Ground plane on 34

[johnharch]

My '91 34 has the factory installed copper ground plane and dynaplate. I know what its purpose is, but little else about its routing and connections. I have a 2" strap coming out from the hull linner behind the breaker panel and the dynaplate under the sole just starboard of the head with five heavy wires coming off it. Can anyone enlighten me as to where these go and how the foil ground plane is routed through the hull? Is this system connected in to the ships DC negative? A simple continuity test says says it is, but I don't see right off where or how it is tied in.

Also where in this configuration would I hookup the SSB ground if I ever get around to installing one.

Thanks
John

[MC1]

John,
I'm not an expert on these issues, but while you're waiting for someone more informed to respond, a few comments since I've observed a few things on my '97 34 . . .

Pacific Seacraft installed the flat copper foil HF radio counterpoise and glassed it in around the interior circumference of the hull near the waterline (and I believe also running port - starboard from there down through the bilge over the keel bolts and backup the other side in a couple cases) while it was being manufactured. You can easily see it if you look closely in the bow chain locker or in the propane tank locker. Very few manufacturers do this and it's an example of how Pacific Seacraft has kept blue water cruiser requirements in mind. My assumption is that you'd ground the SSB equipment to the 2" strap coming out from the hull liner behind the breaker panel. I haven't checked into whether it's connected to the DC ground, but I know that's discouraged by some. I'll leave it to the experts to comment on that aspect.

The heavy wires coming off the dynaplate are part of the lightning ground system. These wires run to the forestay, backstay, and shroud chainplates and also to the mast base so that if the mast is struck, the current runs down the standing rigging and mast, and hopefully out the dynaplate into the water. You may want to check to see if there's also a wire running from the dynaplate to a forward keel bolt; I believe PSC may have changed their approach concerning that over time (I've heard) based on consultation with Nigel Calder. Again you can easily see the connection of these wires to the chainplates in the stem/stern lockers.

My boat did not come with the optional cutter rig hardware installed, so I purchased the inner forestay tackplate from PSC. When I install it, I plan to also run heavy wire from that forward to the heavy wire connection point on the forestay chainplate.

Regards,
MC1

[johnharch]

Thanks MC, that helps. I'm trying to get a good understand of the different ground systems and how they interact. As I see it I have four different grounding systems:

1. The RF gound plane.
2. Lightening protection through the dynaplate to sea
3. The DC negative which is tied into the engine block and maybe minimally to the sea through the shaft.
4. The ac ground (not to be confused with AC common)

I'm kind of thinking out loud here trying to understand how these systems are tied together and how they are supposed to be tied together and where. If the ground plane and the dynaplate are both connected to the keel, then they are pretty solidly tied together. I can do continuity tests, but that only tells me if they are connected, not where and whether it is intentional or maybe inadvertently through a fine signal cable somewhere. There certainly are a lot of wires on this little boat.

So is the ground plane supposed to be connected to the dynaplate or is the dynaplate strictly for lightening protection?

Is the DC negative and/or AC ground supposed to be tied into the dynaplate?

I guess I'd better read Nigal's book again


John

[Norstar]

We have a 1990 34 with the dynaplate and copper ground foil installed. I have solid continuity between the copper strap, dynaplate and dc ground. I have no evidence of lightning protection cables intalled and seem to remember this was offered as an option. It also appears that the chainplates are bonded to the copper foil or at least I have continuity between them. I have been considering running a heavy cable from the chainplates to the keel for lightning protection but not sure if this would make us more of a target or at least minimize damage if we were struck. Don't even like the thought of that!!!

John Schwab
PSC 34 #201
"Norstar"

[Alannc44]

Originally Posted by Norstar

We have a 1990 34 with the dynaplate and copper ground foil installed. I have solid continuity between the copper strap, dynaplate and dc ground. I have no evidence of lightning protection cables intalled and seem to remember this was offered as an option. It also appears that the chainplates are bonded to the copper foil or at least I have continuity between them. I have been considering running a heavy cable from the chainplates to the keel for lightning protection but not sure if this would make us more of a target or at least minimize damage if we were struck. Don't even like the thought of that!!!

John Schwab
PSC 34 #201
"Norstar"

I can't believe having the chain plates attached to the copper strip would be a good thing. For one, the counterpoise that the strap is supposed to function as ( not really a ground) would really throw the antenna system out of whack if other parts of the boat were attached to it. The idea of a ground plane is just that, that there's a plane created that counters the vertical half of the antenna. The vertical portion shouldn't have the 'ground plane' part next to it as would be the case if the shrouds were part of the antenna system. For another, I don't want my copper strip 'hot' with lightning when it's an integral part of the hull. Surely that would cause the electricity from a bolt to blow through the fiberglass hull.

Alan White
WN4HOG
Kon Jeni-Al

[MC1]

Based on the discussion so far, I took a closer look at a pic I have of the bilge in my 34 with the fuel tank removed. It looks like the glassed in foil that runs port-starboard down through the bilge passes just in front of the keel bolts, which I'm taking as an indication that the counterpoise is not electrically connected to the keel, and I see no indication of it being connected to the dynaplate either. This is consistent with Alan's comments that the counterpoise should be seperate from the lightning protection system. I haven't had a chance to do the continuity tests though.

I'm less clear on why you're seeing the counterpoise showing continuity with the ship's DC negative. If they are connected, it was probably intentional on PSC's part since it's not likely a prior owner would have attempted to connect anything to the copper foil unless he or she was also installing an SSB, but I've read that this is not the best approach (for reasons similar to Alan's response). I'm still waiting for the experts to chime in here and clarify this further. I guess most PSC'ers with SSB installations are actually out cruising the world for some reason instead of paying attention to us here at Sailnet . Worst case, we could resort to calling PSC directly to see what their current practice and rationale are.

[Alannc44]

Originally Posted by MC1

If they are connected, it was probably intentional on PSC's part since it's not likely a prior owner would have attempted to connect anything to the copper foil unless he or she was also installing an SSB, but I've read that this is not the best approach (for reasons similar to Alan's response). I'm still waiting for the experts to chime in here and clarify this further. I guess most PSC'ers with SSB installations are actually out cruising the world for some reason instead of paying attention to us here at Sailnet . Worst case, we could resort to calling PSC directly to see what their current practice and rationale are.

I sure doubt PSC connected any DC ground to same copper strip. The copper strip, ideally, will only be connnected to the antenna. There's some discussion prior chats on sailnet regarding DC current grounding and RF grounds.

I written Raul (the electrical engineer at the factory) for confirmation on this.

Alan

[Alannc44]

Okay, here's the response I got from Raul by way of Steve Brodie:


Good morning Alan.


That is correct that we use a capacitive connection to the water. However a good portion of that capacitive connection is through the keel. Because the keel is epoxy coated and bottom painted it does not have a direct connection with the water but adds a significant amount of echo grounding plane. The standing rigging is also grounded to the keel with the 4 gauge grounding wires so the two systems are not completely isolated.



All this being said, I am no SSB expert and know enough only to be dangerous. This is however how Pacific Seacraft has been building the systems for a long time.



Cheers,



Steve

[johnharch]

Ok, so the ground plane and lightening systems are directly coupled to the keel and thus to each other and to the sea through the dynaplate. This just leaves me the DC negatived connection to figure out. I suspect that all three systems are tied into the engine block and thus directly connected, but I'll wait to look into that until I get all my NMEAA 0183 instruments talking to each other. (yes, I'm kind of a gadget freak, but it keeps me out of trouble)

That reply did give the definitive answer to the keel encapsulation question too, didn't it?

John

[samchristo]

We use the SSB for SailMail and weather while cruising and have been very happy with two dynaplates, installed beneath the nav seat, as a ground. We consistently get a 5x5 from the WLO operator if we do a radio check and the Pactor operates without issues.

I think it's better to keep the ship's DC and AC grounds separate from the SSB ground to prevent noise feedback.
I also believe there should be one heavy gauge wire running from the bonding dynaplate (stbd of the head) to the ships DC ground as multiple wires can create ground loops. Again, a noise source.

The SSB setup was probably the most complex and time consuming project we did on the boat. The Internet experts usually disagreed with one another and the resulting flame mail was discouraging, to say the least. (Check out ssca.org as a source). Our solution was a middle-of-the-road approach but seems to work well.

Good luck,
Sam
s/v Grace PSC34#163