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starlightventure 11-01-2009 03:11 PM

Wood Boat Maintenance
I am restoring a 1956 38 foot wooden sail boat. I am replacing all the through hull bolts and fasteners. The rusty original through hull bolts are galvanized carriage bolts. The rust has destroyed portions of some of the wood shoulders they seat on. I was thinking of replacing them with silicone bronze. I am getting a lot of different conflicting information on how to proceed.

The surveyor said to replace with what ever was there, but the future rust factor and damage to wood is my concern.

The under water hull has three different kinds of metal on it, galvanized through hull bolt about 75 of them, 130 stainless 2"screws. and 5 Bronze through hull valves. On this I have been informed that all the metal should be the same kind, to prevent relectrolysis between different metal. Makes cense.

Also I have been informed that the wood boats should not be bonded because the wood would will be damaged by electrolysis around the Zinc fitting,

In conclusion my plan is to, remove all fasteners and treat the wood with smiths epoxy, and replace all galvanized and stainless fasteners with silicone bronze.

Dose anyone have advice on weather or weather not to replace rusty galvanized bolts with bronze bolts in a wood yaught.


deniseO30 11-01-2009 06:13 PM

Yes replace all the galv with bronze, it will be $$$ The wood where the old bolts were will stll rot. and if you stabilize it with penetrating epoxy is good better still is to plug and redrill after you stabliize the wood. Have you joined the wooden boat forums? Lots more help there! good luck!and welcome to the forum

CharlieCobra 11-01-2009 07:39 PM

Starlight, check out my latest thread on Oh Joy in the Maintenance section. My advice is to replace the bolts as well. I'm waiting on answers whether to treat or replace some of the wood on several forums. Oh Joy was bonded with bronze straps and the SSB with copper tubing and a large bronze ground plate. Any fasteners exposed to seawater of dissimilar metals will be subject to electrolysis. My luck holds there as Oh Joy was C-Flexed in '94 so NONE of the fasteners are exposed at all. Good thing as I have several hundred of those bolts of dissimilar metals...

paulk 11-01-2009 07:48 PM

I'd post on Woodenboat's forum to get the most exposure (and answers) to your questions about repairing a wooden boat with this many issues.

timmynocky 11-02-2009 02:11 AM

Wooden Boat fastenings
You donít say what kind of wooden boat you have.

Is it carvel, lapstrake, plywood?

All those stainless screws would suggest that it is plywood but I could be wrong.

Itís difficult to advise without more information.


DIY Wood

celenoglu 11-02-2009 02:26 AM

Electrolisis is said to occur on metals that are open to sea. But my boat says the opposite. All the metals even on deck are affected from electrolisis. The boat is built with copper and galvanized nails are used in different repairs. Although all are in the wood without any connection to outside the galvanized nails (although they are newer) are completeley gone or their thicknesses are equal to a pin. Do not use any dissimiliar metal even is they are inside the wood. They will be affected from electrolisis faster than you can imagine.

starlightventure 11-02-2009 04:27 AM

This is what the surveyor said. " Only replace the bolts with what ever was there." My inference was that the original 50 year old bolt material atoms and ions have soaked deep into the wood around the bolts. introducing new bolts of different metal into the old holes would establish two different metals in extremely close proximity. Electrolysis

Celenoglu, if your boat has galvanized fasteners that have replaced bronze fasteners I would suspect that the old bronze atoms and coatings are imbedded in the wood around the new galvanized repacments. Bronze having much lower corosion would attract ions away from the new galvanized fasteners, especially in such close proximety, a small battery is set up. The bigger problem in this is what effect it has on the wood, like a battery acid it destroys the wood.

starlightventure 11-02-2009 05:30 AM


Originally Posted by timmynocky (Post 537652)
You don’t say what kind of wooden boat you have.

Is it carvel, lapstrake, plywood?

All those stainless screws would suggest that it is plywood but I could be wrong.

It’s difficult to advise without more information.


DIY Wood

Mike. It is carvel planked, mohogany 1 1/4" x 4". Planks are fastned with one 3/8 galvanized lag bolt with one two inch stainless screws on either side of said lag bolt.

cormeum 11-02-2009 04:32 PM

Replace them all with Bronze. if the planking is really "iron sick" you may want to replace the worst of the planks. If it's just a little soft under the heads Smiths may work, but if more than half of the thickness is gone, it's not salvagable..

On bonding- correct, do not bond.

CharlieCobra 11-02-2009 06:17 PM

I'm going back with the galvanized bolts in replacement. Have any of you priced a 6" Bronze bolt lately? I'm not paying $17 per bolt when there's 200 of them. I'll be dipping mine in non-conductive liquid rubber but leaving the last bit of thread free for the nut. I'll then coat the nut and remaining threads with the LRB after I tighten them up. No moisture and no conductivity, therefore, no electrolysis. I'll replace whatever wood needs it and CPES the rest.

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