I have a 1981 CD25;Question #1:There is heavy-duty wire connecting port/starboard shrouds under the deck and running back to the bilge under the cockpit, where they are joined and connected to a 10' length of similar size wire (battery cable size wire).It was installed by CD when the boat was built.The end of the wire has never been connected to anything; it's just coiled in the bilge.A marine mechanic recommends removing it entirely, does not recommend attaching it to a seacock (there are only 2).Any suggestions or recommendations? Question #2:The bilge extends aft under the cockpit and is totally inaccessible by sight or access to clean it out or even know what is in there. The manual bilge pump hose is 1 1/2" D and is inserted through a 2" hole in the port side bulkhead under the cockpit, with no strainer fitting attached. It is not possible to even see whether this hose is actually positioned to pump out most of the bilge. Would it be advisable to cut out say a 4" Diameter hole in the same port bulkhead under the cockpit, so as to be able to shine a flashlight through and reach into the bilge with one hand to clean it out. The main concern is whether this would cause any structual weakness since this bulkhead is part of the support structure of hull/cockpit, etc. Any advice would be appreciated.
dfclec@erols.com
CD25:Lightning Protection & Access to Bilge
Moderator: Jim Walsh
-
Larry DeMers
Re: CD25:Lightning Protection & Access to Bilge
Hi,
There are two schools of thought as to lightning protection.
1) You do not ground anything to anything, and hope that lightning goes somewhere else.
This belief tries to avoid the bonding of all metallic objects in the belief that to ground an underwater metallic object invites electrolysis, thus necessitating zinc sacrificial anodes.
What happens to you when lightning hits an ungrounded boat? Plenty. The lightning stroke consists of two parts, a "stepped leader", which is a lower powered discharge that searches for the lowest impedance path to ground, starting at ground and working upwards towards the clouds that hold the strongest positive charge. The second part is the main charge, which comes fromthe cloud base, and follows the stepped leader down into your boats interior. It will search for it's own path to ground, and in the process create hundreds of holes along the waterline, and it will also flash over to nearby metallic objects, and again search for the illusive low impedance path to ground..through the laminate usually. A friends Columbia 29 got hit two years ago..200 holes, and over 1 year of repairs before it was ready to get wet again...and he was very lucky not to sink.
2) Second School of thought is to ground everything in the boat that is made of metal. This then will create a pathway to ground for the stepped leader to follow, which also gets followed by the main charge...*if the path has few turns, all of which are slowly radiussed turns..no sharp angles allowed*. In other words, you have a hand in directing the charge to ground, and if it is designed properly, it will keep the damages smaller by comparison to the ungrounded condition. You will still loose all electronics (probably)..plugged in or not (due ot hte EMP pulse generated by the charge).
Summary: So either you don't ground the mast and metal parts, making the mast electrically less visible to the stepped leader, and avoiding some possible lightning strikes, but possibly getting the bottom blown out if you do het hit.
......or,
You do ground the mast to all metal objects and the engine and shaft on the boat, thus electrically moving the ground reference level to the top of the mast rather than 40-45 ft. below it at water level, suddenly becoming a tall object with a good ground path. YOu are probably more likely to get hit, but you are also better protected when it happens, and in fact may not even know it happened until told by someone watching from a distance away (this would be a split strike, where a portion of the charge goes somewhere else..very common occurance).
Finally: In your case, the unattached wire was someones attempt at choosing situation #1 over #2.
You should know that the ABYC rules that all insurance companies go by *requires* a bonded system to discharge the lightning. You will not be covered possibly if you do not have this bonding in place and lightning should involve you and your boat.
How lucky do you feel today? :^)
Bond that puppy..
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing (and ducking lightning) on Lake Superior~~
demers@sgi.com
There are two schools of thought as to lightning protection.
1) You do not ground anything to anything, and hope that lightning goes somewhere else.
This belief tries to avoid the bonding of all metallic objects in the belief that to ground an underwater metallic object invites electrolysis, thus necessitating zinc sacrificial anodes.
What happens to you when lightning hits an ungrounded boat? Plenty. The lightning stroke consists of two parts, a "stepped leader", which is a lower powered discharge that searches for the lowest impedance path to ground, starting at ground and working upwards towards the clouds that hold the strongest positive charge. The second part is the main charge, which comes fromthe cloud base, and follows the stepped leader down into your boats interior. It will search for it's own path to ground, and in the process create hundreds of holes along the waterline, and it will also flash over to nearby metallic objects, and again search for the illusive low impedance path to ground..through the laminate usually. A friends Columbia 29 got hit two years ago..200 holes, and over 1 year of repairs before it was ready to get wet again...and he was very lucky not to sink.
2) Second School of thought is to ground everything in the boat that is made of metal. This then will create a pathway to ground for the stepped leader to follow, which also gets followed by the main charge...*if the path has few turns, all of which are slowly radiussed turns..no sharp angles allowed*. In other words, you have a hand in directing the charge to ground, and if it is designed properly, it will keep the damages smaller by comparison to the ungrounded condition. You will still loose all electronics (probably)..plugged in or not (due ot hte EMP pulse generated by the charge).
Summary: So either you don't ground the mast and metal parts, making the mast electrically less visible to the stepped leader, and avoiding some possible lightning strikes, but possibly getting the bottom blown out if you do het hit.
......or,
You do ground the mast to all metal objects and the engine and shaft on the boat, thus electrically moving the ground reference level to the top of the mast rather than 40-45 ft. below it at water level, suddenly becoming a tall object with a good ground path. YOu are probably more likely to get hit, but you are also better protected when it happens, and in fact may not even know it happened until told by someone watching from a distance away (this would be a split strike, where a portion of the charge goes somewhere else..very common occurance).
Finally: In your case, the unattached wire was someones attempt at choosing situation #1 over #2.
You should know that the ABYC rules that all insurance companies go by *requires* a bonded system to discharge the lightning. You will not be covered possibly if you do not have this bonding in place and lightning should involve you and your boat.
How lucky do you feel today? :^)
Bond that puppy..
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing (and ducking lightning) on Lake Superior~~
David Cook wrote: I have a 1981 CD25;Question #1:There is heavy-duty wire connecting port/starboard shrouds under the deck and running back to the bilge under the cockpit, where they are joined and connected to a 10' length of similar size wire (battery cable size wire).It was installed by CD when the boat was built.The end of the wire has never been connected to anything; it's just coiled in the bilge.A marine mechanic recommends removing it entirely, does not recommend attaching it to a seacock (there are only 2).Any suggestions or recommendations? Question #2:The bilge extends aft under the cockpit and is totally inaccessible by sight or access to clean it out or even know what is in there. The manual bilge pump hose is 1 1/2" D and is inserted through a 2" hole in the port side bulkhead under the cockpit, with no strainer fitting attached. It is not possible to even see whether this hose is actually positioned to pump out most of the bilge. Would it be advisable to cut out say a 4" Diameter hole in the same port bulkhead under the cockpit, so as to be able to shine a flashlight through and reach into the bilge with one hand to clean it out. The main concern is whether this would cause any structual weakness since this bulkhead is part of the support structure of hull/cockpit, etc. Any advice would be appreciated.
demers@sgi.com
-
Jon
Re: CD25:Lightning Protection & Access to Bilge
Dave,
I clean my CD-25's bilge out with a huge wet-dry shop vac. I just take the filter out of the vac and reach in from the cabin floor. The long hard plastic tubes of the vac reach way back into the bilge and has lifted out things as big as old flares. If it is too big to fit up the tube the suction holds it against the end of the tube and you can just pull it out. It's a great way to get that last little bit of water out of there before winter wrap up too. With a good wrap up, the bilge is dry as a bone in the spring.
Jon
I clean my CD-25's bilge out with a huge wet-dry shop vac. I just take the filter out of the vac and reach in from the cabin floor. The long hard plastic tubes of the vac reach way back into the bilge and has lifted out things as big as old flares. If it is too big to fit up the tube the suction holds it against the end of the tube and you can just pull it out. It's a great way to get that last little bit of water out of there before winter wrap up too. With a good wrap up, the bilge is dry as a bone in the spring.
Jon
-
Bill Goldsmith
Re: CD25:Lightning Protection & Access to Bilge
Larry:
I am just a little confused. I understand all you wrote, but I thought that the bonding system actually reduced the chance of getting hit, by making the top of the mast "look" as though it were the surface of the water. Of course, if hit, it also has the effect of leading the charge and reducing damage, as you say. But I thought it had the additional effect of helping the boat to be "transparent."
Here's my anecdote of the day:
In June 1998 I delivered my boat with two friends (still friends) from Long Island, NY to the lower Hudson River. While on LI Sound off Huntington Harbor, we were completely becalmed, the water was like glass and there was a thick fog. As we motored slowly along, we heard rumbles of thunder that became closer and closer. Soon, we were in a full scale thunderstorm, in fog and dousing rain, but no wind at all. The lightning strikes at one point were within yards of the boat, and we could see ripples emanating from the strike points. During the entire storm the mast was pointed straight up and down with minimal movement due to the lack of wind and waves. Yet, despite the mast almost "begging" to be hit by close strikes, it seemed as though the lightning just didn't "see" us. To this day I believe that the bonding system helped to make the boat invisible during that storm in those conditions. Or maybe I'm just one lucky sailor!!
Bill Goldsmith
CD27 #173
Second Chance
goldy@bestweb.net
I am just a little confused. I understand all you wrote, but I thought that the bonding system actually reduced the chance of getting hit, by making the top of the mast "look" as though it were the surface of the water. Of course, if hit, it also has the effect of leading the charge and reducing damage, as you say. But I thought it had the additional effect of helping the boat to be "transparent."
Here's my anecdote of the day:
In June 1998 I delivered my boat with two friends (still friends) from Long Island, NY to the lower Hudson River. While on LI Sound off Huntington Harbor, we were completely becalmed, the water was like glass and there was a thick fog. As we motored slowly along, we heard rumbles of thunder that became closer and closer. Soon, we were in a full scale thunderstorm, in fog and dousing rain, but no wind at all. The lightning strikes at one point were within yards of the boat, and we could see ripples emanating from the strike points. During the entire storm the mast was pointed straight up and down with minimal movement due to the lack of wind and waves. Yet, despite the mast almost "begging" to be hit by close strikes, it seemed as though the lightning just didn't "see" us. To this day I believe that the bonding system helped to make the boat invisible during that storm in those conditions. Or maybe I'm just one lucky sailor!!
Bill Goldsmith
CD27 #173
Second Chance
Larry DeMers wrote: Hi,
There are two schools of thought as to lightning protection.
1) You do not ground anything to anything, and hope that lightning goes somewhere else.
This belief tries to avoid the bonding of all metallic objects in the belief that to ground an underwater metallic object invites electrolysis, thus necessitating zinc sacrificial anodes.
What happens to you when lightning hits an ungrounded boat? Plenty. The lightning stroke consists of two parts, a "stepped leader", which is a lower powered discharge that searches for the lowest impedance path to ground, starting at ground and working upwards towards the clouds that hold the strongest positive charge. The second part is the main charge, which comes fromthe cloud base, and follows the stepped leader down into your boats interior. It will search for it's own path to ground, and in the process create hundreds of holes along the waterline, and it will also flash over to nearby metallic objects, and again search for the illusive low impedance path to ground..through the laminate usually. A friends Columbia 29 got hit two years ago..200 holes, and over 1 year of repairs before it was ready to get wet again...and he was very lucky not to sink.
2) Second School of thought is to ground everything in the boat that is made of metal. This then will create a pathway to ground for the stepped leader to follow, which also gets followed by the main charge...*if the path has few turns, all of which are slowly radiussed turns..no sharp angles allowed*. In other words, you have a hand in directing the charge to ground, and if it is designed properly, it will keep the damages smaller by comparison to the ungrounded condition. You will still loose all electronics (probably)..plugged in or not (due ot hte EMP pulse generated by the charge).
Summary: So either you don't ground the mast and metal parts, making the mast electrically less visible to the stepped leader, and avoiding some possible lightning strikes, but possibly getting the bottom blown out if you do het hit.
......or,
You do ground the mast to all metal objects and the engine and shaft on the boat, thus electrically moving the ground reference level to the top of the mast rather than 40-45 ft. below it at water level, suddenly becoming a tall object with a good ground path. YOu are probably more likely to get hit, but you are also better protected when it happens, and in fact may not even know it happened until told by someone watching from a distance away (this would be a split strike, where a portion of the charge goes somewhere else..very common occurance).
Finally: In your case, the unattached wire was someones attempt at choosing situation #1 over #2.
You should know that the ABYC rules that all insurance companies go by *requires* a bonded system to discharge the lightning. You will not be covered possibly if you do not have this bonding in place and lightning should involve you and your boat.
How lucky do you feel today? :^)
Bond that puppy..
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing (and ducking lightning) on Lake Superior~~
David Cook wrote: I have a 1981 CD25;Question #1:There is heavy-duty wire connecting port/starboard shrouds under the deck and running back to the bilge under the cockpit, where they are joined and connected to a 10' length of similar size wire (battery cable size wire).It was installed by CD when the boat was built.The end of the wire has never been connected to anything; it's just coiled in the bilge.A marine mechanic recommends removing it entirely, does not recommend attaching it to a seacock (there are only 2).Any suggestions or recommendations? Question #2:The bilge extends aft under the cockpit and is totally inaccessible by sight or access to clean it out or even know what is in there. The manual bilge pump hose is 1 1/2" D and is inserted through a 2" hole in the port side bulkhead under the cockpit, with no strainer fitting attached. It is not possible to even see whether this hose is actually positioned to pump out most of the bilge. Would it be advisable to cut out say a 4" Diameter hole in the same port bulkhead under the cockpit, so as to be able to shine a flashlight through and reach into the bilge with one hand to clean it out. The main concern is whether this would cause any structual weakness since this bulkhead is part of the support structure of hull/cockpit, etc. Any advice would be appreciated.
goldy@bestweb.net
-
D. Stump, Hanalei
Re: Bill, you're correct...reduced potential...
Bill,
The same holds true for the old lightning rods on a barn. By grounding the rods the potential of the barn is reduced, ie. it looks to lightning as if it were at the same level as the surronding landscape. Think about it, if the lightning was hitting close aboard that foggy, slack wind day, and your vessel was at the same potential as the surrounding sea, you WERE taking a chance of being hit, but much less than if the mast had not been grounded! So, the answer is YES, you were lucky, but no more so than any of the rest of us mortals walking the surface of the earth!!!
Fair winds and following seas...
Dave Stump
Captain Commanding
s/v Hanalei CD-30
The same holds true for the old lightning rods on a barn. By grounding the rods the potential of the barn is reduced, ie. it looks to lightning as if it were at the same level as the surronding landscape. Think about it, if the lightning was hitting close aboard that foggy, slack wind day, and your vessel was at the same potential as the surrounding sea, you WERE taking a chance of being hit, but much less than if the mast had not been grounded! So, the answer is YES, you were lucky, but no more so than any of the rest of us mortals walking the surface of the earth!!!
Fair winds and following seas...
Dave Stump
Captain Commanding
s/v Hanalei CD-30
-
Bruce Bett
Re: CD25:Lightning Protection & Access to Bilge
Larry:
I've heard speculation that grounding plates for fresh water need to be huge relative to those needed in much more conductive salt water. I've also heard that porous grounding plates, while increasing surface area run the risk of boiling trapped water and blowing up. I must say the more I read and hear about this issue the less certain I becoume. Any comments.
Bruce
Hi,
bettb@macomb.cc.mi.us
I've heard speculation that grounding plates for fresh water need to be huge relative to those needed in much more conductive salt water. I've also heard that porous grounding plates, while increasing surface area run the risk of boiling trapped water and blowing up. I must say the more I read and hear about this issue the less certain I becoume. Any comments.
Bruce
Hi,
Larry DeMers wrote: There are two schools of thought as to lightning protection.
1) You do not ground anything to anything, and hope that lightning goes somewhere else.
This belief tries to avoid the bonding of all metallic objects in the belief that to ground an underwater metallic object invites electrolysis, thus necessitating zinc sacrificial anodes.
What happens to you when lightning hits an ungrounded boat? Plenty. The lightning stroke consists of two parts, a "stepped leader", which is a lower powered discharge that searches for the lowest impedance path to ground, starting at ground and working upwards towards the clouds that hold the strongest positive charge. The second part is the main charge, which comes fromthe cloud base, and follows the stepped leader down into your boats interior. It will search for it's own path to ground, and in the process create hundreds of holes along the waterline, and it will also flash over to nearby metallic objects, and again search for the illusive low impedance path to ground..through the laminate usually. A friends Columbia 29 got hit two years ago..200 holes, and over 1 year of repairs before it was ready to get wet again...and he was very lucky not to sink.
2) Second School of thought is to ground everything in the boat that is made of metal. This then will create a pathway to ground for the stepped leader to follow, which also gets followed by the main charge...*if the path has few turns, all of which are slowly radiussed turns..no sharp angles allowed*. In other words, you have a hand in directing the charge to ground, and if it is designed properly, it will keep the damages smaller by comparison to the ungrounded condition. You will still loose all electronics (probably)..plugged in or not (due ot hte EMP pulse generated by the charge).
Summary: So either you don't ground the mast and metal parts, making the mast electrically less visible to the stepped leader, and avoiding some possible lightning strikes, but possibly getting the bottom blown out if you do het hit.
......or,
You do ground the mast to all metal objects and the engine and shaft on the boat, thus electrically moving the ground reference level to the top of the mast rather than 40-45 ft. below it at water level, suddenly becoming a tall object with a good ground path. YOu are probably more likely to get hit, but you are also better protected when it happens, and in fact may not even know it happened until told by someone watching from a distance away (this would be a split strike, where a portion of the charge goes somewhere else..very common occurance).
Finally: In your case, the unattached wire was someones attempt at choosing situation #1 over #2.
You should know that the ABYC rules that all insurance companies go by *requires* a bonded system to discharge the lightning. You will not be covered possibly if you do not have this bonding in place and lightning should involve you and your boat.
How lucky do you feel today? :^)
Bond that puppy..
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing (and ducking lightning) on Lake Superior~~
David Cook wrote: I have a 1981 CD25;Question #1:There is heavy-duty wire connecting port/starboard shrouds under the deck and running back to the bilge under the cockpit, where they are joined and connected to a 10' length of similar size wire (battery cable size wire).It was installed by CD when the boat was built.The end of the wire has never been connected to anything; it's just coiled in the bilge.A marine mechanic recommends removing it entirely, does not recommend attaching it to a seacock (there are only 2).Any suggestions or recommendations? Question #2:The bilge extends aft under the cockpit and is totally inaccessible by sight or access to clean it out or even know what is in there. The manual bilge pump hose is 1 1/2" D and is inserted through a 2" hole in the port side bulkhead under the cockpit, with no strainer fitting attached. It is not possible to even see whether this hose is actually positioned to pump out most of the bilge. Would it be advisable to cut out say a 4" Diameter hole in the same port bulkhead under the cockpit, so as to be able to shine a flashlight through and reach into the bilge with one hand to clean it out. The main concern is whether this would cause any structual weakness since this bulkhead is part of the support structure of hull/cockpit, etc. Any advice would be appreciated.
bettb@macomb.cc.mi.us
-
John R.
Lightning and Boats
There's a hell of a lot of theory and commentary on this subject and I have one thing to say. It would be in any boaters best interest if they read a small black book called "LIGHTNING and BOATS" a manual of safety and prevention, written by Micheal V. Huck Jr. He has comprised a lot of good information in the book.
I originally got my copy from West Marine. The publisher is Seaworthy Publications of Brookfield, Wisconsin.
I originally got my copy from West Marine. The publisher is Seaworthy Publications of Brookfield, Wisconsin.
-
Jim Burke
Re: CD25:Lightning Protection & Access to Bilge
I was in the cabin of my CD30 Eventide, hull #111, moored in the St. Johns River in front of my house, reading manuals and waiting for a thunderstorm to pass when the windvane atop the mast was blown away by a ligntning strike. Smelled a slight electrical fire smell for just a second or two, but sufferred no damage except to my knotmeter and VFR, the only electronics I had aboard. Eventide is factory grounded.
jburke2046@fl.freei.net
David Cook wrote: I have a 1981 CD25;Question #1:There is heavy-duty wire connecting port/starboard shrouds under the deck and running back to the bilge under the cockpit, where they are joined and connected to a 10' length of similar size wire (battery cable size wire).It was installed by CD when the boat was built.The end of the wire has never been connected to anything; it's just coiled in the bilge.A marine mechanic recommends removing it entirely, does not recommend attaching it to a seacock (there are only 2).Any suggestions or recommendations? Question #2:The bilge extends aft under the cockpit and is totally inaccessible by sight or access to clean it out or even know what is in there. The manual bilge pump hose is 1 1/2" D and is inserted through a 2" hole in the port side bulkhead under the cockpit, with no strainer fitting attached. It is not possible to even see whether this hose is actually positioned to pump out most of the bilge. Would it be advisable to cut out say a 4" Diameter hole in the same port bulkhead under the cockpit, so as to be able to shine a flashlight through and reach into the bilge with one hand to clean it out. The main concern is whether this would cause any structual weakness since this bulkhead is part of the support structure of hull/cockpit, etc. Any advice would be appreciated.
jburke2046@fl.freei.net
-
Larry DeMers
Re: CD25:Lightning Protection & Access to Bilge
These stories may have merit. Lightning protection is not an exact science, and the lightning always wins in face-offs. ie: It sometimes disobeys the rules we foolishly establish.
I think to mitigate the worries that the sintered ground cannot handle the lightning charge (it was never intended to handle it. It is only for a good RF ground, required for LORAN receivers, and SSB systems, as well as Ham HF transcievers that want to increase their ground image, Radar Receivers etc.), realize that there is a lot of metal in contact with the water besides that sintered ground plate. .
The main charge of lightning is going to exit through the engine to shaft path, as well as through the seacocks all in parallel, and of course the keel. These are all good heavy conductors, which means a low impedance pathway to ground.. Some people have added a quite large copper plate exterior to the hull, near the keel, and this is their lightning ground plate. It can be coated with a conducting barrier so it does not grow over. I don't fel that this buys anything over an grounded and encapsulated keel, as the thin fiberglass covering the encapsulated lead -or steel will be in RF contact with the water..especially salt water -through capacitative coupling.
But these ideas are all experimental as far as I have read. You guys may have heard of other methods to ground that charge. I sure would love to hear about them. This topic fascinates me. It must be the immensity of the charge, and the relative randomness of it's strikes that make me listen harder to lightning stories.
That and local black bears..I do not know how to handle them either, I have had intiment encounters with both, and do not understand either encounter very well.. that intrigues me.
Cheers!!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing in Snow -on Lake Superior yesterday!~~
demers@sgi.com
I think to mitigate the worries that the sintered ground cannot handle the lightning charge (it was never intended to handle it. It is only for a good RF ground, required for LORAN receivers, and SSB systems, as well as Ham HF transcievers that want to increase their ground image, Radar Receivers etc.), realize that there is a lot of metal in contact with the water besides that sintered ground plate. .
The main charge of lightning is going to exit through the engine to shaft path, as well as through the seacocks all in parallel, and of course the keel. These are all good heavy conductors, which means a low impedance pathway to ground.. Some people have added a quite large copper plate exterior to the hull, near the keel, and this is their lightning ground plate. It can be coated with a conducting barrier so it does not grow over. I don't fel that this buys anything over an grounded and encapsulated keel, as the thin fiberglass covering the encapsulated lead -or steel will be in RF contact with the water..especially salt water -through capacitative coupling.
But these ideas are all experimental as far as I have read. You guys may have heard of other methods to ground that charge. I sure would love to hear about them. This topic fascinates me. It must be the immensity of the charge, and the relative randomness of it's strikes that make me listen harder to lightning stories.
That and local black bears..I do not know how to handle them either, I have had intiment encounters with both, and do not understand either encounter very well.. that intrigues me.
Cheers!!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing in Snow -on Lake Superior yesterday!~~
Bruce Bett wrote: Larry:
I've heard speculation that grounding plates for fresh water need to be huge relative to those needed in much more conductive salt water. I've also heard that porous grounding plates, while increasing surface area run the risk of boiling trapped water and blowing up. I must say the more I read and hear about this issue the less certain I becoume. Any comments.
Bruce
Hi,Larry DeMers wrote: There are two schools of thought as to lightning protection.
1) You do not ground anything to anything, and hope that lightning goes somewhere else.
This belief tries to avoid the bonding of all metallic objects in the belief that to ground an underwater metallic object invites electrolysis, thus necessitating zinc sacrificial anodes.
What happens to you when lightning hits an ungrounded boat? Plenty. The lightning stroke consists of two parts, a "stepped leader", which is a lower powered discharge that searches for the lowest impedance path to ground, starting at ground and working upwards towards the clouds that hold the strongest positive charge. The second part is the main charge, which comes fromthe cloud base, and follows the stepped leader down into your boats interior. It will search for it's own path to ground, and in the process create hundreds of holes along the waterline, and it will also flash over to nearby metallic objects, and again search for the illusive low impedance path to ground..through the laminate usually. A friends Columbia 29 got hit two years ago..200 holes, and over 1 year of repairs before it was ready to get wet again...and he was very lucky not to sink.
2) Second School of thought is to ground everything in the boat that is made of metal. This then will create a pathway to ground for the stepped leader to follow, which also gets followed by the main charge...*if the path has few turns, all of which are slowly radiussed turns..no sharp angles allowed*. In other words, you have a hand in directing the charge to ground, and if it is designed properly, it will keep the damages smaller by comparison to the ungrounded condition. You will still loose all electronics (probably)..plugged in or not (due ot hte EMP pulse generated by the charge).
Summary: So either you don't ground the mast and metal parts, making the mast electrically less visible to the stepped leader, and avoiding some possible lightning strikes, but possibly getting the bottom blown out if you do het hit.
......or,
You do ground the mast to all metal objects and the engine and shaft on the boat, thus electrically moving the ground reference level to the top of the mast rather than 40-45 ft. below it at water level, suddenly becoming a tall object with a good ground path. YOu are probably more likely to get hit, but you are also better protected when it happens, and in fact may not even know it happened until told by someone watching from a distance away (this would be a split strike, where a portion of the charge goes somewhere else..very common occurance).
Finally: In your case, the unattached wire was someones attempt at choosing situation #1 over #2.
You should know that the ABYC rules that all insurance companies go by *requires* a bonded system to discharge the lightning. You will not be covered possibly if you do not have this bonding in place and lightning should involve you and your boat.
How lucky do you feel today? :^)
Bond that puppy..
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing (and ducking lightning) on Lake Superior~~
David Cook wrote: I have a 1981 CD25;Question #1:There is heavy-duty wire connecting port/starboard shrouds under the deck and running back to the bilge under the cockpit, where they are joined and connected to a 10' length of similar size wire (battery cable size wire).It was installed by CD when the boat was built.The end of the wire has never been connected to anything; it's just coiled in the bilge.A marine mechanic recommends removing it entirely, does not recommend attaching it to a seacock (there are only 2).Any suggestions or recommendations? Question #2:The bilge extends aft under the cockpit and is totally inaccessible by sight or access to clean it out or even know what is in there. The manual bilge pump hose is 1 1/2" D and is inserted through a 2" hole in the port side bulkhead under the cockpit, with no strainer fitting attached. It is not possible to even see whether this hose is actually positioned to pump out most of the bilge. Would it be advisable to cut out say a 4" Diameter hole in the same port bulkhead under the cockpit, so as to be able to shine a flashlight through and reach into the bilge with one hand to clean it out. The main concern is whether this would cause any structual weakness since this bulkhead is part of the support structure of hull/cockpit, etc. Any advice would be appreciated.
demers@sgi.com
-
Larry DeMers
Re: CD25:Lightning Protection & Access to Bilge
Well, it sure would seem so. But consider this analogy:
On a golf course, Trees are growing out of the ground, they get soaking wet during storms, so the electrical pathway is fairly low in resistance, making that tree a very good ground. Effectively, and viewed from an in-space viewpoint of the fields near the earths surface near the tree, the ground seems to rise up and enclose the whole tree. The problem is that the tree is also now the very highest point of ground all around him, and that is what the stepped leader looks for to get the shortest pathway to the +cloud chrge that is building up. The tree gets hit.
On our boats, the grounded mast raises the ground potential physically higher than the surrounding air. It becomes quite attractive to a stepped leader, which may or may not form into a full charge. Heck, sometimes it just causes a gaseous glow (St. Elmos Fire on Plane wings), or it can form Ball Lightning..a really discarnatly scary event. So ok, that damn stick is attractive to lightning, so how do I avoid being the punching bag of every storm in the county? By several methods. You can dissipate the minor charges that accompany the stepped leader, which will eliminate that leader from forming. Unfortunately, there will probably be another right behind it forming as long as you remain in that particular area, so the dissipation technique needs to be continuous. A bottle-brush shaped dissipator would possibly be your answer here.
So the lightning wins, and takes the stepped leaders pathway to your mast tip. Here is where your hard work in grounding the boat pays off. The charge follows the mast with the majority of the charge (shrouds are far too high a resistance compared to the cross section of a mast). The mast is bonded, with the wire going as straight as you can make it..so the charge comes along (this thing can be 12 in. round), turning your conductor to plasma as it goes. This is as intended, as plasma is a far lower impedance to lightning, and it will contain most charges, as long as the path is fairly straight.Now the charge encounters the grounded thru-hulls, all in parallel so it dumps a portion of the charge into that ground. It continues to the engine, keel and underwater structure. You are relatively safe now, as the charge is outside the boat now. Sure..there will be damage. but more than likely, you will be able to motor back tot he marina and get repaired.
The alternative of no bonding allows the lightning to choose it's own pathway..and that will do far more damage.
Hope this didn't muddy up the situation too much.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30
demers@sgi.com
On a golf course, Trees are growing out of the ground, they get soaking wet during storms, so the electrical pathway is fairly low in resistance, making that tree a very good ground. Effectively, and viewed from an in-space viewpoint of the fields near the earths surface near the tree, the ground seems to rise up and enclose the whole tree. The problem is that the tree is also now the very highest point of ground all around him, and that is what the stepped leader looks for to get the shortest pathway to the +cloud chrge that is building up. The tree gets hit.
On our boats, the grounded mast raises the ground potential physically higher than the surrounding air. It becomes quite attractive to a stepped leader, which may or may not form into a full charge. Heck, sometimes it just causes a gaseous glow (St. Elmos Fire on Plane wings), or it can form Ball Lightning..a really discarnatly scary event. So ok, that damn stick is attractive to lightning, so how do I avoid being the punching bag of every storm in the county? By several methods. You can dissipate the minor charges that accompany the stepped leader, which will eliminate that leader from forming. Unfortunately, there will probably be another right behind it forming as long as you remain in that particular area, so the dissipation technique needs to be continuous. A bottle-brush shaped dissipator would possibly be your answer here.
So the lightning wins, and takes the stepped leaders pathway to your mast tip. Here is where your hard work in grounding the boat pays off. The charge follows the mast with the majority of the charge (shrouds are far too high a resistance compared to the cross section of a mast). The mast is bonded, with the wire going as straight as you can make it..so the charge comes along (this thing can be 12 in. round), turning your conductor to plasma as it goes. This is as intended, as plasma is a far lower impedance to lightning, and it will contain most charges, as long as the path is fairly straight.Now the charge encounters the grounded thru-hulls, all in parallel so it dumps a portion of the charge into that ground. It continues to the engine, keel and underwater structure. You are relatively safe now, as the charge is outside the boat now. Sure..there will be damage. but more than likely, you will be able to motor back tot he marina and get repaired.
The alternative of no bonding allows the lightning to choose it's own pathway..and that will do far more damage.
Hope this didn't muddy up the situation too much.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30
Bill Goldsmith wrote: Larry:
I am just a little confused. I understand all you wrote, but I thought that the bonding system actually reduced the chance of getting hit, by making the top of the mast "look" as though it were the surface of the water. Of course, if hit, it also has the effect of leading the charge and reducing damage, as you say. But I thought it had the additional effect of helping the boat to be "transparent."
Here's my anecdote of the day:
In June 1998 I delivered my boat with two friends (still friends) from Long Island, NY to the lower Hudson River. While on LI Sound off Huntington Harbor, we were completely becalmed, the water was like glass and there was a thick fog. As we motored slowly along, we heard rumbles of thunder that became closer and closer. Soon, we were in a full scale thunderstorm, in fog and dousing rain, but no wind at all. The lightning strikes at one point were within yards of the boat, and we could see ripples emanating from the strike points. During the entire storm the mast was pointed straight up and down with minimal movement due to the lack of wind and waves. Yet, despite the mast almost "begging" to be hit by close strikes, it seemed as though the lightning just didn't "see" us. To this day I believe that the bonding system helped to make the boat invisible during that storm in those conditions. Or maybe I'm just one lucky sailor!!
Bill Goldsmith
CD27 #173
Second Chance
Larry DeMers wrote: Hi,
There are two schools of thought as to lightning protection.
1) You do not ground anything to anything, and hope that lightning goes somewhere else.
This belief tries to avoid the bonding of all metallic objects in the belief that to ground an underwater metallic object invites electrolysis, thus necessitating zinc sacrificial anodes.
What happens to you when lightning hits an ungrounded boat? Plenty. The lightning stroke consists of two parts, a "stepped leader", which is a lower powered discharge that searches for the lowest impedance path to ground, starting at ground and working upwards towards the clouds that hold the strongest positive charge. The second part is the main charge, which comes fromthe cloud base, and follows the stepped leader down into your boats interior. It will search for it's own path to ground, and in the process create hundreds of holes along the waterline, and it will also flash over to nearby metallic objects, and again search for the illusive low impedance path to ground..through the laminate usually. A friends Columbia 29 got hit two years ago..200 holes, and over 1 year of repairs before it was ready to get wet again...and he was very lucky not to sink.
2) Second School of thought is to ground everything in the boat that is made of metal. This then will create a pathway to ground for the stepped leader to follow, which also gets followed by the main charge...*if the path has few turns, all of which are slowly radiussed turns..no sharp angles allowed*. In other words, you have a hand in directing the charge to ground, and if it is designed properly, it will keep the damages smaller by comparison to the ungrounded condition. You will still loose all electronics (probably)..plugged in or not (due ot hte EMP pulse generated by the charge).
Summary: So either you don't ground the mast and metal parts, making the mast electrically less visible to the stepped leader, and avoiding some possible lightning strikes, but possibly getting the bottom blown out if you do het hit.
......or,
You do ground the mast to all metal objects and the engine and shaft on the boat, thus electrically moving the ground reference level to the top of the mast rather than 40-45 ft. below it at water level, suddenly becoming a tall object with a good ground path. YOu are probably more likely to get hit, but you are also better protected when it happens, and in fact may not even know it happened until told by someone watching from a distance away (this would be a split strike, where a portion of the charge goes somewhere else..very common occurance).
Finally: In your case, the unattached wire was someones attempt at choosing situation #1 over #2.
You should know that the ABYC rules that all insurance companies go by *requires* a bonded system to discharge the lightning. You will not be covered possibly if you do not have this bonding in place and lightning should involve you and your boat.
How lucky do you feel today? :^)
Bond that puppy..
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing (and ducking lightning) on Lake Superior~~
David Cook wrote: I have a 1981 CD25;Question #1:There is heavy-duty wire connecting port/starboard shrouds under the deck and running back to the bilge under the cockpit, where they are joined and connected to a 10' length of similar size wire (battery cable size wire).It was installed by CD when the boat was built.The end of the wire has never been connected to anything; it's just coiled in the bilge.A marine mechanic recommends removing it entirely, does not recommend attaching it to a seacock (there are only 2).Any suggestions or recommendations? Question #2:The bilge extends aft under the cockpit and is totally inaccessible by sight or access to clean it out or even know what is in there. The manual bilge pump hose is 1 1/2" D and is inserted through a 2" hole in the port side bulkhead under the cockpit, with no strainer fitting attached. It is not possible to even see whether this hose is actually positioned to pump out most of the bilge. Would it be advisable to cut out say a 4" Diameter hole in the same port bulkhead under the cockpit, so as to be able to shine a flashlight through and reach into the bilge with one hand to clean it out. The main concern is whether this would cause any structual weakness since this bulkhead is part of the support structure of hull/cockpit, etc. Any advice would be appreciated.
demers@sgi.com
-
Bill Goldsmith
Re: CD25:Lightning Protection & Access to Bilge
Larry,
No mud there. What you are saying really makes sense. Lightning is a very important discussion to have and this board is a great way to increase all CDers' understanding of it. Here's more: A sailor friend of mine keeps a few extra jumper cables on his boat. When he encounters lightning he hooks the cables onto the shrouds and stay and throws the other end into the water. The boat is grounded as well (not a CD). Does that make sense to you? Is is helping, neutral, or asking for trouble?
Bill
, : Well, it sure would seem so. But consider this analogy:
goldy@bestweb.net
No mud there. What you are saying really makes sense. Lightning is a very important discussion to have and this board is a great way to increase all CDers' understanding of it. Here's more: A sailor friend of mine keeps a few extra jumper cables on his boat. When he encounters lightning he hooks the cables onto the shrouds and stay and throws the other end into the water. The boat is grounded as well (not a CD). Does that make sense to you? Is is helping, neutral, or asking for trouble?
Bill
, : Well, it sure would seem so. But consider this analogy:
Larry DeMers wrote: On a golf course, Trees are growing out of the ground, they get soaking wet during storms, so the electrical pathway is fairly low in resistance, making that tree a very good ground. Effectively, and viewed from an in-space viewpoint of the fields near the earths surface near the tree, the ground seems to rise up and enclose the whole tree. The problem is that the tree is also now the very highest point of ground all around him, and that is what the stepped leader looks for to get the shortest pathway to the +cloud chrge that is building up. The tree gets hit.
On our boats, the grounded mast raises the ground potential physically higher than the surrounding air. It becomes quite attractive to a stepped leader, which may or may not form into a full charge. Heck, sometimes it just causes a gaseous glow (St. Elmos Fire on Plane wings), or it can form Ball Lightning..a really discarnatly scary event. So ok, that damn stick is attractive to lightning, so how do I avoid being the punching bag of every storm in the county? By several methods. You can dissipate the minor charges that accompany the stepped leader, which will eliminate that leader from forming. Unfortunately, there will probably be another right behind it forming as long as you remain in that particular area, so the dissipation technique needs to be continuous. A bottle-brush shaped dissipator would possibly be your answer here.
So the lightning wins, and takes the stepped leaders pathway to your mast tip. Here is where your hard work in grounding the boat pays off. The charge follows the mast with the majority of the charge (shrouds are far too high a resistance compared to the cross section of a mast). The mast is bonded, with the wire going as straight as you can make it..so the charge comes along (this thing can be 12 in. round), turning your conductor to plasma as it goes. This is as intended, as plasma is a far lower impedance to lightning, and it will contain most charges, as long as the path is fairly straight.Now the charge encounters the grounded thru-hulls, all in parallel so it dumps a portion of the charge into that ground. It continues to the engine, keel and underwater structure. You are relatively safe now, as the charge is outside the boat now. Sure..there will be damage. but more than likely, you will be able to motor back tot he marina and get repaired.
The alternative of no bonding allows the lightning to choose it's own pathway..and that will do far more damage.
Hope this didn't muddy up the situation too much.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30
Bill Goldsmith wrote: Larry:
I am just a little confused. I understand all you wrote, but I thought that the bonding system actually reduced the chance of getting hit, by making the top of the mast "look" as though it were the surface of the water. Of course, if hit, it also has the effect of leading the charge and reducing damage, as you say. But I thought it had the additional effect of helping the boat to be "transparent."
Here's my anecdote of the day:
In June 1998 I delivered my boat with two friends (still friends) from Long Island, NY to the lower Hudson River. While on LI Sound off Huntington Harbor, we were completely becalmed, the water was like glass and there was a thick fog. As we motored slowly along, we heard rumbles of thunder that became closer and closer. Soon, we were in a full scale thunderstorm, in fog and dousing rain, but no wind at all. The lightning strikes at one point were within yards of the boat, and we could see ripples emanating from the strike points. During the entire storm the mast was pointed straight up and down with minimal movement due to the lack of wind and waves. Yet, despite the mast almost "begging" to be hit by close strikes, it seemed as though the lightning just didn't "see" us. To this day I believe that the bonding system helped to make the boat invisible during that storm in those conditions. Or maybe I'm just one lucky sailor!!
Bill Goldsmith
CD27 #173
Second Chance
Larry DeMers wrote: Hi,
There are two schools of thought as to lightning protection.
1) You do not ground anything to anything, and hope that lightning goes somewhere else.
This belief tries to avoid the bonding of all metallic objects in the belief that to ground an underwater metallic object invites electrolysis, thus necessitating zinc sacrificial anodes.
What happens to you when lightning hits an ungrounded boat? Plenty. The lightning stroke consists of two parts, a "stepped leader", which is a lower powered discharge that searches for the lowest impedance path to ground, starting at ground and working upwards towards the clouds that hold the strongest positive charge. The second part is the main charge, which comes fromthe cloud base, and follows the stepped leader down into your boats interior. It will search for it's own path to ground, and in the process create hundreds of holes along the waterline, and it will also flash over to nearby metallic objects, and again search for the illusive low impedance path to ground..through the laminate usually. A friends Columbia 29 got hit two years ago..200 holes, and over 1 year of repairs before it was ready to get wet again...and he was very lucky not to sink.
2) Second School of thought is to ground everything in the boat that is made of metal. This then will create a pathway to ground for the stepped leader to follow, which also gets followed by the main charge...*if the path has few turns, all of which are slowly radiussed turns..no sharp angles allowed*. In other words, you have a hand in directing the charge to ground, and if it is designed properly, it will keep the damages smaller by comparison to the ungrounded condition. You will still loose all electronics (probably)..plugged in or not (due ot hte EMP pulse generated by the charge).
Summary: So either you don't ground the mast and metal parts, making the mast electrically less visible to the stepped leader, and avoiding some possible lightning strikes, but possibly getting the bottom blown out if you do het hit.
......or,
You do ground the mast to all metal objects and the engine and shaft on the boat, thus electrically moving the ground reference level to the top of the mast rather than 40-45 ft. below it at water level, suddenly becoming a tall object with a good ground path. YOu are probably more likely to get hit, but you are also better protected when it happens, and in fact may not even know it happened until told by someone watching from a distance away (this would be a split strike, where a portion of the charge goes somewhere else..very common occurance).
Finally: In your case, the unattached wire was someones attempt at choosing situation #1 over #2.
You should know that the ABYC rules that all insurance companies go by *requires* a bonded system to discharge the lightning. You will not be covered possibly if you do not have this bonding in place and lightning should involve you and your boat.
How lucky do you feel today? :^)
Bond that puppy..
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing (and ducking lightning) on Lake Superior~~
goldy@bestweb.net
-
Larry DeMers
Re: CD25:Lightning Protection & Access to Bilge
Hi,
Well, it certainly is usefull, especially if he increases the contact square footage by a significant amount (ie; clamping a fistful of copper screen to the cables also). But the one limiting factor here is the damnably high resistance of S.S. wire rope compared to the low resistance of that mast cross section. It is so much higher that the beneftis may be quite small..although no doubt they are real.
I would not do this myself because of the mess of cables, sloppy connection to the shrouds, abrasion and the clamp striking the hull with waves etc. It's an old idea, used for a long time, and may really help. But I have not got any data to suggest this, and my intuitive sense says it is probably of little help, based on the resistance of those shrouds, and what not
I think I would opt for the bonded system, with straight as possible runs..and any turn having a large radius, and being say less than 30 deg. max overall. Use #2 or 4 solid aluminum wire for that lightning ground..copper is ok, but either will work here, and Al is cheaper and quite effective. It is a pain in the rear to hookup though, so think this through carefully. Use a large current connector to the mast base, and use dielectric grease on that connection betweent he aluminum mast, aluminum wire and copper/tinned lug. There is galvanic troubles possible here, so be wise.
From what I have read and experienced, this will give you the best protection possible today. But stay tuned, as this topic is ever advancing and changing slightly. New evidence accumulates daily, especially in the Florida Lightning Labs.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing Lake Superior~~~
demers@sgi.com
Well, it certainly is usefull, especially if he increases the contact square footage by a significant amount (ie; clamping a fistful of copper screen to the cables also). But the one limiting factor here is the damnably high resistance of S.S. wire rope compared to the low resistance of that mast cross section. It is so much higher that the beneftis may be quite small..although no doubt they are real.
I would not do this myself because of the mess of cables, sloppy connection to the shrouds, abrasion and the clamp striking the hull with waves etc. It's an old idea, used for a long time, and may really help. But I have not got any data to suggest this, and my intuitive sense says it is probably of little help, based on the resistance of those shrouds, and what not
I think I would opt for the bonded system, with straight as possible runs..and any turn having a large radius, and being say less than 30 deg. max overall. Use #2 or 4 solid aluminum wire for that lightning ground..copper is ok, but either will work here, and Al is cheaper and quite effective. It is a pain in the rear to hookup though, so think this through carefully. Use a large current connector to the mast base, and use dielectric grease on that connection betweent he aluminum mast, aluminum wire and copper/tinned lug. There is galvanic troubles possible here, so be wise.
From what I have read and experienced, this will give you the best protection possible today. But stay tuned, as this topic is ever advancing and changing slightly. New evidence accumulates daily, especially in the Florida Lightning Labs.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing Lake Superior~~~
Bill Goldsmith wrote: Larry,
No mud there. What you are saying really makes sense. Lightning is a very important discussion to have and this board is a great way to increase all CDers' understanding of it. Here's more: A sailor friend of mine keeps a few extra jumper cables on his boat. When he encounters lightning he hooks the cables onto the shrouds and stay and throws the other end into the water. The boat is grounded as well (not a CD). Does that make sense to you? Is is helping, neutral, or asking for trouble?
Bill
, : Well, it sure would seem so. But consider this analogy:
Larry DeMers wrote: On a golf course, Trees are growing out of the ground, they get soaking wet during storms, so the electrical pathway is fairly low in resistance, making that tree a very good ground. Effectively, and viewed from an in-space viewpoint of the fields near the earths surface near the tree, the ground seems to rise up and enclose the whole tree. The problem is that the tree is also now the very highest point of ground all around him, and that is what the stepped leader looks for to get the shortest pathway to the +cloud chrge that is building up. The tree gets hit.
On our boats, the grounded mast raises the ground potential physically higher than the surrounding air. It becomes quite attractive to a stepped leader, which may or may not form into a full charge. Heck, sometimes it just causes a gaseous glow (St. Elmos Fire on Plane wings), or it can form Ball Lightning..a really discarnatly scary event. So ok, that damn stick is attractive to lightning, so how do I avoid being the punching bag of every storm in the county? By several methods. You can dissipate the minor charges that accompany the stepped leader, which will eliminate that leader from forming. Unfortunately, there will probably be another right behind it forming as long as you remain in that particular area, so the dissipation technique needs to be continuous. A bottle-brush shaped dissipator would possibly be your answer here.
So the lightning wins, and takes the stepped leaders pathway to your mast tip. Here is where your hard work in grounding the boat pays off. The charge follows the mast with the majority of the charge (shrouds are far too high a resistance compared to the cross section of a mast). The mast is bonded, with the wire going as straight as you can make it..so the charge comes along (this thing can be 12 in. round), turning your conductor to plasma as it goes. This is as intended, as plasma is a far lower impedance to lightning, and it will contain most charges, as long as the path is fairly straight.Now the charge encounters the grounded thru-hulls, all in parallel so it dumps a portion of the charge into that ground. It continues to the engine, keel and underwater structure. You are relatively safe now, as the charge is outside the boat now. Sure..there will be damage. but more than likely, you will be able to motor back tot he marina and get repaired.
The alternative of no bonding allows the lightning to choose it's own pathway..and that will do far more damage.
Hope this didn't muddy up the situation too much.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30
Larry DeMers wrote:Bill Goldsmith wrote: Larry:
I am just a little confused. I understand all you wrote, but I thought that the bonding system actually reduced the chance of getting hit, by making the top of the mast "look" as though it were the surface of the water. Of course, if hit, it also has the effect of leading the charge and reducing damage, as you say. But I thought it had the additional effect of helping the boat to be "transparent."
Here's my anecdote of the day:
In June 1998 I delivered my boat with two friends (still friends) from Long Island, NY to the lower Hudson River. While on LI Sound off Huntington Harbor, we were completely becalmed, the water was like glass and there was a thick fog. As we motored slowly along, we heard rumbles of thunder that became closer and closer. Soon, we were in a full scale thunderstorm, in fog and dousing rain, but no wind at all. The lightning strikes at one point were within yards of the boat, and we could see ripples emanating from the strike points. During the entire storm the mast was pointed straight up and down with minimal movement due to the lack of wind and waves. Yet, despite the mast almost "begging" to be hit by close strikes, it seemed as though the lightning just didn't "see" us. To this day I believe that the bonding system helped to make the boat invisible during that storm in those conditions. Or maybe I'm just one lucky sailor!!
Bill Goldsmith
CD27 #173
Second Chance
demers@sgi.com
-
Dennis
Re: CD25:Lightning Protection & Access to Bilge
Hi Larry,
How did you bond the base of your mast? And where did you run the cable without sharp bends, etc.? On my CD28 the access hole from the cabin doesn't give me access to the mast base only the electrical wires thru the deck.
The older manuals I've seen state 8g cable, current standards are 6g or larger I believe. Have you replaced the factory installed bonding from the stays and shrouds? How did this go?
Thanks,
Dennis
dennis.driscoll@roche.com
How did you bond the base of your mast? And where did you run the cable without sharp bends, etc.? On my CD28 the access hole from the cabin doesn't give me access to the mast base only the electrical wires thru the deck.
The older manuals I've seen state 8g cable, current standards are 6g or larger I believe. Have you replaced the factory installed bonding from the stays and shrouds? How did this go?
Thanks,
Dennis
dennis.driscoll@roche.com
-
Don S.
Re: CD25:Lightning Protection & Access to Bilge
I once owned such a gizmo. The idea was to clamp one end at the base of the mast and toss 3' long fluted, aluminum tube into the water. The clamp and tube were connectd with battery wire. I left my wife aboard during a squall with the feeling she was safe because I hooked up the gizmo before I left. We had very big electrical storm. I returned to the boat to find everything safe and sound, except when I pulled up the tube, it wasn't there. The connection had corroded and the tube kept going when I tossed it in!
Don Sargeant
~~COQUINA~~
CD25D #189
grounded in Greenwich Cove
don@cliggott.com
Don Sargeant
~~COQUINA~~
CD25D #189
grounded in Greenwich Cove
Bill Goldsmith wrote: Larry,
No mud there. What you are saying really makes sense. Lightning is a very important discussion to have and this board is a great way to increase all CDers' understanding of it. Here's more: A sailor friend of mine keeps a few extra jumper cables on his boat. When he encounters lightning he hooks the cables onto the shrouds and stay and throws the other end into the water. The boat is grounded as well (not a CD). Does that make sense to you? Is is helping, neutral, or asking for trouble?
Bill
, : Well, it sure would seem so. But consider this analogy:
Larry DeMers wrote: On a golf course, Trees are growing out of the ground, they get soaking wet during storms, so the electrical pathway is fairly low in resistance, making that tree a very good ground. Effectively, and viewed from an in-space viewpoint of the fields near the earths surface near the tree, the ground seems to rise up and enclose the whole tree. The problem is that the tree is also now the very highest point of ground all around him, and that is what the stepped leader looks for to get the shortest pathway to the +cloud chrge that is building up. The tree gets hit.
On our boats, the grounded mast raises the ground potential physically higher than the surrounding air. It becomes quite attractive to a stepped leader, which may or may not form into a full charge. Heck, sometimes it just causes a gaseous glow (St. Elmos Fire on Plane wings), or it can form Ball Lightning..a really discarnatly scary event. So ok, that damn stick is attractive to lightning, so how do I avoid being the punching bag of every storm in the county? By several methods. You can dissipate the minor charges that accompany the stepped leader, which will eliminate that leader from forming. Unfortunately, there will probably be another right behind it forming as long as you remain in that particular area, so the dissipation technique needs to be continuous. A bottle-brush shaped dissipator would possibly be your answer here.
So the lightning wins, and takes the stepped leaders pathway to your mast tip. Here is where your hard work in grounding the boat pays off. The charge follows the mast with the majority of the charge (shrouds are far too high a resistance compared to the cross section of a mast). The mast is bonded, with the wire going as straight as you can make it..so the charge comes along (this thing can be 12 in. round), turning your conductor to plasma as it goes. This is as intended, as plasma is a far lower impedance to lightning, and it will contain most charges, as long as the path is fairly straight.Now the charge encounters the grounded thru-hulls, all in parallel so it dumps a portion of the charge into that ground. It continues to the engine, keel and underwater structure. You are relatively safe now, as the charge is outside the boat now. Sure..there will be damage. but more than likely, you will be able to motor back tot he marina and get repaired.
The alternative of no bonding allows the lightning to choose it's own pathway..and that will do far more damage.
Hope this didn't muddy up the situation too much.
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30
Larry DeMers wrote:Bill Goldsmith wrote: Larry:
I am just a little confused. I understand all you wrote, but I thought that the bonding system actually reduced the chance of getting hit, by making the top of the mast "look" as though it were the surface of the water. Of course, if hit, it also has the effect of leading the charge and reducing damage, as you say. But I thought it had the additional effect of helping the boat to be "transparent."
Here's my anecdote of the day:
In June 1998 I delivered my boat with two friends (still friends) from Long Island, NY to the lower Hudson River. While on LI Sound off Huntington Harbor, we were completely becalmed, the water was like glass and there was a thick fog. As we motored slowly along, we heard rumbles of thunder that became closer and closer. Soon, we were in a full scale thunderstorm, in fog and dousing rain, but no wind at all. The lightning strikes at one point were within yards of the boat, and we could see ripples emanating from the strike points. During the entire storm the mast was pointed straight up and down with minimal movement due to the lack of wind and waves. Yet, despite the mast almost "begging" to be hit by close strikes, it seemed as though the lightning just didn't "see" us. To this day I believe that the bonding system helped to make the boat invisible during that storm in those conditions. Or maybe I'm just one lucky sailor!!
Bill Goldsmith
CD27 #173
Second Chance
don@cliggott.com
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Larry DeMers
Re: CD25:Lightning Protection & Access to Bilge
Well, yes and no. Heh, we are inthe midst of a complete rewire and repower of our CD30. The repowering is done (rebuilt the engine), and the rewiring is started, with new Heart Interface breaker panels, battery monitors (Link 2000 for the two house batteries and a Link 10 for the starting battery), and charging (Heart 15-12).
Bonding to the mast is hard on the CD30. What I found was that the mst itself was not wired in, but rather the mast step was grounded, and the mast was in direct contact with it when mounted. I have replaced the 8awg wire that came with the boat to 4 awg in some cases (where I could get at the wire, leaving the stretches where it will have to be fished through for another time). The section from my mast step down into the boat is an impossibly tight curve, so I mounted the wire to the bottom of the step, with access provided by the removal of the mast access plate (teak round pad mounted on ceiling in head compartment. The wire droops down through the area between the liner and the boats deck, heading over to the sink area in the head compartment. Here the old wire took a 90 deg. turn down to the keel, but did it too tightly. My radius is about 1 ft., but left most of the 1 ft. exposed, but up against the foreward bulkhead. It is admittedly not my wifes favorite piece of wiring that I have done, and it is not pretty. In time, I will figure out a better way to dress this lead, or better yet, a more direct pathway to the keel. I felt it necessary to make the change in the limited amount of time I had to work on it, so the work is temoporary for now.
The trouble is that the natural exit from the mast would bring that wire straight down through the middle of the head compartment..not good. ;^) So, we look for gentle curves to guide that charge, but there is no vertical room to do this in..only horizontal room. To use it, I believe I will have to remove the top liner and install the wire in a large 1-2 ft. radius half circle to get it to the side of the bulkhead, where it can be transitioned into a straight shot to the keel, where you will want to attach it with hefty cable clamps coated in vaseline or grease. Now attaching to the keel lead is another area I am not too sure about. What is best here? Drill into the darn thing and then thread in a s.s. rod? I used a self tapping threaded rod..s.s., I think it was 1/4-20 (or 5/16), possibly larger. That was done 3 years ago now. So I have more work to do yet, but the intention is to make the whole boat 4awg wire rather than the 8awg it is from start.. I have probably 1/2 of the boat left to convert to the larger size. Trouble for me has been the routing of the wires from the head to the engine. There is a turn in there that hangs them all up..under the shower drain pan (I am threatening to remove that thing and use the space for stowage). So later this year or next, I will be removing the teak and holly sole and finding the culprit. Seems like a lot of work for no improvement in boat speed though. ;^))
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30
demers@sgi.com
Bonding to the mast is hard on the CD30. What I found was that the mst itself was not wired in, but rather the mast step was grounded, and the mast was in direct contact with it when mounted. I have replaced the 8awg wire that came with the boat to 4 awg in some cases (where I could get at the wire, leaving the stretches where it will have to be fished through for another time). The section from my mast step down into the boat is an impossibly tight curve, so I mounted the wire to the bottom of the step, with access provided by the removal of the mast access plate (teak round pad mounted on ceiling in head compartment. The wire droops down through the area between the liner and the boats deck, heading over to the sink area in the head compartment. Here the old wire took a 90 deg. turn down to the keel, but did it too tightly. My radius is about 1 ft., but left most of the 1 ft. exposed, but up against the foreward bulkhead. It is admittedly not my wifes favorite piece of wiring that I have done, and it is not pretty. In time, I will figure out a better way to dress this lead, or better yet, a more direct pathway to the keel. I felt it necessary to make the change in the limited amount of time I had to work on it, so the work is temoporary for now.
The trouble is that the natural exit from the mast would bring that wire straight down through the middle of the head compartment..not good. ;^) So, we look for gentle curves to guide that charge, but there is no vertical room to do this in..only horizontal room. To use it, I believe I will have to remove the top liner and install the wire in a large 1-2 ft. radius half circle to get it to the side of the bulkhead, where it can be transitioned into a straight shot to the keel, where you will want to attach it with hefty cable clamps coated in vaseline or grease. Now attaching to the keel lead is another area I am not too sure about. What is best here? Drill into the darn thing and then thread in a s.s. rod? I used a self tapping threaded rod..s.s., I think it was 1/4-20 (or 5/16), possibly larger. That was done 3 years ago now. So I have more work to do yet, but the intention is to make the whole boat 4awg wire rather than the 8awg it is from start.. I have probably 1/2 of the boat left to convert to the larger size. Trouble for me has been the routing of the wires from the head to the engine. There is a turn in there that hangs them all up..under the shower drain pan (I am threatening to remove that thing and use the space for stowage). So later this year or next, I will be removing the teak and holly sole and finding the culprit. Seems like a lot of work for no improvement in boat speed though. ;^))
Cheers!
Larry DeMers
s/v DeLaMer
Cape Dory 30
Dennis wrote: Hi Larry,
How did you bond the base of your mast? And where did you run the cable without sharp bends, etc.? On my CD28 the access hole from the cabin doesn't give me access to the mast base only the electrical wires thru the deck.
The older manuals I've seen state 8g cable, current standards are 6g or larger I believe. Have you replaced the factory installed bonding from the stays and shrouds? How did this go?
Thanks,
Dennis
demers@sgi.com