Steel Boats and Welding

[Yachts66]

Ok Matt, since you asked. I own a steel boat which is currently undergoing a refit. This is my second steel boat. I hope to start building my third in a year or so. So, my experience is hands on, been there, done that kind of experience. There are folks here who talk a lot, but have no real world experience.

Step one, quit talking to West Marine. Unless the guy you're talking to actually owns a steel boat, he's not going to be a good source and his job is to push the products sitting on West Marine's shelf. Absolutely nothing wrong with that. West Marine has some very knowledgeable folks in their employ and some good products, I'm not knocking them at all. It's just that hands down, the best product line for steel boats is not to be found on West Marine's shelves. That being the case, they are unlikely to recommend it to you.

I have no experience with Phospho. I have looked at it, I've talked to a lot of steel boat owners about it and the jury is still out. Some seem to like it, some have had bad luck with it. I chose not to use it. It is a mild acid that....(oh shoot, read the product literature if you want to know exactly how it works) anyway, the problem is it's an acid and if you don't get it all off it can cause the paint you apply over it to bubble. It's not commonly used in the Commercial and Fishing Industries nor the Oil Industry, so that should tell you something right there. If this were my boat, I'd contact my local Ameron Rep and ask him what to do, then following his instructions to the letter. I know the rep for the PNW, he's a great guy and very patient with my sometimes inane questions. PM or email me and I'll give you his contact info. He will also talk to you about Phospho...maybe as I remember he isn't a big fan, but then his job, like the guy at West Marine is to sell his product line. Sometimes these questions are hard to get answers to. Ya' know?

Basically, after you shot blast, you follow that immediately (I'm talking minutes, not hours) with a zinc rich primer. After that Ameron 235 is what almost everyone uses, including me. Paint everything, inside and out (if new construction). Mascoat has some interesting products on the market that I'm going to try on new construction. One is an anti-condensation product the other a sound dampening product. Steel boats tend to rust from the inside out, condensation on the interior above the waterline surface is the bug-a-boo for all steel boats. After all interior coatings are applied, the above the waterline surfaces should be sprayed with a high density polyurethane foam (non-flammable, closed cell) A coat of latex paint on top of this once it's cured will make it easier to clean and won't hurt.

Exterior, after multiple coats of Ameron 235 I'd use Ameron 229 as a topcoat. It's got the look of a polyurethane, but unlike the ones you buy at West Marine, this one can be recoated to repair inevitable damage. It's good stuff and comes in a variety of colors. I believe it's less costly than what you will buy at West Marine as well, but even if it's not, it can be retouched which their products can't.

Now, since yours is an existing boat, it's sometimes hard if not impossible to find a yard that will allow sand blasting and spray painting. So, here's what I've been doing, and it seems to work ok. I buy poly-carbide abrasive disks at Harbor Freight. The 4" disk is item #94016 but I mostly use the 4.5". They cost less than $5 each. I love these things!! They mount on your 4.5" angle grinder and will remove rust and old paint in a jiffy. So, I go to a rust spot and start cleaning with the grinder until I get to good paint (paint that won't lift easily), then (depending on the size of the area) brush or roll 235. I try to use 4 coats, 3 if I'm in a hurry. Word of caution, epoxy paints don't like anti-fouling paint. Remove all the anti-fouling paint from the area you are repairing. If you don't, the 235 may not adhere well. My current boat was sadly neglected before I bought her, so we have rust issues. Properly maintained steel boats don't have rust issues.

It's pretty hard to have too much paint on a steel boat, but if you do the job right, you should have no rust problems.

As mentioned earlier 133 is the product of choice for potable water tanks. It's NSF certified for that purpose. Concrete will give the water a "sweeter" taste, but getting it to stick on the inside of the tank is a trick. I don't like the taste of water from plastic tanks. Call me picky.

Out of time. Email or PM me if you would like.

Regards,

Thomas

[SaltyMonkey]

wow good post Y66!!

[Matt sachs]

Thank you thank you. Thats what I was need in to hear. tell me more...

[S/V Alchemy]

I think he's given you a good start.

I am refitting a steel boat, my first steel but my second boat requiring plenty of attention. I agree with the idea that if your technique and products are sound, short of bashing in a plate, you will have few rust problems in steel. I am using Endura for touch-up currently, but will likely repaint the exterior in Ameron.

[Matt sachs]

Which faring material is best to use under the Ameron235? She has a few dings and such that I need to hide.

[Honey Ryder]

i have a steel trawler and can assure you that she is very strong. i've hit things that i'm sure would have holed a fibreglass boat, and it just dented my keel a little. very impressive.

as to your questions; if you can handle an angle grinder and a paint brush then you shouldn't have any big problems, as long as you buy a good boat.

what do i mean by a good boat?

i mean a boat with plenty of metal left. as others have said, a metal boat rusts from the inside. why? because it is hard to get in there and take a good look. typically, the boat will be insulated and then covered with ply. it will be all sealed up. so how are you gonna see it unless you take it all apart? and if it isn't your boat, who is gonna let you do that to their pride and joy?

if the stringers are horizontal, and if they have no limber holes, then you can bet that you will have some rust. why? because condensation will form and then run down the inside of the hull and collect on the sill, and it will stay there for years. it will work at the paint, and in time, the paint will lift and then you have bare steel, water, and oxygen. give it some time and you will have rust. add some salt and it happens quicker.

so, if you can't take a look at the inside of the hull, then how do you know what you are buying? a marine surveyor can measure the thickness of the hull with an instrument specially designed to do this from the outside, but it means removing paint to bare steel to do this accurately. again, how many people will let you do this to their boat, and in how many places?

the great thing about steel, apart from the strength, is that anything can be repaired. if it is very bad, just cut it out and weld in some new plate. there are plenty of steel dutch boats that are 100 years old and still going strong.

talking about dutch boats, they are excellent. the north sea is a tough place for boating, so the designs and build are usually excellent. their painting is superb.

so, what to buy? if you could find a 30 year old steel boat that was built in holland, had been lightly used on inland waterways (fresh), and you could inspect the bilge and get at the steel interior then you could be buying a great boat. however, if it has been used in salt water, and if you can't look at the hull from the inside then i would be very careful. i know of steel boats that looked great from the outside but upon inspection by a marine surveyor (who genuinely knew what he was doing) was literally condemned and sold for scrap because the hull was only paint in places.

bottom line; buy a boat with plenty of steel left (3mm minimum) and you can repair anything with some easily acquired skills and some grunt. buy an older boat with bad design features (e.g.horizontal stringers with no limber holes, chain locker with no drainage holes) and no access to the inside of thehull and you are taking a big chance.

if the owner tells you that the boat is fine but you can't see the state of the hull for yourself and he says not to worry, you should worry!

i am refitting the interior of my steel trawler, and i intend to do it in such a way that i can unscrew sections of the hull lining so that i can then remove insulation so that an inspection is relatively easy. that way i can fix things that may crop up in the future.

even good boats can have design faults that cause big problems over time. i imagine that when my boat was built in holland in 1979 that the builders didn't think it would still be around over 30 years later. but it is, and if i take care of it properly then it will last another 30 years.

so, when buying a steel boat, don't worry too much about the skills needed for maintenance. worry about buying the right boat. and get the best marine surveyor you can afford to take a look at it for you. it will be the best investment you ever make.

[S/V Alchemy]

Honey knows what she (?) is talking about. I am insulated in our steel cutter TO the waterline, not below. I can see and remediate problems easily.

Boats foamed from the keel up are unknowns in many respects.

[Yachts66]

I will surely open a can of worms saying this, but here goes anyway. I'm not a fan of faring compounds. When you hit something (or something hits you) the steel is fine (usually) but the faring compound has but a small fraction of the strength of the steel, so it breaks off, then more breaks off, and sometimes takes some paint with it, then you get rust.....you get the gist. I simply don't care if my steel boat does not look like a glass boat, it's not supposed to it's steel! Screw the faring compound, I'm sticking with pure hard wonderful strong steel. Ya'll do what you want, that's what I'm doing!! LOL

Foam: There are two ways to foam a boat, the spray in poly-urethane kind (best way in my opinion) and the stick it on with rubber cement blue board way. A lot of labor involved in that approach. Each piece has to be cut and fitted and even then you don't really get the longitudinals or the transverse frames, so what's the point? Some argue that because it's only stuck in place with contact cement it's easy to inspect the underlying paint. Ok, kinda true, if you don't mind tearing out all the joiner work that lies on top of the blue board. Again, what's the point? Spray foam it at the beginning, then you don't have to worry about it, it's done and should be good for the life of the boat. My $0.02 anyways!

Now, if you really want to know what's going on under the foam and under the paint ante up for a audio gauge (also called an ultrasound). It will set you back a little between $1,200 and $2,000 USD depending on the bells and whistles, but it will tell you down to a hundredth of a mm how thick your steel is, how thick the paint is and you will then know where you have rust and corrosion problems. Nifty little device for sure. The really fancy ones will even hook up to your PC and print a spread sheet! With added software, draw you a picture of your hull and give plate thickness on the picture! I'm too cheap for the fancy model, I just take a piece of chalk and write on the hull what the plate thickness is, then stand back and study it. Amazing what your brain can deduce from such an exercise.

Regards,

Thomas

[Yachts66]

Alchemy said:

Boats foamed from the keel up are unknowns in many respects.

To me, boats foamed from the keel up were built by people who simply didn't know what they were doing, so if they must something as obvious as that, what other more subtle things did they miss? That's what I always wonder!

Regards,

Thomas

[S/V Alchemy]

I saw quite a few before we found one with accessible, unfoamed frames and stringers below the waterline. The few spots with rust were easily dealt with and continue to be.

I'm all for insulation above the waterline and particularly in my pilothouse, which can resemble a greenhouse otherwise.

But not below the waterline.

[Yachts66]

Good, because it's not supposed to insulated below the water line!! One of the primary purposes of insulation is to eliminate condensation, which only happens above the water line!

Thomas

[Matt sachs]

Time to wake up an old thread.
I found an area in the hull that was rusted deeper than I thought at first. The area is about 8 inches square rusted %60 thru. Its 1/4' plate. I scaled it and built it up with a 6013 rods. Is this a reasonable (strong as new) repair? Assuming the welding was done properly? Is there a metalurgical (sp) concern with heating this old hull like that? Did I make it brittle?

[Reefmagnet]

Originally Posted by Matt sachs

Time to wake up an old thread.
I found an area in the hull that was rusted deeper than I thought at first. The area is about 8 inches square rusted %60 thru. Its 1/4' plate. I scaled it and built it up with a 6013 rods. Is this a reasonable (strong as new) repair? Assuming the welding was done properly? Is there a metalurgical (sp) concern with heating this old hull like that? Did I make it brittle?

That technique is used quite often for rebuilding worn parts, so there shouldn't be an issue, although it is a method used more for thicker base materials. The plate won't be brittle as such and should be metallurgically sound, but it I'd be surprised if you haven't had some distortion or buckling in the area caused by all that heat input. The only caveat I would suggest is that it can be hard to gauge exactly to what depth the repair has built the total thickness up too.

[Matt sachs]

Thanks, I guess I worry to much. My neighbor is a nuclear certified welder and he was happy with my repair. A second opinion is always nice. Thanks

[haidan]

Originally Posted by Matt sachs

Time to wake up an old thread.
I found an area in the hull that was rusted deeper than I thought at first. The area is about 8 inches square rusted %60 thru. Its 1/4' plate. I scaled it and built it up with a 6013 rods. Is this a reasonable (strong as new) repair? Assuming the welding was done properly? Is there a metalurgical (sp) concern with heating this old hull like that? Did I make it brittle?

For curiosities sake, Why didn't you just cut out and replace the rusted patch?