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Edo Kazumichi 07-23-2006 04:42 AM

The Age of Steel
Yes, I know we're in the Age of Fiberglass but my mind is stuck in The Age of Steel and so I'm intereted in the age of steel - that is, how long will a steel sailboat last?

Let's just say you had a professionally designed and built, well-coated, well-maintained steel boat that had never been re-plated but had been sand-blasted from time to time and had been lovingly looked after over the course of her life. What kind of lifespan would she have? When would she simply no longer be usable?

One thing that makes me wonder about this is that I've come across wooden boats that are 60-70+ years old. Yet I often find that the lifespans of glass and steel boats are discussed in terms of 3 or 4 decades even though these materials are supposed to be superior to wood.

Any thoughts?

sailingdog 07-23-2006 11:14 AM

Wooden boats can last a long time with care. Look at the USS Constitution, which is well over 200 years old, yet still a float. The biggest problem with traditionally constructed wood boats is probably rot and moisture related problems. Epoxy-coated, cold-molded wood boats, like those made by the Gougeon brothers, are more akin to GRP boats than they are traditional wood boats, but have some problems of both traditional wooden boats and GRP boats.

Sixty years is not all that unusual for well made steel boats. Some of the naval ships from WWII are still afloat. Granted, a recreational boat is likely to have less rigorous maintenance and be made on a bit lighter scale. Corrosion is the real enemy of a steel or aluminum hull. Steel boats need to have serious maintenance, as do wood boats.

The reason you see fiberglass boats often die before wooden boats is the level of maintenance, and the fact that fiberglass is very susceptible to fatigue issues. Since many people think that fiberglass is low-maintenance—they fail to do even the basic maintenance to presever the boat's structure. The three biggest enemies for GRP hulls that I see are osmosis-related damage, delamination/core rot, and fatigue from allowing the hull or deck to flex.

Edo Kazumichi 07-23-2006 12:46 PM


I knew I could count on you for valuable input. Thanks.

So would it be correct to say that, all things being equal, all that pounding at sea is going to cause more fatigue damage to fiberglass than to steel? Is metal fatigue even a real worry? From what I recall from mechanical engineering 101 the forces involved really aren't large enough to cause a fatigue failure on a steel boat. If they're not then it seems safe to say that as long as it is kept corrosion-free it will pretty much be as strong as it was when it was first launched. Is this correct?

So anyway, how do boats get pronounced dead? Do they simply come up for survey and get declared to be more expensive to fix than to replace? Or do they just split in half and sink?

seabreeze_97 07-23-2006 01:55 PM

Don't look now, but we're entering the age of carbon fiber. There are no absolutes in the strength area. I remember seeing a program about WWII and one of the many storms the US Navy encountered. In one such storm, one of the ships, a destroyer I believe, was his by a couple stout waves, then slammed by an even meaner wave. The last wave totally knocked the forward bow section off. I don't mean 3 or 4 feet, but more like 30 feet, including airtight compartments (which actually kept it afloat, allowing retrieval and re-attachment a few days later). Points being, while steel doesn't fatigue under normal conditions the way aluminum does, it can still be stressed beyond design tolerances. Toss in a bad weld, some get the picture. Any material has good and bad. Any material can be over-stressed to failure, and any material (well, except carbon fiber) can be used with relatively moderate expense if you're the one doing the work. If you're building a minesweeper, go with wood, an icebreaker, go with steel. Gulf Coast shrimp boat...wood. Sailboats? Your choice. Regardless, you have to take care of them.

sailingdog 07-23-2006 02:24 PM

Fatigue isn't really a major problem for most steel, as it has to be stressed a certain amount before it starts to fatigue...where aluminum does not... Just flexing aluminum can fatigue it, IIRC. Fatigue isn't that much of an issue on a steel boat... but it can be one on an aluminum one—however, I would rate corrosion as a much more common and harder to control problem in the case of a well-designed, well-build steel or aluminum boat.

The real problem with fiberglass is that it isn't all that rigid... and that when it isn't rigid enough, or properly reinforced, it flexes. The hull on some poorly built boats will show this if you take them out in rough conditions... they'll oilcan... with the sides going in and out... A properly designed GRP boat doesn't really have fatigue issues to same degree, as long as the flex is prevented... the material doesn't really fatigue AFAIK.

This lack of rigidity is one reason that they make cored fiberglass decks. A cored deck is much lighter than a solid fiberglass deck of the same stiffness—and much more rigid and far stronger than a solid fiberglass deck of the same weight. Properly designed and constructed, it is a very good material for making boats—especially if made from the newer epoxy resins, which are very resistant to osmosis-related problems.

Boats generally get pronounced dead, when there is no one willing to take the time, effort and expense to restore the boat to working condition. Doesn't matter if it is steel, aluminum, wood or GRP.

hellosailor 07-23-2006 05:07 PM

Well, there are cast iron hulled tall ships from the 1800's still afloat. Is that long enough for you?

You've not doubt heard the story about George Washiington's hatchet, "the handle has been replaced three times and the head twice, but it's still the original hatchet". Steel boats are like that. Keep a coat of paint on them so they don't rust, and they can and will last literally forever. Bang a hole in them, and you can always weld in a new bit of metal, welding fuses it seamlessly so anything can be replaced and made new. Sandblast it or abrade it too thin, or let galvanic action eat it, and likewise you can always replace a place or add some on.

With proper maintenance? Forever. Same thing on a wooden boat, you just need new wood from time to time.<G>

sailingdog 07-24-2006 07:30 AM

I'd be curious to know what cast-iron-hulled ships from the 1800's are still afloat. Can you name one?

Jeff_H 07-24-2006 08:44 AM

I don't think that he means cast iron, but there are a few 19th century low carbon iron ships around. Iron behaves a lot differently than steel, especially when it comes to rust and ductility.

There is a very big difference between the lifespan of steel ships and small steel yachts. No matter how thick a steel plate is, for any given alloy it rusts at a pretty constant rate. If you lose a 3/32" per decade of 1" thick steel plate used on a small ship, that is far less consequential than losing an 3/32" of 3/16-1/4" steel plating used on a yacht.

Back in the 1980's when I was working designing steel yachts, we generally thought of yacht quality steel boats as having somewhere around a 20 to 30 year lifespan with proper maintenance. It was not that we considered these boats beyond salvage at the end of this period, because steel hulls can almost always be replated and restored, but we felt that the cost of doing the major rebuild involved would way far exceed the value of the boat in question once restored.


Dewey Benson 07-24-2006 11:18 AM


Originally Posted by sailingdog
I'd be curious to know what cast-iron-hulled ships from the 1800's are still afloat. Can you name one?

The "Star of India" The last sailing East Indiasman in the world. Located on the San Diego Waterfront and operated by the Maritime museum here.

She sails once a year and causes quite a crowd out on the water. Lots of boats vieing for a view! Square rigged the crew handles sails the traditional way. Up the ratlines ye scurvy dogs! It's quite a show.


Dewey Benson 07-24-2006 11:24 AM

Is the Mooshuloo (or perhaps mushulu) still afloat? Last I heard she was a Resturant on the east coast. I know much of her hull was filled with sand. Some folks I knew were considering spending a large fortune on sailing her again. After some initial exploration, they figured that she was too far gone.

Ther might be another one or two in the Falkalands. There is a collection of rotting and rusting old square riggers there, many still float, but most are wood.


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