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Old 13-02-2011, 20:51   #1
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Steel Hull Maintenance

Still on the long winding path of finding a sailing boat here . Just got some info on a steel monohull boat, about 38’ long – with a recent survey.

I’ve read lots about steel on CF and generally like the idea, and I’ve read a bit about the maintenance side. But I’m trying to get a better feel for what I would be in for if I get steel. Can steel hull owners tell me what exactly it’s like to own one. That is, how much time and what do you do for maintenance, for boats that sit in salt water full time.

Also, what do anodes, stripping compounds and paint / antifoul etc cost per year; how often sand blast hull and what does that cost? I’m fairly handy but not a tradee - what things could I do myself and what things need to be done by a pro?

Also, this boat has 4mm thickness steel hull – is that a bit light on? Any comments?

Cheers
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Old 13-02-2011, 21:08   #2
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4 mm is pretty thin, just over 1/8". I would think it would be hard to keep a hull that thin from deflection, but perhaps they took that into account in the design.

The key to low effort steel maintenance is the same it is with everything else relating to boats. Preparation. If the all steel is properly coated with an appropriate 2 part system, the maintenance is no more, and probably less than it is with other materials. I've maintained fiberglass, wood and steel, and can't say I see a lot of difference. However, if steel is not properly prepared, it would be a chore and a half to keep the vessel looking good.

If you want the ultimate in low maintenance steel, you might consider metallizing the vessel.
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Old 13-02-2011, 21:28   #3
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Steel is only scary when it's been utterly neglected. I'm a bit ashamed to say that I ran my anodes off awhile ago and caused a few hot spots on the hull, as a result. Repairing them is so incredibly simple (and it's not that expensive), either by welding rod directly onto the compromised sections of hull, or by cutting/replacing a section of bad plate. This is not a terrifying proposition. The main concern is creating fire inside the boat. After that, a newly welded section of metal is at least as good as what's around it.

If you keep your anodes up, and use a proper epoxy system with effective antifouling, steel is no more 'regular upkeep' than any other material. It requires regular haulouts, anode replacement and observation to deal with problematic areas in the paint system before that lall-important ayer is breeched.

For steel (and I assume wood) boats, you have to think of the hull as nothing more than a structure. It provides strength and a framework for the paint system to go on. The paint system is generally what you need to think about maintaining and observing. If the paint hasn't been penetrated by the critters, or an impact, then the metal underneath is going to be fine (with very, very few exceptions).

Most people I know who have steel boats, who do (or have done for them) regular maintenance only talk about blasting/re-coating every 20-30 years. Costs for maintenance vary significantly, depending on which part of the world you're in. My latest welding was done locally here in the Philippines by an excellent welder (who works in Australian shipyards as an all-purpose welder) for about $3.50/hour plus materials and power for the welder. But having it done in the USA/Europe/Australia would easily cost ten times that much, although materials are generally no different, from place to place.
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Old 13-02-2011, 23:47   #4
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I second Notquitelost on this. He has more experience also. I have two steel boats but they have not been in the water that much so I must defer to others on longer term maintenance.

However, I'm getting better at buying other peoples boats and then finding what is wrong and fixing them up. If you are looking to buy I may be able to contribute.

First of all I think it is really pretty darn hard to tell if a steel boat is OK or not. Not impossible, but it will take effort on your part, not a surveyor, you couldn't afford that kind of survey. You need to spend a considerable amount of time in the bilges with the boat out of the water and with a big straight slot screwdriver and a good flashlight. Poke around every thing. If you find a little rust, poke it. Bang on stuff and get to know how it should sound. Some areas will sound different for a reason. Some of the reasons are not good. I can't tell you what I mean but eventually you will get the idea. Any place that can have water dripping can be a problem. The bilges should be dry.

Last year we were look at some aluminium boats and I was poking around one from the outside on my back on the grass. I saw a white spot and flicked at it with my pocket knife. It when right through the hull with no pressure at all. The hole was in a water tank and the boat had been in fresh water so the owner didn't notice I guess.

Issues I have found over two boats include:
1. Water dripping in from a radar mast caused a hole to rot out in my transom.
2. I found a small hole in the keel, adjacent to the ballast. No obvious rot, just a tiny hole through the metal, like a blemish in the sheet. Go figure.
3. Under the sink a persistent drip caused a rust spot. The PO welded in some metal but something didn't go right. Clearly something was wrong and when I wacked it with a hammer a big chunk of metal came out. We cut that out and welded in a patch. Not a big deal.
4. Leak around bow light let water drip into forepeak. Forepeak tends to be wet anyway so this just made matters worse. Really hard to get to. Had to work with a grinder on an extension pole. But I got it. I think.
5. Bow sprit for no obvious reason had two holes. Small until I wacked them. One got welded over with some plate. The other I found later and that got some JB weld until next haulout when I will weld over again.
6. Water tanks had some kind of epoxy coating that had bubbled badly and the bubbles filled with water. But NO RUST even though there was long term water in contact with the metal. I stripped off all the old epoxy I could and then recoated with a two part system topped with a potable water two part system. Should last my lifetime.

I have a couple of little spots in the big boat that are almost impossible to get to that have some light surface rust. I only discovered these areas after having the boat several months and having gone over the bilge a few times. One spot I had to pull out some interior to get to. But it is below water line and everything below water line needs to be inspected. I need to wait until warmer weather to prepare and treat these areas.

All this said, I had an incident this summer that would likely have sunk another boat. Completely out of the blue I hit something (submerged pile) very, very hard. Not a drop of water. PO on my other boat creamed something with the keel. A big ol dent down one side. No leaks at all.

Hope this helps.
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Old 14-02-2011, 00:14   #5
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good book avaiable to buy and download here - Metal boat maintenance-A do it yourself guide by Scott Fratcher in Engineering
and here - Metal boat maintenance-A do it ... - Google Books

Inside is the tricky bit, getting to the hidden nooks and crannies.
4mm sounds too thin to me.
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Old 14-02-2011, 14:21   #6
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The only steel boats I have seen that looked fine were those that were built professionally and maintained meticulously. This includes a couple dozen of Dutch tubs and single boats from other locations (e.g. the USA).

A steel boat, if designed, built and maintained well may well be the next to ultimate cruising tool (alloy one being IMHO the ultimate one ;-)).

All other things equal, I would always select steel or alloy for any serious / long term relationship.

If you look at the expedition end of the spectrum, steel boats constitute a vast sector of the picture. There are also countless seriously cruising steel boats around.

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Old 14-02-2011, 14:30   #7
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How old is the boat.... is the 4mm below the waterline.... I'da thought 7mm would be a minimum... if its an old boat.. maybe not much life left before replating...
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Old 14-02-2011, 15:04   #8
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Quote:
Originally Posted by conachair View Post
good book avaiable to buy and download here - Metal boat maintenance-A do it yourself guide by Scott Fratcher in Engineering
and here - Metal boat maintenance-A do it ... - Google Books

Inside is the tricky bit, getting to the hidden nooks and crannies.
4mm sounds too thin to me.
Ah, figure the guy with a Pape to know his stuff. Conachair, downloaded the book and gave it a once over. Very, very good stuff there. Real practical. Very worthwhile.
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Old 15-02-2011, 00:26   #9
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Hi all, thanks a heap for all the comments. Re the thickness, its a Roberts design built locally here, so I hope it's ok. Survey says deck 4mm, keel 6mm and keel base 10mm, whereas sale note says 4mm for hull so I'm hoping that wrong but intend to check. With all the comments, steel sounding better to me know. Cheers
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Old 15-02-2011, 02:41   #10
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Ok we have found maintenance on our steel boat to be easier than on the fiberglass in some respects. Meaning we find it easier to paint than clean, wax and polish.
This boat was sandblasted in 2010 so lets see she was commissioned in 1982, we expect the job to last a similiar amount of time. One must prepare the surface properly for this to be true.
Steel boats mainly rust from the inside out, so check all those nooks and crannies, places where frames join and may form a spot that damp can sit.
Anodes, well keep them up and don't stint on the number.
A surveyor can ultrasound the boat, and in fact if you are getting a survey done make certain it is someone who is familiar with that hull material. Ours cost the same rate per as did all this chaps surveys, it was not more expensive for steel. Perhaps it's different in othe places.
Although we are in fresh water now, before we purchased the boat she lived in salt water for nine full years, and we have take her to salt as well.
As for thickness, designers often specify what is appropriate for different parts of the boat, as you have noticed with the deck plating being different than the keel base and so on, this means the topsides may be a different thickness than the below the waterline portion.
Enjoy. I love my steel boat.
Fair Winds
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Old 15-02-2011, 18:26   #11
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Plate thickness

On the plate thickness question of which there has been some discussion in this thread...

I've consulted the doyen of steel boat construction, Thomas E Colvin, and he says the minimum plating for small vessels (about 30 feet) is 1/8" or 3mm. The heaviest plate would not exceed 5/16" or 8mm for vessels 79 feet and over.

It seems the most common hull plating size for pleasure yachts is 4mm (having constant displacement, unlike cargo vessels, means there is no need for reserve plate strength).

Of course, it all comes down to the total design package - scantlings of frames and hull shape etc.

Thus if the Roberts boat in question was built to plan, and you trust the designer, then the 4mm would surely suffice. The real query for the buyer would be just how much of that 4mm is left after 30 years of (potential) rust and electrolysis damage.

It's worth noting also that Scott Fratcher in the book mentioned above says that the minimum remaining steel plate that he'd be comfortable going to sea in would be 3mm in the hull and 2.8mm in the topsides.

So, if this is to be a guide, then the Roberts could have lost 25% of its plate thickness and still be good for the sea.
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Old 15-02-2011, 19:17   #12
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Boy, I'm not sure where the idea that 4 mm is sufficient for the hull of any boat over 30 feet or so. Delfin is 1/4", or 6.4 mm, and prior to fairing, showed deflection in the bow plates with the ribs on 18" centers. If the steel was Corten, maybe 4 mm would work, but Corten steel has other issues.

I suspect when you look into it, you will find the designer specified 1/4" for the hull plates.
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Old 15-02-2011, 19:25   #13
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Well I figured 7mm below the W/line brand new... but WTF do I know.... seems I'm not a death wish guy after all....
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Old 15-02-2011, 19:40   #14
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Well I figured 7mm below the W/line brand new... but WTF do I know.... seems I'm not a death wish guy after all....
If there are any doubters left, here's the word of a trusty Englishman, Paul Fay.

FAQ
Can I increase the plate thickness?
I am constantly approached by builders who are thinking of increasing the thickness of the plate, either all over the hull or just below the water-line. The thought is usually to increase the thickness by 1mm from the 3 or 4mm plate specified by the designer, to make the yacht stronger.
This has two adverse affects. The first is that the yacht will be overweight, in some cases by so much that the amount of ballast has to be reduced. This is often coupled with the other effect which is that by thickening the plate the centre of mass of the yacht is raised, reducing the stability.
In an effort to overcome this some builders over ballast their yachts and raise the water-line, while others just accept that the yacht is tender.
On one 40 foot steel yacht, the builder decided to increase the deck thickness from 3 to 4mm as this would help to reduce the welding distortion. Good idea you may think. But hold on, that is an increase in weight of 33%, or in real terms about 500lb. and this weight is acting about 4ft. above the centre of mass. This can be represented as 4 x 500 = 2000ft.lbs or nearly a ton extra acting against the righting moment, which meant that the yacht needed extra ballast.
DON'T INCREASE THE PLATE THICKNESS. Steel yachts are incredibly strong! Most 30 to 40ft yachts could be built from thinner plate. The reasons why thicker metal is used, is the difficulty of welding thin plate, also to resist denting while alongside quay walls etc. and traditionally as an extra margin for corrosion, which has now been overcome with modern paint systems.
When designing the Fay 32 we specified 3mm rather than 1/8 inch plate. Only 3% thinner, but this represents a saving of 160lb overall. Which in real terms means that an extra 180 tins of food can be carried for those long passages.
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Old 15-02-2011, 22:07   #15
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Also, what do anodes, stripping compounds and paint / antifoul etc cost per year; how often sand blast hull and what does that cost? Iím fairly handy but not a tradee - what things could I do myself and what things need to be done by a pro?

The hull plating on my Roberts is 4mm thick. Most of the steel has been 4mm since it was built 20 years ago and is still 4 mm because it was prepared carefully and epoxy coated. Some has corroded and been renewed - the usual suspect areas under the head and galley.

Over the years the hull coating thickness will have built up due to over coating. The time may arrive - 10 yrs - 15 or 20 ???? when stripping back to bare metal is desirable, probably because the profile resemlbes the Himalayas, - and then the steel has to be prepped for paint. The choice is to blast (if allowed) or prep the steel as best as possible with power tools. Blasting is going to be expensive - even in Asia. Europe or the USA (governed by much green legislation) more so.

The cost for stripper, zincs and coatings on an annual basis - You will only need stripper if you want to remove paint. Why would you want to do that, unless you are going back to bare steel ? - once every blue moon.

A 40 foot boat is going to need about 10 litres of A/F for a touch up coat, plus a full coat. How much is A/F in your chandler ? As for zincs - pretty cheap where I am, and it is a no brainer to change them each year, even if they look like they got another year in them. You should also allow for a few touch spots of epoxy - and therefore need to make sure the A/F you use will accept an epoxy paint on top of it. Read the label on the A/F tin. Finally put some fancy coating on the propellor.

As for getting things done by a pro - even if you can weld then any hull welding should be done by a pro (preferably a certified welder to keep your insurers happy). And many CF posts point out how difficult that can be ! As for other issues on a steel boat - the same apllies to any other construction - either you have the time / skill to do it yourself - or pay a man who can.
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