Please Teacher??

[simon barefoot]

I'm currently doing some work on my old Princess. One of the main jobs I want to get done is to remove and service or replace all the seacocks and skin fittings, and replace the anodes.

I've searched the threads on here and am still confused. I've narrowed it down to DZR or plastic (marelon) skin fittings and valves. That will probably end up being decided by cost. However I am guessing that I will have to factor in the need (or not) to fit anodes to the new fittings (obv not to plastic if I take that route).

I am usually on a marina berth. What I need to know is when/if I fit the anodes, what needs to be bonded...prop...propshaft...rudder...trim tabs (obv)...bathing platform legs? Do DZR fittings get bonded too?

The guys at the yard are great, very helpful, but I dont want to be plaguing them with questions every time I see them, they've obviously got paid work to do!

The one thing I think I do know is that I need zinc anodes. After that I need to find out about Mr Galvanic Isolator and his job in all of this.

Sorry to sound like a complete numpty, and thanks to anyone who can give me a reply or put some links up!

 

[Tranona]

DZR are fine - just make sure from your supplier that they are to that specification. You can get them from ASAP Supplies mail order if you can't found a local source.

No need to bond either skin fittings or valves to anodes. Anodes are will almost certainly be there already bonded to the stern gear - that is prop through the shaft (may also have shaft anodes, or even an anode on the end of the prop), P brackets and rudders. If you are hooking up to shorepower regularly you need a galvanic isolator. I would be surprised if the boat is not already wired correctly, so it is a case of replacing the anodes and checking that the bonded wires to the various bits are sound and low resistance.

You can get useful information from the MG Duff website - they are the leading supplier of anodes.

 

[capetown]

If you go the marelon route, size for size compared to bronze/dzr, you may have to enlarge the hole in your hull, well we did on ours.

Just a heads up.

 

[mitiempo]

Here are a few links that might help.

http://www.pbase.com/mainecruising/seacock_primer

http://www.pbase.com/mainecruising/replacing_thruhulls

And I agree zincs and/or bonding of through hulls is not necessary or wanted.

 

[VicS]

After that I need to find out about Mr Galvanic Isolator and his job in all of this.

A galvanic isolator is a device which is included in the shorepower earth connection. It will be needed if you leave the boat plugged into shorepower for prolonged periods, even if not actually in use.

Its function is to block current from very low voltage, or galvanic, sources such as dissimilar metals flowing in the earth connection with a return path through the water via your under water bits and pieces which may cause corrosion and in particular rapid wastage of the anodes

Although current from these low voltage sources is blocked it still allows current from high voltage sources, the shorepower, to flow and therefore maintains the effectiveness of the earth as a safety conductor.

More detailed explanation at http://www.sterling-power.com/products-galvanic-why.htm

.

 

[ccscott49]

IMHO, go real bronze/gunmetal or marelon. Dont like DZR, after all it is only "de-zincification RESISTANT", not completely inert, like marelon or bronze.

That's the way I do it, but lucky that when built my boat has all bronze seacocks and through hulls and any new ones I have had to fit are also bronze..

 

[vyv_cox]

IMHO, go real bronze/gunmetal or marelon. Dont like DZR, after all it is only "de-zincification RESISTANT", not completely inert, like marelon or bronze.

That's the way I do it, but lucky that when built my boat has all bronze seacocks and through hulls and any new ones I have had to fit are also bronze..

Fair enough but bronze can be horrendously expensive, especially from local chandleries. My boat was built in 1985 and fitted with Blakes seacocks which I believe at that date were made in DZR. They remain in excellent condition.

 

[Tranona]

IMHO, go real bronze/gunmetal or marelon. Dont like DZR, after all it is only "de-zincification RESISTANT", not completely inert, like marelon or bronze.

That's the way I do it, but lucky that when built my boat has all bronze seacocks and through hulls and any new ones I have had to fit are also bronze..

Bronze are getting increasingly difficult to source - mainly because they are so expensive, typically twice the price off DZR, but mainly because DZR has proved satisfactory over 30 or more years.

 

[simon barefoot]

Excellent replies, thank you very much! This particular job shouldn't be too hard to get done-famous last words! At least I've got long arms to reach down and get to the valves.