Reply
 
Thread Tools Display Modes
 
Old 04-25-2013, 03:17 AM   #1
Veteran Member
 
tiku's Avatar
 
City: Espoo
Country: Finland
Vessel Name: Carpe Diem
Vessel Model: Storebro 34
Join Date: Nov 2012
Posts: 74
Zincs how many are needed?

I have changed the anodes on my propshaft, we use the ones that screwe to the end of the shaft and they are mated against the bronze fasteners, which in turn are in good contact with the prop (the picture does not show them installed).

So my question is do I need to install anodes to my rudders and trimtabs too? They are not bonded with any wires etc. There have not been any installed by the previous owner. The only ones are in the propshaft.

The marina where my boat is staying for the most of the time has limitations for the use of shorepower (24hour) max time per boat so there wont be too much current in the water. In addition my boat has a copper grounding plate installed in the bottom...

So what do you guys think, is it time to take the drill in hand make some holes for zincs?
Attached Thumbnails
Click image for larger version

Name:	image-2259989428.jpg
Views:	92
Size:	47.7 KB
ID:	18605  
__________________
Advertisement

__________________
Storebro 34 Royal Cruiser - 1969
Twin Volvo Penta Tamd 40b with shafts
www.storebro34rc.blogspot.fi
tiku is offline   Reply With Quote
Old 04-25-2013, 04:32 AM   #2
TF Site Team
 
Peter B's Avatar
 
City: Brisbane
Country: Australia
Vessel Name: Lotus
Vessel Model: Clipper (CHB) 34 Sedan/Europa style
Join Date: Jun 2008
Posts: 6,669
Send a message via Skype™ to Peter B
I have mixed feelings about this issue of zincs and bonding. I am gaining the impression the bonded fittings corrode faster than the un-bonded ones. Also the prop shaft looks worse when the brush is on it than off it. How to get to the real truth..?
__________________

__________________
Pete
Peter B is offline   Reply With Quote
Old 04-25-2013, 10:23 AM   #3
Guru
 
Phil Fill's Avatar
 
City: Everett Wa
Country: US
Vessel Name: Eagle
Vessel Model: Roughwater 58 pilot house
Join Date: Oct 2007
Posts: 2,919
Is the boat in fresh or salt? Fresh water does not conndect electricity very well, so zincs don't protect very well.

Also it appears there are not many through hulls or metal fitting below the water line, so you might be OK. the color of your prop looks OK as there is not pink to it. If it was pinkish that mean the zinc in the prop is being used up.
Phil Fill is offline   Reply With Quote
Old 04-25-2013, 10:31 AM   #4
Veteran Member
 
tiku's Avatar
 
City: Espoo
Country: Finland
Vessel Name: Carpe Diem
Vessel Model: Storebro 34
Join Date: Nov 2012
Posts: 74
The boat is in seawater, but in the Baltic sea. The salinity here is rather low, it is actually a kind of mix between sea and freshwater, to be more precise the baltic sea has salinity of 6 to 8 ‰ vs. 35 ‰ found in oceans..

There are only four submerged thru- hulls in the boat..

I was originally thinking that I'm fine as it is now, fresh anodes behind props.
__________________
Storebro 34 Royal Cruiser - 1969
Twin Volvo Penta Tamd 40b with shafts
www.storebro34rc.blogspot.fi
tiku is offline   Reply With Quote
Old 04-25-2013, 11:00 AM   #5
Guru
 
Phil Fill's Avatar
 
City: Everett Wa
Country: US
Vessel Name: Eagle
Vessel Model: Roughwater 58 pilot house
Join Date: Oct 2007
Posts: 2,919
The Eagle is moored at the mouth of the Snohomish rive so its what we call brackish, fresh on top with salt below. Fresh is lighter than salt so the first couple of feet is fresh but the 6 ft keel is in salt. However being we are planning moor and go into the salt it has two big 3 X 6Ē zincs on the stern and one 3 X 6 for the bow thrust which last 3+ years. I have a diver come every 6 months, main to clean the running gear and the keel, the rest is green fuzzy yucky stuff. You might want to scrap the through hulls from the interior of the boat to check the color. If not pickish color your good to go.

I been told that a wood boat can be over zinced, but I donít remember the reason why?
Phil Fill is offline   Reply With Quote
Old 04-25-2013, 11:27 AM   #6
OFB
Guru
 
OFB's Avatar
 
City: Richmond bc
Country: Canada
Vessel Name: Invader no1
Vessel Model: Kishi Boat works
Join Date: Mar 2012
Posts: 636
As long as nothing has changed in or around the vessel there is no reason to add zincs. The current protection system is balancing the different metals exposed through the shaft ( if there are any ). That's all you probably need.

Unless something changes leave as designed IMO. If you see signs of metal corrosion re visit the zinc question.

My two cents.
OFB is offline   Reply With Quote
Old 04-25-2013, 11:37 AM   #7
Senior Member
 
City: Maine
Country: USA
Join Date: Feb 2011
Posts: 109
Quote:
Originally Posted by Phil Fill View Post
Is the boat in fresh or salt? Fresh water does not conndect electricity very well, so zincs don't protect very well.

Also it appears there are not many through hulls or metal fitting below the water line, so you might be OK. the color of your prop looks OK as there is not pink to it. If it was pinkish that mean the zinc in the prop is being used up.
I'm not sure if I understand you. I thought all water, except deionized water, conducted electricity. And that the difference between salt and fresh is that the sodium and chloride in salt can part from each other when introduced to electricity, thereby making the chloride a more negatively charged ion and the sodium becomes a positively charged ion, which helps conductivity. The lack of salt in freshwater just seems to mean that the natural minerals have the job of disassociation and becoming ions. These minerals could be any mixture of metals found in the watershed. Zinc is a softer metal than most of the metals found on boats. When electrolysis occurs, due to the unbalanced state between the metals and the stray current from the marina or the boat itself, the zinc is sacrificed and not a prop or rudder stock. Fiberglass and wood boats are less susceptible than steel boats. If the blades look sharp and there are no signs of wear that look like tiny pits or mountain ranges, than your boat seems to be well grounded and neutral. And as stated, discoloration is also an indicator of electrolysis.
Anthonyd is offline   Reply With Quote
Old 04-25-2013, 01:09 PM   #8
Guru
 
Brooksie's Avatar
 
City: Cape Cod, MA
Country: USA
Vessel Name: Island Seeker
Vessel Model: Willard 36 Sedan
Join Date: Oct 2007
Posts: 954
I am a "non-bonder" myself but I do understand why some recommend & do it. Don't confuse stray current corrosion with galvanic corrosion.

Zincs will be little help on stray current corrosion either from your marina situation or from your own batteries (even if moored out). The zincs may disappear so fast that you won't notice they were ever there.

Galvanic corrosion (different metals connected electricaly in water), many times caused by bonding, will be helped by zincs as the zincs will be the first to corrode thus saving other parts till later.
Brooksie is offline   Reply With Quote
Old 04-25-2013, 03:10 PM   #9
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Our boat has two "license plate" zincs on the transom and two shaft zincs on each shaft. That's it in terms of boat-mounted zincs. The bronze rudders are tied into the bonding system at the steering gear so there is no need for zincs on the rudders themselves.

We did install shaft wipers to ensure a good connection between the shafts and props to the bonding system.

Because the bay our marina is in usually has a layer of fresh or brackish water on top due the outflow of several high-volume streams and a sizable river, many boaters in our marina including us hang a zinc on a heavy cable about six to eight feet under the water off the side of the boat. The other end of the cable is connected to the bonding system. In our case it's clamped to one of the bronze rudder posts.

We do this because in the marina, transom zincs on boats like ours are sitting in the layer of fresh or brackish water so the connectivity is very low. This forces the much smaller shaft zincs to do all the work By hanging a zinc down into the saltwater below the fresh/brackish layer, it has good connectivity and helps "take the load' off the shaft zincs and they last much longer. And since we can pull it up we can make sure conditions haven't changed in the water--- if the zinc goes away at it's normal rate nothing has changed. If it starts going away faster then we know there is problem that needs to be traced down and solved.

We have a relatively 'hot" harbor so most boaters here change zincs every six months.
Marin is offline   Reply With Quote
Old 04-25-2013, 03:51 PM   #10
Veteran Member
 
tiku's Avatar
 
City: Espoo
Country: Finland
Vessel Name: Carpe Diem
Vessel Model: Storebro 34
Join Date: Nov 2012
Posts: 74
We used those overboard zincs as well in our all aluminium search and rescue vessels. Those machine guys were pretty sharp with stray currents and they had good systems to discover elecricity leaks, well they had to...
__________________
Storebro 34 Royal Cruiser - 1969
Twin Volvo Penta Tamd 40b with shafts
www.storebro34rc.blogspot.fi
tiku is offline   Reply With Quote
Old 04-27-2013, 02:08 AM   #11
Senior Member
 
fstbttms's Avatar
 
City: Under a boat, in a marina in the San Francisco Bay
Country: USA
Join Date: Mar 2012
Posts: 447
__________________

__________________
Clean bottoms are FastBottoms!
fstbttms is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 10:33 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012