Alright Dave you win, However the reason for my post is I see alot of people buying fiberglass gulf umbrelles thinking the nonconductive nature of the shaft will make them safe from lighting. It may make them a little safer. They should seek cover, they can. On a kayak we may not be able to. For this reason I have to agree that non-conductive is safer but only a little. We may not agree on the details but alumimium is out. With that I have said my piece. Jim >>> Dave Kruger <dkruger_at_seasurf.com> 05/05/98 09:45am >>> Jim Martin wrote: > > Don't worry about coductivity. There is no way to insulate from the high > voltage. Remember it has enough voltage to arc across thousands for > feet of air. It takes roughly 18,000 volts to arc a fraction of an inch. The > problem with being on the water in a lighting storm is your the highest > point. i.e. the one electrode in a circuit. [snip] > >>> Dave Kruger <dkruger_at_seasurf.com> 05/05/98 05:03am >>> > Bob Denton wrote: > > > > I wonder if Carbon Fiber is a positive or negative feature (no pun > > intended) in a lightning storm. > > Probably not a significantly better conductor than a wet (with water) > glass/epoxy shaft, but I don't know the specific conductance of a > carbon fiber/epoxy laminate. Well, Jim, not to put too fine a point on this pencil, but I suspect the conductivity of the stick we swing over our heads *might* make a difference. Here's the physics, as I understand it: When a voltage (potential) difference builds up between cloud and ground (preparatory to a lightning strike between the two), the distribution of the intensity of the electric field along the ground will partially (entirely?) determine the point on the ground the lightning strikes. If there is a pointed object *which readily conducts electricity* sticking up, the local electric field off the tip of the pointed object is more intense than it is on the surrounding, flat, relatively nonconductive surface. This means the pointed object is much more likely to take the hit, as the "step leader" arcs down from the cloud, "searching" for the path of least resistance. This is one of the reasons lightning arresters on the tops of buildings are purposely pointed and made of conducting metal electrically connected to ground. A *nonconductive* pointed object, especially one without a good conductive path to ground, thus is less likely to be the struck object by a lightning bolt. I think your assertion is correct that it makes no difference what you are holding on to *once the bolt has chosen you*: It could be a long, air-filled party balloon, and it would get ionized and turned to plasma just like the air the stroke passed through on its way down. I think, on the other hand, holding a long, pointed, conductive rod to the sky makes it *more likely* the bolt will pick you or your location. Re: the original question: I question whether carbon fiber laminates are significantly more conductive than glass fiber laminates -- and doubt the difference is enough to increase the chance a strike will hit a carbon fiber shaft. I'm not a physics guy, but I think this is correct. I'd be happy to be corrected if I'm wrong, however -- THAT happens a lot! I'm copying this to Les Uhrich, physics instructor up near Tacoma, for his scrutiny, in case I've got it wrong. What say, Les? -- Dave Kruger Astoria, OR chemist *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ *************************************************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************Received on Tue May 05 1998 - 09:52:36 PDT
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