Weighting Paradox

[Pinecube]

But, with my current setup, if I empty my BC at the safety stop, I sink. Conventional wisdom says that means I'm over weighted. However! When I start my dive I always have to work a little to get down the first few meters. I flap like an injured seagull on the surface when I'm trying to descend. Once I'm down to about 3m, I then sink just fine.

The one thing that I was taught was that people will exhale and deflate their BCD at the same time. The problem is that it takes a bit for the BCD to deflate and by the time the diver starts to sink, they are already inhaling. The trick (if you can call it that) is to inhale as you deflate your BCD. As it becomes empty, slowly exhale. One other thing is to also be mindful of your feet. Even small movements of your knee or ankle can move your fins enough to slow or stop your descent.

I'll echo what others have said too, if you need another 0.5-1kg it's really not a big deal.

 

[sunnyboy]

Nice summary, but I would disagree with you on one relatively minor point: Just because your weighting allows you to hang horizontally, does not mean you can hang head up or head down as needed. That takes some additional tweaking of your weight distribution to be able to hang in whatever attitude you need at the time. I have spent a LOT of time messing with this...

You should not have to spend a lot of time messing with trim, if other things are good.

For example, my first drysuit is now way too big. If I dive it I do notice it's much harder to hold good trim because I'm chasing the bubble in the suit. With that suit, it's easier to just take off squeeze and use the wing for buoyancy.

On the other hand, my new suit fits beautifully - not too loose or snug. As as result, I can use the suit for buoyancy and still have no issues with trim or position because there's no bubble of air in the suit that's throwing me off.

An other example - my first wing was way too big, even for doubles. I had a hard time with trim. I thought it was me. Then I bought a correctly sized (smaller) wing and in one dive the trim issues were gone.

 

[mnjhuz76]

What makes me wonder a bit is, that (according to your profile) it took you 100-199 dives to figure out you might have a weighting problem.
Or did you change your config recently and struggle since? If so, what did you change?

 

[cainslie]

Thanks for all the helpful comments guys. Firstly, here's a little more info on my gear (for context) and I've replied to some of the comments inline below.
Mares Pioneer 5mm wetsuit
Tigulio T52 Hover BCD with 2kg in each pocket
15lt steel tank.

During a dive (most of my diving is between 20m and 30m), I can get my buoyancy pretty much perfect every time. Invariably I get down, add some air and then use my breath to control my depth. I would say I'm pretty damn good with my buoyancy - I'm just being fussy with this question.

I should also clarify - all this nonsense is only a 10 or 15 second affair - it's not that I spend a minute or two trying to descend. I'm probably making a fuss about nothing - nobody has ever commented on my descent - I'm just a bit of a perfectionist. (And I'm that guy who will continue to work on my weighting until I can dive safely with no weights... - might have to lose some belly first though, haha.)

Stop chasing your tail. If you're sinking SLOWLY at the end of the dive with no air in your BC, I wouldn't worry about it.

I do sink slowly at the safety stop. I'd love to be able to do the motionless hover at 5m though. TBH, I'm not worried about my weighting, I just like to get things very right.

How much gas do you have at the safety stop? The key thing is to remember that if you are at that stop with 20 bar in an Alu tank you will have different buoyancy to 60 bar in a steel.

I agree it is a worthy goal to reduce lead as much as possible but it is also important to be able to hold a mandatory deco stop in an OOG (empty tank) situation, breathing on your buddy's gas, if you are decompression diving. You might find the difference between - for example - 60 bar and empty is enough that you can consider yourself "correctly" weighted.

Agree completely. Typically I end a dive with somewhere between 40 and 70 bar in my 15lt steel. As mentioned, I think I am correctly weighted which is why this is my "paradox."

I rank the priorities as follows: Most important - holding a 20ft stop with 'near empty' tank. I actually want to be able to stay on the bottom in any depth less than 10 ft. but holding a 20ft stop without needing to grab rocks is pretty much mandatory in my books.

Second is trim. You should be able to hold a horizontal position without pivoting in an uncontrolled manner (i.e. tilting to the right or left, or tilting head down etc.). If you can hold horizontal without effort then you should be able to position yourself in any orientation. I consider this extremely important if you wish to take good photos.

Third is submerging. On the surface, you should be able to RELAX, exhale and sink at a pace that does not rocket to the bottom, but does descend nicely. From surface to 10 ft, if you watch your depth gauge I like to see it drop about 1 ft per second or two (that's 30-60ft /min).

You should be able to get deeper than 4ft before you need to inhale, and don't fill your lungs - just breath easy on that first breath so you continue to descend.

<EDIT> Once I am at about 4 ft down (sometimes less), I do rotate from feet first to horizontal and continue the descent in a horizontal orientation so I can look about easily. </EDIT>

The only time I had to "duck dive" was very early on when I was borderline underweighted and very inexperienced. It takes time to learn to relax and 'let it happen' on descents.

As to diving like a "real diver", and not like you are taught in OW class, what utter B.S. Even the "GUI dive gods" teach feet first descent. If they still do it, it must be the right way. ;-)

Thanks for this. I have 1 and 2 down pat, it's 3 that I fight with! Thanks for the tips though. As it is, I exhale to start my descent, but I'm going to monitor my breathing more and see what I can adjust. (BTW, once I'm sinking, my preferred descent is almost horizontal "skydiver style" with a slight head down tilt. I just enjoy it that way.)

I would also say that if you are sinking at your stop with nothing in your BC then you are not fully dumping your BC on initial descent. If you simply hold your inflator up and dump air it should properly squeeze any hidden air out of your wing. If you are going head first then I agree with @nolatom that stated you are more then likely not using your rear dump or you have air trapped on the side that does not have a dump.

Thanks - I'm going to check this out further. My BC is a back inflate type and it's quite possible that I'm not quite dumping it fully.

The one thing that I was taught was that people will exhale and deflate their BCD at the same time. The problem is that it takes a bit for the BCD to deflate and by the time the diver starts to sink, they are already inhaling. The trick (if you can call it that) is to inhale as you deflate your BCD. As it becomes empty, slowly exhale. One other thing is to also be mindful of your feet. Even small movements of your knee or ankle can move your fins enough to slow or stop your descent.

I'll echo what others have said too, if you need another 0.5-1kg it's really not a big deal.

Thanks, I'm going to monitor my breath a little more conciously than I do now.

What makes me wonder a bit is, that (according to your profile) it took you 100-199 dives to figure out you might have a weighting problem.
Or did you change your config recently and struggle since? If so, what did you change?

Err, no. I've had this gear since I started diving and my weighting has been tweaked a little since I started. I think it's pretty clear that I *don't* have a weighting problem, I have a weighting conundrum that I'm looking for tips on.

 

[halocline]

T

Err, no. I've had this gear since I started diving and my weighting has been tweaked a little since I started. I think it's pretty clear that I *don't* have a weighting problem, I have a weighting conundrum that I'm looking for tips on.

I agree, tweaking your weighting to get the absolute minimum you need is an ongoing adjustment. Not a problem, just part of the process of improving your diving. If everything is just the way you want it underwater but you're having trouble descending, and your BC has lots of padding (most do) then that's definitely not helping you out.

 

[cainslie]

I agree, tweaking your weighting to get the absolute minimum you need is an ongoing adjustment. Not a problem, just part of the process of improving your diving. If everything is just the way you want it underwater but you're having trouble descending, and your BC has lots of padding (most do) then that's definitely not helping you out.

Yeah, I think I'm just not venting the back of the BC properly - will have to work on that.

Pic of my BC (found online) attached.

 

[boulderjohn]

Being able to hold a safety stop is not a function of being perfectly weighted, although the closer you are to perfect, the easier it might be. It is a function of skill. I used to try to get that weight very precise. Used to.

When I became a technical diver, I found myself in a world where I was overweighted during stops on every dive. I had no choice. When you are losing 20 pounds of gas or more on every dive, you start very much overweighted, and you are not going to be right on for every stop at the end of the dive. You should never be in an empty wing situation, because that means you have not brought along sufficient gas reserves. Moreover, your stops are expected to be much more precise in their depths than is a safety stop. Under those circumstances, you learn how to adjust the buoyancy in your wing (and dry suit if wearing one) to match the degree to which you are overweighted.

After I got used to that, I stopped obsessing with getting my weight perfect on recreational dives. I learned, in fact, that it can be easier to control buoyancy with a couple extra pounds. Why? If you have a very small bubble of air in the wing and need to ditch some of it, you may have trouble maneuvering that bubble to an exit point. If the bubble is a little larger, it is much easier to dump some of it.

 

[The Chairman]

I do sink slowly at the safety stop. I'd love to be able to do the motionless hover at 5m though. TBH, I'm not worried about my weighting, I just like to get things very right.

Then you're fine. Re-read the link in my post and understand that if you're not %100 horizontal, then you'll still be chasing your tail. Your kicks have to be horizontal as well. Adjust your bladder slowly. No, much, much slower than that.

EDIT=> How do you know that you're horizontal? Have a friend take pics of your throughout the dive. Or, in a pool, position yourself 4 inches above the bottom. Get comfy and be sure you're completely horizontal and neutral. Close your eyes for half a minute. What's your attitude? How about after a minute? How about more? Adjust weights back/forward and left/right so that you can hold your attitude and thus hold your depth with your eyes closed for at least a minute. I've done three.

 

[cainslie]

EDIT=> How do you know that you're horizontal? Have a friend take pics of your throughout the dive. Or, in a pool, position yourself 4 inches above the bottom. Get comfy and be sure you're completely horizontal and neutral. Close your eyes for half a minute. What's your attitude? How about after a minute? How about more? Adjust weights back/forward and left/right so that you can hold your attitude and thus hold your depth with your eyes closed for at least a minute. I've done three.

This is something I will definitely try! I know I'm not horizontal all the time - I've got heavy feet I need to figure out a way to mount some weight on my shoulders.

 

[DiverDownD3]

This is something I will definitely try! I know I'm not horizontal all the time - I've got heavy feet I need to figure out a way to mount some weight on my shoulders.

Maybe a backplate in your future? Would move weight off your hips/waist and evenly distribute it across your back (well, depending on the BP design). Just a thought