Riveted iron Hull repair

Greetings,
I wish to solicit some opinions on a repair. I own a 73' Dutch Sailing Barge built in 1893. The hull is rivetted iron about 1/4" thick. In the 1970's the exterior of the hull was fiberglassed because the rivetts were begining to weep. Recently a crack developed in the fiberglass along a joint between the steel plates. The previous Owner had concreted the bilge so I can't inspect the crack from above. I am hauling the boat out and hoping to patch the fiberglass from below. Is that sufficient? Should I weld the plates? I am sure the water is migrating thru the joints between the plates. Prior to the crack the bilge has been bone dry. Are there any consequences of welding a rivetted iron hull?
All opinions are welcome. Thanks.

 

Do you know the tune 'Dixie'? Learn it and start walking & whistling!

 

I assume in your opinion I am in trouble?

 

It sounds fixable, it also sounds horrendously expensive to do right. The fibreglass ain't helping matters. You need a professional surveyor to take a good hard look at the entire hull and structure. It's hard to believe that one crack is the only problem. If the rivets were weeping before the glasswork, that problem is still there, and now the glass may compound any rust issues. Get a surveyor pronto.

 

The hull was water tight up untill about 11 months ago. I beleive the problem started when I dinged a piling getting into my slip. Untill that time the hull wa bone dry. The concrete ballast was done about 5 years ago after the hull was tested and worked on and sealed w/ coat tar epoxy on the inside. The upshot is that I beleive whatever damage is present is due to the recent crack in the fiberglass.
I expect to haul the boat and reglass the crack. I am not sure whether I should scrape the fiberglass and weld the plates together or inject epoxy into the crack then reglass the hull. Once the leak is fixed I wanty to flush the hull with fresh water to get the salt out then let it all dry out. If no moisture is present then the minor rust stops correct? Is there any thing I can do to terminate the oxidation that has started?

 

new member here i need help

I've been trying to get on this to ask a few questins dont see a way to do it help

 

Dar,

Welcome aboard. It sounds like you're asking how to start a new thread, so you can ask your questions and wait for replies.

If that's the case, click on "Boat Design Forums" in the upper left portion of this page. Then scroll down and look for a button marked "New Thread". Click on it, give your post a title so others will know what subject you are asking about, then type your questions and post. Sooner or later someone will give a response. good luck!

 

As Walrus implied (he never speaks clearly if there's an opportunity to obfuscate but he does have a lot of experience at sea) and marshmat stated, anything on a boat is fixable, but some are more costly than others. Yours, unfortunately, falls into the latter. I suspect the fiberglassing was done because it appeared less costly than repairing the rivets. Here is an excellent article on rivet repair by someone who does it for a living:

http://www.maritime.org/conf/conf-dvorak.htm

The one critical point in the article, as the author stated, is that his experience is on the Great Lakes, so chloride (salt) corrosion is not a factor. Apart from the fiberglass repair itself, you will have to deal with the question of damage from moisture and salt both in weakening the iron plates, and in contributing to delamination of the fiberglass. There was an in depth report a few years ago on preservation of the hull of SS Great Britain, a riveted iron hull steamer built in 1844. The report is long and complex, but it covers all of the major issues, even fiberglass. Not exactly light reading, but it is thorough. Your hull is much better off than Great Britain's, but the principles are similar:

http://www.eura.co.uk/ssgb.pdf

Again, marshmat had some accurate points. Apart from your crack, the fiberglass may have allowed moisture in through osmosis and wicking. I'm sure you've read articles on porosity of fiberglass hulls. It's something not known much in the 70's, came to light in the 80's. Concrete does not make an impermeable seal with iron, either. Both of those materials are masking damage, and may be contributing to it.

Sorry if this sounds pesimistic. Actually, it's not. Everything is fixable, and a survey by someone with experience with old iron hulls in salt water really is an important element. So all you need is lots of money ... but if you willingly invested in a 100+ year old vessel with a riveted iron hull...you knew it would be an even larger than average hole in the water into which you would pour your money, so no surprises there!! LOL.

Seriously, you have a piece of history there. The articles will give you some valuable knowledge, after that I would recommend seeking out a surveyor and a yard with the appropriate experience.

The one area in your repair effort in which I am an expert is dehumidification. It is not a simple as it appears, and it is difficult to maintain, but if you can maintain a consistently low absolute humidity, you can slow down corrosion significantly. I can show you some alternatives if you are interested, by private message. good luck, you have a unique vessel, worth a lot of effort to preserve.

 

Right; Joking over, if you really want to sort this job out GET RID of the Concrete it is slightly acidic and is not helping the corrosion of the cast iron hull! Get rid of the fibreglass it's holding the salt moisture in and this moisture is also corroding like mad! To do a proper repair you will have to replace the rivests and/or any plates - you can not weld Cast Iron (besides which it don't look right - the idea is to have a boat that looks the part I take it) But firt and foremost you do need expert help! as the man said it can be done BUT hell it's going to cost! My first move would be a full survey and then a survey of the bank - see if I could afford it!! You could possibly get a grant if the boat is in the right place, old enough and has a historic connection with the area, but dont bank on it (no pun intended)! If you decide you want to do it by all means go ahead, there will probably benothing more satisfying! But as I've said learn to whistle 'Dixie' you may need it!!! and don't be too disappointed if you do! If you do have to walk away DO NOT look back it will 'kill' you!! Best of luck in your endeavours - I hope you make it!! really! but realistically...........

 

Well have we found something that walrus actually knows something about.

Concrete is corrosive and is not helping the cast iron hull?

Well Ille stand corrected here but weve been building buildings in this way for hundreds of years.

I know for a fact that iron girders set into cement are fine even after 100 years. Its the bit where the girders stick out of the concrete that gets the surveyors going.

Have you never sledge hammered into cement to find re bar in perfect condition?

Riveting is not so difficult. Red hot and quick, a good man on the weight and a good man on the hammer. If its pitted though it will leak.

Fibre glass Oh yuk.

 

I had assumed the same. I hope the concrete is bonded to the hull and the rust is occurring where it gets access to water and oxgen, ie at the perimeter of the inside of the hull at the water/air barrier. If the water is stopped I hope the damage is light. I have head that cast iron corrodes less than Steel. But I have been told the hull is steel. It was built in 1893 when there were no standards on steel. The steel hull was coated w/ two layers of 5200 sealant then the fiberglass was laid up. I have some cores that show the bond is good. Thanks for the comments. All opinions are welcome.

 

The Norwegen Whaling ship "Hagenes" lives here built in Oh some where like yours,--Google it.

I know it has cement floors and the hull is half welded and riveted.

At some thing like 90 foot he doesnt bring it into the marina any more, so I cant ask him.

You can tell with a grinder if its cast or steel by the sparks.

 

I really don't believe they make hulls out of cast iron. Maybe iron, but not "cast". "Cast iron" appears in post #9, from nowhere. I think they riveted them because they didn't have welders. Is anything else welded to the hull anywhere and has that held up? I would guess you can weld it. If the glass was put on 30 years ago and has only recently sprung a leak in a damaged area, and cores show the 5200 and glass are holding up and still bonded to the hull tightly with no corosion underneath, I would lean toward grinding away some glass and 5200, welding the damage and redoing with 5200 and glass. If that system is working, it's because of the 5200 and its flexibility and stickability. The cement inside the hull doesn't sound like a good idea, if for no other reason than that it blocks accessability to the hull. I have seen steel houseboat hulls where the major damage is on the inside. You could tell exactly where the waterline was because the cold/cooler river water would chill the hull and cause humidity to condense inside wherever the hull was in contact with the water, which was everywhere below the waterline. Sam

 

Down, Walrus, down, boy!

Actually, concrete is alkaline, not acidic (cement is mostly calcium compounds), and it does act as a protectant, as far as it goes. Freshly poured concrete has a pH in the 11-12 range. Exposed to the elements, the pH at and just under the surface will decline to 8.5-9.5 range, still well within the alkaline range. It is the facts that: 1. concrete is porous and 2. has a drastically different coefficient of expansion and contraction than either iron or steel that make for potential problems. The real culprit is the "usual suspect" moisture, particularly moisture with salt dissolved in it, or, as we who mess about with boats are fond of saying, "salt water".

RCardozo, for esthetic reasons, we have voted unanimously that you must grind off all the fiberglass, jackhammer out the concrete (replacing it with pig iron ingots or rocks), re-rivet the entire hull, replace any severely corroded plates with custom wrought (not cast) iron or steel plates made from carefully researched ore blends, and hand coat the entire thing with paint containing extremely high levels of lead (you're not allowed to wear a mask or respirator during this entire process, of course), thereby retaining full historical accuracy. We also have voted unanimously not to help you pay for any of it!

So I guess your vote trumps ours. From your description, the fiberglassing seems to have been done well, and a local repair should work. Weeping of rivets can be fixed in place by the method described in the first article I gave you. The really big question is to determine where and in what quantities moisture is contacting the metal surface. You'll know more when you haul it. It might not be necessary to do anything with the joint between metal plates. Even if they are butted flush, there were ways of sealing the seams when the vessel was built. The seam may or may not be dry. Any recommended drying and sealing methods that would be used for substrates under fiberglass should work. I'd stay away from any welding whatsover. Whether iron or steel, the old ship plates are known to have high amounts of carbon, and are brittle. Heat from welding would only make it more susceptible to corrosion, and might create stress cracking that you'd end up chasing all over the hull.

Interior corrosion will be caused either by leakage of salt water, or condensation on interior surfaces, or both. Fixing any leaks and installing a dehumidifier should enable you to control corrosion. You were right in your earlier post about that. If you keep the interior dry enough, corrosion will stop, or at least slow drastically. The trick is in keeping it dry. There are compact dehumidifiers using regenerable desiccant impregnated on a slowly revolving wheel, electrically powered, that will keep the interior bone dry. The machine was invented during WWII, literally to "keep the powder dry" on North Atlantic and Pacific convoys carrying ammunition. As the Nazis and Japanese discovered, it works.

 

Thanks,
While a full refit would be fun It would bankrupt me. I will have to go with CharmC. The inside was bone dry untill 11 months ago. The location of water on the inside corresponds with the location of a crack in the glass. The vessell has cross wise beams spanning side to side that seem to be acting as dams and retarding the flow of water aftward. I have a bilge pump that is keeping the water level forward about 3" under the surface of the concrete. Hopefully that help keep oxegen at bay. What I plan is to haul the boat the grind off the glass in the area of the cracks. I will use an underwater epoxy to caulk the joint in the wrought iron then coat the iron w/ two coats of 5200 sealant and then reglass the area.
Afterward I will make a deep sump pit in the concrete and try to flush out the salt. (Not sure how exactly). When that is done I will dehumidify and hope for the best. It seems the low humidity option is the easiest way to have the biggest impact. The hull is about 1/4" thick and prior to the concreteing of the bilge the hull was tested w/ sledge hammers and some areas replated (at water sources). I hope the hull is primarily in good shape. The big unknown is the coal tar epoxy. The inside surface of the hull was coated w/ coal tar epoxy prior to concreting the bilge. If it is still bonded to the steel it will help minimize corrosion at least over the short term.
Everybody pray for me. I will need it.