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Improving trim?

Discussion in 'New Divers & Those Considering Diving' started by alex_can_dive, Jul 22, 2021 at 1:14 PM.

  1. lowwall

    lowwall Contributor

    # of Dives: 200 - 499
    Location: Chicago
    1,914
    2,040
    The amount of air to add to your BC is just enough to make you neutrally buoyant. Trim is what happens when you are neutral and stop moving.

    So what happens at depth when you are neutral and stop moving?

    Next question is what kind of BCD and how much weight do you have? BCs with large lift capacity can make holding a desired trim difficult as the air moves around. The weight is because I'm trying to figure out whether to recommend a steel or aluminum backplate to replace your BCD :)
     
    ginti likes this.
  2. Marie13

    Marie13 Great Lakes Mermaid ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Great Lakes
    9,161
    7,828
    I’m 5’5” and a HP100 was almost too big for me single tank.

    You should see about trying a smaller tank. A HP80 would be ideal. They are nice little tanks for us shrimps for single tank diving. They are about 4” shorter than a HP100.

    Sometimes gear doesn’t work for you and you have to try something else.

    Know someone who is 4’11”. AL80s are too big for her. She has to dive AL63s.
     
  3. Wibble

    Wibble Contributor

    # of Dives: 500 - 999
    Location: UK
    1,004
    750
    Wonder if your air consumption will improve with correct weighting and trim. Your SAC (Surface Air Consumption) will get much better as you get used to diving and become more comfortable underwater. Being overweighted and out of trim will definitely mean you use more air.

    Generally speaking, smaller people consume less air -- simply because there's less mass.

    Smaller tanks could be better for you as they may reduce your SAC.
     
    Merlyne and Marie13 like this.
  4. Scott

    Scott Technical Instructor

    # of Dives: 2,500 - 4,999
    Location: Salt Lake City, Utah
    2,517
    844
    Sometimes we make poor purchasing decisions that no matter the effort put in to making them work, it just doesn't.
    My wife is 5'3 also and the only time she uses an AL80 is on vacation. For local, she took over a pair of LP80's I had and those fit her perfectly. For teaching it's an AL63.
    I would really consider trading someone for another cylinder if possible or selling the 100 and buying something else, a HP80 as Marie mentioned. See if a another diver has another cylinder you can try. You might be surprised at the difference.
     
    Marie13 likes this.
  5. lowwall

    lowwall Contributor

    # of Dives: 200 - 499
    Location: Chicago
    1,914
    2,040
    Agreed. I suspect swapping the BCD for BP/W may help more then swapping an HP100 for an HP80. But it's a lot easier to test the HP80 hypothesis since you can just rent a tank. It would also be a cheaper fix given the resale value of HP100s.
     
  6. formernuke

    formernuke ScubaBoard Sponsor ScubaBoard Sponsor

    # of Dives: I just don't log dives
    Location: New England
    3,109
    2,799
    If you decide to sell the 100, let me know. At 6'2 they are my preferred single tank tanks.

    I would highly recommend renting a steel 80.

    Reminds me of many many years ago when a 5'5 guy couldn't wanted to use HP 120's.
     
  7. Marie13

    Marie13 Great Lakes Mermaid ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Great Lakes
    9,161
    7,828
    Can steel 80s be rented in your area?
     
  8. Moerae

    Moerae Registered

    23
    24
    I think a lot of people are waaaay jumping the gun talking about trim, changing tanks, etc etc.

    This sounds a lot less like OP needs help fixing trim and a lot more like OP needs an overall lesson on weighting, buoyancy control, and then trim.


    As a first step, are you weighted correctly, @alex_can_dive?

    Trim is a lot harder to work on if you're over-weighted.

    Have you done a weight check at the end of the dive with roughly 500psi @ roughly 15ft (this means checking that you are neutrally buoyant at 15ft with 500psi in your tank, and zero air in your BCD, and minimal air in your drysuit if you use one)?

    Can you hold a neutrally buoyant position and adjust up and down with your lung volume?

    Do you have an instructor you're working with you can talk about buoyancy with? Maybe get a pool session in?
     
  9. formernuke

    formernuke ScubaBoard Sponsor ScubaBoard Sponsor

    # of Dives: I just don't log dives
    Location: New England
    3,109
    2,799
    East coast divers had them pre covid not sure now that they have remodeled.

    I'm not not sure which part of the state the OP lives in.
     
    Marie13 likes this.
  10. formernuke

    formernuke ScubaBoard Sponsor ScubaBoard Sponsor

    # of Dives: I just don't log dives
    Location: New England
    3,109
    2,799
    I tend to agree with you in general hence why I asked if the OP had done that check.

    With that being said hp100 and 5'3 is not a good combination.
     
    Marie13 likes this.

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