Confused about weights

[Skittl1321]

Yesterday I went on dive 2 post certification.
So far, my weight history has been
3mm in pool - 10 pounds, felt heavy. Never got to less than half a tank of air
3 mm in pool- 8 pounds, felt good, but a leak in the tank brought me down to 800 psi by the end and around 1200 psi I was floating so much the DM gave me 4 more lbs to keep me down- so on that dive I guess I used 12 pounds
7 mm in quarry- 16 pounds, and that seemed too light; so the next day with the same gear I used 18, and again it seemed to light but instructors said I had plenty. (By too light I meant "I cannot stay on my damn knees". When we did the free swim, I kept crashing down into the sand.)

So back to yesterday, I was in a 3 mm in the quarr, so I went to 10 pounds. I actually think it went rather well. I have trouble sinking past the initial fall of like 6 feet, but I think that is because I don't let my breath out enough. I wasn't floating back up.

But - not once on the entire dive did I add air to my BC. Does that mean I was wearing too much or not enough weights? During the class, all the buoyancy exercises stressed adding tiny amounts of air to your BC. During these dives, I think I did pretty well with my bouyancy. I never crashed into the ground. I never floated up to the surface. When we tried hovering motionless, it was a bit difficult to keep the number on my computer constant- rising/falling 1 or 2 feet, but when we swam, I was able to stay level the whole time. (My trim sucks though... but we didn't kick up a silty mess, and that was kind of the goal.)

I'd appreciate any opinions about the weight situation. I'm not sure if height/weight helps, but I'm 5'0", midly overweight, and quite buoyant, unfortunately...

 

[Rich Keller]

But - not once on the entire dive did I add air to my BC.

If you were able to do this without floating up or sinking down too fast then I would say you have the amount of weight set perfectly. Now you just need to move the weight around a bit until you are satisfied with the trim.

 

[MrChen]

You should always be heavy with a full tank. Tanks lose weight and can become positively buoyant when low. So at the end of a dive with assistance of your buddy see how many pounds you can shed. Make sure to purge any air from your bcd first.

Of course it'll help if you become more consistent on your gear. And tanks have different weight ranges when full vs empty.

Sent from my Kindle Fire using Tapatalk 2

 

[AfterDark]

OP did you empty your tank 500psi? Where you able to hold at 15'? If the answer is yes to both, then you got it as close to perfect as mortals can get. Fat floats. The more body fat the more weight needed to compensate. Some times different people will post different weight requirements with similar equipment i.e. 7mm wet suits, steel tanks similar size, body fat is probably the cause of the difference. Don't try to compare what you find in these posts, find what works for you. It seems you may have hit it dead on.

Varying 1-2' in depth is hovering. The part about not adding air to your BC, it may have had air in it already. It isn't uncommon not to completely empty a bc on the surface. A little struggle to get down and at depth you're neutral without adding air.

 

[dfx]

But - not once on the entire dive did I add air to my BC.

Something is not right with that. The air in your AL80 tank weighs about 6 lbs, so at the start of the dive, at the surface, you should be at least 6 lbs negative. At depth, your suit loses buoyancy, so you should be even more negative. You must compensate for that by making your BCD positive, so you become neutral as a whole

If you were neutral at depth without any air in your BCD, then you must have been positive at the beginning of the dive. And through the dive, you'd become even more positive (losing the weight of the air). You'd have serious trouble getting down at the beginning of the dive, and have trouble staying down later on.

I've heard (and seen) that before. What may have happened was that at depth, you were actually negative (i.e. sinking), but unaware. We tend to compensate for sinking by movement... swimming, finning, kicking, sculling, without even realizing it, as a natural reaction. Your "motionless hover" may not have been that motionless. That's especially likely if you were doing it in the vertical, it's very easy to keep yourself afloat by kicking downwards. My wife used to have this exact issue.

Either that, and/or your breathing wasn't relaxed enough, you were constantly gasping for air, not breathing out normally/fully. That would have the same effect as having air in your BCD.

OR none of that actually happened and you managed to pick your weights just so that you were perfectly neutral at depth without air in your BCD (which you shouldn't be) and managed to push down the initial positive buoyancy. Not likely IMO, but possible.

 

[Skittl1321]

OP did you empty your tank 500psi? Where you able to hold at 15'?

No, we came up at 750 psi. Our hover was around 15', and like I said I held it to a few feet. However, max depth was only around 17-18 at that point, so holding really just meant not crashing into the ground.

---------- Post added August 11th, 2013 at 08:10 AM ----------

Something is not right with that. The air in your AL80 tank weighs about 6 lbs, so at the start of the dive, at the surface, you should be at least 6 lbs negative. At depth, your suit loses buoyancy, so you should be even more negative. You must compensate for that by making your BCD positive, so you become neutral as a whole

The dives aren't very deep in our quarry- 20-25 feet, and because of the really cold thermocline we stayed around 15 so there wasn't much chance for compression of the suit. But I agree- that's why I was wondering if something was wrong. Because I know you need to be negative at the beginning of the dive (my experience in the pool where my tank leaked really taught me how floaty you get when you don't have enough weight. But here I never really got floaty.)

I've heard (and seen) that before. What may have happened was that at depth, you were actually negative (i.e. sinking), but unaware. We tend to compensate for sinking by movement... swimming, finning, kicking, sculling, without even realizing it, as a natural reaction. Your "motionless hover" may not have been that motionless. That's especially likely if you were doing it in the vertical, it's very easy to keep yourself afloat by kicking downwards. My wife used to have this exact issue.

90% of the dive was spent swimming, so this may have been what was going on. I was maintaining my depth by swimming. The hover definetly wasn't motionless, as it had a lot more up/down than good divers who can keep it within inches, but I never crashed into the ground. It was done horizontal though, and I wasn't finning or moving my hands.

Either that, and/or your breathing wasn't relaxed enough, you were constantly gasping for air, not breathing out normally/fully. That would have the same effect as having air in your BCD.

Very possible. I'm definitely not a relaxed breather, but I wasn't gasping, I know that. Maybe you are right that I am holding air in my lungs. This is probably what is going on.

 

[Panama Jones]

Skittle...I dive thick suits in cold water most of the time. I'm guessing in a quarry, 3 mil was for near surface practice. With 3 mil, you are not going to get that much compression to need to make much adjustments with depth. However, 7 mil, and higher if you add vests, is going to mean you are managing you buoyancy with your LP inflater throughout the dive. Like it or not, this is necessary for cold water wetsuits unless you can do the whole dive at one depth.

1. Dive with the suit that you would normally need for a good quarry dive (normally cold)
2. Your best bet is to do a proper weight check at the surface so you know that you are buoyant at 15 ft with 500 lbs. Leave it at that.
3. After that (in 7 mil) you will have to continually compensate for increased/decrease buoyancy due to suit compression/decompression as you ascend and descend as a normal part of the dive. I see this with cold water divers all the time. They crash into the bottom once they get passed 20 feet and keep going down faster and faster, then they are scrambling to dump air as they get closer to the surface. And yet, they may have a ton of Caribbean dives in a 3 mil shorty.

Once you have done a good buoyancy check, you need to "drive your wetsuit". Slow bursts as you are descending to control you descent and come to neutral where you want. Slow deflation shots as you feel you are starting to rise too fast. More of this is you are doing up and down dives. At places where you can stay neutral for a while, this is where you use your breath for buoyancy control..

I think that most instructors in cold water areas teach according to the books. The books must be based on pool or warmer areas that assume that once you are neutral, you are reasonably neutral at any depth. I wish the shops in cold water areas would add a "thick suit addendum" to the course.

Finally, if you think that "driving your wetsuit" with your LP inflater will take you through a ton of air, I guarantee it is a whole lot less than the amount air you will breathe by constantly fighting it by swimming etc.

 

[Skittl1321]

I'm guessing in a quarry, 3 mil was for near surface practice.

The quarry we dive in is not too deep. I've heard it goes to 30 feet, but the deepest we've found was 25 feet. Below the thermocline (at about 18 feet) it got to about 62 degrees, which was cold but okay in the 3 mm; above it it was like 70-75 degrees, 78 at the surface, which was just fine: not cold at all (it was very cold 2 months ago, with 65-70 being the surface temp and getting a lot colder as you went down!). So at least until the summer weather turns, we won't be in 7mm for awhile. [/quote]

I definitely know when summer weather turns and we go back to 7 mm, I'll have to change the weights around again. I'm just not sure if this dive I was weighted properly or not...

 

[Karibelle]

When you stop kicking (swimming, moving, whatever you call it) you will need to add air to your bc at depth to be neutral. The point of the hover skill is for YOU to be motionless... if you're neutral, you should expect some rising/falling with your inhalation/exhalation - the point is to not be sculling with your hands or finning with your feet to stay where you are.

Sounds like you're doing well. Asking good questions, wondering about the right things. Keep it up! (and when you get to coz and are drift diving, stop kicking. :blinking: )

---------- Post added August 11th, 2013 at 01:38 PM ----------

I wish the shops in cold water areas would add a "thick suit addendum" to the course.

Indeed. When teaching in Canada, I'd encourage OW referral students to get the "thick suit" early and take it to the pool, so that they could get their proper weighting sorted out in that environment, rather than in the chilly lake on OW day. There's a lot to a 7mm suit, and not adding that to the stress of "the first time I did EVERYTHING" can make for a lot better experience!

 

[Skittl1321]

Indeed. When teaching in Canada, I'd encourage OW referral students to get the "thick suit" early and take it to the pool, so that they could get their proper weighting sorted out in that environment, rather than in the chilly lake on OW day. There's a lot to a 7mm suit, and not adding that to the stress of "the first time I did EVERYTHING" can make for a lot better experience!

When we did our checkout the just said "tell us what double of what you had in the pool was"; when I told them that would be 20 pounds they said it was too much, gave me 16 and did a weight check and said it was fine. I DID dive in a hood in the pool though, as I wanted some experience of how that was going to go with the mask removal skills. But then it was warm enough when we checked out I didn't wear the hood. I never practiced in gloves though, and when I tried them on in the store it made me realize I'm going to need to practice with them if I ever plan to dive real cold water...