Steel boat – heaven or hell?

[leftbrainstuff]

With decades of experience in engineering ferrous, non ferrous and composite structures. No material is better. It's all about compromises and tradeoffs.

I favor glass fibre boats. Why?

1) grp is on balance more durable and less of a maintenance burden over time
2) steel has the benefit of much higher hardness and impact resistance. Provided the steel used has appropriate ductile to brittle transition properties. The Titanic and many WWII Liberty ships sank because they were operated in sea temperatures lower than the glass transition temperature of the steels used. Typically 5 -15 deg Celsius. What steel has been used in your desired vessel? Not so much of an issue these days with the microallyed steels in common use.
3) Corrosion is potentially a much bigger issue with metal boats. Coating preparation ideally requires full vessel grit blasting. Any scratches then pose issues. This is often more of a problem on the interior. Corrosion will often start in hard to inspect locations.
4) Condensation and heat soak can pose major comfort issues in some climates.
5) Sensor location on steel boats can add some complexity relative to grp boats.
5) High quality field repairs of non ferrous boats are near impossible. Steel is a little more forgiving to field repairs while grp can be fully repaired anywhere.
6) Shape and aesthetics. I see some ugly steel boats because the builder didnt have capability or ability to form complex steel shapes.

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[double u]

Originally Posted by jheldatksuedu

I have a steel boat, I have owned many fiberglass boats and chose steel for it's strength, I expect I may often sail single handed, and have heard of floating shipping containers that you will never see until to late. I expect steel would be the only thing to survive a collision with one at full speed. I used to teach composite material construction in college, even built the first fiberglass highway bridge. I also have been a professional welder and machinist. You can learn all about the preparation of my boat "Steelin Time" and even also about the bridge on my website

I also plan to travel where there are icebergs during my circumnavigation, I think steel is the only reasonable choice for that. Feel free to connect and ask questions. Jon

for this kind of plans indeed steel is a very good choice. I wonder if Aluminium. done the right way wouldn't be just as strong & less maintenanceintensive:
meta dalu 40 strongall - occasion - Vente Voilier 125000
http://metapassion.free.fr/10inenglish.htm

[UNCIVILIZED]

Guys, I’m very curious about steel boats of late, for many of the reasons already cited in this thread. And I've been pondering on some them in the last 24. Which now has me wondering about some of the supposed perks of metal boats.

When it comes to weight, there’s no way that steel can compare to a glass or composite boat. The math just don’t lie. As if you build a boat out of 3mm steel, you’re looking at 5lb/sqft. Plus; Stringers & Frames, Insulation, & a Glass or Timber Interior/ Liner. So realistically call it 7lb/sqft. And that’s not counting any metal which you build in to deal with corrosion losses over time, as is commonly done in ships.
Where with composites one can build a boat that’s 1/3-1/2 of that weight pretty easily. And it’s not overly tough to build one which will float when holed. A nice perk to have IMO.

So much weight (CG) up high seems to rule out achieving stability on par with a modest displacement composite boat. So if you try & get good stability, you’ll be sailing something with more ballast the composite boat weighs, total. And if you’re like me, & prefer not to motor, you’re out of luck in anything but strong winds.
I do like steel’s toughness, but the performance costs seem pretty high.


Regarding welding, & the supposed ease of same, I’m not seeing it. As, in order to weld, you have to do a LOT of prep work. Especially if you don’t want a nasty fire on the boat’s inside, or to set up a situation where the repair/modification area is ripe for corrosion.

More or less, here’s how it’s done as I know it:
~ Grind off the exterior paint, & fairing.
~ Remove the interior in the area to be welded.
~ Chisel out the sprayed on insulation, or pull the foam panels.
~ Grind off the interior coatings.
~ Weld… with a fire watch on the other side of the area being welded.
~ Inspect or test your welds.
~ Clean/Rust Strip the exterior metal.
~ Apply the exterior barrier coat (epoxy).
~ Fair the exterior (essentially with composites).
~ Paint the exterior.
~ Clean/Rust Strip the interior metal.
~ Barrier coat the interior metal.
~ Add insulation. Though I’m unsure how to spot fix spray-in foam.
~ Re-install the interior liner & furniture.
~ Open some rum 

So then, where is the easy part about repairing or modifying things? And I don’t see such work as being particularly cheap. Or for that matter, the initial building of the boat.

Also, in my experience, most of the above steps for a repair need to be done the entirety of a steel boat every decade or two if she’s allowed to rust much. Or you’re buying her used & want to ensure her integrity.
If I’m incorrect on this stuff I’d surely like to know where the holes are in my thinking.


Edit: Where's the "fire proofness" in steel given that you have plenty of paint, fairing compound, decking, rigging & sails on the outside. And a full interior inside, overtop of several inches of foam insulation which makes some really toxic stuff when burned.
Seems like sideways logic, as that stuff burning will surely destroy & sink the steel shell. Including holing it.

[double u]

"the french" were always at the forefront of cruising-boat technology, & steel was all the rage in the 70 & 80ies. Soon they discovered though that a comparable aluminiumboat would not be more expensive-& please now: nobody quote me plate-prices of steel versus alum.! I'm talking "finished product": the hull is only going to be 30% of the total cost of a 40' cruiser, if that much: the steelhull sandblasted inside (which I very much doubt ANY builder ever did, & if then not 100% i.e. blast 3m² - clean - prime -blast...etc. same on underside of deck...) & then primed is hardly going to be any cheaper than the aluminum one
& an alluminiumboat with a nice hullthickness isn't going to be any more "fragile" than a steel one... (see metapassion...)
& regarding fire: the steelboat is going to be a total loss too if burned out, & sunk too (hoses, skinfittings,...)

[conachair]

Originally Posted by UNCIVILIZED

Also, in my experience, most of the above steps for a repair need to be done the entirety of a steel boat every decade or two if she’s allowed to rust much. Or you’re buying her used & want to ensure her integrity.
If I’m incorrect on this stuff I’d surely like to know where the holes are in my thinking.

The sprayed foam insulation is only above the waterline so there should be no need to remove that, also if it's the whole boat every decade or 2 then your paint system is rubbish. Saying that getting into the bilges and inside the boat below the waterline for touching can be a royal pita.
I would agree with welding anything on deck, major surgery. I don't bother but drill and tap with plenty of sikaflex and just accept a few houfs now and again will be spent removing and touching up below any added fittings which show a rust stain.
Otherwise the subject has been discussed at length many times, many pluses and minuses for any hull material. Personally, in the middle of an ocean thinking about hitting things wins me over

[jheldatksuedu]

Originally Posted by UNCIVILIZED

[COLOR=black]Guys, I’m very
When it comes to weight, there’s no way that steel can compare to a glass or composite boat.

The total weight of a boat has very little to do with the weight of the hull material. A fiberglass boat with bolted on keel might be able to have the CG a couple inches lower than steel, but not significant, the overall weight can be exactly the same but many other factors can be quite significantly different. As pointed out in the many posts there are many other important factors that enter into the decision on the proper hull material for the intended use of the boat.

I find aluminum welding very difficult. For financial reasons I tend to choose to try to do all the work myself. I have not been able to become proficient at welding aluminum. I do fabricate many things out of aluminum, but most connections are SS bolts. I'm sure finding a welder to repair aluminum much harder and much more expensive, but maybe less necessary due to the advantages.

[Captain Krook]

Thanks you so much, everyone! It's been very interesting reading your advice. I'm slowly understanding more and more of the steel boat mysteries.

One thing I would like to ask you guys about is "pit holes" in the hull. Some people owning steel boats write horrifying stories on the internet about those, suddenly appearing out of nowhere. Small holes, but big enough to flood and sink the boat, that suddenly come into existence. Obviously.

In spite of this, most people, expert internet sites and books on metal boats don't even mention "pit holes". How come? To me, it sounds like with a bit of bad luck a "pit hole" can easily kill you, if you use the boat for ocean passages.

Are pit holes a myth? Can anyone solve this mystery for me?

[RaymondR]

Pitting does occur on the underwater surfaces but are seldom very large and would take a long time to sink a boat. I believe they are electrolysis related and provided you don't let your anodes completely expire will not occur. I was responsible for the management of a floating drilling rig which, because it had been converted from an old WW2 barge, had to have all it's welds inspected every 2 years. Rather than blast coatings to access the welds we left the bottom without any paint and relied totally upon the anodes to protect the underwater surfaces from corrosion.

[Iodine]

I'm not an expert but from what I've read pin-holes seem to be caused mostly by stray electric current in the boat itself (the reason may/most metal boats have a the electric system totally isolated from the hull). In any case, it seems like the any leaks from pin-holes would be very small, and more of a pain to repair than a danger.

I own a 35ft steel boat and talking to other (steel boat) owners I've never heard of anyone having this particular problem, so I don't think it's common.

A bigger concern that hasn't been mentioned here is that some marinas have a lot of stray electrical current in the water which over time can eat up the anodes and then start on the hull. I know of one boat that had to be hauled and repainted because of this.

For this reason I'm a bit leery of leaving my boat in a marina for more than a few days.

I've seen one boat that lived in a marina longterm where the owner got some metal cable, bolted it to the hull so it was grounded, and tossed the other end into the water with an anode attached. This way he could pull it up from time-to-time to see how much had been eaten away.

Some smaller boats (Tom Colvin designs in particular) have a steel hull together with a wood or composite deck to keep the weight and center of gravity down. But as others have mentioned, in the +40ft size range you're interested in the extra weight of steel isn't an issue (at least for medium/heavy displacement cruising designs).

All boats need maintenance (rig, sails, systems etc.), and the hull will only be a minor fraction of that, regardless of what material so I wouldn't put too much weight on that.

Of course if you end up buying a GRP boat with osmosis, a metal boat with a major corrosion issue, or a wooden boat with rotten planks, your going to have major work, regardless.....

some may appreciate the security at sea, but for someone like me that does a lot creek-crawling, is that running aground or hitting a rock will only cost me paint. (and my pride). Likewise it makes me a little less stressed about the possibility of someone anchoring too close or dragging down on me..

If your looking for a metal boat in Europe then the Netherlands is probably the best place to look. although often you can find cheaper ones that have been sailed down to the Algarve or Med and are now for sale..

[Scorpius]

I've seen a steel boat pretty well destroyed by "pin holes" caused by a really poor marina electrical system that leaked A LOT of power into the water. The boat was moored there for over six months with nobody watching over it. It was a sad, sad story.

However aluminium is even worse for this and many aluminium boat owners will get quite upset if a steel boat moors nearby. The galvanic action between the two can be pretty terrific and the aluminum loses!

[stillbuilding]

Well, I think I must be something of an expert on pitting corrosion.

Long story but I took on an project boat that had been built of Corten steel by very talented professionals and launched in 1981.

Improperly painted and for the past 10 years plus left to rot without anodes in a marina. Previous owner ran when he found the second pin hole in the hull while sand-blasting the interior.

So, several days of hull plating replacement, grinding, welding and sand blasting later I am about to start refitting - still have all the internals, rig and much equipment so not as bad as it could have been.😆😆

No real complaints cos I knew what I was buying but couple of points;

The boat was not adequately painted when first launched (that is another story) and basic paint was not redone in 20 years in the Pacific.

The boat had no anodes and poor bottom paint for 10 years.

Being Corten made not a jot of difference.

The boat was certainly in a busy marina for 15+ years so electrolysis mighthave been an issue.

The pitting corrosion resulting in pin-holes I had not seen previously but hardly came as a surprise.

The very experienced steel workers who repaired the hull had seen it many times previously and were sure it related to inadequately painted steel with no electrolytic protection.

So yup, steel ain't perfect and can degrade but at least takes a long time to do so and is easily repairable.

Not too sure if I would do another project though.😆😆😆😈


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[a64pilot]

Google " ultrasonic thickness gauge"
I use them to inspect aircraft steel tubing, to determine amount of internal corrosion if any. A good one can be had for about $300 and will tell you to the .001 of an inch the thickness of the metal by simply placing the transducer to the metal.

I think if I had a steel boat, I'd have one to check the bottom when I was doing a bottom job, if checked every now and again, you will know when and if your losing metal to corrosion probably in time to do something to stop it.


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[stillbuilding]

I agree with the Ultrasonic device - I have one and it does clarify some plating defects. In my case it was not really required cos the corrosion was so apparent.

Interestingly, the pitting corrosion was very focal and obvious- full penetration divots in 6mm plating immediately beside almost intact plates.

It was the electrolytic pitting noted earlier in the thread which I was alluding to - not just general thin or rusting plating.

My new boat is done in Corten steel too - not sure if it limits rust in any real way but sure as hell does not stop electrolytic corrosion.

At the risk of thread drift I would note that in the 80's it was common for zinc based paint to be used as primer coat. The shipyard staff who repaired my project boat reckoned that unless that was followed by coal tar epoxy top coats, many of those boats are now rusting badly. Apparently the zinc primer was electrolytically corroded and the steel followed suit. Not what I was expecting to hear.

I should stress that I knew the plating issues before I even saw the boat cos the original builders had done repair work on it a few years before.

Actually, the same builders did my new boat as well so I knew the issues precisely.


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[stillbuilding]

Still more thread drift-

When I was moving my project boat to a yard which could repair the plating, I had to leave it in a marina for several months.

The marina allocated me a berth immediately next to one of Dashews alloy boats. I felt badly for the possible effect on that boat and requested a move to another berth in view of this but the management seemed not the slightest concerned. I hope the alloy boat checked their anodes.

Must give any thoughtful owners of alloy boats bad dreams at times. And I have had an alloy boat with corrosion issues so do understand that reality.


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[Cheechako]

Nothing stronger than steel. But if buying used, I'd want a very well kept one. Bottom line is you just aren't going to break a fiberglass boat that was well constructed with a long keel, protected rudder and enclosed ballast.
Steel easy to repair? For a welder maybe, not for the layman.