Question about Bronze VS Iron or Galvanized fastenings in tropical climates

[rkarakai21]

Hello there. My girlfriend and I have been searching for the right gaff rigged ketch for a bit now, I have been researching and researching designs and fastening material advantages etc.. I have heard it said before that you don't want a galvanized or Iron fastened boat in the tropics. Is this true and if so what is the reasoning, does the galvanic action increase in the warmer climes? Could this be counteracted by changing the zinc configuration? My boat search has a few complicated caveats, mostly being that the boat A. Need's to be an inherently robust and heavily built design, as it will be sailed on ocean passages, and B. Considering the age of most of the 32-36 foot wooden cruisers around the Canadian Northwest to me it seems like a good idea to look for a bronze fastened boat as a galvanized fastened boat after 25-40 years could potentially need re-fastening before seeing heavy sea service, which is a level of project I'd rather not get into at this stage. Id rather pay a bit more up front for a strong boat that needs cosmetic love, some re-caulking of decks, etc.., but I am not looking to restore a project boat with structural issues in its lower members. That being said, there are also Galvanised fastened boats, that have been kicking around for 60+ years and are still sound, I work aboard one.

Looking for a boat like this in BC that is currently for sale, and not a for sale "maybe someday" boat has been a bit of looking for a needle in a stack of needles. So I guess what I'm getting at is, with a view to the boat eventually being sailed to the South Pacific should I even consider an Iron or galvanized fastened boat. Is it possible to mediate the potential problems so that the boat stays in solid condition over a number of years of cruising and beyond?

Obviously my boat searching options are severely limited by the Pandemic, as travel to Washington to look at boats is not essential by any means, and would in our opinions constitute too much risk at this point anyway Pandemic wise. There is one lead in BC, it's an old english cutter built around the turn of the last century, so I would assume it's either Iron or Trunnels in that one, I might have a look at it in the new year when our BC restrictions get a bit eased, havn't seen hardly anyone outside of my household in over a month due to our current restrictions.

Cheers

Ryan

[debenriver]

Galvanic action is certainly affected by the temperature and salinity of the water. Warmer water and higher salinity both increase the activity. So it is correct that iron (or more likely steel) fastenings will tend to corrode more quickly with warmer water temperatures.

Personally I would never go for a ferrous fastened boat unless it were maybe truly iron (as opposed to steel, galvanized or not) fastened and kept in frigid northern waters. I would look for bronze screw fastened or copper clench fastened – of a mixture of the two. North American built boats tend towards screw fastenings whereas UK built boats tend towards copper nails clenched over copper roves. Both are long lived and seldom affected by galvanic action.

This is assuming you are looking at traditional carvel construction. If you are looking at more modern epoxy construction, maybe strip planked for example, then the type of fastenings becomes perhaps less important. Plenty of strip planked hulls will have galvanized nails for the strip to strip edge fastenings – but these are well buried and the epoxy coatings should keep the moisture content of the timber below corrosion levels.

Cheers -- George

[wizbang 13]

Zinc will do nothing to preserve the steei fastenings. Added zincs usually damage individual screws and nails...not to mention the timber.Anodes are for the shaft and wheel,not thousands of screws/nails
Keep zincs to a minimum on a woody.
Be super aware of stray current in any marina.
(unless it is the actual galvanizing ,of course)
IF you find a decent ol boat, one can still put some epoxy on the bottom. It is not a magic bullet, but it will help to isolate the fastenings from the copper paint, which certainly attacks the galvanizing.
I'd dry an old boat..grind (strip/wood) the bottom, tear open the bungs or whatever, ospho over and over for days , then CPES the bung holes ( heh heh). That would keep the seawater away as well as anything short of sheathing.
Also ,epoxy is a worm barrier...no small subject either.
good luck!!
bruce

And for gods sake, if you bring a woody to the tropics,paint the dang thing white. decks too.
gaff ketch ? dem is fo wackoz

[rkarakai21]

Thanks for the insightful replies! What is the inherent advantage to Iron if I might ask? I ask because there is an old english gaff cutter for sale here that a local shipwright has told me is in quite good shape but she was built around 1894, so I think it would be highly unlikely she'd be galvanised, got to be either Iron or Wood trunnel fastened.

Epoxy the bung holes eh?? Interesting.

This might be a stupid thought process but how would true copper sheathing affect the hull, accelerate the corrosion even more than the bottom paint? Like 19th century style copper plates nailed to the hull like shingles. It would probably give excellent worm protection.

Also, I am definitely a certified wacko so a gaffer is perfect for me.

[rkarakai21]

This is the boat, Might go look at it if it's still for sale in the spring. Really prefer a ketch but if the right cutter comes up you never know. I just love the adaptability of a ketch to a multitude of situations, love using a mizzen and staysail combo when it's blowing, and the balance always seems to be great.

https://victoria.craigslist.org/boa/...249934877.html

[wizbang 13]

19th century copper clad bottom technology...made the boat last 20 years instead of 10. Like the myth of "salting" the bilges


I'd sure be interested in this 1894 boat...to see it mind you.
I recon the only advantage of iron was the cost...maybe availability.
Folks build a boat and think 40 years is far far in the future...it's not.
CPES applied to dried, torn up wood around the holes/nail heads.CPES is very good stuff, if you use it to its advantage, not randomly and magically splashed around. It would waterproof the small area only.
Putting regular resin over it ,or an epoxy primer like Interlux 2000, be a different thing. A thumb nail on the bottom.
(both my boats are gaff ketches)

[rkarakai21]

Yeah, as scary as it is to look at a boat thats potentially a hundred years old, the registered passenger vessel I work on was built in Norway and mostly trunnel fastened in 1939, and she is one of the stoutest most well found wooden boats I've seen.

Also it was Rob Abernethy that recommended I look at this cutter. He said he was very surprised at how good of shape it's in age considered. He says below decks is immaculate and beautiful.

So would you pop the fastener bungs, dry everything out, Put CPES in the hole ontop of the fastener and re-bung?

[wizbang 13]

I think re bunging would be impossible after what I envision. The round hole would be no more. As blasphemous as it sounds, I'd use epoxy. Just not a strong filler(like 403 or 404), but weak balloons(407).
Horror stories of removing epoxy bungs aside...a heat gun pretty much disintegrates epoxy.
Rob knows which end is up. A pro in his shop is constrained from using the unconventional methods I employ.

[Peerie Maa]

This is the boat, Might go look at it if it's still for sale in the spring. Really prefer a ketch but if the right cutter comes up you never know. I just love the adaptability of a ketch to a multitude of situations, love using a mizzen and staysail combo when it's blowing, and the balance always seems to be great.

https://victoria.craigslist.org/boa/...249934877.html

Probably originally built with galvanized wrought iron spikes, then renailed at least once with galvanized steel. Get a thorough survey, and look to see how many nails have been banged into every plank at every frame. Sometimes renailing can ruin the planking.
If the fastenings and planking is sound, copper sheathing over tarred Irish felt will be OK.

[rkarakai21]

tarred irish felt eh?? I figured they would have slathered the sheathing in tar but I didn't know about the felt.

[Jim Ledger]

The iron used in old boats was wrought iron, not the more familiar cast iron produced today. Wrought iron comes out of the furnace as a pasty lump which has to be well hammered with a trip hammer to drive out the impurities and condense the lump. It's this working that gives it the ability to withstand corrosion. If you see and old anchor that looks like it's rusting in layers, that's wrought iron. The layers are from the folding of the raw lump during hammering.

Wrought iron was never made into screws, instead it was formed into boat nails or rod. The boat nails I'm referring to are not the familiar ring shank nails, but instead nails sheared off a sheet of iron. The would have a square or rectangular cross section, a small head formed by upsetting, and a swelled section midway along their length. The were never bored for plugs, but instead driven in and set below the surface, the hole being filled with putty. Sometimes they went right through plank and frame and bent over on the inside.

Apart from the disintegration of the fasteners a bigger problem is the iron sickness of the wood, there's no permanent cure apart from replacement of the piece. As the iron rusts it expands, opening up the wood making little rot pockets all over. Oak is particularly susceptible to iron sickness, pitch pine much less so.

Anyway, I think most of this is somewhat correct, I hope it's helpful, and I welcome any corrections or further information on the topic.



Here's a good example of an iron sick boat fastened with boat nails. She's seventy years old here and way past her useful life, repaired many times and held together by force of habit. The cypress planks are not too bad, considering, but the white oak has been demolished by iron sickness, not rot. Most of the frame was pitch pine which held up rather well.

[Canoeyawl]

What is the inherent advantage to Iron if I might ask?

The cost

[Peerie Maa]

The iron used in old boats was wrought iron, not the more familiar cast iron produced today. Wrought iron comes out of the furnace as a pasty lump which has to be well hammered with a trip hammer to drive out the impurities and condense the lump. It's this working that gives it the ability to withstand corrosion. If you see and old anchor that looks like it's rusting in layers, that's wrought iron. The layers are from the folding of the raw lump during hammering.

Wrought iron was never made into screws, instead it was formed into boat nails or rod. The boat nails I'm referring to are not the familiar ring shank nails, but instead nails sheared off a sheet of iron. The would have a square or rectangular cross section, a small head formed by upsetting, and a swelled section midway along their length. The were never bored for plugs, but instead driven in and set below the surface, the hole being filled with putty. Sometimes they went right through plank and frame and bent over on the inside.

Apart from the disintegration of the fasteners a bigger problem is the iron sickness of the wood, there's no permanent cure apart from replacement of the piece. As the iron rusts it expands, opening up the wood making little rot pockets all over. Oak is particularly susceptible to iron sickness, pitch pine much less so.

Anyway, I think most of this is somewhat correct, I hope it's helpful, and I welcome any corrections or further information on the topic.


Here's a good example of an iron sick boat fastened with boat nails. She's seventy years old here and way past her useful life, repaired many times and held together by force of habit. The cypress planks are not too bad, considering, but the white oak has been demolished by iron sickness, not rot. Most of the frame was pitch pine which held up rather well.

The beauty of wrought iron is that it is so pure that its corrosion products do not cause nail sickness. There is a (apocryphal ?) tale around here that when a shipwright was renailing a wrought iron nailed boat, the nails came out leaving a firm clean hole into which he was able to bang in new nails without any remedial work. That will have been larch or pitch pine on oak.
Jim, the swelled section to which you refer is the effect of the cut nail being squeezed in vice jaws so that the head could be upsett.

[sp_clark]

https://www.realwroughtiron.com/abou...-wrought-iron/

[rkarakai21]

Really great info here guys. I heard back from a representative of the seller, he is a rigger who has done work on and knows the boat fairly well, he's doing online advertising for the elderly couple who own the boat. He said she would need significant structural work to be sound enough for what I want to do. To me the 55000 sticker price coupled with "needs significant structural repairs" sounds like a recipe for a big headache. I think the sticker price is reflecting the "prestige" factor of this being a real workboat from England. Which while it adds to the mystique might not be the recipe for success in a sound boat I'm looking for. I should probably just be patient and wait for something bronze or copper fastened and less than 40 years old to fall out of the sky. Girlfriend and I are chomping at the bit, but we need the right boat, not a bigger headache than we bargained for. The devil is in the details.

[wizbang 13]

Sounds like a free boat, not 55 grand.

[rkarakai21]

Yeah. I was thinking less than 20 grand for anything around that size needing a major facelift, but you are probably closer the mark. Of course it's all a mystery until the surveyor starts smacking things and hearing dull wet thuds. He said the owner is willing to pay half the survey but by being honest about his opinion of the boats condition he may have just saved me from getting embroiled at all. I'm sure I'll know the right boat when it comes up and slaps me in the face.

[swoody126]

this picture is of rudder parts from a boat that is a lot younger than the above pictured vessel

ferrous dowel pins

IMG_1047.jpg

once this begins the fasteners end up breaking the wood open/apart

IMG_1041.jpg

then it gets stupid

IMG_1043.jpg

once it starts it never stops

sw

[rkarakai21]

Yup, you guys are really making a good argument for Bronze/copper. There is a Bronze fastened Jay Benford Boat in Victoria that I really like, Owner showed me inside the bilge and everything looks great, smells great, hull is bright varnished and can see planking is in great shape. silicon bronze keelbolts looked perfect, whole boat is bronze screw fastened, gumwood stem, keel, oak frames, yellow cedar planking and deck, but owner is not quite sure when he wants to sell. Patience, patience.....Patience.