new to steel boats #2 neg ground - SailNet Community
Reply
 
LinkBack Thread Tools
post #1 of 30 Old 09-03-2011 Thread Starter
Senior Member
 
Join Date: Mar 2005
Posts: 713
Thanks: 3
Thanked 2 Times in 2 Posts
Rep Power: 11
 
new to steel boats #2 neg ground

So I noticed on my 'new' steel boat that the PO has wired up the windlass with a single positive cable, and the Windlass grounded to the hull.

is it kosher to use the hull itself as part of the circuit?
xymotic is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 30 Old 09-03-2011
Senior Member
 
tommays's Avatar
 
Join Date: Sep 2008
Posts: 4,296
Thanks: 1
Thanked 30 Times in 30 Posts
Rep Power: 7
 
No

1970 Cal 29 Sea Fever

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

1981 J24 Tangent 2930
Tommays
Northport NY


If a dirty bottom slows you down what do you think it does to your boat
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
tommays is offline  
Quote Quick Reply Share with Facebook
post #3 of 30 Old 09-03-2011
Senior Member
 
mitiempo's Avatar
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,498
Thanks: 0
Thanked 96 Times in 87 Posts
Rep Power: 8
   
There should be no connection between the negative and the hull - it is a surefire way to create a huge problem. Total isolation is the best. On many steel (or aluminum) boats the entire DC system is switched with double pole breakers so that when off there is no chance of a leak through a chafed negative.

Brian
Living aboard in Victoria Harbour
mitiempo is offline  
Quote Quick Reply Share with Facebook
post #4 of 30 Old 09-03-2011
Senior Member
 
Join Date: Oct 2006
Location: Virginia
Posts: 725
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 9
 
A boat is not a car and should not be wired like one. If the windless is wired to the hull I would be concerned of what else is.

That derelict boat was another dream for somebody else, don't let it be your nightmare and a waste of your life.
badsanta is offline  
Quote Quick Reply Share with Facebook
post #5 of 30 Old 09-03-2011 Thread Starter
Senior Member
 
Join Date: Mar 2005
Posts: 713
Thanks: 3
Thanked 2 Times in 2 Posts
Rep Power: 11
 
Thanks everyone. I kind of thought it was hinky but was unsure.

BUT... how the heck do you isolate the Negative completely when the engine block is grounded?

I can certainly see not using the hull as a short-cut for a circuit, but it is going to be grounded and bonded to both AC and DC isn't it?
xymotic is offline  
Quote Quick Reply Share with Facebook
post #6 of 30 Old 09-03-2011
Senior Member
 
mitiempo's Avatar
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,498
Thanks: 0
Thanked 96 Times in 87 Posts
Rep Power: 8
   
Should not on a steel boat. If the engine has a flexible coupling the shaft and prop are isolated. Alternators and starters are available without the case as part of the ground system. If this is done the engine block isn't part of the ground.

The other solution is to isolate the engine circuits except when the engine is running and this is easier. When not using the engine both positive and negative are isolated with 2 separate switches.

Any terminal blocks or switches can be attached to a material like plastic and it attached to the hull for isolation.

Brian
Living aboard in Victoria Harbour
mitiempo is offline  
Quote Quick Reply Share with Facebook
post #7 of 30 Old 09-03-2011
Senior Member
 
Join Date: Jan 2005
Posts: 103
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
 
Google "galvanic corrosion" "noble metals" and "zinc protection"
wescarroll is offline  
Quote Quick Reply Share with Facebook
post #8 of 30 Old 09-10-2011
Senior Member
 
Join Date: Sep 2010
Posts: 249
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 5
 
What's wrong with having the hull being a common point of a circuit (the ground)?

The only time this would ever cause trouble is when connected to shore power. You can use an isolation transformer to isolate the shore power completely. I guess the other option is to isolate the whole hull. But all it takes is one slip up. One metal device that is plugged in and has its grounded chassis touching part of the boat will ground the whole boat to the shore power ground.

You could isolate all the 120v devices on the boat. Then make sure that the device which connects the hull grounded 12v system with the 120v system -- the battery charger -- is isolated. It should have its own internal transformer so isolating it should be easy.

When shore power is plugged in and the grounded hull is hooked to shore ground and shore neutral there may still be a difference in ground voltages by a few volts. That can cause problems with your hull since some current is returning through the water instead of back through the cord.

You can always measure the voltage between your hull and the shore neutral and ground lines. I'm not sure which voltage level starts to become harmful.
steel is offline  
Quote Quick Reply Share with Facebook
post #9 of 30 Old 09-10-2011
Senior Member
 
Join Date: Jan 2008
Posts: 444
Thanks: 3
Thanked 8 Times in 8 Posts
Rep Power: 8
 
Quote:
Originally Posted by steel View Post
What's wrong with having the hull being a common point of a circuit (the ground)?
The problem with the sort of wiring mentioned in the OP is that the various ground connections will have a different potential. This is ideal for stray current corrosion which can be a very rapid.
Its a very poor idea and should be changed.
noelex77 is online now  
Quote Quick Reply Share with Facebook
post #10 of 30 Old 09-10-2011
Senior Member
 
mitiempo's Avatar
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,498
Thanks: 0
Thanked 96 Times in 87 Posts
Rep Power: 8
   
Steel

By grounding to the hull you are providing a way for stray DC current to flow through the hull. Corrosion will result between the anode of the hull and any cathodic metal nearby, with the hull being eaten away. Shorepower is not the only cause of galvanic corrosion.

Brian
Living aboard in Victoria Harbour
mitiempo is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
new to steel boats xymotic Gear & Maintenance 20 09-10-2011 10:27 PM
Don't condemn steel boats! Therhodesianlackmsimth Introduce Yourself 0 02-20-2011 09:52 AM
Boats on hard ground so lets talk grounds anemoneii Gear & Maintenance 12 12-17-2009 10:40 AM
Why are steel boats so cheap? Edo Kazumichi General Discussion (sailing related) 19 12-09-2006 09:22 AM
Steel Boats flicker Boat Review and Purchase Forum 2 10-29-2002 04:47 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome