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Statistical 27-04-2021 06:21

So my boat lacks a lightning ground.
 
So my boat lacks a lightning ground. Not sure how that happened but I have double checked to make sure I am not crazy and it is true. The mast is tied directly into the DC negative bus which is turns goes to the electrical ground at the propshaft.

Not sure if this omission is original to the boat or something done by a prior owner. How big of a problem is this? I am thinking really big problem. My understanding is that there should be a separate lightning ground going to a ground plate in the water disconnected from the normal DC electrical system. As it exists now pretty sure a lightning strike would destroy the electrical system, batteries, and possibly engine.

Has anyone seen this before. It seems the fix would be simple (well it will require a haul out) so wondering why it wasn't done or if it was done originally why it was removed.

Frankly 27-04-2021 07:03

Re: So my boat lacks a lightning ground.
 
Somebody just took the easy way out. You are embarking down a treacherous path (asking that particular question on this forum). You will get a wide variety of opinions. My suggestion (from someone that worked in the LP business for buildings), get a large copper plate (approx, 6 X 24 X 1/4") mounted on the exterior with 4 substantial silicone bronze bolts (say 1/2"), and connect it to the base of the mast with a pair of 1/0 tinned copper battery cables (your choice of insulation color) in the most direct and shortest path avaliable. Check in on the assy every few years to make sure corrosion has not taken over.

What I did, and sleep pretty well at night.

Do not refer in any way to this as a lightning protection system but consider it a lightning mitigation system. This is to protect the craft and it's occupants against a visit from Zeus. If he shows up really mad then all bets are off. Protection of your less valuable electronics is a bit of a crap shoot and much more complicated.


Frankly

Statistical 27-04-2021 08:03

Re: So my boat lacks a lightning ground.
 
Quote:

Originally Posted by Frankly (Post 3395930)
Somebody just took the easy way out. You are embarking down a treacherous path (asking that particular question on this forum). You will get a wide variety of opinions. My suggestion (from someone that worked in the LP business for buildings), get a large copper plate (approx, 6 X 24 X 1/4") mounted on the exterior with 4 substantial silicone bronze bolts (say 1/2"), and connect it to the base of the mast with a pair of 1/0 tinned copper battery cables (your choice of insulation color) in the most direct and shortest path avaliable. Check in on the assy every few years to make sure corrosion has not taken over.

What I did, and sleep pretty well at night.

Do not refer in any way to this as a lightning protection system but consider it a lightning mitigation system. This is to protect the craft and it's occupants against a visit from Zeus. If he shows up really mad then all bets are off. Protection of your less valuable electronics is a bit of a crap shoot and much more complicated.


Frankly

Thanks for confirming what I suspected. Yeah the route you describe is what I have seen in Nigel's "Boatowners Mechanical and Electrical Manual". First time boatowner, I just kinda assumed it was there and we know what assuming does.

"Do not refer in any way to this as a lightning protection system but consider it a lightning mitigation system. "

That is a very good way to frame it. Keeps a bad event from being an even worse event.

Paul L 27-04-2021 08:09

Re: So my boat lacks a lightning ground.
 
How many years has it been like this?

Is this really the top of the list items you want to do on the boat?

Statistical 27-04-2021 08:13

Re: So my boat lacks a lightning ground.
 
Quote:

Originally Posted by Paul L (Post 3395958)
How many years has it been like this?

Is this really the top of the list items you want to do on the boat?

I don't know how long it has been like this. It is a pretty niche thing to find out how it was originally done on a boat that is 40 years old. If it is original to the boat it has been like this for a very long time. I think it is more likely something done by a prior owner so it could be a lot less. I have only owned her for less than a year.

I don't anticipate it being a complicated fix. It will require a haul out so I will wait until this fall when I need to paint the bottom anyways.

Jammer 27-04-2021 08:50

Re: So my boat lacks a lightning ground.
 
Quote:

Originally Posted by Frankly (Post 3395930)
You are embarking down a treacherous path (asking that particular question on this forum). You will get a wide variety of opinions.


This topic is on a long and growing list of electrical questions I no longer try to answer.


Quote:


My suggestion (from someone that worked in the LP business for buildings), get a large copper plate (approx, 6 X 24 X 1/4") mounted on the exterior with 4 substantial silicone bronze bolts (say 1/2"), and connect it to the base of the mast with a pair of 1/0 tinned copper battery cables (your choice of insulation color) in the most direct and shortest path avaliable.


I will make the (hopefully uncontroversial) suggestion that tinned copper braid will be far more effective than battery cable.

OS2Dude 27-04-2021 09:26

Re: So my boat lacks a lightning ground.
 
I would remove the lightening ground from the electrical system first thing. You are right, if you were to get struck your systems would all be fried and your'e boat likely sink from the lightening trying to get out the shaft.

That said, our boat has no lightening mitigation in place. When we first got our boat, I researched lightening protection quite a bit. Half said it will attract lightening, half said (as above) that it can only mitigate the effects and the last half swore by the latest fad.

lvictorlucas 27-04-2021 09:28

Re: So my boat lacks a lightning ground.
 
One more opinion that is worth what you paid for it. I won't bore you with reasoning. I prefer to isolate the mast and standing rigging from the electrical system. I connect the base of the mast to a large (at least several square feet) grounding plate below the waterline with a short as possible and straight as possible, copper pipe that has been pressed flat at the ends then drilled for a large bolt. Use conductive compound (NOT non-conductive) on the cleaned attachment bolts then seal well with a long lasting sealant. If your bilge is wet paint the bare copper to reduce corrosion.

Scubaseas 27-04-2021 09:56

Re: So my boat lacks a lightning ground.
 
Do you not have these? https://www.ftp.tognews.com/Projects/.../rudder003.jpg
Some Ty37 owners added ground straps. Look at Projects on the TOG news site

MartinF 27-04-2021 09:57

Re: So my boat lacks a lightning ground.
 
I suspect that 90% of boats have no lightning protection better than a pair of crossed fingers. Wandering around the marina yard I see no grounding plates.:confused:

Tomodore 27-04-2021 10:08

Re: So my boat lacks a lightning ground.
 
What style keel do you have? Encapsulated keels benefit from adding something external, bolted on iron or lead keels only need protection run to keel bolt. One more thing before the other posts correct my ignorance do not use a sintered bronze ground shoe that is designed for HF radio for your external ground. The sudden charge of a lightning bolt can violently boil\steam the shoe from the inside since it is a honey comb. I realize that lighting and actual instances are unknowable, my favourite example was the ketch at anchor that was struck on the lower mizzen mast aft and then grounded out the anchor chain forward fusing the links.

Statistical 27-04-2021 10:24

Re: So my boat lacks a lightning ground.
 
Quote:

Originally Posted by Tomodore (Post 3396057)
What style keel do you have? Encapsulated keels benefit from adding something external, bolted on iron or lead keels only need protection run to keel bolt. One more thing before the other posts correct my ignorance do not use a sintered bronze ground shoe that is designed for HF radio for your external ground. The sudden charge of a lightning bolt can violently boil\steam the shoe from the inside since it is a honey comb. I realize that lighting and actual instances are unknowable, my favourite example was the ketch at anchor that was struck on the lower mizzen mast aft and then grounded out the anchor chain forward fusing the links.

it is encapsulated so I will need an external plate. Nigel Calder makes the same warning as you. Looks like the consensus is 1 sq ft solid copper plate as a lightning ground thru bolted and connected to the mast by heavy gauge wire. Should be isolated from the DC system.

It doesn't seem particularly hard (famous last words on a boat) and will give me peace of mind.

Statistical 27-04-2021 10:29

Re: So my boat lacks a lightning ground.
 
Quote:

Originally Posted by Scubaseas (Post 3396045)
Do you not have these? https://www.ftp.tognews.com/Projects/.../rudder003.jpg
Some Ty37 owners added ground straps. Look at Projects on the TOG news site

Thanks for that resource. Not sure how that would connect to mast for lightning ground but will look into it.

donradcliffe 27-04-2021 10:45

Re: So my boat lacks a lightning ground.
 
There is a reason a lot of boats don't have lightning grounds. They can create electrolytic corrosion loops.

sinnerman 27-04-2021 10:56

Re: So my boat lacks a lightning ground.
 
Boat's electrical "bonding" systems will sometimes connect to the prop shaft (bonding the electrical grounds in the boat together to prevent stray voltages).

They utilize electrical brushes on the shaft to maintain contact while the shaft rotates.

Lightning dissipation systems would NOT be connected to the DC system (or the prop shaft). This would be the equivalent of routing a lit dynamite fuse through your powder keg room.

cheers


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