Improving trim?

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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.

Yeah, but did you see his answer? Read it carefully:

I've done both full and empty actually. When it's full, I sink below the surface - when it's ~800psi, I'm at eye level.

That sounds like he *didn't* do the check, or at least doesn't understand it.
 
Yeah, but did you see his answer? Read it carefully:



That sounds like he *didn't* do the check, or at least doesn't understand it.

What is the proper check? Hmmm...
Hold a breath with no air in BC and see where you float, yes?
I did that and with 12lbs, I sunk below the surface (about 1 feet below) I can't remove any more weights because I already had slight trouble descending with that weights (previously, I used to dive with 14 lbs).

Edit: by "slight trouble" I meant I usually had to bring a rock or two :D then throw them away once I reach the bottom (~15-20') ...
 
Sounds like you need to find an instructor that will do a non cert workshop focusing on buoyancy and trim tailored to you specifically. I do this for people all the time. I once had a guy come in and we spent 4 hours in the water where we got him trimmed and properly weighted using his 3 mil suit, 5 mil suit, and 7 mil suits. Then we wrote down all the various weights that were needed and where they were placed. We used al80s because that was what he usually rented.
I've also done it with people using steels.
You don't hold the breath to see where you float. You weight yourself so that you can exhale and descend and with a cylinder at 500 PSI you should be able to hold your safety stop.
If you can't descend with an empty BC upon exhaling, you don't have enough lead.
"Edit: by "slight trouble" I meant I usually had to bring a rock or two :D then throw them away once I reach the bottom (~15-20') ..." This is a good way to end up in a bad situation when you don't have enough weight to hold a stop.
What kind of BC are you using? Does it have trim pockets? Many do but they are placed so they are mostly useless.
Are you using a weight belt in combination with the BC if it's weight integrated?
How do you have your weight distributed?
How many times did your instructor make you do a check?
I have an entire chapter in my book on weighting and trim and I tried to post an excerpt but it won't let me copy and paste.
 
If you can't descend with an empty BC upon exhaling, you don't have enough lead.

I'm not super convinced that 12lbs is not enough for me. (I've previously asked for advice here since I was over-weighted before and 12 seemed like a sweet spot).
With 14lbs, I kept sinking to the bottom as soon as I stopped kicking. Even if I inhale fully, I barely raised from the bottom.
Hard to do 13lbs (odd number), so 12lbs it is, right?
 
@alex_can_dive

Position yourself in 15 feet depth of water, empty your BC and purge your second stage till your tank is at 500 psi. If you sink your overweight if you gloat your under.
 
I'm not super convinced that 12lbs is not enough for me. (I've previously asked for advice here since I was over-weighted before and 12 seemed like a sweet spot).
With 14lbs, I kept sinking to the bottom as soon as I stopped kicking. Even if I inhale fully, I barely raised from the bottom.
Hard to do 13lbs (odd number), so 12lbs it is, right?

At the beginning of the dive with a full tank you will be heavy. As you use your tank the weight will decrease so less air in the BC. The idea is to be able to hold your safety stop.
 
@alex_can_dive , so far your descriptions of buoyancy checks are not good buoyancy checks, nor are your descriptions descriptive enough of the details to really answer if you're even doing them well or not.

Here is details about how to tackle this stuff. In reality you should get in the water with an instructor for a session to do this. This is taken from another reply I wrote for someone having trouble with controlled descents, but I felt it might be relevant here.

You'll need to do this the first few times you make big changes to your equipment. Overtime you'll be able to ballpark equipment changes without going through the whole process, but for now I'd do this with each configuration you do.

Note, you might be "forced" into something uncomfortable with the hp100 given your height to trim out. But, importantly, you can trim just about anything. Whether it's comfortable is another question, and you might have to change gear. But before you worry about trim you should really have these things on point:
  • Weight
    • Solution (fixing this first will make practicing everything else easier):
      • Do this in an easy location where you can take your time. I find easy shore dives (protected cove or lake) are good for this (not a lot of surge, current, etc)
      • To get the minimum weight you need to dive, go to a place that has a 12-18ft bottom (15ft is ideal). You can do it off a boat with a good buddy but I prefer a shore dive since you aren't in a rush or anything, and it's easier IMO.
      • At the end of the dive, with around 500 psi, empty all the air our of your BCD. Get it totally empty.
      • If you're in a drysuit dump air until you've got the minimum air to be comfortable and warm.
      • Start removing a little bit of weight at a time (easier if you do this exercise with pouches)
      • After removing weight, wait a second, and see if you can go up and down with your breathing alone
      • If you can't control your buoyancy comfortably (without excessive inhalation), remove more weight
      • Once you hit the point where you feel too light, meaning even slight inhales start to cause you to rise up, add back 1lb at a time until you can breath comfortably while gently rising and falling. That's "neutral".
      • Repeat this exercise every once in a while as your breathing and buoyancy control gets better (you'll likely need less weight).
      • Repeat this exercise when you make big gear changes (drysuit, different mm wetsuit, different tank size/type, etc).
  • Over-relying on your BCD for buoyancy control
    • Common issue for new divers
    • Compounds with being overweighed, but still an issue if you're not overweighted
    • Are you frequently are adding and removing air from your BCD during your dive? Do you end your dive by adding air, and begin your descent by rapidly releasing air until you start descending?
    • This can cause divers to over-weight themselves since they think they "can't" stay down without being overweighed.
    • Solution (easier to practice if you're not overweighted):
      • Do this in an easy location where you can take your time. I find easy shore dives (protected cove or lake) are good for this (not a lot of surge, current, etc)
      • Step 1
      • Descend to 10-15 feet normally, however you do it now.
      • At the bottom, get neutral and practice hovering a few feet of the bottom. If staying still is hard, that's ok. Lightly moving forward/in a circle is Ok. Eventually try to do this staying still.
      • "Play" with the air in your lungs and how it impacts your buoyancy. Take a deep full breath and feel yourself rise. Exhale fully and feel yourself sink. Try breathing "full", keeping lungs 40-80% full (don't do this for long, full exhales are important to get rid of CO2). Try breathing "shallow", keeping lungs 20%-60% "full". In both cases you should gently move up and down, but a little more up over time or a little more down over time depending on full/shallow.
      • Once you're comfortable with this, and can manage your buoyancy with a 5ft swing up and down without using your BCD, go to step 2.
      • Step 2
      • Get positively buoyant at the surface.
      • Test your regulators at the surface with five good, full breaths, and watch your SPG (if it drops dramatically or wiggles when breathing check your valve is open all the way). You'll be descending with empty lungs so you don't want a surprise when you try to inhale.
      • At the surface, over a 10-15 foot bottom, release only a little air at a time from your BCD. If you start to sink, add a tiny bit more back in.
      • Each time you release a bit of air, wait a second, and then completely and forcefully exhale air out of your lungs. If you start descending, then don't release any more air from your BCD. And don't take any deep breaths. Leave your lungs empty for a few seconds as you descend. Make sure you aren't kicking sub consciously.
        • Let yourself descend a few feet and then take a slow, shallow breath. If this makes you shoot back up to the surface that's OK. That's why you're practicing.
        • Try again a few times, see if you can descend down to 10-15 ft without releasing any more air from the BCD.
        • Try again, but this time, control your breathing like you did in step 1 and see if you can descend down to 10-15 feet, and then hover, without using your BCD, only your lungs. .
        • When you go deeper, do the same thing for your initial descent from the surface (Just enough air in BCD that you can exhale to descend), only this time add tiny shots of air to the BCD as you descend. But only add enough air so that you can control your buoyancy primarily with your lungs. Exhaling at any time should make you descend, inhaling should make you ascend.
        • At any time you should be able to stop going down by breathing in deeply, or stop rising by exhaling fully.
 
Back to trim for a second, can you describe exactly what happens when you try to hold a position in the water? Set your BCD, use mid-lung capacity and try to hover off the bottom enough that your fins don't touch, and don't move. You will then rotate head down, feet down, or maybe stay in good trim - you want to figure out which. With this info about your basic trim tendency, you can make a better determination where weight needs to be placed.

If you feel your feet are too heavy then you can do a bunch of things (reverse these if you're head heavy):
- shift your tank higher or put trim weights nearer the valve.
- bend your knees to bring the legs closer to your body so the lever arm is reduced.
- extend your arms out
- lighter fins

If you're not able to get your body into horizontal trim and you sink when not swimming, then you may be foot heavy. Your goal is to be able to swim, stop finning, and stay in nice trim while you coast to a stop. I think several posters are asking the same thing.

Your trim is likely contributing to your buoyancy problems if you sink when you stop finning. It's that upward attitude from your trim that contributes an upward force while you fin, which compensates for having insufficient air in your BCD. Then when you stop, you sink because your BCD doesn't have enough air for neutral buoyancy. When you check your weighting, make sure you're not finning at all. It sounds like your weighting might be in the right ballpark anyway and it's trim that you should be looking at right now.

Given an HP100 is roughly the same dimensions as the AL80s that many divers seem to be OK with, I think you should be able to make it work by moving weights around before trying to go down the HP80 route.
 
Thanks! haven't got a chance to go dive yet - will try out these tomorrow !
 
I'm not super convinced that 12lbs is not enough for me. (I've previously asked for advice here since I was over-weighted before and 12 seemed like a sweet spot).
With 14lbs, I kept sinking to the bottom as soon as I stopped kicking. Even if I inhale fully, I barely raised from the bottom.
Hard to do 13lbs (odd number), so 12lbs it is, right?

Advices here have the purpose of giving you a direction for actual in-water tests. The conclusions should then come from the in-water test.

Empty your mind, go out and do a proper weight check, possibly with a good instructor. That will give you the answer about the right amount of weight.

Then, think about your trim.

Good in-water time :)
 
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