Steel boats

Not from precut kit, but I have designed and built my own gaff schooner.

Building from a kit is certainly easier than cutting it all your self.

Regards ongolo
 
There were a series of articles in PBO about 12 years ago (I think) re building a 34' Van de Stadt design from a pre-cut kit - I think I have a rather poor photocopy of that article somewhere.

Pre-cut is certainly the way to go - and the same procedure can be applied if you are using steel, aluminium or plywood.
I suppose you could even use it to cut out frames and hull panels from fibreglass sheets as well.

I was involved with building a couple of power cats (one in steel, and the other in aluminium) here some years ago.
The conventional route (after first lofting the design full size) would have been to mark out on the steel / aluminium sheets all the frames and panel shapes, and then cut them out by hand.
But life is so much easier if you can send the data re the frames and hull panels directly from the computer to the plasma cutter which then nests the panels for best fit, and proceeds to cut them out with amazing (usually!) accuracy.
It is then a case of assembling it all together and welding it up.
 
The Structural integrity of a steel boat is depended on the quality of the welds. Therefore, welding will be the critical factor, you will need a moisture free environment to reduce oxidation, sand blasting ect. Steel is a very forgiving material but must be protected at every stage of construction and beyond. Good luck
 
Just found the above mentioned articles - they were in the September and October 1992 issues of PBO, about building a Van de Stadt 34 from a kit, written by a gentleman called Frank Mason.

My copies are just rather poor quality B & W photocopies, but if you would like a copy of them I can scan them (8 pages) and email them to you.
Or you could try the IPC Copy Shop for better resolution copies (?)
 
When I was having my boat treated for osmosis I made friends with the yard director who was doing the work. He himself had a wooden boat, but in his yard he had everything from ferro to ally via steel wood and grp. In conversation (as you would) about which material was best we passed a steel boat. Thats got to be good , says I (steel industry background). "Dont you believe it, says he. We've just had to replace half the side of that boat because of corrosion from the inside. And every year the owner has some painting to do, whatever preparation he takes. They're more work even than wood, and I couldnt afford a wooden boat if I wasnt director here, or willing to spend weeks of my own time in maintenance."

Mind you, his wooden boat was one of those with acres of clear varnish on a splined hull

You ought to have heard his views on ally. In the end, he thought GRP was the best of a bad lot in that it was infinitely repairable (unless you set fire to it) and maintenance wasnt much more than a yearly polish and an osmosis treatment after 20 years.

Up to you, and certainly a laser cut kit off a cad system is the way to go if you choose steel. But after all those years in the steel industry (and the ability to buy good steel at scrap price and get it cut by friends in the trade) I chose grp. That either says something about me or something about the material
 
G'day John,

Is this pre-cut and rolled: if not rolled you get some variation in shape and the 'fit' may need filling or grinding. in any event you are going to have to fare the hull and not a simple or easy task.

Care is needed to ensure areas that can to be accessed after welding are treated first or welded air tight, this is almost impossible on the structural frames. Many designs make replacing one of these frames more than a little expensive later on if you did not get it right the first time.

Good Luck.

Andavagoodweekend......
 
If thinking of going this route get prices for steel kits cut in Poland, then ask them how much to weld it up. Polish built hull may be cheaper than Kit in UK.
 
Hi All,

Thanks for the varied advice.

The boat that I'm contemplating building is a 12 metre power cruiser from Girraween. The steel is plasma cut from pre-grit blasted and primed steel so the main prep for the steel will have been completed. I realise that it will be critical to keep all the welds and any ground areas primed prior to the main paint job. The internals of the steel will be sprayed with foam insulation but will also have the duel effect of keeping the surface of the steel protected from oxygen/condensation etc. The steel is rolled and sections are preformed where required.

I have arrived at my present situation following a long period of research which started by considering importing a fairly sound hulled De Fever Trawler Yacht from the US which was in need of serious internal restoration following a sinking in a hurricane in a mariner! That came to a dead end as it turned out the boat was too large to be transported by road in the US or UK. There was also the impossible issue of complying with the EU Craft Directive.

I then started searching for a supplier of GRP mouldings suitable for building a Trawler Yacht - cut a long story short - that also came to a dead end!

Hence the current proposal to build from Steel.

Scanned copies of the artical would be welcomed if you dont mind going to the trouble - e.mail is John@peet.fsnet.co.uk

John
 
[ QUOTE ]
The Structural integrity of a steel boat is depended on the quality of the welds. Therefore, welding will be the critical factor, you will need a moisture free environment to reduce oxidation, sand blasting ect. Steel is a very forgiving material but must be protected at every stage of construction and beyond. Good luck

[/ QUOTE ]

Utter piffle....steel is one of the best boat building materials to use, I've been building steel boats for years and most of them out side in the open, in fact it's an advantage to build in the open as oxidation of the surface removes the mill scale that can be very difficult to remove even when gritblasting to SA2.5 as long as you wire brush well the sections you are going to weld as you go, you will have no problems.
As for maintenance with todays paint systems you will proberbly have less then GRP..... how many steel boats have you come across with osmosis ?
 
Yes steel is strong. And here is a shocker. First of all, steel expands 11 times as it takes in oxygen as it rusts. This means that 1mm steel will convert to 11mm rust. So rust always looks worse than it is.

Structural strength: A 50mm long weld of of a section of 5mm steel plate can handle 50x5x35x.65 kg/mm^2 can stand a force of 5800kg before tearing off. The multiplier of 0.65 is the reduced strength of a weld over normal steel.

Considering my boat with a frame length of an average of 11m and staggered weld of 5cm on either side, still makes the equivalent 0f 11m weld for each of the 24 frames of my schooner. I am not even doing the calculations, but no matter how bad the weld are, the boat will be stronger than you can imagine.

Regards ongolo
 
interesting; just out of interest are you able to give any idea on the cost of a finished hull built this way ie kit cost and manufacture cost. I would be interested to know how it compares to buying a production 34fter (although I understand there are arguments about construction materials and seaworthyness as compared to a GRP AWB).
 
Not sure about a 34' er but the steel kit for a 12 metre aft cabin with fly bridge, all windows vat and delivery to my home will be less than £25k, the build will cost me my time over 2 to 3 years as I plan to do everything myself. The remaining cost will be based on the quality and choice of fit out, engine/s etc
 
Hi ongolo,
I have been restoring and sailing GRP and wooden boats for about 8 years and am a compenent DIYer. I am going to either build a steel boat or buy a steel hull and fit out. Are you aware of any good links of either steel hull plans or complete hulls in UK. I live in NI. Thanks
 
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