Do you have specific advice for posture and anatomy as it relates to trim?

[Ryan Neely]

So ... I know it has been a while since I started this thread. It's taken me that long to implement some of the advice offered and to make minor adjustments over the course of several (five) dives ... and I'm still struggling. I have to say, however, that it feels like my buoyancy is coming along great ... so long as I'm moving. (I say this at the same time I'm going to share a video of me kicking up muck at the bottom of my lake. *sigh* Seriously, though, things are coming along.)

What I'm trying to figure out is why I'm rotating to the vertical when I stop moving in the water ... anytime I attempt to maintain neutral buoyancy in a stationary position. I've attempted several of the suggestions mentioned within this thread (thanks for all of that). I've attempted to get footage of myself so I can demonstrate what I'm experiencing, but northern Minnesota lakes don't have the best clarity and my wife (and buddy) struggles with camera equipment, or task loading, or both. I'm not certain.

Anyway, what you'll see in the following video is the following. I'm at 10 feet in a fresh water lake. I'm wearing a [relatively] brand new exposure suit (5mm wetsuit, 7mm hood, 5mm gloves, 5mm boots ... the gear has 12 dives under its belt). Oceanic Viper fins, an aluminum eighty tank, and fifteen pounds of lead. The lead is distributed as six pounds in each of the integrated weight pockets (or a total of twelve pounds) and three pounds in a trim pocket mounted directly below the tank valve.

As I attempt to get into horizontal trim, I feel like my buoyancy is good (for what it's worth, my core is engaged here, my abs and glutes are working to keep my body in a solid horizontal position). However, my entire body rotates around the x-axis, as if a string has been passed through my body directly at my hips and someone has decided to spin me ... and then I start to sink. My tank is relatively high (higher than I had it during my open water checkout dives) in an attempt to add more weight to my upper body.

Of course, I could be entirely wrong about what is happening. I'd love it if anyone had any comments on what they think is going on and what I could do to improve.

(I'll also apologize ahead of time for the terrible quality of this video. It's the best I can do for now (and I'm a little embarrassed to be posting it here, but you have to learn somehow and sometimes that means allowing people to see the bad stuff so you can get to the good stuff).

[For what it's worth, I am exploring an opportunity to take GUE Fundamentals early next year. Many of you have suggested that and I'm seriously considering it. I need to get my wife on board, however. She has this fear that learning all that "technical diving" won't translate back to our recreational rig and since we don't have the funding to purchase all new equipment yet she sees it as a potential waste.

Anyway, here's the video. Any thoughts and comments sure would be useful. Thanks!

 

[WarrenZ]

Have you done a proper weight check to verify that you need all 15lbs, it looks to me that you have a fair amount of air moving in your bcd so that as you start to go head up it rushes up and rotates you.

Check your weight at the end of a dive tank at 500 psi you are aiming to have almost no air in your bcd at the end of the dive. That is also a good time to check trim as well.

As a new diver it is sometimes counter intuitive to get the correct weight. You are trying to get enough weight to sink with a half breath of air when your tank is empty at the end of a dive. Your bcd is compensating for the loss of bouancy as your suit compresses / re-expands and the about 4.5 pounds of air you will use on a dive. The more air running around in your bcd, wing, or drysuit the harder it is to trim and get neutral.

 

[MichaelMc]

You need to move more of your weight higher.

You have two centers of mass. Well you have one and the water you displaced had one.
A body wholly or partially submerged is bueyed by a force equal to the mass of the fluid displaced.

Gravity will try to put your center of mass directly below that of the water you displaced.
If the waters center was at your lower chest, and your center is at your hips, because of all the lead there, then you will rotate until your hips are down.
You need to move more of your lead higher.

Do an exercise. Take two pounds out of each hip pocket and hold them in your hands. Move you hands up your chest toward your head until you hang level. That should tell you how much you need to move your lead.

Did you play on a play ground seesaw as a child?

What you are asking is the same thing as “I have this play ground seesaw with a bunch of stuff on it and 12 lb at some spot on one side and 3 lb. at some spot on the other side. But the seesaw keeps tipping really strongly to the side with the 12 lb. What should I do to level it?”
The answer is very simple. Either:
- Move some of the 12 lb. to the other side.
- move the 12 lb. closer to the balance point.
- move the 3 lb further from the balance point.

It is that simple.

Now this particular seesaw is well lubricated. So keeping it level would be near impossible if everything on the seesaw stays fixed. So getting the weight distribution right will not keep you level forever. But moving your legs a bit will shift your balance. So a bit of dynamic adjustment will keep you level.

But your distribution looks far from close.

 

[Bob DBF]

My [perhaps illogical] understanding was that, as a means of helping to attempt to achieve good buoyancy, one must also achieve good trim. I realize that the two are different beasts, but somehow they seem related. Maybe I'm wrong there.

Good buoyancy is maintaining your position in the water column, it can be done when severely overweighted. I've been neutrally buoyant while salvaging a 15# anchor.

The best way to check for proper weighting is to have an empty BC at 15' with about 500# in the tank holding a safety stop. Just hand off weights to your buddy or place them on the bottom if it's close. I do this check regularly, it's easy if you are close already. (You can do this with any tank pressure, but will have to calculate the difference in weight of the air.). Once you have your ballast correct move on to trim.

Proper weighting is the first issue, trim is just figuring out where to put it. If you have intergral weights, check where the weights ride, a weight belt may move the weights further up on your body than the jacket placement.

Then I'd address the tendency to roll, if it still exists.

I have to say, however, that it feels like my buoyancy is coming along great ... so long as I'm moving.

Problem is that moving, if you have any up angle, will act as positive buoyancy. The only way to accurately check actual buoyancy is if you are still.


Issues of of weighting, trim, and buoyancy will be the same with any gear. Granted it may be somewhat easier with a BP/W, assuming you like the rig when you try one, however you have your own gear and are well on your way to mastering its operation already. It isn't the gear that makes a diver.


Bob

 

[leadduck]

1) In the video the breathing rate is a bit high, looks stressed. Note that the breathing pattern should be inhale-exhale-rest-inhale-exhale-rest-... Breathe slowly, do not rest inhaled, do not hold your breath. Rest with empty lungs. This makes a big difference for trim; a full lung adds some 6lb lift to your upper torso.

2) too much lead is a problem, and again, resting inhaled makes you need more lead to descend, so get calm and breathe slowly first, then you can certainly get rid of some weight and adjust trim easily.

3) steel tanks were suggested above. In cold water lakes I see no reason for aluminum. Steel has only advantages here; you'll need less lead and the weight is better distributed higher. Rent an HP80 next time.

4) how tight are your shoulder straps? You can move the BCD weight pockets further up a little by tightening the shoulder straps and shifting the whole jacket further up.

 

[chillyinCanada]

Do you have air in your bcd? At 10', you shouldn't have any air in the bcd.

You looked good there though for a moment or two.

 

[rongoodman]

Do you have air in your bcd? At 10', you shouldn't have any air in the bcd.

Assuming a near-empty tank.

 

[Ryan Neely]

Thanks for the feedback, folks. In the video, there's probably 1,600 psi of air in that tank. BCD Straps are cinched as tight as they will go. Unfortunately, the best weight check I can do right now is to gauge based on a full tank (I have yet to bring a tank down to 500 psi. We're diving so shallow that after 90 minutes the closest I can get is 1,200 psi remaining.

I'll check my breathing and look at your suggestions there. I didn't feel panicked or over-exerted, but I also haven't had "proper" breathing explained much. "Don't hold your breath," and "you should breathe the way you do sitting on the sofa watching teevee," is what I've learned so far (and, for me, breathing on the sofa watching television means long, slow, extremely deep, almost meditative breaths which, ultimately, only fill my lungs to capacity and affect this buoyancy thing ... so it's something I'm still working on).

As for air in the BCD ... I don't think there was air in the BCD, but there could have been. I feel like I hold that release valve open until nothing comes out each time I descend, but it's possible I'm only thinking that and not actually doing it. Now I can't remember. I'll make notes for next time.

Thanks again for the feedback.

 

[PfcAJ]

I think you need to get “long” under the tanks. Thinking long and extending your body will give you a longer lever to play with when adjusting the below items:

The bulk of your weight is low on your body. Your lungs are super floaty.

Minor, but your fin tips are pointed down. That’s also shifting your CoG rearward.

Your arms are out, but not forward. That’s less weight forward than you could have.

I would invest time in doing a real weight check (empty tank, empty Bc, how much weight do you need to be neutral?), not the Padi thing.

 

[laikabear]

We're diving so shallow that after 90 minutes the closest I can get is 1,200 psi remaining.

At the end of your dive, get on the surface and purge your reg til the SPG shows 500 psi. Then descend to 10 feet and see if you can hold position at 10 feet without floating up or without having to keep kicking down. If you sink below 10 feet and have to add gas to your BCD, then get back on the surface, hand off some weight, and try again, til you can sit at 10 feet without having to add gas to your BCD, but also being able to stay at 10 feet without finning down.

A lot of times new divers think they need more weight than they do to descend, because they are trying to descend while sitting vertical at the surface, and either unconsciously finning, keeping them from sinking, and/or holding their breath before descending. The end of dive 500 psi weight check should tell you how much weight you need. If you find it hard to descend with less, look at those 2 items - try crossing your legs on the surface so you aren't unconsciously kicking as you mean to descend, and make sure you're releasing the air in your lungs as you try to descend.