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Author Topic:   grounding electronics
Eric posted 08-01-2001 10:13 PM ET (US)   Profile for Eric   Send Email to Eric  
I'm getting ready to install a VHF, paper chart recorder, and (if working) a loran. The references that I've looked at talk about adding a grounding system, like a ground plate, copper foil, etc. Not much of an option for using the lead keel method with a Nauset. While I'm not using a SSB, I get the impression that some sort of grounding system would help the performance of the above electronics. In addition, I live in the lightning capitol of the world (Tampa Bay area), and wonder about some sort of lightning protection derived from a good grounding system.
LarrySherman posted 08-01-2001 10:28 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     
Eric,

the DC system on boats is a closed loop system. Do not ground the DC system to Earth. The result will be a large amount electrolsis (sp?). SSB's need to be grounded to the transmission charicteristics of the Types of antennas used, and the transmission power used.

JimH knows MUCH more about this than I do. Ask him directly.

Tom W Clark posted 08-01-2001 10:34 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Eric,

Others here will give you more specific and scientific information but of the three devices you've mentioned, the LORAN is the one which needs the grounding plate.

I installed a Dynaplate on my Outrage 18 for the sake of my LORAN. Very easy to install so long as you have a place to do it. The trick here is finding a place where the plate can be bolted onto the bottom of the hull and the end of one of the bolts still be accessible on the inside for attaching the wire. On my Outrage, the sump for the drain hole and bilge was the only area where the two skins were close enough together that I could get a bolt all the way through. I still had to buy longer silicone bronze bolts in order to make it. On a conventional hull it would be no problem, but of course Whalers are not conventional.

I used the 8" x 2.5" model and bedded it with Sika 231 and used a "backing plate" in the bilge made of a piece of marine grade 1/2" teak-over-mahogany plywood.

Dick posted 08-01-2001 11:19 PM ET (US)     Profile for Dick  Send Email to Dick     
I might be a little ignorant on this one but why install Loran? It is my understanding that it is outdated and GPS is far better. Electronics are not my expertise, just going on what I have read.
Dick
triblet posted 08-01-2001 11:30 PM ET (US)     Profile for triblet  Send Email to triblet     
The antennas typically used with LORAN require
a good earth (in this case, water) ground.
However, the 12V ground is usually tied to
the case of the outboard, and thence to the
outboard's zincs, so you should be OK.

If lighting hits your boat, your electronics
are probably toast. At voltages that high,
we humans have little control over where they
go.

Chuck

Eric posted 08-02-2001 12:02 AM ET (US)     Profile for Eric  Send Email to Eric     
Thank you for such prompt replies. As far as the logic in using a loran, I already own one. The longer I wait to get a GPS, the cheaper it'll be and the sophistication of the technology is increasing all the time. Last year I hadn't even heard of WAAS, wouldn't buy a GPS without it now.
It seems that the consensus as shaping up is that a good ground to the battery and thus to the outboard may be sufficient. The grounding plate as described here would continue to be an option if I see a problem with performance. Installation would be a real hassle with my hull however.
Thanks again, Eric.
Eric posted 08-02-2001 12:03 AM ET (US)     Profile for Eric  Send Email to Eric     
BTW, if my boat gets hit by lightning, I don't care about property damage, just my own hide!
Whaletosh posted 08-02-2001 09:25 AM ET (US)     Profile for Whaletosh    
Chuck,

the zinc and a stainless prop (alumnims are painted) are going to provide a path to ground. But, the plate that Tom suggested is going to be better. It as a plate that looks like foamed bronze or brass. Because of all of the pores the surface area is immense, much higher than the surface area the a zinc or a prop can provide. The more surface area the better the contact with the water and the beeter the ground. The ground provided by the zinc on Eric's motor may be sufficient to get the Loran to work well however.

Eric for more information:

http://www.westmarine.com/webapp/commerce/command/ExecMacro/west_advisor.d2w/show_advisor?fn=lightning.htm&store_num=9

AND:

http://www.westmarine.com/webapp/commerce/command/ExecMacro/west_advisor.d2w/show_advisor?fn=50.htm&store_num=9

Kim posted 08-02-2001 11:59 PM ET (US)     Profile for Kim  Send Email to Kim     
you only need to groung the system if yoy have a bonding type of system like a steal boat with zinks ! a bond . I would say do nothing with this ground . as I do on my furuno 582l just don't hook it to any thing.
my two cents.

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