On the front side of what I would call a large rib across the keel sump (the forward one with the base for a table) is a terminal block. #8 green wire from the chain plates and engine are all led to this block. I don't think you can see or access this block normally without the sole removed, but am not positive about that. If this is all part of the boats grounding system shouldn't these all be jumpered together and be common? It seems like this should be bus bar and not a terminal block. Also none of these wires go to the keel bolts and I would think that would be important thing to do. If you wanted to get a wire attached to the bolts how would you do it? There are no extra threads available to add a 2nd nut and I don't want to break a keel bolt loose either.
Electrical is not my specialty, so set me straight on what if anything I need to do here.
Last edited by Coastie; 03/20/1706:14 PM.
Dave Graf
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Re: Common Ground
[Re: Coastie]
#17188 03/20/1709:42 PM03/20/1709:42 PM
That is not what I had on Rhapsody - e.g. no terminal board like that in the bilge. I'm going from memory here. There was a series of green wires (10 gauge?) daisy chained throughout the boat, some of it glassed in the deck. It was bolted with lugs in the following locations
Stem head fitting bolts
Bow Pulpit Bolts
Port & Stbd Chain Plates
Keel Bolts
Engine Block
Stern Rail Bolts
Backstay Chainplate bolts
The wire glassed in the bilge was severely corroded in the center section where it ran to the keel bolts. I ended up running a parallel replacement since I did not dig up the area as you have done. Since you now have everything accessible, I would replace all the wires in the ground grid and rerun the daisy chain.
Edit: I just looked at some old pictures and the bronze through hulls, fuel fill connection and fuel tank also were connected to the daisy chain ground grid.
Last edited by Rhapsody #348; 03/20/1710:00 PM. Reason: Through hull comment
Bill, to a point I think my boat is daisy chained similar to yours, but it is completely goofy that these wires lead to a terminal block and not a bus. I didn't notice any wires glassed into the keel sump but I will look closer. The issue of this kind of ground or bonding is a much bigger topic than I care to get into, particularly since lightning strikes here in the Pacific Northwest are much more rare than in other locations and that is what this part of the grounding system is really about. What the reading I just did on the subject elsewhere tells me that the system in place (even if it were in the new condition) is wholly inadequate to deal with an actual strike. The wire grades are way too small and there isn't a proper place for all that energy to be transferred to the water. I will R & R much of this wire and the terminals, but I now understand that this is at best a cosmetic system.
If I were a boater in an area where lightning was a bigger issue I think I would do much more investigation and then do some serious upgrading of this grounding system. Here is a link to some information about the very basics of this topic from West Marine:
This morning I replaced the terminal block with a Bus Bar so now all of these heavy #8 wires are actually tied together. I have led one line aft to replace the tie in to the back stays, but the others are going to have to wait for another day. There is no tie in to the keel bolts and I don't see a practical way to do that now. If there were even one or two threads left on one of the bolts I could add a 2nd nut, but all of the nuts fully cover all of the threads. It might be possible to to tack weld a lead, but again that will have to wait. The original wires were just standard copper and were seriously green but I cleaned the ends up and put new terminals on and called it good for now.
I doubt that anyone would see this terminal block because of its location under the forward part of the sole. I don't think you could have accessed it even if you could see it with the original sole in place. On another day I will rethink this whole common ground. As is, it seems wholly inadequate to deal with high energy lightning. If it is about improving radio transmission then it still seems inadequate even in a new pristine condition.
Again this is not an area of my expertise, so if someone has some additional input here I am all ears. But for now this is going to the bottom of the rebuild list.
Last edited by Coastie; 03/22/1710:35 PM.
Dave Graf
Re: Common Ground
[Re: Coastie]
#17195 03/23/1707:59 AM03/23/1707:59 AM
In the J/109 Owners manual at this link there is a diagram of the grounding system on page 33 listing the gauge wire used for each interconnection. The basics should apply to the J/30 and you could use this as a guide on how to redo your ground grid. The J/109 has Marelon body hull valves so these obviously are not connected. If you have bronze hull valves, add them the the ground grid. The key points are:
The keel is an integral part of the grounding system
The engine (and sail drive on J/109) appear to be the central connection point on the system
Metal components on the fuel system are grounded
Rigging is grounded through the mast base and all chain plates
If you have an AC system, the DC and AC grounds are connected together
Wires are sized to handle some substantial currents
Bill it looks like the J/109 has an improved layout and heavier gauge wire for much of that layout.
Getting attached to the keel bolts on my boat is going to be my next target when I work on this in the future. Any ideas how to do that beyond getting a terminal welded to the bolt?
Dave Graf
Re: Common Ground
[Re: Coastie]
#17197 03/23/1710:17 AM03/23/1710:17 AM
The J/109 has a plate under the keel bolt that has a threaded hole where a ring terminal may be attached with a screw.
Click this link for photo - I can't figure out why this doesn't display as a picture in the forum. I should check with the guy who setup the forum.... oh that would be me
That would work. I checked all of the keel nuts to make sure they were tight with a 2' long breaker bar and they didn't budge. Now I wonder if I can get one to back off. It would be easy to make a plate like this in mild steel, but tracking down a source for SS may be interesting, since I only want a small piece. I think getting some kind of attachment to the keel bolts is critical to making this part of the system work. I think I will have to crawl all over the engine too so I can find where this ground is attached. The old ground lead runs under the engine tub and I can only see it exit well behind the engine. There should be a connection there somewhere, if there isn't one I will make one. It's a good thing this boat is a diesel, if it were gasoline then I would be seriously concerned with the condition of this very simple system. I have to believe that what I am seeing is what was done at the factory. No one would have any reason to mess with this stuff over the course of time. The existing copper wire also shows very well why we use tinned wire on boats. What ever the amperage capacity of #8 wire was when it was new has been severely reduced by this corroded stuff I'm seeing.
When you see the images of the boats that have been hit by lightning it is impressive all the many holes in the hull. Makes you want to make sure your manual bilge pump still works, cause nothing else is going to work and keep you from blowing tiny bubbles on your way to the bottom.
Dave Graf
Re: Common Ground
[Re: Coastie]
#17199 03/23/1711:45 AM03/23/1711:45 AM
I wouldn't use mild steel as it would basically dissolve over time and you would have a loose keel bolt. If you have a marine consignment shop near you see if there is an old chain plate or some other SS discarded piece that could be modified.
On Rhapsody with the 2GM there was a ground terminal screwed on the port side that I believe was on the bolt that attached the starter motor.
Agree about the stainless, it is a requirement. The mild steel would dissolve and then you have a loose nut like you mentioned. There is a local fabricator here in the area that supposedly does SS. I need to go meet them and find out their capabilities. My other minor SS issue is the bottom bracket holding the rudder gudgeon has been bent slightly and cracked one of the bolt holes. That is what I can see. I suspect that if the bracket got pulled hard enough to bend it that there is going to be some cracking in the glass too. But that problem is for another day. Time to go fit up the forward wings on the sole.