Copper Sheathing

[BuccaneerCapn]

In about a month I will be pulling my 48' Pinky Schooner for an extended bottom job and I planned on copper sheathing the bottom. I have found a source for the copper and the copper nails, but have now been made away that there are other issues to resolve. First, I know that the planks are not fastened with a copper based nail, and second, the rudder mounts and tube are not copper. Could someone provide some additional clarification as to whether I have to completely refasten the hull planks or what?

[Thad]

Boats and ships to be coppered were never iron fastened. The copper electrically accelerates corrosion of iron so your iron fasteners will need to be replaced soon if not before coppering. More rust will also compromise her planks and frames.

[Gary E]

Boats and ships to be coppered were never iron fastened. Ohh??? Why?

I have seen a lot of power boats, most of them older than dirt, that were fastened with nails that created a lot of rust stains running down the sides of the hull. The hull color was either red or black, so I have to guess those were iron nails etc. These boats were covered with copper roof flashing aprox 12 inches wide nailed on top of roofing tar. Now this was done to let the boats run in ICE, and maybe that's not the same as your intent, but it does work.

[BuccaneerCapn]

I have heard several say that the copper plating causes electrolysis that eats the iron nails. Is this the case, or is copper plating over iron nailed wood planking acceptable?

[BuccaneerCapn]

I understand about painting on tar and then applying tar paper, then more tar, and the copper sheets I intend to use will measure 18" x 72". I think I have the copper clading process down, it's the refastening that I hadn't planned on, and honestly, if I have to re-fasten, I may not be able to do the copper plating at this time.

[paul oman]

Another cheap option is copper filled epoxy. $60-$80 worth of copper powder and $80 or so worth of epoxy.... probably not as good as the copper sheathing but easy and probably cheaper then most bottom paints! I think you'll find a number of links if you do a google search.

paul oman
progressive epoxy

[PeterSibley]

I assume you mean your hull is galv nail fastened ?
It would be worth doing a search of our sponsors magazine index.I can remember at least 3 articles on coppering bottoms from older issues.One at least was of a large vessel that was probably iron fastened. The information you require is probably there.

Here are some of the entries in the index :
/Mulville, Frank, author:/"Resheathing a Copper Bottom," 67:35

Rocha, Louisa, and John McCarthy, authors:/"A New Copper Bottom," 111:58

/Masone, Steve, author:/"Coppering GAZELA," 74:19

The last mentioned ,Gazela,is the large vessel I mentioned.

good luck,keep us posted about your results.

[Dan McCosh]

A friend who did a copper bottom on a boat with a stainless rudder shaft had the shaft break in two. The cause seemed to be hydrogen embrittlement due to the electrolytic interaction with the copper.

[Bob Cleek]

Paul, given your "Progressive Epoxies" moniker, I gather you're in the business. Can you explain just how copper filled epoxy works as bottom paint? Assuming you get it stuck to the bottom and in the seams where the critters seem to like to live, how does the copper work? It seems to me that the copper powder would be pretty much encapsulated in the epoxy resin. Doesn't that pretty much neutralize its antifouling properties?

[htom]

How does the epoxy change the electrolysis equations? I would think that abrasion would soon remove enough of the encapsulation that copper to water contact would occur. Now the bits of copper are tiny ... but there are a great many of them.

[Bruce Hooke]

On the copper & epoxy mix, my other concern would be that it would fail to protect exactly the areas that copper plates are so good at protecting, which is places where cracks have opened up after the coating or bottom paint has been applied, say between parts of the deadwood. These are the areas that worms love to use as a way in, and with an epoxy coating these cracks would likely not be protected because the epoxy would crack.

[paul oman]

Bob,

Yes, as shown when I 'sign out' I'm in the epoxy business and folks do use epoxy and copper powder on the bottoms of their boats.

You can make your own or buy it premade from several vendors (not me!)

Of course only the copper at the surface of the epoxy is exposed. In theory you keep sanding the bottom to expose fresh copper.

Some folks do it because it has a nice hard finish and looks good.

I don't know how good it actually is. Seems like there are many in favor and many against it - no matter what stand you take on it, someone will counter it.

You could probably search the web for 'copper epoxy' and get some interesting comments.

I consider it experimental and would probably be too conservative to try it on a boat if I owned one needing anti-fouling.

However, I have often wondered if it would help 'regular' bottom paint be more effective if you added a pound or two of copper powder to the anti fouling paint. - sort of a long term, slow acting backup?????

I don't know.

paul oman
progressive epoxy polymers