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  #1  
Old 02-20-2012, 07:48 PM
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SuenosAzules SuenosAzules is offline
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Need Input / Advice for Owners with Copper in their Keel for Older SSB Radios

Hello everyone. I need some input and / or advice. I currently have a client that purchased a 1975 42' Grand Banks 42 Classic. During the refit, he decided to have some of the superficial fiberglass re-done on the full keel. During the time the upper two layers of fiberglass were taken off on the keel he discovered some copper flashing that covered most of the keel that was approximately one mm thick. Anyway the re-fiberglass job was not done so well and needed to come off as I discovered some delamination and sea water trapped in the fiberglass after the vessel was briefly splashed. The owner of this vessel called me back out to inspect the copper sheeting once the newer fiberglass was taken off in some areas. It turns out (after some researching) that this copper sheeting was in fact the counterpoise for the SSB radios that were used more commonly back in the 1970's. The actual copper had partially disbonded and appeared to have some type of caulking like adhesive that had originally held it on. My question is this: Is there anyone out there that has owned a boat with this kind of copper sheeting built in between the fiberglass layers? If so, has an owner of such a vessel ever re-done the fiberglass and copper on the vessel and what worked best? How was the fiberglass re-applied and secured? The owner wants to keep the copper on the boat as he wants to install another SSB radio on this vessel and use the existing copper counterpoise. Any suggestions on how owners have dealt with this issue on similar yachts or similar Grand Banks yachts would be helpful. The owner is thinking about using brass or bronze screws to help re-secure the disbonded copper back to the boat and then glass over it, although I have been told by others the best bet for this situation is to re-bond the copper with straight epoxy to the underlying fiberglass. The pictures are below. Any input / advice would be helpful as this is not a usual situation I run in to. Thanks.











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  #2  
Old 02-20-2012, 08:24 PM
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bntii bntii is offline
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Never seen it.

Just off hand it looks like a liability to me and not placed primarily for a grounding plane/counterpoise.
Someones ideal of waterproofing the hull?
Don't put back any of the exposed copper and wait till the rest fails to address the delam issues.

There are far simpler ways to get a counterpoise for the SSB.
Par- you ever seen this??
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Old 02-21-2012, 03:08 AM
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This is a clear case of someone without the necessary technical background taking the concept of a ground plane literally, ruining a ship's hull in the process.
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  #4  
Old 02-21-2012, 09:18 AM
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Rip it out and advise the client . Who has the qualifications you or him.

A grand Banks 42 should not be going that far offshore to need SSB.

But as said there are other ways.
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  #5  
Old 02-21-2012, 09:18 AM
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philSweet philSweet is offline
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CDK, That's a little bit harsh. It did, after all, work for 35 years.

Odd, never the less. If you have to replace it, there are electrically conductive adhesives and sealants available that you can use to bond the new to the old, but quite expensive. They are specifically made to keep RF noise out of things, so their vendors should be able to help you with this problem.
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Old 02-21-2012, 10:52 AM
michael pierzga michael pierzga is offline
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Ive never seen that done...

A common ground plane on sailing yachts was copper screen...I cant remeber how many sq meters...

Typically bonded to the bottom of the cockpit , the tops of watertanks or other suitable interior surfaces. .

Manytimes these instalations had a cosmetic layer of glass over the screen.

Underwater just doesnt sound appealing to me.
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Old 02-21-2012, 12:02 PM
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viking north viking north is offline
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Copper a good choice for a ground plane but a poor choice of it's structure. This should have been in mesh form so the laminating resin could have penetrated thru to bond on the underlying layer of GRP. The electromagnetic radiation rule is, the squares in the mesh have to be less than 1/2 the wavelength of the frequency of the band of frequencies you are working in. The propagated radio wave E&H fields then see the mesh as a solid piece of copper. My recommendation- remove the non bonded/ delaminated old copper sheets-replace them with copper mesh, 1/8 to 1/2 in. squares which will the resin to flow thru and create a good bond between thr GRP layers. Spot solder this to the existing copper sheet that has not delaminated from the GRP. Solder the copper mesh to the coppersheet edges say every 4 to 6 in to make electrical contact between the two and re glass over using epoxy resin. Note when soldering do not use acid flux use resin flux. Excellent post in that you included good photos of the problem.

A yacht is not determined by the vessel but by the care and love of her owner--

Last edited by viking north : 02-21-2012 at 09:55 PM. Reason: added recommended copper mesh size.
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Old 02-21-2012, 12:30 PM
michael pierzga michael pierzga is offline
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But why put the copper underwater in the first place ?

Ive never been told that this is more effective ground plane and it certainly presents a maintenance issue. How is the radio earth fastened to this ground plane ?
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  #9  
Old 02-21-2012, 12:46 PM
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viking north viking north is offline
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The chassis of the radio-the braid shield of the coax-and the electrical image of the physical radiating antenna are all electrically bonded via a conductor that connects to the copper ground plane.(Which is actually the electrical image of the radiating ant.) Just came in to put another log on the house fire have to get my butt back to the shop Michael just take it from me, Too much theory to cover,it's an excellent ground plane--Geo.
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Old 02-21-2012, 01:48 PM
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Quote:
Originally Posted by philSweet View Post
CDK, That's a little bit harsh. It did, after all, work for 35 years.
How well it did or didn't work is not documented, the fact remains that a ground plane never requires submerged copper sheets.

For high frequencies (> 20 Mcs) the ground plane is just 4 or 8 radials at the base of the antenna, slightly longer than 1/4 wavelength, or any metal surface with sufficient surface area. For lower frequencies the required size of the radials becomes prohibitive, so the end of the braided shield under the antenna is connected to any large metal structure, the ship's ground system and/or a ground electrode. For best performance the conductor between the antenna base and a ground electrode must be as straight as possible.
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  #11  
Old 02-21-2012, 04:08 PM
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viking north viking north is offline
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CDK-While I agree to a point with what you're saying. however the fact is: FRP and wood construction have a weakness as far as antenna groung plane surface is concerned. Any added conductor surface (ground plane) below a marconi antenna setup only enhanses the probagation regardless of frequency. Agree this is non linear over the spectrum but it's the old story some is better than none. The unknows here is was the copper bonded to a dynaplate or some other system to electrically connect it to the water. I would assume so and as such it would in "theory" aid to a greater extent in the performance even at the lower frequencies. What wer're discussing here is the alchemy world of antenna radiation and while it follows the laws to a great extent as you well know there are always surprises. Was this a case of a radio fanatic custom installing copper sheet to gain a fraction of a DB gain ??? If not then Grand Banks must have encountered a problem in antenna performance, researched and rectified it with the added cost of copper and installation labour. We're assuming here that this was for comm. and not some elaborate lightning protection set up, however can't see that being the case. My present build will have copper mesh as well as 1/2 in. by 7in. by 7ft. copper shoe as a combo. ground plane enhansement/ liightning protection. Then again i'm a Radio Nut also runnuing HAM gear.
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  #12  
Old 02-21-2012, 05:25 PM
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Perhaps the previous builder is using an old English method of preventing marine organisms from damaging the keel.

Ref: http://www.shesails.net/2012/01/a-co...eel-in-photos/

With today's materials & hull coatings (e.g. Interlux Micron CSC, which contains built in copper molecules) I would say this thin copper plate is not needed and would probably remove it to save you the hassle of downstream maintenance. It's a lot easier to maintain today's anti-fouling paint than a thin sheet of copper.

Others have suggested an integrated copper mesh as a better process. I would agree that would be a better method, but do not see a practical use for it in this case. Just get ride of (or fix what you can) and use some Interlux.
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  #13  
Old 02-21-2012, 05:39 PM
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viking north viking north is offline
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Joseph- this was not used as anti fouling - the copper sheet is sanwiched within the GRP laminations. I've heard of laminating copper mesh thus allowing the GRP layers to maintain their bond thru the mesh openings but agree this system was just asking for eventual trouble. Strange that such a high quality company as Grand Banks would do this--something doesn't seem right here --As i posted above --wonder if this is a case of a custom after market install by some radio fanatic. Be interesting to investigate further.
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  #14  
Old 02-22-2012, 02:10 AM
michael pierzga michael pierzga is offline
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Perhaps there is a technical reason involving radio performance but from a boatbuilding perspective a huge mass of wet copper in seawater is a battery.

Use best craftsmanship to re encapsulate that copper keel and waterproof whatever thru hull fitting connects the copper to your antenna coupler. Keep it dry.
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  #15  
Old 02-22-2012, 02:38 AM
BertKu BertKu is offline
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I asume that the new owner does not have to work with the old 40 year SSB radio anymore, but will have a more modern 100 dB - 120 dB sensitive product. The idea of having a such a large groundplate is to have the mobile? SSB working at different points in the boat. I am using a small groundplate (plane) in my product to get a few meters better transmission, just to make sure. I cannot see this needed on a boat with a modern SSB.
Bert
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