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Old 12-12-2010, 08:10   #16
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Originally Posted by boatman61 View Post
Cheaper/easier to home build maybe... also maybe he figures the greater base weight will reduce capsize dangers...
To me building in steel negates the positive attributes of a multihull. Keeping them light to enhance sailing abilities and making them unsinkable which is a debate in itself.

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Old 12-12-2010, 16:11   #17
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Boatman61 got it pretty much right on the money although I really wasn't thinking about the capsize danger. Additionally there are 16 zillion people out there (exactly 16 zillion I counted) who can weld steel, fix steel, paint steel and do a pretty good job. There are 6 who can do all those things with aluminum alloys and they are reputed to live under rocks in the black forest. Glass reinforced plastic can be made look beautiful by any moron who is not overcome by the toxic fumes and will function perfectly until the warranty expires or you are equal distant from either shore of an ocean whichever comes first. Unless you are there to supervise or yell at those poor sods who have been dragged in off the street to run the chopper guns. Or you do it yourself (see note re toxic fumes)

From a slightly serious note. There are hundreds of really good boatyards with lots of experience with steel that are crying for work, but as has been pointed out steel is heavy and that makes it less than ideal for multihull purposes. However it is also my understanding that as the boat gets bigger the structural requirements of fiberglass also make it relatively heavier per foot and all that entails. Same with aluminum alloys and if there are any weld points at or near flexion points one can be in a world of hurt.

By the way thanks Tenchicki and Maxingout for the name Canvas back. I have been wondering for years what happened to her but I thought the name was leatherback as in the turtle.

FSmith I assume if you knew/remembered the name of the Ausie couple you would have mentioned it, but if it comes to you or you hear of them again I would appreciate a note.

I am not likely to run out and start buying steel any time soon but think about how sweet it would be to weld on a stanchion and not have to worry about reinforcing anything and not getting fibers in your beard, xylene on your hands and plastic dust in your lungs. Now before everyone jumps on me I know there is the rust thing, and the condensation, and the noise and all the other issues but in these trying times it might be worth a thought. Maybe not two thoughts but at least one.

Actually what I really want is a 60 foot cat made from spun carbon nanotubules in a matrix of spider silk proteins that will come from genetically modified goats milk. That will solve all the problems except of course the cost which is what got me here in the first place. Sigh

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Old 12-12-2010, 22:58   #18
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I know a guy who built a wonderfully unique steel (cor-ten) with space frame sailing cat called "Zig-Zag" (because of the look of the framing). When last I saw it the boat was being converted into a motor only tour boat. Yes, it can be done... And, if it turns you on why not? But, on smaller boats it's hard to believe that the money you might save on building the hulls would be a very large amount of the total cost of the yacht. If the motivation is purely economic I'd be leery.

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Old 13-12-2010, 05:18   #19
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A steel cat needs to be large enough to offset it's weight. As large as you need a generator would be in order, and a small mig welder, and you don't need a boat yard to fix anything. You're welding most likely won't be pretty, but it will get you someplace where it will be. My wife was laying a descent bead inless than 2 afternoons...........i2f
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Old 13-12-2010, 05:32   #20
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Take a look at the the Wharram Designs.... not so much for the styling... although I do think the Tiki range are gorgeous... but more for building set-up's and framing... also the way they use horizontal stiffeners to utilise thinner lighter ply....
also their flexible beam technique is pretty neat... would not recommend the cord with steel though... maybe brackets and bolts....

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Old 09-12-2012, 14:01   #21
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Re: Steel Sailing Cat - Is it Possible ?

AdventureCat is not steel, she is 5 layers of plywood epoxied together. Her keel would not break when the USCG tested it for strength. She was built in Napa in a shed, and is operated by her builder.
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Old 09-12-2012, 15:30   #22
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Cold moulded wood would be way better then steel, but hey knock yourself out. There lots of steel catamarans to look for inspiration.......................

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Old 09-12-2012, 20:24   #23
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Re: Steel Sailing Cat - Is it Possible ?

Years ago (Late 70's) I saw a steel cat ( about 60 ft I think) which was sailing up the east coast of Aus. He had hydraulic rams with feet on each side so he could "walk" it up a beach. Don't know what happened to it but was a fairly eccentric outfit.
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Old 09-12-2012, 20:50   #24
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Re: Steel Sailing Cat - Is it Possible ?

There's a Russian Cat out there (name is Blagovest) that is built out of Titanium. Probably one of the most eccentric of cruisers. However their website is a tad out of date, so don't know their whereabouts. They do occasionally end up in one or another European port though.
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Old 26-11-2017, 17:35   #25
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Re: Steel Sailing Cat - Is it Possible ?

Originally Posted by tenchiki View Post
... a 70-ft ketch-rigged catamaran out of aluminum...was a travelling medical/dental hospital...workboat styling and finish... I can't remember the name
The name of the 70' cat dental hospital was.CANVASBACK, like the duck.
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Old 27-11-2017, 01:47   #26
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Re: Steel Sailing Cat - Is it Possible ?

It really comes down to the relationship between material density, tensile strength and bending/puncture strength.

- Fiberglass: 100lb/cubic foot
- Aluminum: 167 lb/cubic foot
- Steel: 488lb/cubic foot

Of course that comes with a trade off in tensile stength (there is a lot more variability depending on specifics here both production of GRP and specific alloy of the metals):
- Fiberglass: 43,000psi (basic fiberglass not carbon fiber or other high end)
- Aluminum: 65,000psi
- Steel: 85,000psi

As you can see, the steel weighs 3-5 times as much bu is only 1.5-2 times as strong. But the real impact comes when considering bending strength. Relative bending strength can be compared by looking at thickness times tensile strength (this is a relative comparison not the actual bending strength). Assuming a 1sft panel has the same weight:
- Fiberglass 4.9" thick by 43,000psi = 206,000psi-in
- Aluminum 2.9" thick by 65,000psi = 190,000psi-in
- Steel 1" thick by 85,000psi = 85,000psi-in

As can be seen, Fiberglass & Aluminum are pretty close. Steel is far weaker for the same weight.

In smaller boats, the required bending strength is small enough that even though heavier, the steel plate is so thin that puncture strength becomes a concern (also working with very thin sheets is more difficult), so you need to up-size the thickness and make the hull even heavier. This can affect aluminum but to a lesser extent.

As boats become larger, the thickness required to handle bending strength becomes thick enough that aluminum thickness handles puncture issues and is thick enough to be easier to work with and you start to see lots of larger cats done in aluminum.

Steel never really gets to be effective. In very large monohulls, steel can have cost and simplicity advantages even though it is heavier but since monohulls pay far less of a performance cost by being overweight, owners can overlook the weight issues.

So far the analysis has assumed solid GRP. If you do a cored hull, the GRP easily has the best strength to weight ratio but it does come with requirements for quality construction methods. You can also get into carbon fiber and other high end composites that outperform just about everything.

PS: I believe the premise that there are lots of marine steel welders desperate for work is a false assumption. In most areas, steel pleasure boats are a rarity, so there are probably 10 times as many fiberglass guys as there are steel welding guys and the skilled welding guys are specialists in marine applications.

Unless you are building your boat, it's really simpler to work on fiberglass boats. Any chemical issues are largely offset when you realize, you need to sand, prime and paint regularly on a steel boat if you don't want it rusting away.
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Old 01-12-2017, 15:35   #27
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Re: Steel Sailing Cat - Is it Possible ?

Wilf O'Kell Custom 43ft Looking for offers For Sale | Fraser Marine
Darren at Fraser Marine has steel sailing cat for sale. I have never seen her sailing, but the owner does motor her around a lot.
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Old 01-12-2017, 16:13   #28
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Re: Steel Sailing Cat - Is it Possible ?

Concrete is available everywhere.

Why not build one in ferrocement!

People have actually done this!
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Old 01-12-2017, 16:31   #29
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Re: Steel Sailing Cat - Is it Possible ?

Originally Posted by pressuredrop View Post
a catamaran that could sink?, gasp, the fraternity would never allow it
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Old 01-12-2017, 19:12   #30
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Re: Steel Sailing Cat - Is it Possible ?

Steel and ferro-cement sailing cats??? This is getting a bit silly.

It is within the capabilities of most folks to build your own cat with resin infusion and/or a panel boat in foam, and then you'd have something worth sailing.

Steel or ferro-cement? Go build a cat trawler with a couple of serious diesels in it.

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