Steel Hull Maintenance

[markpierce]

Originally Posted by At sea

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.

As far as the 35-foot Coot is concerned it is: 4mm superstructure, 5mm decks, topsides and bottom, 6mm garboard plank, 8mm keel sides, and 12mm keel and rudder skeg.

[Wand]

Originally Posted by markpierce

As far as the 35-foot Coot is concerned it is: 4mm superstructure, 5mm decks, topsides and bottom, 6mm garboard plank, 8mm keel sides, and 12mm keel and rudder skeg.

That sounds consistent with my posts. While the Coot is 35 feet, it couldn't be more different from a cruising yacht of that same length. Shows what a poor general description overall length really is.

The motor boat (with steadying sail) Coot will be about 13 tonnes; a steel crusing yacht of the same length about 8 or 9 tonnes. Further, allowance would have to be made in the Coot design for the potential additional loads motor boats are sometimes subject to (as per Colvin above).

Thus 5mm decks, topsides and bottom would be expected.

BTW, interesting boat Mark and a helluva project; very comfortable too but I couldn't afford the fuel bill

[hpeer]

Originally Posted by kjames

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

Besides talking to us blokes here I would suggest talking to Bruce Roberts himself. I know that he does provide some casual consultation and there is an off chance he even knows the boat.

Bruce checks in on CF sometimes so he is around and active.

Go to the horses mouth.

[markpierce]

Originally Posted by At sea

BTW, interesting boat Mark and a helluva project; very comfortable too but I couldn't afford the fuel bill

??? A gallon or less an hour at about 7 knots. Max. speed is a little more.

[boden36]

SteveA's comment : "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). " makes it seem harder than it really is.
I am a qualified welder and arc welding with a stick electrode is really very simple. Usually (unlike MIG) if a stick weld looks good, it is.
To address any quality issues, it would be wise to go to your local training establishment and do a short welding course. After that you should have no problems as although it may look complicated it is pretty straightforward. Anyone can weld well with a little training and practise.
This idea that only the experts can do things is very self limiting. With care, some thought and diligent research most people can do almost anything, you just have to be prepared to do it again and again until you get it right!!

Regards,
Richard.

[bob kingsland]

Boden 36 has it right, there's no reason to limit yourself in any way... if you're reasonably handy you can learn to weld. I taught myself just by playing with the equipment, and since then have been certified and have welded many different things... from metal sculpture to parts for power plants to ultra high stainless vacuum chambers to aluminum for satellites to titanium rocket parts to mazes for ferrets, with the occassional roll bar for a Lotus race car or steering mechanism for a Model T bucket thrown in, and some bow and stern rails too. The molten puddle acts about the same no matter the material or the type of welding... oxy acet, stick, MIG, TIG, flux core, whatever. It's all just watching the metal flow.

Through it all I built the 50' boat shown in the link. In this country by far the most common thickness for sailboats up to 50' or so is 10 gauge, or about .135" with decks of 11 gauge, or .120". My keel sides are 3/16", keel bottom 1/2". A lot depends on the framing dimensions and spacing.

With today's epoxies corrosion just shouldn't be much of a concern if the boat is properly prepped. We've been in the water for 4 seasons now and I have yet to touch up any rust, inside or out... there isn't any. Likewise, the plate thickness has not diminished at all. Of course I still have to keep bottom paint and zincs on her, but maintaining what little exterior teak I have takes much more time than the steel does. Now obviously this will change when she's been in the water for 20 years; at that point she'll probably need to be blasted back to bare steel and start over. I'll worry about that then.

If she's properly built and coated in the first place, then rust does sleep for quite a long time.

Best, Bob S/V Restless

[Jim Cate]

"With today's epoxies corrosion just shouldn't be much of a concern if the boat is properly prepped. We've been in the water for 4 seasons now and I have yet to touch up any rust, inside or out... there isn't any. Likewise, the plate thickness has not diminished at all. Of course I still have to keep bottom paint and zincs on her, but maintaining what little exterior teak I have takes much more time than the steel does. Now obviously this will change when she's been in the water for 20 years; at that point she'll probably need to be blasted back to bare steel and start over. I'll worry about that then. "

This sounds pretty convincing for a newish, well prepared steel boat. But, as is often quoted, steelies usually rust from the inside out. Now, when buying an older steelie, how can one reasonably determine if there is rust in out of the way spots (behind frames or stringers, below the anchor locker floor, behind the fridge, etc). Further, after the 20 year period of grace mentioned above, how in the hell can you sandblast the INSIDE of the boat back to bare and re-coat?? Sounds like a pretty serious refit, like starting the interior all over again.

Our steel guru Brent Swain says that he spends a couple of hours a year maintaining his steel vessel. My observation of others in the real world of cruising in steel boats says that this is woefully understated. While it could be true for his professionally prepped and built boat, for the chap buying the 20 year old Bruce Roberts home-built, a considerably larger time investment is likely to be required. This issue bothered me so much that when we were searching for Insatiable II we ruled out steel construction. YMMV.

Cheers,

Jim and Ann s/v Insatiable II lying Little Pittwater Cove, NSW, Oz

[hpeer]

Well, when buying a 20yo steel boat you have to do the survey yourself, and be slow and careful about it. You need to do this to insure that the previous owners took adequate care of the boat.

If you don't you can get screwed.

If you do, you can get a good deal because steel carries a negative premium, just 'cause.

So, it is up to the buyer to make sure of what he is getting. Not easy but worthwhile.

[Jim Cate]

Originally Posted by hpeer

Well, when buying a 20yo steel boat you have to do the survey yourself, and be slow and careful about it. You need to do this to insure that the previous owners took adequate care of the boat.

If you don't you can get screwed.

If you do, you can get a good deal because steel carries a negative premium, just 'cause.

So, it is up to the buyer to make sure of what he is getting. Not easy but worthwhile.

It's all very well to say "be slow and careful about it"and "it is up to the buyer", but in the real world of boat buying, just how can you access the hidden areas? Most owners quibble about your disassembling their joinery, removing the insulation from the fridge, or otherwise accessing the critical areas. These areas are just where one might expect to find rust, because the PO couldn't get to them either. For that matter, the builder couldn't get to them all that easily, so they are prime suspects for errors in the coatings.

I'm not trying to slag off all steel boats, but the risks associated with buying an older one seem far greater than those associated with many other forms of construction. Again, YMMV in what sort of risks you are willing to assume.

Cheers,

Jim and Ann s/v Insatiable II lying Towlers Bay, NSW, Oz

[SabreKai]

Sabre Dance is a Roberts Offshore 38 constructed in a shop in Markham Ontario. I email Bruce Roberts-Goodson about her thinking she may have been built with pirated drawings. He came back with a reply that he actually knew the boat, had seen her being built and that she was not built to pirated plans. He also stated that she was a well built solid boat.

For what its worth, she's plated with 1/8 on the hull and deck.


Sabre

[hpeer]

Originally Posted by Jim Cate

It's all very well to say "be slow and careful about it"and "it is up to the buyer", but in the real world of boat buying, just how can you access the hidden areas? Most owners quibble about your disassembling their joinery, removing the insulation from the fridge, or otherwise accessing the critical areas. These areas are just where one might expect to find rust, because the PO couldn't get to them either. For that matter, the builder couldn't get to them all that easily, so they are prime suspects for errors in the coatings.

I'm not trying to slag off all steel boats, but the risks associated with buying an older one seem far greater than those associated with many other forms of construction. Again, YMMV in what sort of risks you are willing to assume.

Cheers,

Jim and Ann s/v Insatiable II lying Towlers Bay, NSW, Oz

Agreed, that is why you have to do it yourself to your own satisfaction.

Because that is the prevailing attitude steel does not have the resale value. But, if you are willing and able, you can get a steal.