Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 06-08-2010, 15:01   #1
Registered User

Join Date: Aug 2009
Location: Kimberton PA
Boat: Cabo Rico 38 / Bayfield 32
Posts: 573
Images: 1
Attaching a Hull Zinc Plate

My (new to me) Bayfield 32 came with a hull zinc bolted to the side of the keel. The zinc was one of those 6" x 4" x 1/2" deals with about 6 different holes so it can be bolted in a number of different installations. Anyway, the zinc bolts to the side of the keel in the area of the keel that is (supposed to be) encapsulated. This part of the keel has the lead ballast in it. The bolts for the zinc go into the keel into "some kind of metal" (can't tell from the outside what it is). Whoever installed the last zinc stripped the threads in the encapsulated plate and botched things up by trying to use a larger diameter bolt to fasten the zinc. They (attempted) to seal things up with a bunch of sealant around / behind the zinc plate. The metal plate in the keel is connected to a bolt in the bilge above it and is the central bonding point for the boat. It seems to me I have two options: Option 1) drill and tap the exiting encapsulated plate to the next size bolt (5/16"). Then install studs sealed to the hull with 5200-washers-nuts. Then install the new zinc plate over the nuts and with additional washers and nuts. Perhaps I should recess the back of the new zinc plate to allow for the nuts between the hull and zinc so the zinc plate would be flush to the hull. The negative of this approach is that without access to the inside of the keel here, I can't seal the inside. I can only seal the studs to the hull under the capture washers and nuts. Option 2) Abandon the existing zinc plate location. Repair / fill / glass over the existing holes in the encapsulated portion of the hull and move back to the deep bilge part of the hull. Here I could drill new holes and attach a zinc plate with a stainless backing plate inside the deep bilge. Then connect this plate to the existing central bonding point that is forward in the shallow bilge (over the encapsulated keel). The negative of this approach is that I don't have much room in the deep bilge as it is and this very small area already has 2 bilge pumps in it. I'm not sure which is the best approach here. The added fly in the soup here is that the keel had water in it. I'm pretty sure that the water go in there from in the bilge above it as the water that came out was clear and soapy. I think this was the soapy water from my cleaning this bilge of the remnants of a previous owners "holding tank incident". (A whole 'nuther story!) This bilge is not normally accessible except that I have some of the fiberglass pan / sole cut out due to rot in the core. Hopefully this all makes sense. Thanks for any advice.
- Tom
__________________

__________________
Saltyhog is offline   Reply With Quote
Old 06-08-2010, 16:12   #2
Registered User
 
Maddog's Avatar

Join Date: Jul 2005
Posts: 318
Are you sure this isn't a grounding plate for lighting protection? Does any part of this lead bck to the mast?
__________________

__________________
It's kind of like tearing up $100 bills while standing in a cold shower.
Maddog is offline   Reply With Quote
Old 06-08-2010, 16:29   #3
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
If the original plates are really zinc - you should be able to tell the softer zinc metal by gouging or scraping away any built up material away to expose new zinc - then your options are pretty much what you outlined.
- - The big question is what has actually been used to attach the external plates to the hull. If there was a bolt that went through the hull and into the lead inside the keel then you are dealing with a stainless/bronze bolt into soft lead where it is real easy to strip out the threads. If there is some sort of internally threaded "hard" metal stud or bolt it gets more complicated.
- - Your option #2 - installing a new system aft where you have access through the hull to an accessible bilge area is probably the best and easiest and quickest way to solve the problem. You can install new "bronze" bolts outwards from the bilge through the hull and put fender washers and nuts - well coated with T5200 - to make a mounting for the new zincs. The new bronze bolts are permanently installed and bedded and with a second bronze nut/lock washer holding the new zinc in place.
- - If you suspect the keel is full of water then the only thing to do is to haul the boat and cut open access holes through the hull at the bottom of the encapsulated keel and try to drain any water out. That will take some time. Afterwards you fiberglass over all the drain holes and the remnants of the original zinc mounting holes.
__________________
osirissail is offline   Reply With Quote
Old 07-08-2010, 06:33   #4
Registered User

Join Date: Aug 2009
Location: Kimberton PA
Boat: Cabo Rico 38 / Bayfield 32
Posts: 573
Images: 1
Maddog: Yes this does connect to the mast and the chain plates / standing rigging withsome pretty heavy duty (looks like #4 AWG) grounding wire. The plate on the outside of the hull was definitly zinc and was only about 6" x 4". I thought a lightning plate needed to bigger.

Osirisail: I should have mentioned that the boat is currently on the hard. I've already drilled a couple of drain holes in the bottom of the side of the keel and am letting it drain. I plain to install a garboard plug as well. I "believe" the failure of the keel encapsulant is in the shallow bilge above as I mentioned. The garboard plug will let me keep an eye on things every year when I pull the boat for the winter. The water that drained out was clear and soapy so I think it was the water I used to clean the shallow bilge earlier in the summer. I can't do a proper job of fixing the bilge until I pull the mast and that's not happening this year. I figure the garboard plug at least lets me keep an eye on things.
Regarding your first point, I believe that whatever the zinc bolts threaded into inside the keel was a hard material. I probed around inside the hole with a pick and it doesn't "feel" like a soft lead. If I had to guess, I'd say there is a steel plate in there that is (was) threaded to accecpt the zinc mounting bolts. All the grounding / bonding wires terminate in the bilge above to a single stainless bolt that goes down into the keel. Again, if I had to guess, I'd say that bolt threads into a bent tab at the top the steel plate. I'll remove that bolt tomorrow and see if I can determine anything from there. If I move the zinc back to the deep bilge area, it all becomes moot.
__________________
Saltyhog is offline   Reply With Quote
Old 07-08-2010, 07:16   #5
CF Adviser
Moderator Emeritus
 
Hud3's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: Virginia
Boat: Island Packet 380, now sold
Posts: 8,929
Images: 49
Tom,

If the plate is zinc, is it mounted so it can be periodically replaced? I'd expect it to erode away in the water, just like a shaft zinc does due to electrolytic action. Normally, grounding plates are made of sintered bronze.
__________________
Hud
Hud3 is offline   Reply With Quote
Old 07-08-2010, 07:27   #6
Registered User

Join Date: Aug 2009
Location: Kimberton PA
Boat: Cabo Rico 38 / Bayfield 32
Posts: 573
Images: 1
The plate that I took off was definitly zinc. That's not to say that a previous owner didn't replace it incorectly. Another point here is that this is the only zinc in the water. There is no shaft/prop zinc. There is only a little less than 1/2" of shaft exposed and the castle nut holding the prop on dosn't leave any threads or space for prop nut zinc. I believe the engine and fuel tank also connect to the hull plate / zinc, so I believe that it was designed to be the sacrificial anode. Perhaps Ted Gozzard tried to design a dual purpose anode / ground plate.

Hud: I thought that Gozzards had a similiar setup. How is your hull zinc wired / connected? <edit> I thought I rememberd you had a Gozzard 36. ?
__________________
Saltyhog is offline   Reply With Quote
Old 07-08-2010, 19:16   #7
CF Adviser
Moderator Emeritus
 
Hud3's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: Virginia
Boat: Island Packet 380, now sold
Posts: 8,929
Images: 49
My boat was an Island Packet. I had a shaft zinc and replaced it every year. PBlais has a Gozzard and may be able to help you.
__________________
Hud
Hud3 is offline   Reply With Quote
Old 08-08-2010, 06:14   #8
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
Your line: " If I move the zinc back to the deep bilge area, it all becomes moot." is the best method. You can engineer a new better place for the zinc and then run heavy thick marine stranded wire to the keel bolts and mast and to the rest of the systems.
- - Not fixing the leaks in the keel is not a good idea. As water/sea water gets down into the area around the lead it will promote the separation of the hull skin from the lead in the keel. Now you have a flexing skin that is not attached and will fracture or worse. I would strongly suggest getting access to the top of the keel where you think the leaks originate. Then open up and repair those leaks so they do not leak again.
- - If you can determine separation or flexing in the skin that covers the lead then you might need to do the "ultimate" proper fix and cut out the whole side of the keel where the lead is located. ** Make sure the boat is being supported 100% by the jackstands and not by the keel blocks.**** This may entail removing a 3 or 4 foot wide/high piece of hill material.
- - The mechanically dry the whole lead and internal area. Finally fiberglass and epoxy the removed skin back to the keel and fair the area. If properly done, you will not be able to tell that the side was removed and now you have a safe and secure keel.
- - This is assuming that the keel is integral to the whole hull and not a "bolted-on" keel assembly that was then "glassed" to the main hull. That is a different repair procedure and is actually easier to do.
__________________

__________________
osirissail is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Hull Indents ( Chain Plate Locations ) ggromack Monohull Sailboats 2 03-06-2010 12:32
Attaching Two Lengths of Chain ? CAELESTIS Anchoring & Mooring 36 16-04-2010 19:11
Wood Backing Plate for Thru-Hull Soft and Rotten dubhouse Plumbing Systems and Fixtures 51 27-10-2009 12:18
Attaching Equipment Adaero Construction, Maintenance & Refit 4 30-08-2009 13:32
Attaching Halyard Rick1 Deck hardware: Rigging, Sails & Hoisting 13 22-06-2009 19:37



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 03:44.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.