We had a thread going over the last few years about trawler lightning protection. I'm on the hard at the moment and I want to put in a bronze plate for this purpose and I'd appreciate any info anyone has. Websites. Etc. What size plate for a 47' boat? Regards. Larry

Here are some links you might find helpful. I think the bottom line is that nothing is going to guarantee protection, but they might help limit the damage. The little bottle brush thingies were dismissed as ineffective a few years ago; now there is some more evidence that they may help. Who knows... maybe the mfg's sponsored a study? Anyway, the gist of it is that you should put a lightning rod up high (still arguments over whether it should be pointy or blunt, I think the latter is winning out right now), run a BIG conductor as straight to the water as possible, then put some sort of grounding plate. I've heard arguments for and against the Dynaplates. For sheet metal copper, the charge will dissipate out of the edges, so edge length is more important than square footage. A long strip 2" wide will work better than a square plate. For what I did on the Krogen (quick and dirty). Pointy lightning rod from West Marine up top, #4 copper cable down the mast, over the edge, with a copper plate with a lot of slits cut in it (for edge) thrown in the water. Obviously not for while underway, but it makes me feel better while in the slip. The only evidence that it MIGHT have worked one time... I pulled it up to get underway and the plate was gone. The cable looked like it had been cut off cleanly, and was dark. The discoloration could have just been from being in the water. However, the cable had a battery lug crimped to the end, so the insulation was stripped back and the whole thing had about ten coats of liquid electrical tape on it. It looked like it had been cleanly cut off. Now I can't imagine anybody on the dock going to that much trouble, but it sure didn't look like the wire had pulled out of the lug. That's one of the problems with lightning protection, unless you're on the boat, you never know it worked if it did... you only know if it didn't! For more expert info... http://www.kastenmarine.com/Lightning.htm http://www.thomson.ece.ufl.edu/lightning/ http://www.lightningsafety.com/ http://www.lightningsafety.com/nlsi_lhm/lightning_rod_recent.html http://www.powerquality.com/ar/power_prevent_lightning_strikes/ http://www.lightningmaster.com/Structural.htm More than you probably ever wanted to know! Keith __ Get forgiveness now -- tomorrow you may no longer feel guilty. ----- Original Message ----- From: "Larry N. Brown" <lnb@charter.net> > We had a thread going over the last few years about trawler lightning > protection. I'm on the hard at the moment and I want to put in a bronze > plate for this purpose and I'd appreciate any info anyone has. Websites. > Etc. What size plate for a 47' boat?