Hull Anode?

tbag · Posted: Sun Jan 06, 2013 6:37 pm Post subject: Hull Anode?

I have a CD22 and was just doing some winter maintenance. One of the things on the list was to replace the hull anode but searching around here and looking at the newer owners manual, it looks like anodes are not something that most CD have on the hull, which makes sense because they are fiberglass. Of course I have anodes on my outboards and those look to be in good shape. The anode is below the water line on the starboard side of the transom. So what should I do? Remove it, replace it or ignore it? One of the bolts is seized (cant get it loose even with my impact driver!!) and the other is pretty tough to move, so ignore it would be nice. Also if it makes a difference the boats lives on a trailer.

Thanks for you input

rogerbum · Posted: Sun Jan 06, 2013 6:50 pm Post subject:

What else is the anode connected to? It's hard to believe that it's just attached to the hull without an electrical connection to something else that needs protection.

Bill K · Posted: Sun Jan 06, 2013 7:10 pm Post subject:

On my boat, ( not a C-Dory ) the hull anode is connected by wire to all metal that comes in contact with the sea water.

Bill Kelleher

journey on · Posted: Sun Jan 06, 2013 7:13 pm Post subject:

The only hull anode that I know connected to/thru a fiberglass hull is a grounding anode for radios. I put one on the sailboat for a marine HF radio ground plane.

Since anodes are provided for stray currents, and (last I heard) fiberglass doesn't conduct electricity, that anode probably was put there for a ground of some sort. I run the chassis grounds from the electronics to the brass through hull that's in the rear of the C-25 cabin. That should dump all the stray noise into the ocean. I think the only thing it does is makes me feel good (well).

Boris

colobear · Posted: Sun Jan 06, 2013 7:14 pm Post subject:

Is there a way you can see the other side, inside the hull, to see what if anything the anode (zinc) is connected to? If it is not connected to anything that would allow for current flow it is just a decoration. In that case I'd just leave it and keep an eye on it to make sure the bolts don't corrode away and leave a hole in the hull.

tbag · Posted: Sun Jan 06, 2013 9:57 pm Post subject:

got it off!! had to move a fuel tank and unbolt it from inside the hull. one of the bolts had a ground wire connected to it so it must be useful for something. so now I have two questions:

1)when I put the new anode on, what and how should I seal up the thru bolts ? assume 3m 4200 or something of the like smeared on both sides of the transom.

2) and then the big question. this is the first time i have had the look at the transom core. How do I check if moisture has gotten into the holes? I poked around with a pick and it felt soft but I didn't see water gush out. I don't have moisture meter. is there an alternative way to check for moisture intrusion?

Thanks

thataway · Posted: Sun Jan 06, 2013 10:13 pm Post subject:

Many C Dorys do not have thru hull fittings. If there are not thru hull fittings, probably no reason to have the anode. But I agree see where the wire goes. I don't like to use Zincs for a RF ground--a bronze or copper plate is best, but again unless you are using SSB or Ham HF no reason for a ground.

If there is a 110 V system on the boat, it may have the ground tied to this, or it may have a galvanic isolation system tied to this. I prefer to float the ground and use GFI for a boat like this.

As for the transom--assume that there is moisture. Use a heat gun to slowly heat this area, and let it dry out. Then take drill and over drill this hole, --maybe 3/8" if it is 5/16" now--then undercut the core around this area, and put in thickened epoxy thru the entire area--making a solid epoxy plug. Redrill the bolt holes (if you want to put the anode back in place), and then bolt in place. One of the 3 m sealants, such as regular 4200 would be fine for a sealant. The older polysulfides also work very well.

rogerbum · Posted: Sun Jan 06, 2013 10:20 pm Post subject:

If it feels soft, keep poking and see if you can get to dry material. Dig out all the moist stuff and if you're lucky, it only goes back a cm or so. If it goes deeper than you can reach (with a dental pick or bent nail), then see if you can borrow a moisture meter from someone a check the entire transom. Also, it won't hurt to drill out a somewhat larger hole (say 1/2") to check and see what you have. If you can get to clean wood with a fairly small hole, then you'll want to undercut the core, and fill the hole with thickened epoxy. Do a search on the site here and you'll find good instructions on how to do that. Once the hole's filled with epoxy, then you can re-drill the small hole and remount the zinc. If you use a countersink, to flare out the hole a bit, you can put a nice bead of caulk in behind that will make a good seal. There's a lot of possible sealants you can use for that but perhaps life caulk would be a bit better than 4200.

Sunbeam · Posted: Sun Jan 06, 2013 10:20 pm Post subject:

thataway · Posted: Sun Jan 06, 2013 10:35 pm Post subject:

For those who suffer from sealant confusion there is a good, but slightly dated article from "Good old Boat"
http://www.goodoldboat.org/reader_services/articles/sealant.php
Which has a nice table at the end. It does not mention 4000, the colors, or fast set 4200, and I didn't see BoatLIFE, Life Seal, (which is a combination polysulfide/silicone.) which I like to use on plastic and fiberglass joints.
Keep sealants in the freezer between uses.

wailedcentipede · Posted: Mon Jan 07, 2013 12:49 am Post subject:

electrolysis ... if theirs a wire connected to the metal fuel tanks that may be the reasoning .. may want to plug the hole, if needed run a wire to the engine ?? my departed old boat had a very light wire connecting every fixture to the motor electrolysis was the reason .. wc

thataway · Posted: Mon Jan 07, 2013 4:14 pm Post subject:

tbag · Posted: Wed Feb 20, 2013 3:21 pm Post subject: Dynaplate

OK an update that leads to a question. I did not have a zinc attached to the transome but a bronze Dynaplate. when I removed it the damn thing cracked. I do not have a ham radio on board and do not plan on installing one. seems like the main reason to have a Dynaplate is to sluff extra current. So I am planing on installing trim tabs in the same spot the Dynaplate was. electronics on board are VHF, AM/FM radio, Lights, and GPS/Sounder. SO can fill the holes and forget about the plate or do I need to move it and reinstall?

T

thataway · Posted: Wed Feb 20, 2013 3:38 pm Post subject:

The only reason for the Dynaplate is for a ham radio ground (some have used for lightning ground--but not as effective as a flat copper plate). So no reason for the Dyna plate. Definitely fill the holes, and be sure that there is no water in the transom. Check, to be sure that the place you are installing the screws for the trim tabs are solid glass; if not, then epoxy fill, and then drill new pilot holes.