Can you help? Buoyancy Control - I know this question has been asked a million times?

[RoadWarrior]

I did a search and know this has been asked a million times but I would appreciate suggestions.

I'm the classic Rec diver... moderate to low experience with 52 logged dives)... 3mm fulls or shorty's... back-inflate BC but not a backplate kinda guy... Florida, Carib, Mexico. BC is weight integrated. I weigh 190 and it's not all muscle either.

I don't own tanks and as you can imagine I'm usually strapped to a A80.

The descriptions below are based on the 3mm full suit. I'm actually not sure how much difference the shorty makes. I only wore it once last year and none so far this year although Cozumel is coming up in September.

Full suit - If I start out with 14 lbs of weight I have to swin down or pull myself down. At about 60-70 feet or more I'm perfect. Zero air in the bladder. Perfect trim, horizontal, very good buoyancy control. Hover almost motionless. Like 1 mm off the bottom and never disturb a particle. Not much up/down movement when breathing either.

The ascent - well that's a different story entirely. With about 700psi or less in the tank holding a safety stop is impossible. No line to hold to of course. I can get pretty slooooow but never a full stop.

If I start with 16 lbs I'm still good at depth. I tend to be a little heavy without air in the BC but do a pretty good job controlling that with my breathing. Sometimes just a squirt of air helps.

The ascent with 16 lbs... I'm working hard to stay at 15 feet. sometimes I can and sometimes I can't. No I've not tried 17 lbs.

Yes, with 18 lbs I have no problem with the safety stop but I just hate using that much weight. It messes everything else up at depth. I find myself fiddling with my air a lot and control at depth is a lot more difficult.

Can you recommend anything other than a diet - I'm already on one. Do you think the answer is another pound or two with more air in the bladder.

Comments appreciated.

 

[El Orans]

I'm the classic Rec diver... moderate to low experience with 52 logged dives)... 3mm fulls or shorty's... back-inflate BC but not a backplate kinda guy... Florida, Carib, Mexico. BC is weight integrated. I weigh 190 and it's not all muscle either.

I don't own tanks and as you can imagine I'm usually strapped to a A80.

The descriptions below are based on the 3mm full suit.

When I was in Bonaire last year I used a similar set-up. What you need to do is determine the amount of lead you need for holding a safety stop at 15 ft with 500 psi left in your tank and no air in your jacket. That's the amount you should use.

Furthermore, you'll probably find that as you dive more the amount of lead you need now is more than what you'll need for your 100th dive. I found out that after I had passed 50 dives that I became much more comfortable in the water leading to less lead, longer bottomtimes and a more relaxed dive.

Laurens

 

[RoadWarrior]

When I was in Bonaire last year I used a similar set-up. What you need to do is determine the amount of lead you need for holding a safety stop at 15 ft with 500 psi left in your tank and no air in your jacket. That's the amount you should use.

Furthermore, you'll probably find that as you dive more the amount of lead you need now is more than what you'll need for your 100th dive. I found out that after I had passed 50 dives that I became much more comfortable in the water leading to less lead, longer bottomtimes and a more relaxed dive.

Laurens

I think that answer is 17 or 18 lbs. Thing is, the problem now goes to the bottom and buoyancy control at depth it a struggle. Is there an answer to both situations? I guess it's just to put more air in the bladder - Huh?.

 

[The Kraken]

Yep. You can't have your cake and eat it too.

To back up El Orans, the critical factor is to be able to maintain neutral buoyancy at your safety stop.

Unfortunately no one has come up with a way yet to change the physical properties of weights at different depths. Woo hoo !!! Wish I could !!!

Dive, dive and dive some more . . . I think if you conciously work at it for a bit, IE make dives specifically to focus on your weighting, you'll come along quite nicely.

Safe dives . . .
. . . safer ascents

the K

 

[Charlie99]

Full suit - If I start out with 14 lbs of weight I have to swin down or pull myself down. At about 60-70 feet or more I'm perfect. Zero air in the bladder

Don't forget that the air in your tank weighs about 6lbs for 80 cu ft. Between the weight of air in a full tank (about 6 pounds for AL80) and wetsuit compression, it is normal to have to put some air in at depth to be neutral, particularly at the beginning of the dive when your tank is nearly full. No air in the bladder in the condition you describe means that you are underweighted.

 

[RoadWarrior]

Don't forget that the air in your tank weighs about 6lbs for 80 cu ft. Between the weight of air in a full tank (about 6 pounds for AL80) and wetsuit compression, it is normal to have to put some air in at depth to be neutral, particularly at the beginning of the dive when your tank is nearly full. No air in the bladder in the condition you describe means that you are underweighted.

Yeah I suppose you're right. Guess I just need to bite the bullet and add the weight/air.

 

[Spoon]

i have the same problem bro. iam diving this weekend and will try to weight myself properly enought to hold a nice hover at 15ft at the end of the dive even if i have to carry the extra weight for 90% of the dive

 

[lairdb]

To back up El Orans, the critical factor is to be able to maintain neutral buoyancy at your safety stop.

...and to be able to maintain the desired (slow) ascent rate from your last stop to the surface. If you can manage that with variable breathing, great. If you can hold at 15 feet, but can't control from 15 to zero (50% pressure differential), that's not good enough.

 

[String]

Problem struggling to remain neutral with 35bar/500psi in a tank is what if you need to stop with LESS than that or an empty tank. You need a bit of extra weight to work on the worst case scenario.

 

[japan-diver]

Not having seen you in the water, a few things to check before adding more weight.

A lot of newer divers with rear inflate BC have a tendency to trap some air on ascent. The horseshoe shape of the bladder tends to hold some in one side of the BC this little amount of air can lead to the inability to hold a stop. Ensure that all the air is out of the BC, use the bottom pull dump on the BC and roll a little to the side the dump is on to get all the air out on the way up. (Have a buddy check your BC next time you dive on the ascent- they can see it alot better than you)

The other problem may be with your breathing as you ascend, anticapating the problem at 15ft your breathing changes and you don't fully exhale leading to more positive buoyancy. Concentrate on relaxing and full exhalations while ascending and this may help.