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Question on weighting for no BC diving

Discussion in 'Vintage Diving & Equipment' started by aquacat8, Aug 18, 2018.

  1. USdiver1

    USdiver1 Divemaster

    # of Dives: 2,500 - 4,999
    Location: Southwest Ohio

    It is important to know the buoyancy properties of your scuba cylinder: full, 1/2 and empty. Weigh yourself according to the cylinder, and your thermal protection suit. Also know how your suit changes buoyancy with depth. Neoprene compresses and loses buoyancy at depth, trilam not. If you are diving dry, stay as uncomfortable [squeeze-wize] as possible, because air will expand and really mess up your buoyancy upon ascent.

    Keep your buoyancy range within what you can control with your lungs. It takes a little practice, but once mastered, the added freedom is awesome.
    aquacat8 and captain like this.
  2. aquacat8

    aquacat8 Solo Diver

    # of Dives: 100 - 199
    Location: Savannah, GA
    Great pics @captain look be the oval mask ;-)
  3. aquacat8

    aquacat8 Solo Diver

    # of Dives: 100 - 199
    Location: Savannah, GA
    Spell check grrr I said love the oval mask!
  4. aquacat8

    aquacat8 Solo Diver

    # of Dives: 100 - 199
    Location: Savannah, GA
    My PST High pressure e-7 80 is pretty negative, about 7 1/2 pounds. Empty it is 1.5 pounds. I don’t think that includes the valve, and I imagine that plastic back pack may be a bit negative too. With what feels like an empty wing and wearing three mill I am diving it with no weight in salt. So it has a 6 pound buoyancy shift though in reality I experience less because I don’t drain the tank. Say five. It might be too heavy for this type of diving, In which case I may try an aluminum 63, for the shallow shore dives. I am so over aluminum 80s, they are just too heavy and bulky for me! My favorite tank was my steel 72s, but they don’t seem to be making those anymore.
  5. aquacat8

    aquacat8 Solo Diver

    # of Dives: 100 - 199
    Location: Savannah, GA
    Yeah the PST E7-80 is -2.5 empty, -8.5 full with valve
  6. herman

    herman Divemaster

    # of Dives: 500 - 999
    Location: Raleigh,North Carolina
    The actual buoyancy of the tank really does no matter as long as you are not over weighted with it alone, it just means you need less lead. If you are over weighted by more than a couple pounds at the beginning of the dive, that's too much. The shift in buoyancy is what matters and a 5-6 shift is not bad as long as you weight yourself at mid tank pressure, if nothing else, you can end the dive a little early and control the swing that way....just gives you extra reserve gas. This gives you a +/- 2 to 3 lb swing which is easy to control unless you are a really small person, the larger your lung capacity, the more swing you can easily handle. I typically dive AL 80s, in fresh water I use no lead, in salt I use around 4 lbs.

    Steel 72s are pretty easy to find. Keep an eye on the local for sale papers, they show up fairly often and unless abused, even very old ones are usually fine.
  7. aquacat8

    aquacat8 Solo Diver

    # of Dives: 100 - 199
    Location: Savannah, GA
    Cool thanks Herman! I guess I won’t know til I try... hopefully this weekend :)
  8. Bob DBF

    Bob DBF Solo Diver

    # of Dives: I just don't log dives
    Location: NorCal
    +1 on old steel 72's. It's a lot easier learning old diving skills with the equipment that was used at the time, and then work up. Also old 72's are pretty cheap.

    Another thing, a snorkel is your friend. With neutral buoyancy you can rest on the surface snorkeling, if you go vertical you will need to fin to keep your head up, tireing. A snorkel vest can be used for surface buoyancy, unfortunately they don't make them with co2 inflators anymore.

  9. kablooey

    kablooey Divemaster

    # of Dives: 1,000 - 2,499
    Location: San Diego
    I remember my first backpack dive, and how worried I was.

    Would I sink to the bottom, never to return?

    So, I planned for weeks before actually making the dive.

    At the time, I didn’t know anyone else diving a backpack who I could ask about weighting.
    I just did some rough calculations, and hoped for the best.

    I also gave a lot of thought about where to make the first dive. I wanted a place where I could abort easily if something went wrong. I finally decided to do it at the Avalon Dive Park on Catalina Island. It’s an easy shore dive with cement steps leading into the water, and east facing so no surf entry.

    My buddies were carefully chosen. Both highly experienced, and well known to me.
    I knew they’d watch over me.

    In the end it was no big deal.
    My weighting calculations were close enough, and I drifted through the kelp forest comfortably neutral.
    It was a beautiful dive, which included several Giant Black Sea Bass sightings.
    And the light streamlined feeling of the backpack… I was hooked.
    captain, Eric Sedletzky and aquacat8 like this.
  10. Eric Sedletzky

    Eric Sedletzky Contributor

    # of Dives: 500 - 999
    Location: California
    When I started backpack diving I just used my freediving experience and techniques.
    I adjusted my weights about 5 lbs lighter based on calculations I made and went for it. It was about the same as freediving except I could breathe underwater. I’m pretty sure the very first scuba techniques including backpack diving grew out of skin diving.
    Bob DBF and aquacat8 like this.

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