Safety stop - loosing my buoyancy

[Pink rach]

Thank you so much to everyone's replies. I have checked my weight and I'm not under weighted. On my next dive I'm going to make sure I dump all the air from my BCD and remain horizontal at the safety stop and hopefully I'll be able to control it more. It didn't help last time that the BCD I used was in very poor condition. As soon as I'm able too I'm going to be buying my own kit, I'm starting to understand the importance of it now. I'm really enjoying diving though and constantly learning new skills.

 

[Bob DBF]

I'll give the alternative answer. If you are overweighted and have an air bubble in your BC, it becomes harder to maintain your stop because the air bubble increases in size and buoyancy for a small decrease in depth, making it harder to stay at depth. Also, with an AL80, it will tend to pull up at the butt, and if it pulls your jacket, with an air bubble in it, shallower, it makes matters worse.

I base my weighting on holding a 15' stop with an empty BC and about 500# in my tank. I usually carry a couple more pounds, then more or less depending on the buoyancy of my kit at the time.


Bob

 

[RayfromTX]

Practice getting the last bit of air out of your bc while horizontal before you need to do it on your safety stop. It takes a little practice to get all or most of the air to move to the dump valve and vent it. Practice rolling your body slightly as needed to allow trapped gas to find it's way to the high point and dump it. Stop dumping when it is all out to avoid filling the bc with water.

 

[yle]

I'm betting the OP has one of them popular cheap aluminum80 tanks. And the problem is not that you are shallow, not that you are doing the safety stop, but that those cheap Alu80's have positive buoyancy when they are nearly empty, which is the case when you are making a safety stop.

Sorry red, the type of tank is not the problem in this case. It's the change in buoyancy during the dive due to the consumption of the air in the tank. Hopefully you're breathing the same kind of air from your steel tank as the OP is breathing from their aluminum tank.

And while steel tanks might be great for some people, they are not a universal cure (and should not be promoted as such) for buoyancy issues.

 

[Diesel_Diver]

I am no pro, but I did catch one thing you had said. Rental gear. Not sure how the place you rent from works, but my LDS rents three or four different brands and models. Hard to get used to things when you have a different BC every time!!

 

[Russoft]

When I was newly certified, I couldn't maintain safety stops. It was the Red Sea (higher salinity made everything more buoyant) and we had 7 mm wetsuits. I had enough lead at the beginning of the dive, but by the end with about 50 bar (700 psi) in the cylinder, I was buoyant.

These days, I dive somewhere nice and shallow (or a shore dive where the end of the dive is shallow) and start the dive with extra lead, and at the end of the dive with low tank pressure start dropping weights until I can maintain neutral buoyancy with little to no air in my BCD. I keep careful track of the weight I use on every dive and consult these numbers each time I'm diving. I also log the cylinder type and amount of exposure protection (was I wearing a hood or gloves?), etc.

 

[Edward3c]

Thank you so much to everyone's replies. I have checked my weight and I'm not under weighted. On my next dive I'm going to make sure I dump all the air from my BCD and remain horizontal at the safety stop and hopefully I'll be able to control it more. It didn't help last time that the BCD I used was in very poor condition. As soon as I'm able too I'm going to be buying my own kit, I'm starting to understand the importance of it now. I'm really enjoying diving though and constantly learning new skills.

Not all tanks of the same size have the same mass.

I've got 12Lt 232bar tanks with mass of 13.4Kg and one with mass 17Kg, so I need to change the amount of lead I wear depending which cylinder I'm diving.

 

[scubadada]

Thank you so much to everyone's replies. I have checked my weight and I'm not under weighted. On my next dive I'm going to make sure I dump all the air from my BCD and remain horizontal at the safety stop and hopefully I'll be able to control it more. It didn't help last time that the BCD I used was in very poor condition. As soon as I'm able too I'm going to be buying my own kit, I'm starting to understand the importance of it now. I'm really enjoying diving though and constantly learning new skills.

The safety stop with an empty cylinder and the ascent to the surface is the ultimate, and only, valid buoyancy check. You should easily be able to hold the safety stop within a couple of feet. You should also be able to ascend slowly to the surface over at least 30 seconds to a minute. Get all of the air out of your BC, I think it helps to use your butt dump and rolling so the side of the dump is up and your butt is up.

 

[stuartv]

What @scubadada said. If your BC is empty and you can't stop from floating up, then you are, by definition, under weighted.

The key there being to make sure your BC is really empty.

 

[RayfromTX]

What @scubadada said. If your BC is empty and you can't stop from floating up, then you are, by definition, under weighted.

The key there being to make sure your BC is really empty.

Other factors could include nervous finning while in a vertical position as has been noted already and having a full set of lungs (breathing on the top of your lungs) due to being nervous.