Need Input / Advice for Owners with Copper in their Keel for Older SSB Radios

The outer shied of the coax is electrically bonded to the transievers (transmitter/receiver) chassis (ground) and also to the mounting bracket of the antenna which in turn is bonded to your hull. This will be the case weather your antenna is mounted to the deck-cabin top-antenna arch-or mast top-providing these are all fabricated in metal. The hull will then act as the ground plane or counterpoise. I see no problem with stray currents as the electrical energy involved is not in the form of Ac (alternatind current) or DC(direct current) but in the form of a radiating electromagnetic radio wave emitted from what we refer to as a resonant circuit. (the inductance and capacitance of the antenna ) That is there is no current draw thru you hulls metal to act as a conductor to power a device. Your hull is simply acting as a electromagnetic reflector to represent the other half of your antenna. --- Geo.

 

Thanks viking but is it possible for a bad ssb to cause current to go to ground?

 

The only current involved in the installation of your SSB is that which powers your SSB thru the two DC conductors. The black(negative) is connected to your ground buss(In your case as you Prev. stated is one not connected to your hull thus a common floating buss (ground) bar or strip. The other conductor is the red(positive) fed to your SSB from the electrical panel thru a fuse or circuit breaker. Neither of these is connected to your hull thus no current flow should take place using the hull as a return conductor. The only connection to your hull is thru the coax/antenna ground which should not cause current flow thru the hull. If by a bad SSB you mean a short circuit somehow occurs between the positive side of the SSB's circuits to the radios chassis and thense to the coax shield to your hulls metal, no current will flow thru the hull as the radio supply fuse will immediately blow and cut the power or By the mere fact that you have a floating common ground buss bar there is no way that i can see a closed return closed circuit path thru your hull. As i have stated i have been out of the electrical/electronics field for some 20yrs. but to the best of my theory recall this and my prev post should be fairley accurate unless this rusty old brain has missed something which of course it is always open to correction .-Geo.

 

MyDaupin--one other point further i'd like to make --I built an aluminium hulled motorsailer and setup the electrical as you have with an isolated groung buss bar. I had no problems with stray current with my comm. gear/antennae set up as described above. I am privare e mailing you on this related item---Geo.

 

Thanks Viking, as you can tell I am a little paranoid about stray currents.

 

Not to worry my good man--be more paranoid of stray cats deficating in your vegatible garden--However i have some training on solving that problem also.

 

Any electricified equipment connected to earth is a possible source of stray electricity. A system to monitor for leaks and the abilty identify and isolate them in the only solution. Double pole electric systems are worthwhile .

 

Michael agree- thus by bonding the neg. conductors of all devices to a common buss bar isolated from the hull is in effect such a system. The only other "extreme" measures is to ensure all electrical devices have totally floating grounds from their mounting chassis(including lighting sockets) or that the devices themselves are electrically insulated from the metal hull. The theory here is current flow will always take the path of least resistance,(thru the hull) however even then it would be a parallel run with the offending device(s) commonly bonded conductor(s). Because the common bonding buss bar is isolated from the hull,the route would have to be between two devices whose chassis are not insulated from their mounting fasteners which in turn of course would also have to be connected to the hulls metal. Thus current flow in theory could take place as a parallel run (hull and conductor) between the two or more devices back to the common isolated buss bar. We're getting to extremes here but a simple way to overcome this is to do an omage test on all the electrically fed devices and those not having floating isolated conductors, mount them insulated from the vessels metal hull. Will there occur any other possible stray currents --very unlikely within the vessels system--My biggest concern has always been external stray currents from poorly wired other boats or shore power. Thus the importance of ample and properly bonded zincs. There is another extensive thread on this with much excellent info by CDK one of whom I consider well qualified and knowledged in this here "alchemy electrical field" ---Geo.

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

 

Hi Viking - The project on this 42' Grand Banks is progressing. The keel is now being properly wrapped around the bottom of the foot of the keel. From what the owner is telling me (I was only there for the survey of the keel once the outer fiberglass was removed) is that the copper will be re-secured with a bonding compound and re-fiberglassed over. He said they were going to secure the copper with brass screws but a boat builder said that small air bubbles might form around these areas and leave a void. So they are going to glass over the copper with at least two layers of matting. I did like the idea of copper mesh and see how that would be excellent to use in a case like this, but it is very expensive for the owner of this vessel to do. The owner of this Grand Banks will install a SSB radio into this copper once the vessel is splashed. Once that install happens, I will write back to explain the details of the install and how well it worked. This was a very unique situation. Thank you everyone for all for the input and for sharing your experience and knowledge.

 

Thanks--John, I was very interested on the progress as it is a unique situation I also have not run into before. I am also keen on this because a friend of mine from North Carolina is seriously looking to purchase a Grand Banks. I am surprised Grand Banks did not use mesh. This is not typically what I would expect from a builder of such a good reputation, IE, seperating layers of GRP with a smooth difficult to bond layer of material. Possibly this could have been a one time occurance due to a shortage of mesh, behind delivery schedule and an irate customer. Still I don't think a good design feature. Thanks again--Geo.

 

Well anyone owning an AL boat has to always concerned. Any device can go to ground and somehow touch boat or water. Is it possible to use a diode to isolate ground in at lease one direction.

 

MMmmmm -- good question, however DC flow should take place in only one direction and any stray current would flow likewise--From the low to the high potential--Neg. to Pos.(electron flow theory). Thus any diode placed in the circuit would have to favour both. (cathode to anode)(supplier to collector). MyDaupin-- My alum. hull was built in 1952 --after conversion to a motorsailer, wired as your's, 6 pairs of hull zincs equidistant along the hull plus one on the shaft (bronz prop)and rudder-antennae hull bonded ground plane--Epoxy painted below the waterline, proper alum. compatable anti fouling (now illegial Tin based),-- In addition whenever i visited a yacht club I hung a big zinc over the side. After 10 yrs. ownership before I sold her --zero-zilch-nada- electrolisis corrosion. If you have not already done so read the thread on such by CDK. From your construction description you have little to worry about.---Geo.

Off to the shop--land yacht prep.--cheers Geo.

 

Hi Geo - I agree. Anything goes on some of these models. I run into varying design and material issues such as this on several different brands of boats on Marine Surveys here in South Florida. One such boat is Prout. Especially Prout catamarans that were built in the late 80's to early 90's. Back then they were having financial difficulties when they were still building the boats in England. They were behind with payments to suppliers and some suppliers would cut off there credit supply accounts so they would use whatever was in the yard or what they could get from other suppliers. It is not uncommon when surveying Prouts of the same year that some of the original equipment is different from one hull number to the next. The owner had told me that another similar 42' Grand Banks has just arrived in the boat yard with leaking water coming from the keel between the fiberglass layers. I will see if I can get a look at that one as well if I can chat with the owner. If I can, I will post my findings of that Grand Banks here as well.

 

Wow--leaking between the FRP layers--- not looking good Amigo. I did a lookover of a Taiwan built power cruiser for a friend in Toms River N.J. back in the 70's. He was concerned that upon doing some maintenance the workers had run into layers of Newspaper sanwiched between the FRP layers. Apparently this was one of the sneeky techniques they used in saving construction costs. I.E to gain thickness. After that nothing surprised me although that was the worst i've ever run into. Much appreciate the followup--Geo.