désolé c'est en anglais mais c'est écrit par un ingénieur en "avionics", son point de vue est intéressant seul interet de relier les passe coques (relier = bonding) est pour les bateaux connectés à un chargeur sinon il se demande si une anode sur l'arbre d'helice protege vraiment le passe coque des gogues AV sur un bateau de 35 pieds ou plus .. pour ma part je vais changer les passe coques pour des "marelon" ou équivalent français, c'est du plastique chargé de résine indestructible ou presque jean As far as Terry's comments are concerned, this is a source of confusion to me in as much that purely theoretically, Terry's right. Good quality bronze should be stable in salt water, providing it is electrically neutral and there is no imposed DC current flow through it. According to that theory, (the 'European' approach) adding the bonding system indeed only provides additional paths for creation of damaging galvanic cells. So far, so good. In reality, my boat (no bonding system, dry bilge) almost sank due to a badly corroded head sink through hull, the through hull being only 7 years old. Subsequent replacement of all other through hulls revealed all were badly corroded. That made me think that there were possibly other influences here that I was not aware of. Having a bonding system (the 'American' approach) actually adds protection to your through hulls and other linked hardware, providing there is a good zinc wired in the circuit. It eliminates the uncertainty of the European approach, which relies on electrical neutrality of the immersed metal (add an unforseen ingredient and you're in trouble). It also has positive implications re lightning protection. On the negative side, should your zinc fail, or the bonding circuit fail, or should you have shore power without a galvanic isolator, you stand to cause yourself a lot more damage than by having an unbonded system. Related to this, there is always a question in my mind as to the 'maximum range' of a zinc of a certain size. Will a 2 inch zinc on the shaft protect a bonded through hull in the forward head, 35+ feet away? I guess the only way to answer this is to have a bonded system like that and conduct two measurements using the Ag/AgCl probe - one with the bonding wire on and then with the bonding wire off. Would be interesting to know the result. I should also add to this that the galvanic isolator will work if and only if there is a hard connection wired between the AC earth and DC ground on the boat. I installed the galvanic isolator on my boat just to discover that there was no such connection wired up (French built '94 OC440), rendering the device virtually unnecessary. If you read up on the subject, there is *always* advice to the effect that AC earth should be connected to DC ground, for various reasons of safety. There is always an accompanying disclaimer that such connections carry the increased risk of galvanic corrosion, for familiar reasons. I now have two theories - either B does not install that connection (to justify the lack of galvanic isolator and bonding system installation?), or the previous owner of my boat disconnected it. Both hard to believe. Fellow listers, can you tell me if your (new) boat came with this connection wired up or not and if so, where is that connection made on your boat? Thanks, Dan -----Original Message----- From: bensail@earthlink.net [mailto:bensail@earthlink.net] Sent: Friday, 14 February 2003 2:03 To: beneteau-list@sailnet.net Subject: Re: [beneteau] Bonding Pic The galvanic isolator will only work if the problem is coming from shore power -- You obviously have a hot dock or boat nearby. I installed one also, but it did no good because the problem was the lack of a bonding system. The bonding problem fix is for the B boats that do not have bonding at all (majority, I guess). My guess as to the reason/cause is that each thru hull is acting like a small battery with different potentials. The bonding system eliminates this and makes it easier for the prop zinc to do its job - hence lasts longer. Terry O'Rourke wrote: > Marston, > > I installed a galvanic isolator about 18 months ago. My boat is two years > old. Prior to the galvanic isolator installation I was going through a prop > zinc every month. Now my prop zinc lasts six months. My boat stays in salt > water year round. > > During the time when I was learning first hand about galvanic corrosion I > discovered that it can not happen without an unbroken DC path between > dissimilar metals. The galvanic isolator breaks this path and allows the > prop zinc to service only the small galvanic cell created by the prop shaft > and prop instead of serving as an anode for nearby boats. > > Bonding all the through hulls merely adds several new paths for galvanic > current to flow and will ultimately corrode whichever metal turns out to be > less noble (the anode). > > I found this article in the West Advisor section of the West Marine web site > informative, comprehensive, and concise: > > http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorDisplayView?a > dvisor=50.htm > > It discusses the larger topic of all marine grounding and devotes a couple > of paragraphs to "Bonding and Electrolytic Corrosion Due to Hot Marinas". > The article was written by Stan Honey, "a renowned sailor, navigator and > electrical engineer", and first published in Practical Sailor. I work as an > avionics technician and everything in this article fits nicely with my > knowledge of of basic electricity and electronics. -------------------------------------------------- Cette liste est destinée à ceux qui veulent...