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Old 18-06-2010, 15:32   #181
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Het guys, It is ussually understood that aluminum is STRONGER than steel as built. Not that it really matters but I hate to see missinformation flying around. This article summerises it pretty well if anyone really cares. They both will take what you can give them.
Aluminum Strength vs Steel Strength
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Old 18-06-2010, 15:41   #182
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Well, a fella can't help but wonder why virtually all ships are made of steel if aluminum is "stronger" ya' know?

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Thomas
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Old 18-06-2010, 15:42   #183
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Certainly is a wealth of opinion and experience on this subject. Having built steel and aluminum yachts, and sailed a steel one 80,000 nm over ten years, my two cents worth is this;
As others have stated, so much of it is in the design/build stage. If you get it right there the rest is easy. If you build in corrosion traps they will haunt you until you fix the design, not cover up the rust. Urethane foam insulation 50mm+ thick is a great way to protect the inside, and yes, painting the foam surface really does work in making it vastly more durable where it might get knock around a bit. Think inside a locker full of canned food beating to windward for a week. After a decade of hard use the insulation on my steel cutter was good as new, and never did we have a problem with rust inside the boat.

Welding is not hard to learn, but it is hard to do really well. As an engineer I have been appalled by some of the builds/repairs that I have seen. Another thing that I have not read on here is about selection of rods(electrodes). There is a vast range available to suit all of the different applications/positions. If you are going to try and do it all with a box of GPs from the hardware store you will end up with a sub-standard result. Use the right tool for the right job. Some electrodes require AC others DC so have a machine that will output both.
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Old 18-06-2010, 15:50   #184
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Originally Posted by Yachts66 View Post
Well, a fella can't help but wonder why virtually all ships are made of steel if aluminum is "stronger" ya' know?

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Thomas
Because it's a cheaper material...
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Old 18-06-2010, 15:54   #185
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Because it's a cheaper material...
Even if the price was the same, aluminum wont take the flexing that a large ship endures. Test this for yourself with a strip of steel and a strip of ali. The ali will give after 2 to 3 bends.
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Old 18-06-2010, 15:55   #186
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Ahhhh but that's not what they are claiming. They say that because it has no need for paint and is faster to build with, the original higher price for the material becomes moot. Still, ships and large fishing boats are made of steel. Imagine that!

One thing is very true, resale value on an aluminum boat is higher. I can't help but wonder if some of that is due to the public's perception of the material though. I mean there are actually people out there who like Chevy's for Pete's sake!

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Old 18-06-2010, 15:57   #187
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Well, a fella can't help but wonder why virtually all ships are made of steel if aluminum is "stronger" ya' know?

Regards,

Thomas
Seems like just the kind of logic that leads to the missinformation. Do you think designing and building a 100 ton ship is similar to a relatively small yacht? Do you think strength is in and of itself the determining factor in ship construction? The information is out there. Take a look.

Anyway, heres a good example of the wonderful strength of steel. Center mass T-bone with a tanker. Increadible! It sailed quite a distance but probably with a little less effiiency.

(If you understand aluminum vs steel you can see the increadible plasticity of steel here. Aluminum wouldn't have "yielded"..would have bounced.)
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Old 18-06-2010, 15:58   #188
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Ya' know, we could really make this thread interesting and discuss the relative merits of mono hulls over cats! ;-)

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Thomas
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Old 18-06-2010, 15:58   #189
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Seems like just the kind of logic that leads to the missinformation. Do you think designing and building a 100 ton ship is similar to a relatively small yacht? Do you think strength is in and of itself the determining factor in ship construction? The information is out there. Take a look.

Anyway, heres a good example of the wonderful strength of steel. Center mass T-bone with a tanker. Increadible! It sailed quite a distance but probably with a little less effiiency.

(If you understand aluminum vs steel you can see the increadible plasticity of steel here. Aluminum wouldn't have "yielded"..would have bounced.)
Oops, here's the pic...
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Old 18-06-2010, 15:59   #190
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Because on larger ships, the skill factor required for alum may be higher and costly - more skilled workers. On small vessels the labour may offset material cost, but these costs are not a steady state and linear as the size and thickness increases.

Because its easier to melt down the mega ships out there and recycle to new ships.

i dunno
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Old 18-06-2010, 16:01   #191
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Darn those tankers anyway! They think they own the ocean! Worse are the tow boats on the ICW, they not only think it, they know it! LOL

Regards,

Thomas
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Old 18-06-2010, 16:04   #192
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Even if the price was the same, aluminum wont take the flexing that a large ship endures. Test this for yourself with a strip of steel and a strip of ali. The ali will give after 2 to 3 bends.
Aluminum as built doesn't flex like steel. It is built to different limmiting factors. It isn't "better" wood isn't "better" than fiberglass or fiberglass than aluminum. It is different though and understanding the materials before spreading missinformation is probably a good idea.
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Old 18-06-2010, 20:42   #193
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Sure is, and he eventually sold it for $5.00 as scrap.
To be fair, as I know the story, he had her moored almost in the surf line, and he was inside yucking it up with some famous author (Miller?) when the storm hit. Apparently there were several rows of boats all crowding the beach. He, and several others, tried to get out but could not because of boats outside of him dragging.

His hull was fine but she was down flooded with sand.

I can't recall who wrote the story, but I read it within the last year. Lin and Larry perhaps.

Yes, there it is. Lin and Larry "Capable Cruiser" chapters 30, 31, 32.
30 - What Happened at Cabo San Lucas
31 - Voyagers Lament
32 - Technical Report from Cabo San Lucas

And Bernard got another boat, a 31 foot steel boat. He thought the Joshua was too large for him. As I recalled he got the hull built and took off with no interior furnishings opting to work on her as he went.
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Old 19-06-2010, 00:17   #194
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As I recall, Joshua was battered by the surf for several days, as were all the boats who were anchored off the beach. This accounts for her being full of sand and water. She was also the only boat to survive that battering, the rest (mostly fiberglass and wood boats as I remember the story) were destroyed.

Say what you want, I'll still go with steel or maybe aluminum.

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Thomas
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Old 19-06-2010, 06:49   #195
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A few got off, the lucky ones, many did not. Joshua's hull was OK. It was not so much she was battered by big surf but partially submerged at high tide. That eventually got through her topsides. A couple of young blokes had been trying to help him get her off. He got discouraged and depressed and walked away, feeling the recovery was too much for him, and essentially giving the boat to the good Samaritans.

Apparently there was little to no heavy machinery in the vicinity to help with the recovery. People were digging with borrowed shovels.

Lin and Larry wrote more from the perspective of analyzing the effectiveness of a ground tackle system and methods for staying out of trouble. They were there on the beach one or two days after the event and were first hand witnesses to the recovery efforts and did some forensics.

Now I'm going to have to go back and reread those chapters.
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