ssb and 100 sq feet of copper

[dpollitt]

Hello
I would love to have opinions on the apparent debate between installing 100 sq ft of copper on the inside of the hull versus installing dynaplates and using much less copper plating.

Im new to SSB installation and am facing doing my first. This question has come up.

many thanks
david



I

[btrayfors]

David,

Yes, the question is often debated and there are tons of posts on this subject...here, on the SSCA board, and on SailNet.

The now infamous "100 square feet of copper" has been rather thoroughly discredited by RF-savvy sailors, amateur radio operators, and some professional SSB installers (including me). After carrying out some real-world testing, Gordon West has written that the 100 sq ft isn't required; he suggests just connecting a wide copper strip from the tuner ground lug to the nearest bronze thru-hull. I agree that this is good practice -- and you ought to do this -- but I think you can further improve the RF ground system by adding radials, toerails, pushpit/pulpit/lifeline complex, radar arches, etc. to the radio ground system.

As it turns out, the 100 sq ft recommendation has just been repeated over and over in many texts and in manufacturer's literature, with little to support it, with no empirical testing, and with almost no discussion of alternative RF ground strategies.

Similarly, the external radio ground plate is controversial. I wouldn't bother with it. It's expensive, requires a hole in the hull, and after a few months in the water becomes corroded and virtually useless. Much better to just use a thru-hull -- not otherwise connected to the boat's DC ground system -- and beef up the RF ground system by other means if you want an even better signal output.

For a better understanding of RF grounds, see my post on "RF grounds in the marine environment" on the SSCA board.

Bill

[casique8]

David
I to have the same problem, I dont have bronze thru-holes only the engine and shaft if theres a remedy some one let me Know I all ready have the tape but dont know were to start....

[the keip]

As Bill points out, a Dynaplate IS expensive...but it lasts forever even in saltwater, and it does what it's supposed to do. Yes, it does require a hole in the hull. Hole for hole though, there is far greater surface area exposed than any thru hull can give you. They are extremely reliable, with heavy emphasis on extremely and reliable.
Howard Keiper
Sea Quest
Berkeley

[la5zo]

I rejected the temptation to install exspensive Dynaplates.
Instead I purchased 30 feet of 2" copper ribbon and a sq.metre coppermesh. (Musquito-net)
I connected the ribbon via capacitors to the most forward keel-bolt
and ran it aft to the transom where the auto tuner is located.
I placed the coppermesh under the bunk in the aftcabin connected to the copper ribbon.
Level to the chart table I ran side-track ribbon up to the MF/HF radio.
I used a number of torroids and RF Insulators on DC cables and on the control and coax cables that runs betwen the radio and the auto tuner. The installation is working very well, and I keep getting excellent signal and modulation reports.
I am convinced that a good groundplane is an efficient counterpoise to the aft stay
and the only way to get an efficient antenna system on a small vessel.

Geir
S/Y Destiny, Norway

[Cheechako]

I installed copper in the stern hull interior inside the stern locker. Used 12" wide thin cu sheet horizontally stripped , pounded to shape with a rubber hammer, contact cemented and soldered the sheets together a few places. In the end it was probably closer to only 20 sq ft but it was right below/aft of the auto tuner. I was reported to have one of the best signals around by my two Ham buddies who taught me everything.... It was a lot of trouble. If your thru hulls are bonded wouldnt there be issues sending that signal into the whole boat system?

[the keip]

I succumb to professional curiosity.

Bill, please tell me what it is that's so different about the use of a 'convenient thru-hull' (especially if you have no thru hull) and a Dynaplate? They both are underwater and offer contact with the water which is an idea you have difficulty with; but given that they do, it seems to me that the greater surface area of the plate is way advantageous. Is it the hole(s) in the hull? Doesn't a thru-hull require a hole too?
Your comment about the Dynaplate corroding in water after a few months is empthatically wrong...it's made of bronze and will probably outlast most any boat it's attached to....much the same as a bronze thru hulll.... if not attached or 'bonded' to the vessel's DC ground. It is expensive, however, I'll give you that.
Howard Keiper
Berkeley

[btrayfors]

Howard,

There are numerous references to corrosion problems with Dynaplates. The problem is not with corrosion of the bronze itself, and perhaps "corrosion" isn't the right word, but rather with growths on the Dynaplates in seawater which work to degrade its initial advantage, i.e., of a very large surface area in contact with the water.

The construction of Dynaplates involves a honeycomb of "beads" in contact with seawater. Once these beads become covered by algae and marine growths -- as they inevitably will -- the bronze is no longer in direct contact with the water. Yes, there's no doubt some capacitive coupling going on, but this is not as effective as direct contact.

Here's what the folks at yachtfunk had to say recently with respect to the ARC: "Traditionally, boatyards have installed dynaplates, which allow for a direct contact to seawater, which is a good electrical conductor. At first glance, dynaplates seem to be a clever solution, looking at the way they are built; they consist of little pellets making the contact surface bigger than the holes to be cut into the hull for their installation. Unfortunately, this apparent advantage turns out to be their biggest drawback, because after about six months of sailing algae and shells will have started to colonise the pellets, so they need cleaning or replacement to do their job properly." (from the Noonsite website).

There are many other such references.

Gordon West did some testing of traditional RF ground systems a few years back, and published his results in SAIL magazine. IIRC, he found, inter alia:

1. There's no need for 100 sq ft of copper;
2. A direct connection to the nearest bronze thru-hull is adequate;
3. Large ground plates are unnecessary, and the porosity of some plates effectively reduces their contact with seawater.

However, in the absence of really good empirical data on Dynaplates and other forms of ground plates, and their effectiveness in improving transmitted HF signals -- particularly in comparison to other RF ground systems -- I think we can't say for sure how well they work when new or after prolonged immersion in seawater.

What I CAN say from personal experience, and from professional experience installing HF systems on boats, is that I absolutely agree with points #1 and #2 above. I also tend to think that #3 is substantially correct, leading to my working belief that groundplates and DynaPlates are an unnecessary expense in most cases.

In the past week I have installed three HF systems on cruising sailboats: a 33-footer, a 42-footer, and a 40-footer. None used Dynaplates or ground plates for the RF ground system. All systems work perfectly, tune quickly on all ham and marine bands, and received excellent on-the-air signal reports over daytime distances of 500 to 1,000 miles. This follows my personal experience with HF radio aboard my own boats over the past 40+ years.

When it comes both to antennas and, especially, RF ground systems on boats, some thinking "outside the box" can yield excellent results :-)

Bill

[the keip]

Bill...

i'm not impressed with any argument supported by lack of data, empirical or otherwise, for or against anything.
Good, legitimate data suggest that a Dynaplate system performs as well as--probably not better--a traditional coppered lnstallation.
I've done many installations going either way with about equal success. My personal choice of course, is the Dynaplate for it's simplicity and reliability. It works every time, all the time.
Marine growth does not seem to be a problem on a D'plate any more than similar growth would affect a bronze thru-hull. It is not painted, of course, and when the boat's bottom is cleaned, it's a good idea to scrub the plate with a wire brush, not to improve the plate's efficacy, just to get rid of the critters and algae...which, contrary to popular opinion, do not have the slightest effect on the grounding function. Wouldn't it be great if all we had to do to insulate a metal hull was to allow marine growth to accumulate?
The way I see it, a traditional copper job has one thing to recommend it. If done with care and a strong sense of tradition, one can expect good, predictable results; the methodology has been around a long time. I, myself have been a strong advocate for doing it that way.
On the other hand, if done with equal care...no more, no less...the results, using a fairly modern Dynaplate technology, one can expect good, predictable results., and it won't cost nearly as much in money or sweat.

BTW, I wouldn't pay much attention to Yachtfunk if they keep feeding you baloney.

Howard Keiper
Berkeley

[easterly]

Really stupid question. Why not place a carbon brush, as in an alternator or starter against the stainless steel shaft and let it, and the prop be your ground? Has anyone ever tried this?