If there are any nautical buffs here.

[never_retreat]

Couple of friends of mine just brought up the bow bell of the Andria Dora.

Here is a link to a video of the first ringing since 1956.

http://pierdive.com/andrea-doria-bell-rings-out-again/

[myrockfight]

That is a hell of a feat. Just getting to dive that wreck takes more discipline and training than most people can muster over half their lives. To pull off something of that size and weight isn't something just anyone does - even well-trained/experienced divers.

One of my co-worker's dive buddy died on that wreck. Just recovering his body took a hell of a lot of planning. Made him swear off diving, but we worked together on another project a while after that. However, it wasn't anywhere near as technical.

Congratulations are in order. I'm sure there are a lot of jealous divers out there reading about it.  *thumbs up

[geronimotwo]

i'll give 'em 5 bucks for it!

[never_retreat]

Local fish wrap article.
http://www.nj.com/news/index.ssf/2010/06/two_nj_divers_discover_histori.html

[230RN]

Qs from an almost-total landlubber:

The bell, which weighs about 75lbs and stands two feet tall, is one of the few artifacts which has the ship’s name engraved on it.

Seventy-five pounds seems a little light for a bell that big.

myrockfight made mention of the difficulty in recovering these things.

How do they get these artifacts (like "portholes") to the surface?  Do they bring flotation devices down with them? How's that work?  Do they inflate balloons or something with CO2 cartridges, or what?

Under water, stuff is a lot lighter due to bouyancy, no?  (I remember reading something about some recovery effort where everything went well bringing something up with a winch, but as soon as the article broke the surface, the lines parted due to the sudden increase in weight as it came out of the water.)

Terry, 230RN

[never_retreat]

Qs from an almost-total landlubber:

Seventy-five pounds seems a little light for a bell that big.

myrockfight made mention of the difficulty in recovering these things.

How do they get these artifacts (like "portholes") to the surface?  Do they bring flotation devices down with them? How's that work?  Do they inflate balloons or something with CO2 cartridges, or what?

Under water, stuff is a lot lighter due to bouyancy, no?  (I remember reading something about some recovery effort where everything went well bringing something up with a winch, but as soon as the article broke the surface, the lines parted due to the sudden increase in weight as it came out of the water.)

Terry, 230RN

Good questions.
I'm not sure of the weight but hopefully I will get to touch it in the next few days. I'll let you know.

The usual method of lifting stuff of the bottom is a lift bag. Essentially a waterproof type canvas bag open on the bottom with some attachment hardware. Tie it on with some rope, and then blow air into it with your regulator. Once it starts to rise the air will expand and the extra will come out that open bottom.

Certain things have different weights in water. It has to do with there actually weight and how much water it displaces.
Concrete and rocks are quite lighter underwater than on land. Metal is heavy for the most part either way.

[230RN]

Certain things have different weights in water. It has to do with there actually weight and how much water it displaces.

Thinking about it, I can see that.

A cubic centimeter of water weighs one gram.

If a cubic centimeter of lead, which weighs 11.35 grams, is put in water, it will displace a cubic centimeter of water, which means it will "weigh" one gram less under water, or 10.35 grams due to bouyancy effects.  This is 91% of its original "weight" in air.

But if you do the same thing with a cubic centimeter of aluminum, which weighs 2.7 grams, it will then "weigh" only 1.7 grams under water, which is 63% of its weight in air.

So, as you say, aluminum (or concrete or rocks) will appear to weigh a lot less underwater, compared to lead, which would not weigh that much less.

(This assumes fresh water, of course.  The effect would be magnified in salt water.)

<scratches head>

Does that sound right?

And thanks for the explanation about "lift bags."  Sounds a lot simpler than trying to inflate a balloon down there --and thanks for pointing out that as the air expands as it rises in the water, it can come out the bottom of the lift bag!

Duh.  Told ya I was a land-lubber!

Terry, 230RN


 

[HankB]

Reminds me of a story I heard from the company nurse (now retired) who knew one of the radio operators on the Stockholm, which collided with the Andrea Doria. She got quite an earful from him.

Now, I know I'm a couple of links removed from the eyewitness so I can't personally vouch for his veracity, but he said that the first wave of lifeboats fleeing the sinking liner was filled entirely with crew, not passengers. The crew abandoned ship first  and the Stockholm's crew had to pilot the lifeboats back in order to rescue the balance of the passengers.

I understand the guy made a number of rather disparaging observations about the capability of sailors from the Mediterranean . . .

[never_retreat]

Here are a few pics of lift bags if your interested.

Normal size

Big boy.

[230RN]

So you sink it down to the salvage area with a 10,001 lb weight, hook it onto the goodies, then release the 10,001 lb weight so it floats up, right?

(I'm not signing this one so nobody will know who posted it.)

[Tallpine]

So you sink it down to the salvage area with a 10,001 lb weight, hook it onto the goodies, then release the 10,001 lb weight so it floats up, right?

(I'm not signing this one so nobody will know who posted it.)

Yeah, but how do you get your weight back up to the surface     

[230RN]

Actually, with those numbers, the bag would float a small distance below the surface because the water pressure would collapse the bag just enough to establish neutral bouyancy.

Say, who wrote that, anyhow?