Questions About Steel Boats

[hellosailor]

"The bottoms of my twin keels are bare steel and have been for most of their 23 year llifespan. No corrosion noticeable. The zincs protect then just fine . "
And to think of all those cruise ships, naval vessels, and arctic fishing boats with steel hulls that have been suckered into using tens of thousands of gallons of bottom paint for all these years! Whatever are they doing so wrong?

[Hiracer]

Originally Posted by Louis Riel

The bottoms of my twin keels are bare steel and have been for most of their 23 year llifespan. No corrosion noticeable. The zincs protect then just fine . The zincs on my last boat lasted 10 years . The surveyor said it was because she never tied to docks with 120 volt cords laying around. The bottom of the keel was never painted. It never mattered as long as the zincs were there. Too much zinc is often the cause of tiny paint blisters.
Bare steel below the waterline can be totally protected as long as the area of bare steel is small enough for the zincs to protect it.
Brent

How many zincs, what size, and where?

Our boats are about the same size.

Edit: During survey before I purchased my boat, it was discovered that some of the epoxy zinc paint and white top coat where missing from the keel. Yet the plate testing showed no loss of steel. Zincs were about gone, however.

I generally do not plug in AC unless to equalize the battery banks.

[Hiracer]

Originally Posted by hellosailor

"The bottoms of my twin keels are bare steel and have been for most of their 23 year llifespan. No corrosion noticeable. The zincs protect then just fine . "
And to think of all those cruise ships, naval vessels, and arctic fishing boats with steel hulls that have been suckered into using tens of thousands of gallons of bottom paint for all these years! Whatever are they doing so wrong?

I think what's going on is that they are spending money on bottom paint to stop marine growth, i.e., my guess is that the poster scubs his boat often and without the benefit of bottom paint.

If you apply copper based bottom paint without the benefit of an epoxy paint to isolate the metals, you'll get an electronic cell between the steel and the copper, with the steel giving up metal.

Thus, it's all or nothing, viz, bottom paint and epoxy layer next to the steel, or nothing. Most people can't handle the scrubbing that would be required if no bottom paint is on.

I suppose that one could have just the expoxy paint, with no bottom paint. But you would still be scrubbing like nuts.

Or maybe one could use aluminum based bottom paint without the epoxy isolation. Mmm. Food for thought. But then, I would guess that the aluminum based bottom paint would expensively disappear pretty fast, again from an electronic cell.

Just guessing here.

[Hiracer]

Originally Posted by Louis Riel

The bottoms of my twin keels are bare steel and have been for most of their 23 year llifespan. No corrosion noticeable. The zincs protect then just fine . The zincs on my last boat lasted 10 years . The surveyor said it was because she never tied to docks with 120 volt cords laying around. The bottom of the keel was never painted. It never mattered as long as the zincs were there. Too much zinc is often the cause of tiny paint blisters.
Bare steel below the waterline can be totally protected as long as the area of bare steel is small enough for the zincs to protect it.
Brent

MPR: What's behind the mystery rust

You might want to be conscious where you anchor your sailboat. I know Lake Superior is a long ways away, but its industrial conditions might be common.

[seafox]

No, he just cruises around and when he needs a bottom scrub he runs over a stray container or whale

[Hiracer]

Actually, IIRC he's got twin keels and a skeg, so in any calm bay he can let the boat go dry at low tide and scrub the bottom no problem--a small chore when you don't have to haul the boat out or even tie it to a pier.

If you are looking for a low cost liveaboard, it's not a bad approach.

[ssullivan]

Originally Posted by Hiracer

MPR: What's behind the mystery rust

You might want to be conscious where you anchor your sailboat. I know Lake Superior is a long ways away, but its industrial conditions might be common.

This is definitely a problem! We lost a great deal of our galvanization on our anchor and chain in Michigan. It came up looking like we'd put it down there for a season after only 2 nights! Massive corrosion of the zinc.

[Brent Swain]

I had 4- Z-3s , two at the foreward end two aft as well as one centered on the bottom of the rudder welded on.
Brent

[Hiracer]

Thanks, but I don't know zincs. What's a "Z-3"? TIA.

[GordMay]

A Canada Metals “Z3" Zinc is a 10.3 Lb. Commercial, Semi-streamlined, Strap Anode.
http://www.martyranodes.com/martyrblank.swf

[Hiracer]

Thanks. Seen'm but never had a clue what they are called.

I have smaller zincs, but more of them. I'll compare. I think I'm pretty similar in total mass.

[Brent Swain]

Where the beach grinds the paint off when I'm in a drying anchorage, it also grinds the growth off. The rest is easy to keep clean in BC with 17 to 25 ft tides. Spraying bleach makes the weeds fall off without touching it. In winter , motoring thru thin ice cleans it well , down to the keels.
Brent
Brent

[Brent Swain]

In cooler latitudes , when my boat was a dark colour, in minus 12 degree weather the hull felt warm to the touch when the sun hit it. It was too hot in the tropics so I painted it white. When i went bak to ccooler climes the lockers got musty so I painted her dark again and solved the problem.
My paintjob is 23 years old and except where I've chipped it , is as good as the day I put it on. It was painted over the zinc primer that was put on in the steel shop. It has never been sandblasted. The steel was wheelabraded and primed by the steel supplier. So its not an expensive paintjob, just thick( 30 gallons of epoxy tar on a 31 footer.)
Maintenance has amounted to an hour or two a year.
Brent

[Seeratlas]

For the fellow who was buying a 50k steel hull, assuming the design and construction were reasonable, and the steel solid, you made the right choice. Further, as for banning mentioning of Brent's book (hi brent heheh) that would be a serious injustice to the people this forum is for. It is a remarkable source for common sense boat and cruising information you won't find compiled in one place anywhere else, period. As for me, I've been doing this now for about 40 years.

Next, old solid fibreglass hulls abound and if laid up with the right resins and protected from UV, are better than a lot of the new ones for ocean cruising and things that go bump in the night. Sound steel boats are stronger, lots stronger. As I've heard *someone* observe, take a fibreglass nail and hammer it into a piece of steel plate, then take a steel nail and hammer it into a fibreglass panel...anyone with questions remaining...should consider a 30k or better hull impacting coral, rock, or the edge of the local concrete dock. Fibreglass is wonderful if you never hit anything, Unfortunately if you cruise, sooner or later you're going to hit something..or more likely, something is going to hit you. I singlehanded a fibreglass custom Huntingford 53/54 for ten years off the pac coast from Ensenada to Glacier Bay. One momentary lapse by my father put it into a rock jetty at about 3knots and tore a hole in the bow big enough to crawl through, and this boat weighed about 55k.

Purchase of an older boat heavily favors steel. There are recreational steel boats running around today that are pushing 100 years old...hull prep and paint are everything regarding maintenance intervals and longevity. As for building one yourself, see the origamiboats group on Yahoo. Construction using this technique can get you a completely tacked 36' shell, decks, ph, etc. in less than a week...there's only something like just short of 200 of em out there sooo, yeah it works. I like Dudley's designs a lot, but would suggest a strong look at the origami approach verses the strongback frame first technique. Tanton has some nice 40'ish origami designs out also.

Lastly, buying used steel boats at the present time is a serious opportunity.
Simply put, if I told you what kind of deals are out there, you simply wouldn't believe me. You can take a magnet and check the structure yourself and if it looks good, call in a metallurgist with an ultrasound rig and for a few hundred, he can tell you to the thousandth how thick the steel is in a given area AND where the coatings have separated from the hull.

Building a Welder out of an alternator while not trivial to work out the system, is in the end an extremely useful piece of gear to have on board. The design work has been done, ask Brent.. You can learn what you need to know to weld mild steel plate and stainless in a couple of weeks if you are average. If you're 'quick' you can do it in a few hours with the right instruction. Now you can repair or modify, or add gear to your boat anywhere in the world without anyone's assistance or permission...now that's cruising freedom.

oh, my boat is a 44 brewer blue water custom built in steel and aluminum by Kanter in Canada.

seer