Another new owner and a question - Lightning ground?

[Carolina Dog]

Hi all. I purchased Lucky Dog in May in Oriental NC. Totally pleased with the boat. I have already replaced running rigging, Plumbing, Engine parts and Electrical. I have the Seaward 3121 stove at the house for rebuild (really I am done but considering new guts to bring it to code). LOTS to do but what fun. I have sailed since third grade when my pops brought home a home made El Toro dinghy and stood on the dock shouting instructions. Been infected ever since. After a lot of research I selected the 323 as my next boat. The boat is in Belhaven, NC but as as soon as I replace the thru hulls and paint the bottom I am moving her to Georgetown, SC which puts me right down the road from Frayed Knot. I am having chainplates made and will replace them along with the mast step when I pull her in October. So much of the things I am doing and my knowledge base has been a product of this site. Thanks to the group for that! Hopefully I will be able to contribute a little something to this site.

My question is: Is anybody grounded from the mast to the lag bolts holding down the mast step?
Is this a reasonable thing to do? I read a research article from the coast guard site that suggests a lightening strike to ground through the lead keel would possibly blow off fiberglass from the keel but would not hole the boat. Any thoughts?

Not sure how to insert an image so I will try an attachment... Cheers, Marcus of Lucky Dog

[Dragonstar]

Hi Marcus,

First off, sorry to say that we can't weigh in on your question about grounding. However, we were looking through posts about chainplates and came across your note. As new Pearson 323 owners (3 days!), we've also found that at least one of our chainplates needs to be replaced: the forward lower shroud on the port side was completely corroded through at deck level.

You mentioned having your chainplates fabricated, so would you happen to still have the specs for them?

Thanks,

Cody & Angela of Dragonstar

[Dolce_Vita]

Our 323's shroud chainplates are pretty simple and easily accessible.

I replaced one of the aft-lowers after finding the beginnings of a crack when inspecting it.

All of the chainplates are fabbed from straight 1/4" x 1 1/2" bar stock.
The ones for the fore and aft lower shrouds are just over 12" long while the center uppers are about 14" long.
The exact length is not critical.

I had the new lower fabbed from 316 stainless and had it cut to 12".  The bolthole spacings for the below deck fastenings are somewhat arbitrary, as they appear to have been hand drilled.  I simply gave the old one to my SS fab guy and told him to use it as a template for the new one.

One thing I noiticed when disassembling them was that the fastening bolts were originally inserted from the fiberglass side such that the chainplates rested on the bolt's threads.  Mechanical engineers will tell you that this is a bad thing to do, as it creates stress risers that are potential failure points.  I reversed the bolts so that they went through the chainplate first, then through the fiberglass so that the chainplate rested on the unthreaded shoulder of the bolt.

You can safely replace the chainplates one-at-a-time with the mast up.  Rig a halyard as a temp shroud replacement when doing each of the uppers.

[Dolce_Vita]

...My question is: Is anybody grounded from the mast to the lag bolts holding down the mast step?
Is this a reasonable thing to do? I read a research article from the coast guard site that suggests a lightening strike to ground through the lead keel would possibly blow off fiberglass from the keel but would not hole the boat. Any thoughts?...

Marcus,

  Mine came that way, with a large heavy green bonding wire attached to one of the lagbolts holding down the mast step.  I kept it that way when I replaced the mast step.  Also,  the upper shroud chainplates and all through hulls are similarly bonded.

As for whether its a good thing to do or not, I don't really know.  My research shows that there are recommendations all over the map regarding bonding and lightning "protection", with no clear conclusions.  There seems (by my interpretation) to be a small amount of consensus that bonding may slightly increase the probability of a strike while slightly decreasing the possible damage, while isolating the mast may slightly decrease the probability of a strike while slightly increasing the possible damage.

I take it all with a grain of salt. The damned lightning's going to do as it pleases!    As always, YMMV.

[Frayed Knot]

Carolina Dog Welcome to the hood.  Will you be living in Georgetown or close by?  I love working on my boat and I think that's part of the reason I got her.  Let me tell you I truly love her.  Have sailed every weekend  from the end of May to now.  Might be going to try to race her this weekend.  I know her hull speed is 7 something but she will do 7 to high 8 in 10 to 15 knots feels fast to me...Anyway welcome, if you need anything be glad to help.   Dick Martin (Frayed Knot)

[Carolina Dog]

Thanks everyone! To answer Dragonstar: I had my chainplates made from 304 stainless out of 1/4 by 1.5 inch bar stock. four are 12.5" long and 3 are 15"long. I am drilling the bolt holes myself but I did have the metal guy drill a 1/2 hole 1" down from the polished end and radius the corners like the pictures on this site. I am having the top 3" polished. I will have the forestay reworked when I can pull the fitting and take it to the shop so they can use the original as a pattern.

I am going to do as Dolce Vita and ground to the lag bolts when I replace the step. If I do get hit by lightening I will let ya'll know how that all works out. I agree it all seems like pay your money, take your chances!

Frayed Knot: I live and work in Georgetown. When I bring her down we will get together and compare notes. Did you race?

[Frayed Knot]

That is this comming Saterday.  Dont know how the weather is going to be. We will see..    It's Saturday and the weather was to bad, so no race.  I will let you know what happens.

[Alma]

Mast grounding is made complicated with our internal lead ballast. All the heavy green wires throughout the boat are bonding wires. They should be clean and tight. The bonding wires need to have electrical continuity with the mast itself and the step plate. This is to prevent corrosion and also to try and protect sailors from lightning strikes and shore power electrocution from open grounds on AC appliances. Some folks isolate their mast but that is difficult if you have masthead instruments and VHF radio antennas which bring their small conductors to ground also. NEVER use the mast as the ground for lights or instruments like automobiles do- corrosion will result. The shrouds and stays chainplates are bonded together with the maststep with the bonding wiring at the factory.

The lag bolts securing the maststep do not reach the lead ballast in most 323s. Even if they did, the lead is inclosed in dielectric fiberglass so the grounding to the sea is compromised. Lag bolts float into the non-conductive fiberglass and at this age have little ability to pull a bonding wire terminal tightly against the steel maststep.

I used stainless allthread and tapped through the fiberglass two inches into the lead for mechanical strength. I believe I have electrical continuity with the bonding wires AND the lead. The four allthread studs wouldn't be strong enough to withstand a direct lightning strike. The idea with bonding to the sea is creating an "ionic umbrella" that protects the boat like an invisible Faraday Cage. The ubiquitous stainless bottle brushes at the tops of masts are part of this school of thought. This ionic umbrella is a very low voltage so all connections must be very clean. If you believe this will work buy your bottle brush from a dairy supply at 10% of the cost of the marine items...

I found electrical continuity in my mast to ground with the bonding wires disconnected from the step. This continuity is from the grounded METZ antenna at the masthead and the rig's bonding. Since the mast is grounded by the stays, shrouds and my VHF antenna's ground I chose to run the green bonding wires in the bilge directly to the mast.  I have a substitute steel bolt holding them until I locate a suitable aluminum bolt to fasten them to the mast. I also made an aluminum washer that goes against the mast to prevent dissimilar metal corrosion from the copper wiring terminals attacking the mast. This is not shown in this photo

Sintered bronze Dynaplate radio grounds are not adequate for lightning protection. A copper sheet a few feet long and a half foot wide at the turn of the bilge directly beside the mast on the hull exterior immersed on all points of sail would be the recommended lightning ground for the 323. It would be quite an engineering and installation feat to do this correctly. Copper at least as thick as a penny formed to the contour of the hull and inlayed so it doesn't peel away... A lot of work! Then there is the connection from the exterior plate through the hull to the mast. It must have a fine radius to prevent side flashes and be of significant size to carry huge current- Difficult at best.

Could lightning strike the mast then enter the inclosed ballast and strip the fiberglass keel from it? That would depend on the unpredictable path of current from the mast to the inclosed lead. The energy just might go through the bonded thruhulls or simply vaporize the voids on the hull and result in hundreds of tiny holes. The boat would sink like a kitchen colander...

The best we can do without splitting the atom is to attach the mast directly to the bonding system and jumper that connection to the maststep lagbolts to reduce galvanic corrosion. My boat came with the green wires attached to the tension rod. Go figure!

[Dolce_Vita]

...The lag bolts securing the maststep do not reach the lead ballast in most 323s. ... I used stainless allthread and tapped through the fiberglass two inches into the lead for mechanical strength.

Two inches???!!!  When I drilled and tapped new holes for my mast step lagbolts, I went through about 1/4" of fiberglass and then hit lead.  I used 2 1/2" long 3/8" SS lags, same size as what was there originally.

I had to drill 4 new holes, as the mild steel lags that were there originally had corroded and swelled enough to enlarge the holes so much that the new lags wouldn't hold in them at all.

[Dulcinea]

I had the same experience as Ed.  Hit the lead pretty quickly. Knew I hit it cuz the drill bit broke right off.

[Alma]

Good for you your bolts hit lead so soon. I needed to borrow a longer "gun tap" to reach the lead. A standard 1/4-20 wasn't long enough to reach through the bilge fiberglass to lead. I sure don't mind having the extra fiberglass over 4000 lbs of lead.

[Dolce_Vita]

I had the same experience as Ed.  Hit the lead pretty quickly. Knew I hit it cuz the drill bit broke right off.

I had been warned about that possibility by the folks at our marina.  Went very slow, used copious amounts of cutting oil, and backed out the bit every few turns to clear out the lead shavings.

[Dulcinea]

After breaking a drill bit, I knew it was one of those times when you need to let professionals do what they do, so the yard fixed the mast step and stepped the mast, even though our yacht club has a crane and guys do their own.  I wanted the yard to have ownership in the end product so there would be no debate if something wasn't right.  Worth the money....this time.

[Carolina Dog]

Alma,

Thanks for that excellent  post. I Am pulling the boat in a couple of weeks and will be finding out how deep my glass runs before I hit lead. I am going to decide at that time which route I go for lightening protection. Nigel Caulder has a pretty good chapter on this topic but at the end of the day I find the idea of putting a copper plate to the hull problematic. I will pick a system and go withit when I pull her out. Seems the real big issue is the side flash which, should it jump through a person to get to ground, is the fatal part. That and not sinking. Ugh.