Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 23-09-2009, 13:56   #16
S&S
Registered User
 
S&S's Avatar

Join Date: Jul 2009
Boat: 48' 1963 S&S yawl
Posts: 851
Images: 6
Quote:
Originally Posted by Cheechako View Post
... from behind or ahead,... they are twice as wide! Now I'll sit back and watch the show
Just eggin' them on.

But does twice as much project outside of the cone? Nope. I wonder what the percentage of mast strikes compared to hull strikes are for cats compared to monos?
__________________

__________________
S&S is offline   Reply With Quote
Old 23-09-2009, 14:53   #17
Registered User

Join Date: Feb 2007
Location: Norway
Boat: Fountaine pajot, Belize 43
Posts: 140
from a practicle point of view - does copper wires tied to the chaineplate terminals and dropped into the water protect from a lightning strike?

I'm an electrical engineer but have limted knowledge og this specific problem. I believe there's a lot of mumbo jumbo in what is thought to help protect in these situations. I have read of someone fixing acopper wire to the bottom of the mast and dropping it straight down into thewater underneath the bridgedeck. Could that be the solution to a hit in the mast? It's the shortest path to earth and the theory is that that's what lighting do! But is that the fact?

Questions, questions my first officer demands answers or we'll be landlocked if it looks like thunder.....which is fortunately a fairly rear occurrance in our northens shores in Scandinavia.

Still searching for the solution to this natural phenomena, which causes so much damage and also deaths around the globe.

For the tag along issue of radar reflectors, we have a faily small reflector, tubular approx. 50mm x 300mm fixed to the outer shroud at the first diamond. I have called commercial ferries by VHF when out and have received thumbes up, they can see me as a big blop! So I'm happy with that. So the advice is to call some ships when you see them at a distance and ask them for a visual on the radar. AND many times you will find that they don't even answer the VHF, which to means they don't actually keep listning watch as required by maritime law! So that's another eye opener.

Happy lead free sailin!
__________________

__________________
Lucky is offline   Reply With Quote
Old 23-09-2009, 15:10   #18
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,334
So much still seems to be a mystery. If you create a ground by bonding the mast, are you attracting lightening more than without? (will a free bolt seek a ground more readily than a non-ground?) Or is the power of a bolt such that it is just going to go randomly where it's going to go with little deflection....?
Do as many bolts go up as down? Is gravity an influence or just the ground of the earth?
__________________
Cheechako is offline   Reply With Quote
Old 23-09-2009, 20:55   #19
Registered User

Join Date: May 2009
Posts: 27
This has been a very enlightning thread (pun intended lol).

I have for years been under the understanding that lightning rods actually aren't designed to carry away electrical energy as much as preventing a strike. I believe it's based on physics, something about a point charge from the surface of the earth.

Can anyone elaborate and/or explain where I've misunderstood?
__________________
Live to Dive is offline   Reply With Quote
Old 23-09-2009, 21:34   #20
Registered User
 
mark_morwood's Avatar

Join Date: Jan 2007
Location: Cruising (Atlantic -> Med -> Carib -> Pacific)
Boat: Vancouver 36, Hobie 33, Catana 48, now all with new owners
Posts: 204
I'd recommend the link given above for an overview from someone who at least on paper should know. Made sense to me, but I can't claim to be an expert.

Lightning Protection - Lightning and Boats

Mark.
__________________
mark_morwood is offline   Reply With Quote
Old 23-09-2009, 21:40   #21
CF Adviser
 
Pelagic's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Boat: Van Helleman Schooner 65ft StarGazer
Posts: 6,872
I know that when my friend’s cat rubs up against my leg… I get a lot of static.
__________________
Pelagic is online now   Reply With Quote
Old 23-09-2009, 21:53   #22
Long Range Cruiser
 
MarkJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2007
Location: Australian living on "Sea Life" currently in England.
Boat: Beneteau 393 "Sea Life"
Posts: 12,828
Images: 25
Gords link to Dr Thompsons report was interesting.

One of the things raised is the path for the lightening to travel verticaly from mast down through the bottom of the boat.

here's my theory... does it hold water?

Most mono-hulls have a lead keel (or iron keel for me) electrically attached to the tip of the mast.... Keel, keel bolts, mast footing (compression post footing) mast (deck shoe) Mast to other end of mast.

Where a catamaran doesn't have a lead or iron keel, just a fibreglass keel box.

So monos automatically have grounding between Thor and thea. OK maybe the connections are not real good, even epoxy shoes etc(?) but 1 or 2 mm is nothing for a lightening strike.

My compression post is stainless steel, and of course doesnt conduct like a copper strip, but the amount of metal in it is HUGE compared to a copper strip.



Mark
__________________
Notes on a Circumnavigation.
OurLifeAtSea.com

Somalia Pirates and our Convoy
MarkJ is offline   Reply With Quote
Old 24-09-2009, 08:24   #23
S&S
Registered User
 
S&S's Avatar

Join Date: Jul 2009
Boat: 48' 1963 S&S yawl
Posts: 851
Images: 6
Quote:
Originally Posted by MarkJ View Post
Gords link to Dr Thompsons report was interesting.

One of the things raised is the path for the lightening to travel verticaly from mast down through the bottom of the boat.

here's my theory... does it hold water?

Most mono-hulls have a lead keel (or iron keel for me) electrically attached to the tip of the mast.... Keel, keel bolts, mast footing (compression post footing) mast (deck shoe) Mast to other end of mast.

Where a catamaran doesn't have a lead or iron keel, just a fibreglass keel box.

So monos automatically have grounding between Thor and thea. OK maybe the connections are not real good, even epoxy shoes etc(?) but 1 or 2 mm is nothing for a lightening strike.

My compression post is stainless steel, and of course doesnt conduct like a copper strip, but the amount of metal in it is HUGE compared to a copper strip.



Mark
I'd imagine the insurance companies would have data to see if the strikes go down the stick or down the shrouds. As strikes take the lowest resistance path to ground (meaning potential equalization, not necessarily The ground) you'd think that a mast insulated from the ground plane would be less likely to get struck- just thinking out loud.

Wooden (or carbon fiber) sticks anyone?

My understanding of lightening rods is that they provide a low resistance path to ground, they don't prevent strikes, they just manage the current flow.
__________________
S&S is offline   Reply With Quote
Old 24-09-2009, 10:04   #24
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,334
There are lightening rods and there are diffusers. it's obvious that lightening rods work to help take the charge directly to ground. It's not obvious that diffusers work at all. Probably because the lightening bolts were never told that they were suppose to avoid them!
__________________
Cheechako is offline   Reply With Quote
Old 24-09-2009, 10:48   #25
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,150
I guess its okay to take the thread off track a little at this point. A radar reflector has so much radar reflective material near it that adding one makes little difference. In my 30 years of experience of operating small and large vessels with radars, I have never seen a sailboat that does not show up on a radar screen from a good distance.

There is no doubt a properly designed radar reflector works. The greater question is, do they make any difference? In my personal experience, they don't make any difference because sailboats themselves are already good radar reflectors.
__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 24-09-2009, 11:03   #26
Eternal Member
 
imagine2frolic's Avatar

Join Date: Feb 2008
Location: Las Brisas Panama AGAIN!
Boat: Simpson, Catamaran, 46ft. IMAGINE
Posts: 4,508
Images: 123
Quote:
Originally Posted by Pelagic View Post
I know that when my friend’s cat rubs up against my leg… I get a lot of static.
Would that be girlfriend's cat????????????.......i2f
__________________
SAILING is not always a slick magazine cover!
BORROWED..No single one of is as smart as all of us!
http://sailingwithcancer.blogspot.com/
imagine2frolic is offline   Reply With Quote
Old 24-09-2009, 11:28   #27
Registered User

Join Date: Aug 2009
Posts: 211
It's clear that there are (still) lots of differing opinions about lightning, so could I ask what precautions, if any, are permanently in place on your boat and what extra precautions you take when a storm/lightning is likely to be in your area?

Also, if you currently sail a cat, would you do anything different if you sailed a mono, and vice versa?
__________________
ColdFusion is offline   Reply With Quote
Old 24-09-2009, 11:33   #28
Senior Cruiser

Cruisers Forum Supporter

Join Date: Apr 2008
Posts: 769
I'd think that boats should be exponentially more likely to be hit by lightning, if they are close to shore. I'd guess that most boats "hit" are actually secondary strikes from something attached to land getting hit. Water, even salt water is a pretty poor conductor.

I find it difficult to believe (I could be wrong, of course) that bobbing around out on the ocean, you really have a significant probability of being hit.

Do cats typically have taller masts per unit length? Are they more likely to be spending time near shore?
__________________
anotherT34C is offline   Reply With Quote
Old 24-09-2009, 11:57   #29
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Sitting at my favorite bar next to Bahia Mar one summer afternoon, I watched a particularly violent thunderstorm pass us by. As I watched, a small power cruiser took a direct lightning hit. He was sandwiched between two BIG sailboats in adjacent slips. Those sailboats were not visibly damaged, but the cruiser bore very heavy damage.

That convinced me of the following governing principle with regard to lightning strikes:

Lightning is going to hit where it's going to hit. Period.

I already knew (or thought I knew) of another principle:

Lightning is is going to take not only the shortest path to ground, but ALL AVAILABLE paths to ground.

With these two "principles" in mind, it was clearly time for another Mt. Gay, and studied reflection on the lucky and the unlucky, after which I concluded that it really doesn't matter much what you do: you're going to get hit or not according to immutable laws over which we pitiful humans have little or no real control.

JMO,

Bill
__________________
btrayfors is offline   Reply With Quote
Old 24-09-2009, 12:07   #30
Registered User
 
Sailndive345's Avatar

Join Date: Jan 2009
Location: St Augustine, FL
Boat: Beneteau Oceanis 461
Posts: 349
Quote:
Originally Posted by ColdFusion View Post
It's clear that there are (still) lots of differing opinions about lightning, so could I ask what precautions, if any, are permanently in place on your boat and what extra precautions you take when a storm/lightning is likely to be in your area?

Also, if you currently sail a cat, would you do anything different if you sailed a mono, and vice versa?
Both on my previous and current Beneteaus, the shrouds were connected to the cast iron keel via pretty hefty grounding straps with a large size fuse (don't remember what amperage - I am currently nowhere near the boat) My sailing areas have been previously mentioned lightening prone areas - thankfully, I haven't had to examine how well the system worked after a strike.

Extra precautions; well, perhaps "getting a little religious".... and, afterwards, thanking the powers to be with a little celebratory grog...

Seriously, and it may be related -somehow- to all this; I recently found that my mast (& of course the rigging) has DC- on it... I coincidentally ran into this while replacing my anchor light assembly and have been quite concerned about it. Now, I realize that DC- is connected to the engine block and it "may" be somehow connected to the rigging and/or keel bolts. I'll be digging deeply to see where the source is.

Does anyone know whether this is normal and I am chasing ghosts - or is it something that needs to be corrected (my current position)?

Fair winds, and lightening-free skies to all...

Sailndive
__________________

__________________
Sailndive345 is offline   Reply With Quote
Reply

Tags
lightning

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Lightning irwin28 General Sailing Forum 27 18-07-2009 18:57
Lightning AndyO Seamanship & Boat Handling 13 23-06-2008 12:37
Lightning sneuman Health, Safety & Related Gear 7 05-06-2008 23:25
Struck by Lightning/seeking advice alaskadog Off Topic Forum 26 12-04-2007 01:07
Lightning? ssullivan Health, Safety & Related Gear 55 08-12-2006 16:38



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 18:09.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.