Recently I started to leave my slip for a day of sailing when the sky turned ugly and decided that discretion was the better part of valor. Arrived back at my slip as lightning flashes hit all around. In reviewing the information I have for my 1984 Hunter 25.5 I noted that the boat comes with an 8 gage mast ground. Can any one tell me how I can find a drawing or sketch showing how the grounding system is set up and, more importantly, how is the mast connected to the keel. I know that there is a compression post hidden in the port main bulkhead but what happens when that post reaches the keel area? There does not appear to be any floor panneling that can be removed that will show the keel area near the mast.
Mast to Keel Connection
- Thread starter Tony23670
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Two different things;
The mast ground your manual may refer to is the negative (-) connection to the 12V system that powers the lights. A mast to keel grounding with the purpose of providing protection from lighting strike damage is a different thing. On this second there are various schools of thought but no decisive evidence to back any of them. My personal opinion whether to ground or not depends on the equipment aboard the boat and how you sail. The most important thing aboard the boat is myself so if I'm out there a lot and get caught frequently in electric storms I would not ground for fear of attracting strikes. On the other hand if the boat is ladden with electronics and it mostly sits at the dock with me seldom being aboard during storm I would ground in the hope of minimizing any damages that could occur from one. On a small boat with few electronics I would not bother grounding it either. One thing I would recommend as very effective in those cases is "insurance". A good coverage will replace and repair any damaged components at little cost.
The mast ground your manual may refer to is the negative (-) connection to the 12V system that powers the lights. A mast to keel grounding with the purpose of providing protection from lighting strike damage is a different thing. On this second there are various schools of thought but no decisive evidence to back any of them. My personal opinion whether to ground or not depends on the equipment aboard the boat and how you sail. The most important thing aboard the boat is myself so if I'm out there a lot and get caught frequently in electric storms I would not ground for fear of attracting strikes. On the other hand if the boat is ladden with electronics and it mostly sits at the dock with me seldom being aboard during storm I would ground in the hope of minimizing any damages that could occur from one. On a small boat with few electronics I would not bother grounding it either. One thing I would recommend as very effective in those cases is "insurance". A good coverage will replace and repair any damaged components at little cost.
Similar question about where to ground the mast
I have a similar question regarding my 1977 Hunter 30. The boat is currently at the yard with the mast down for bottom work and to fix the infamous "I-beam". Where is the appropriate place to ground (bond) the mast to for lightning protection, the keel bolts or the engine block? The guy who is doing the work on the boat suggests the engine block, because the keel will be painted and might not be an efficient conductor. I think that it should be the keel bolts because that will isolate the lightning from the electrical system which is grounded to the engine block. Who is right? I'm a relative novice at this but have been pounding the web hard on this subject.
I have a similar question regarding my 1977 Hunter 30. The boat is currently at the yard with the mast down for bottom work and to fix the infamous "I-beam". Where is the appropriate place to ground (bond) the mast to for lightning protection, the keel bolts or the engine block? The guy who is doing the work on the boat suggests the engine block, because the keel will be painted and might not be an efficient conductor. I think that it should be the keel bolts because that will isolate the lightning from the electrical system which is grounded to the engine block. Who is right? I'm a relative novice at this but have been pounding the web hard on this subject.
old sailing book
H.A. Calahan's "learn to sail" , suggests that it doesn't really matter. He says that lighning will always leave the boat above the waterline - that it will jump from shrouds to the water. Which would suggest that it doesn't matter much. From my experience with electricity, grounding doesn't "attract" strikes..the lighning is of high enough voltage to break down the insulating properties of air..to lighning, anything is a conductor. Grounding will make your mast the same potential as the water. That suggests to me that grounding provides the same chance of being hit, as anywhere else in the water. if you are insulated..well you could be on the good side or on the bad side, depending on how the charge in the air is going.
H.A. Calahan's "learn to sail" , suggests that it doesn't really matter. He says that lighning will always leave the boat above the waterline - that it will jump from shrouds to the water. Which would suggest that it doesn't matter much. From my experience with electricity, grounding doesn't "attract" strikes..the lighning is of high enough voltage to break down the insulating properties of air..to lighning, anything is a conductor. Grounding will make your mast the same potential as the water. That suggests to me that grounding provides the same chance of being hit, as anywhere else in the water. if you are insulated..well you could be on the good side or on the bad side, depending on how the charge in the air is going.
The boat floats and so should the mast.
I like the no-ground school and Brian is spot on about the shrouds. Lightning has to jump through air to find earth ground. Why on earth would you want it to intentially go thru your boat if it could go around??? BTW, that paint that you think insulates will break down at less than 1,000 Volts. So, that paint insulation looks like a flee trying to stop a train. But if you must ground as some people think, I would go to the keel. Reason is simple - if current flows to the engine, it will make a jump out the shaft to the water thru the stuffing box. If the stuffing box is damaged, boat sinks. If it goes to the keel, it is a direct connection to the water. Boat floats. There are no guarantees with lightning because each strike is different. Sometimes its like a bomb and sometime its like a M-80.
I like the no-ground school and Brian is spot on about the shrouds. Lightning has to jump through air to find earth ground. Why on earth would you want it to intentially go thru your boat if it could go around??? BTW, that paint that you think insulates will break down at less than 1,000 Volts. So, that paint insulation looks like a flee trying to stop a train. But if you must ground as some people think, I would go to the keel. Reason is simple - if current flows to the engine, it will make a jump out the shaft to the water thru the stuffing box. If the stuffing box is damaged, boat sinks. If it goes to the keel, it is a direct connection to the water. Boat floats. There are no guarantees with lightning because each strike is different. Sometimes its like a bomb and sometime its like a M-80.
What about lightning arrestors
Thanks for the advice. Does anyone have an opinion on those wire brush "Lighning Masters" that mount on top of the mast? Most of what I've read says that they are a waste of money, but since my mast is down, now would be the time to install one> Dean
Thanks for the advice. Does anyone have an opinion on those wire brush "Lighning Masters" that mount on top of the mast? Most of what I've read says that they are a waste of money, but since my mast is down, now would be the time to install one> Dean
lightning arrestors
Our boat had a lightning arrestor on it when we purchased it in 2002. We have never been hit by lightning, but then neither have any of our neighbors.
Our boat had a lightning arrestor on it when we purchased it in 2002. We have never been hit by lightning, but then neither have any of our neighbors.
Wire Brush Lightning Arrestor
There are some very interesting documents that can be obtained via the internet on lightning and boats. Two documents in particular discuss the physics of lightning and applies this to boats. Both are from the University of Florida in Gainesville. As I understand the issue, a positive charge develops from the water up to the mast top. The clouds provide the negative charge and lightning occurs when these two are strong enoough to cause a transfer. A bolt goes from the bottom up and another comes down from the cloud. When I worked at the FDOT, Bridge Department, we used the "wire brushes" on bascule bridges to protect their electrical systems that opened and shut the bridges. You also see them on high mast lights around airports and alont the interstate system near intersections here in Florida. As I understand it, the system is intended to dissipate the positive charge that accumulates at high points and, ergo, prevents lightning from occuring at that point. The most interesting lightning strike I've seen was on the Sunshine Skyway Bridge across the entrance to Tampa Bay. At the top of each of the two pylons, each about 426 feet above sea level, thre are four lighning rods connected to a very heavy copper wire that goes down into the water. In Tampa Bay there are a lot of lightning storms. However, I once visited the bridge and noticed that the approaches had been hit. This was approximately about half a mile away from one of the tall pylons. The bolt had hit the top of the railing, run through the steel reinforcement in the railing and popped out about 6-7 feet away.
There are some very interesting documents that can be obtained via the internet on lightning and boats. Two documents in particular discuss the physics of lightning and applies this to boats. Both are from the University of Florida in Gainesville. As I understand the issue, a positive charge develops from the water up to the mast top. The clouds provide the negative charge and lightning occurs when these two are strong enoough to cause a transfer. A bolt goes from the bottom up and another comes down from the cloud. When I worked at the FDOT, Bridge Department, we used the "wire brushes" on bascule bridges to protect their electrical systems that opened and shut the bridges. You also see them on high mast lights around airports and alont the interstate system near intersections here in Florida. As I understand it, the system is intended to dissipate the positive charge that accumulates at high points and, ergo, prevents lightning from occuring at that point. The most interesting lightning strike I've seen was on the Sunshine Skyway Bridge across the entrance to Tampa Bay. At the top of each of the two pylons, each about 426 feet above sea level, thre are four lighning rods connected to a very heavy copper wire that goes down into the water. In Tampa Bay there are a lot of lightning storms. However, I once visited the bridge and noticed that the approaches had been hit. This was approximately about half a mile away from one of the tall pylons. The bolt had hit the top of the railing, run through the steel reinforcement in the railing and popped out about 6-7 feet away.
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