The electronics, on the other hand (IMHO) will still be susceptible to the strike, as the magnetic field created by the discharge will induce voltage spikes into the ships wiring.

I had a lighting strike years ago in my neighborhood where the lightning hit an electrical telephone pole down the street. Even with the protection I had in my home office (UPS, power strips with everything being properly grounded etc.) the "spike" fried my phones and fax machine.

cheers....

Correct. The bonding system is to provide a path to discharge the strike to ground safely, without punching holes through the boat.

Your experience with your office wasn’t because of the strong magnetic field, but because the surge entered your office through the telephone wiring instead of the power grid. You can insert surge suppressors in the telephone wiring as well, which are highly effective in a similar way as coax surge suppressors for antenna cables.

[MJH]

Originally Posted by aberglas

By providing a thick cable from the mast to the sea, we hope that (most) of any lightning will take that path to the sea, even if it vaporizes the cable in the process (ions are conductive). However, we also provide a path for charge to move from the mast, so the top will be positive and attracting negative strikes.

Alternatively insulate the mast. Let it float, so that it does not attract lightning in the first place.

My boat has the worst of both. Mast is lightly earthed, will attract lightning but not be able to dissipate it.

Many thoughts, any evidence? What do people think?

You need to do your own research and assessment of your probability of a lightning strike...you don't say what or where you sail. There is no full proof method or device to prevent a lightning strike...it's an act of God.

BoatUS has information on lightning strike probability. Monohulls probability is 3.8/1000, multihulls 6.9/1000. Larger boats are more risk: 26-30' are 2.1/1000 but 40-67' are 6/1000.

Location plays a big role: Southeast U.S. is the highest while the Northwest is rare.

With the facts you can decide on whether to take great measures to protect your boat against an act of God.

Lastly, read your insurance policy.

Good luck.

[Cheechako]

"Lightning gonna do whatever lightning wants to do". Including moving horizontal for miles to end up striking "over there".
Ungrounded Airplanes still get struck with lightning.
There seems to be no firm answer. But I thnk it's likely good to provide a path to the water with a big cable. Hopefully that influences it to not pass through your body.
Is the influence of this path to ground an infinitely small attraction in the scheme of things? Probably. But hmmm, hiding under trees in a storm has proven to be a bad idea....

I bought a boat in Annapolis 25 years ago. It was surveyed etc including the mast. I had it docked there for 3 months after purchase. While we were not on the boat one day it had a lightning strike. Amazingly no electronics were damaged. The Windex on the mast top was melted and remains had fallen in the cockpit. There were black carbon traces down both SS plates for side stays on the mast top. This rig was ungrounded and in a small marina of boats.

I was in San Carlos Mexico in the mid 80's. I had gone out of the bay around the point trolling for fish from the dingy. A fast moving storm cell was moving in, I was just rowing. I made it back in the bay and was rowing to the boat when a small homebuilt catamaran was struck with lightning right next to me. Like 30-40 feet away. The mast top was smoking as I rowed away.
I saw another cat struck in my years of sailing. I wonder what it is about cats that influence strikes? Apparently stats say they are more prone...

[dannc]

Originally Posted by Cheechako

...
I saw another cat struck in my years of sailing. I wonder what it is about cats that influence strikes? Apparently stats say they are more prone...

Cats MIGHT have taller masts but I don't think that is the reason they get hit more often by lightning. My guess is that they have more water line than mono hulls.

Later,
Dan

[jhulmer]

During my recent refit, I followed TE-4 as close as I could ( also Nigel Calder). I still have to tie in the chain plates. It's hard to see in this pic but I made shallow cuts in the surface of the 1/4"x 4" copper bar with my table saw to increase surface area and provide sharp edges to aid in the exit of the arc. This is not quite a sqr foot bar, but it is close. The main mast is connected with a short piece of 1/2" copper pipe to the two bronze bolts holding the copper plate on the hull. There are two small zincs on the plate as well, more as an experiment to see if the copper lasts longer. Although, probably not necessary.
I hope I never find out if this works!

The PO had a sintered bronze ground plate that was too small and I understand will vaporize if hit by lightning.