No need to inflate BCD?

[thehotcorner]

Hi all,

I have a question about the BCD inflation. I am about 6' 180 lbs, dive with 6 lbs of lead and just a rashguard and board shorts. I find that on shallower dives (60' or less), I tend to not put ANY air into my BCD and rely exclusively on lung volume to control my buoancy. You can def say I'm a bit on the soft side, so I am probably a bit more naturally buoyant than the next guy, but is this common? Further, might I be better served to have a bit of air in the BCD and not rely on my lungs so much? FYI, I have no problems with my buoyancy or air consumption (60+ min easily for these shallow dives). It just seems odd to me. Any tips or insight appreciated.

 

[Tigerman]

Hi all,

I have a question about the BCD inflation. I am about 6' 180 lbs, dive with 6 lbs of lead and just a rashguard and board shorts. I find that on shallower dives (60' or less), I tend to not put ANY air into my BCD and rely exclusively on lung volume to control my buoancy. You can def say I'm a bit on the soft side, so I am probably a bit more naturally buoyant than the next guy, but is this common? Further, might I be better served to have a bit of air in the BCD and not rely on my lungs so much? FYI, I have no problems with my buoyancy or air consumption (60+ min easily for these shallow dives). It just seems odd to me. Any tips or insight appreciated.

This is a good thing

 

[DevonDiver]

Weighting has only to compensate for equipment (primarily exposure protection) buoyancy and the positive buoyancy of aluminum tanks at the end of the dive. If wearing no exposure protection, you really only need a tiny amount of weight. Thus, a small amount of air in the BCD to compensate (exposure protection compression at depth + weight of gas). ~1 litre volume of gas to balance 1kg of negative buoyancy. An AL80 starts only ~2.5lb negative and shifts to only gets 2-3lbs buoyant by the end of the dive...and this amount of buoyancy can relatively easily be compensated via breathing patterns (the lungs have significantly higher variation in buoyancy breathing in/out).

If using breath control to compensate doesn't cause you any distress at all, there's no problems to continue as you are. Just make sure you have sufficient weight to cater for the worst case (maintaining a safety stop with a near-empty cylinder).

 

[Agility]

The air in the BCD is only used to counter the loss of volume of a neoprene suit at depth and the weight of your breathing gas as long as the tank is full.
So with a rash guard which does not compress at depth and a rather small tank there is no need to put much air into the BCD.

 

[victorzamora]

What you want is to be able to sit at 15ft with NO air in your wing, with an emptyish tank (typically considered 500psi) and be perfectly neutral. I take more lead than that in salt, but I'm definitely "fluffier" than you are.

6 pounds of lead in salt with an aluminum tank is great. Buoyancy control via your lungs is great. SOP should be to use a touch of air in your BCD to help you get neutral, so that you fall slightly upon exhale and rise slightly upon inhale. Any excessive weight will require more air in your BCD, which will make your buoyancy control difficult.

 

[TSandM]

If your breathing strategy works for you, and your gas consumption is where you want it, and you aren't getting headaches at the end of a dive, then it's fine. Just make sure that, if you are distracted in shallow water, you don't end up changing your breathing pattern and losing buoyancy control. I'd challenge yourself with stuff like writing on a slate or shooting a bag or sharing gas, and make sure that you're stable.

Having used this strategy for a while when putting ties in in caves, I will tell you that your gas consumption will go down if you use your BC a little more. The more you can cycle your breathing around a normal midpoint, the better your gas consumption is.

 

[thehotcorner]

Thanks for the responses. I have no problems with being neutrally buoyant at 15' / 500psi, with about a smaller than avg breath of air in my lungs.

If your breathing strategy works for you, and your gas consumption is where you want it, and you aren't getting headaches at the end of a dive, then it's fine. Just make sure that, if you are distracted in shallow water, you don't end up changing your breathing pattern and losing buoyancy control. I'd challenge yourself with stuff like writing on a slate or shooting a bag or sharing gas, and make sure that you're stable.

Having used this strategy for a while when putting ties in in caves, I will tell you that your gas consumption will go down if you use your BC a little more. The more you can cycle your breathing around a normal midpoint, the better your gas consumption is.

I have been diving with a gopro or camera lately and do find when I'm really concentrating on getting a shot I tend to float a bit, something I'm trying to be more cognizant of. Your last tip is along the lines of what I was thinking, that I should just have a bit of air in my BCD to ease the stress on my breathing patterns. Something I'll play around with. I just moved to the Caribbean so I'm gonna have plenty of opportunities to fine tune my diving!

Thanks!

 

[GrumpyOldGuy]

There are a few old time divers who do fine without a BCD, even with a wetsuit. What I found is if everything is perfect, I can avoid using it as long as I am moving. Essentially I am using the forward movement to augment my lung based buoyancy control for my 4lbs of gas used. Once I try to hover for observation of small critters or take pictures, it gets more difficult and being able to dial in the buoyancy with the BCD becomes more important.

 

[victorzamora]

Thanks for the responses. I have no problems with being neutrally buoyant at 15' / 500psi, with about a smaller than avg breath of air in my lungs.

I hope not TOO much smaller. If you're having to deprive yourself of air, you might be building up CO2. CO2 buildup is bad for a lot of reasons. Shallow breathing might also produce some CO, which is really bad. If you're having to purposefully keep a very low lung volume while shallow, maybe an extra pound wouldn't hurt.

 

[DivemasterDennis]

Minimal air in the bcd means you are weighted properly. If you can maintain a safety stop depth hover ( 15 to 20 feet) with no air in the bcd, then you are just fine. If that point of the dive is a struggle you might consider adding a pound, but only if that safety stop is a problem.
DivemasterDennis