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Tank Help

Discussion in 'Tanks, Valves and Bands' started by JSO1, Aug 16, 2001.

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  1. JSO1

    JSO1 Garibaldi

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    I am new to diving, and always research equipment before I buy. I am stuck however on what type of tank to buy for the best service. I suck-up air right now, and know I want at least a 100cf tank. But my problem is Steel or Alum. and High or Low presure. I know most of you experts get this same question a lot, but please one more time ? Thanks
     
  2. Lost Yooper

    Lost Yooper Loggerhead Turtle

    # of Dives: I'm a Fish!
    Location: Panama City Beach, FL
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    The rule of thumb I learned, use, and tell others, is to use AL tanks with a wet suit and either AL or ST (I like steels) with a dry suit. Steel tanks and wet suits may not allow you to ditch enough weight (if any is needed at all) in an emergency. You want all the ditchable weight you can get with a wet suit. Make sure you are correctly weighted and balanced. You SAC will get better as you continue to dive, but bigger tanks are not the entire answer to your problem. You just need to get in the water, and it will come. The AL 100 is a decent tank.
     
  3. large_diver

    large_diver Loggerhead Turtle

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    Mac,

    Take a look at some of the threads in this section of the board -- this is a topic that comes up frequently. Here are a couple of key facts to consider:

    HP Steel Tanks:
    - Smaller in size, weigh less, and have more negative bouyancy than an Aluminum tank of the same capacity. Steel is stronger than AL -- therefore you use less metal and can pump the tank up to greater pressures, resulting in more volume and less weight
    - Some shops/resorts can't fill HP tanks to capacity, negating the lower "weight per volume" advantage.
    - With most HP tanks, you need to use a DIN fitting on your reg.
    - Steels can rust

    LP Steel Tank:
    - Heavier and physically larger than HPs
    - Less negative bouyancy than HP, more than AL
    - Lower pressure rating = easier to get complete fill
    - Yoke or DIN
    - Steels can rust

    Aluminum:
    - AL -- larger/heavier than HPs
    - Neutral bouyancy when full; positive when empty
    - Yoke or DIN

    Check this thread out -- long, somewhat contentious, but informative.

    http://www.scubaboard.com/showthread.php?threadid=905&pagenumber=1

    Hope this helps.
     
  4. scubakat

    scubakat Senior Member

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    I'd be very interested to learn about the buoyancy characterictics of the AL100. I had a buddy who was always changing the size AL tank hw used from dive to dive. I don't think that he understood the differences or adjusted his weight, and he had chronic bouyancy control problems.

    -kate
     
  5. large_diver

    large_diver Loggerhead Turtle

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  6. blacknet

    blacknet Loggerhead Turtle

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    Hello,

    that's why DOT recomends these 'at risk' people do the PSI cert for inspection.

    Another thing that was not mentioned: AL is more oxygen friendly than AA is.

    Ed
     
  7. rcohn

    rcohn Manta Ray

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    Lost Yooper,

    Since the Al vs. steel issue has come up yet again I'll repeat the following which explains the logic behind the dogma that is so frequently repeated and misunderstood. Note that George is talking about LP doubles (only a stroke would dive HP tanks).

    For many of us diving single lightweight HP steel tanks in 7 mm wetsuits, there is no problem is satisfying George's criteria. Divers may carry 25 to 50 lb of lead and a PST HP100 is only 5 lb more negative than an Al80. The cylinder's overall weights are nearly identical, so with 5 lb off the belt the diver is actually safer moving around on a boat. All ballast does not need to be ditched to become positive unless you are diving very deep.

    Ralph

    http://www.aquanaut.com/bin/mlist/aquanaut/techdiver/display?46829

    From: "George Irvine" <kirvine@safari.net>
    Subject: Re: DIHUL, was: Fins question
    Date: Sat, 24 Feb 2001 12:24:09 -0500

    I keep saying it - weight yourself so that with little or no gas you can hover at ten feet, and with full gas you can swim up with no inflation by dropping something.

    That covers it.

    For tank choice in ocean, big heavy tanks are dangerous boat diving, so are not my first choice. I'd rather add a stage and dive it dry , leaving my back gas intact.

    Cave diving is different in that you need more gas to go farther and the decompression is in a safe environment,not open sea with all its vagaries.


     
  8. large_diver

    large_diver Loggerhead Turtle

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    thanks for the props. Eventually even us idiots start to learn something if it is drummed into our heads several times.... :bonk:

    Mac,
    The link below is a VERY useful tank FAQ written by someone over on scubadiving.com. Note that the navigation is a little tricky on this -- there is a Tank FAQ and Tank FAQ part 2....the link takes you to the top of part 1. You can get to both by clicking on the table of contents, but if you simply scroll down through tank FAQ part 1, you won't see tank FAQ 2 -- you'll need to go back up and click on the next topic on the T of C.

    Bottom line -- lots more detail than my brief summary

    Good luck
     
  9. Lost Yooper

    Lost Yooper Loggerhead Turtle

    # of Dives: I'm a Fish!
    Location: Panama City Beach, FL
    2,082
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    Ralph, I agree. However, I used a single HP 120 and a single LP 120 and a 3mm shorty a few times and they were way too negative -- as I didn't need a weight belt. Had something occured that would have required me to get up from 100', it would have been a trick. Those were some of the more foolish days of diving I've done. Caution and awareness has to be used if you intend to use steel tanks and a THIN wet suit.

    Mike
     
  10. JSO1

    JSO1 Garibaldi

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    Thanks to everyone who helped me, I will get the Alum. 100 for now. The information provided has been some of the best I have ever seen on this topic. Again thanks to everyone
     
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