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Old 16-04-2010, 17:07   #31
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Originally Posted by espresso View Post
Hi Evans,
this topic of grounding the Aluminium hull is such a debated point, but the way it was explained to me was:
1) It is almost impossible in real situations to keep the hull insulated from the battery. Just a touch of dirt on the engine mounts, graphite brush dirt from the alternators, temperature or pressure senders can connect the hull to the battery negative.
I guess we have to agree to disagree about the best electrical treatment for aluminium hulls.
I think however you have misunderstood how to isolate the negative supply. This is not normally dependent on the engine mounts, a simple solenoid that only connects the negative to the engine during start is simple, cheap and reasonably foolproof. Likewise 2 wire senders are fairly readily available.
Many aluminium yachts, like mine, ( and for example all Ovni's) have a test for negative isolation that permits easy frequent checks that the isolation is effective.
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Old 14-06-2010, 09:59   #32
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I agree with Jedi. Metal boats make the best ground plane for SSB radios. A metal boat will "spring" the signal far better than a glass boat. There seems to be some confusion however, between creating this plane and bonding. They are not related. In my view ALL boats should be bonded, especially metal and wood boats (with metal fasteners). A non-bonded metal hulls can produce a ground loop when using a SSB which is not good for the radio and worse for the hull.
For this purpose, the ground plane strap from the transmitter and/or tuner must be at least .013" thick and 4" wide (double that if you can) and can be bonded to a separate dyna-plate (outside of hull).
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Old 14-06-2010, 10:24   #33
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In my view ALL boats should be bonded, especially metal and wood boats (with metal fasteners).
Bonding on a wood boat is not a good idea. Sodium hydroxide will form on wet wood around an underwater metal fitting (cathode) that has galvanic current flowing and this will eat the wood turning it into a soft spongy cellulose.

Eric
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Old 15-07-2010, 08:42   #34
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I have an aluminium catamaran and a Lombardini isolated pole engine , I have just noticed that the isolation is in fact short circuited by the throttle and gearchange cables connect to controls bolted the boat . Should these connections be isolated also ?
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Old 16-07-2010, 09:59   #35
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Originally Posted by caver38 View Post
I have an aluminium catamaran and a Lombardini isolated pole engine , I have just noticed that the isolation is in fact short circuited by the throttle and gearchange cables connect to controls bolted the boat . Should these connections be isolated also ?
Use a continuity tester regularly! ..(yes, the controls are a comonly overlooked direct connection. A plastic board mounted to the metal boat to which the controls are bolted works well. Also check your gages..)
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