Add Additional Weight For Shallow Dive?

[BRT]

If you are ever in a situation where your air is really low and you really have pushed your NDL's and you really need to hold your safety stop you are going to wish you had the extra weight.

 

[Trailboss123]

We have worked to reduce the amount of weight we carry, and find it much easier to control buoyancy at depth. At the 15' safety stop we can control our depth by breathing, but we pay a lot of attention to the depth indicator.

On our last diving trip we did two dives at very shallow depths, less then 20', and one dive where the last 20 minutes was at less than 20'. We found ourselves having to work hard to avoid popping up at the end of the dives when our tanks were nearly depleted. We could control the depth by controlling breathing, but it meant we were looking at our computers as much as we were looking at sea life. Does it make sense to add a few pounds when we know we are going to be at a shallow depth for most if not all of the dive?

The point is to be properly weighted and able to comfortably hold a safety stop at 15-20 feet as your are approaching the end of your dive. Based on what you have described, you are really having to work excessively to manage neutral buoyancy at the end of your dive and unable to relax and just enjoy it. Kudos to you for working to reduce lead and get properly weighted- it is so important to the entire dive experience. Appears to me that you might want to add an additional pound, maybe even 2, (at the most). This is not going to detract from anything with regards to the first 90% of your dive (regardless of depth) and will only enhance the last 10%. All of this assumes that all future diving is being conducted with the same exposure protection, peripheral equipment and tanks.

 

[Lorenzoid]

. . . I consider myself neutrally buoyant at 15' on a nearly empty tank, but that position changes with the amount of air in my lungs - deep breath sends me up and exhaling sends me down.

This is the description of being properly weighted.

Try to breathe normally--neither shallow nor deep breaths, and at a steady cadence, in and out. Also, keeping your body horizontal (in horizontal trim, as they say) will help. If you do all that, while each inhalation tends to make you more buoyant and each exhalation tends to make you less buoyant, the steady cadence of your breathing and resistance to movement caused by inertia and water resistance should help keep you at the depth.

But as others have said, if you feel that another pound of lead makes holding a safety stop more comfortable, then by all means go for it--don't flog yourself for not being "properly weighted" by just a pound or so. Sure, being properly weighted is a useful goal in theory, but remember that the ultimate goal is to enjoy your dive.

 

[AiJhae]

Twice as a novice (20 years apart, long story) I have had instructors reduce my weight, despite my protest, and I have "corked" at the end of the dive, having made my best effort to empty my BCD.

Surely a kg too heavy would have been safer?

 

[TMHeimer]

Twice as a novice (20 years apart, long story) I have had instructors reduce my weight, despite my protest, and I have "corked" at the end of the dive, having made my best effort to empty my BCD.

Surely a kg too heavy would have been safer?

I have spoken to at least two instructors who said I use way too much weight. The first was years ago in FL during PPV course. After doing weight checks he said I did in fact need what I wore. I have spoken with other instructors who use the approx. same weight as me with the same exposure suit. For the most part, I've always felt that a weight check is a weight check--whether it's your first dive or your 1,000th. Some people, even instructors, don't take into consideration that everyone's body is different. I also require at least 8 hours of sleep each night, for which I've been told to "suck it up". Everyone is different there also.

 

[herman]

Yes, especially if you are diving with aluminum tanks which become buoyant at the end of the dive.

This is misleading. While an aluminum tank may (some are, some are not) be positive at the end of a dive, it does not matter. What matters is the SHIFT in buoyancy over the dive, which for an 80 cf tank is 4-5 lbs. It makes no difference if the tank is aluminum, steel or anything else. Granted, if you are using an AL tank you will need to add a few pounds of lead as compared to a steel tank but that holds true for the entire dive. The tank material is irrelevant when discussing the shift in buoyancy due to use of the gas in it, only it's capacity matters.

 

[mi000ke]

Interesting. I had understood that the correct weight was the least amount that still allowed you to get down at the start of a dive. After reducing weight, I now get down by deflating my BCD and fully exhaling my lungs until I'm 3' to 4' underwater. I then take a breath, but it seems like water weight and momentum is enough at that point to get down. Is it possible to be too light on weight, even though I can get down with the weight I am using now? I consider myself neutrally buoyant at 15' on a nearly empty tank, but that position changes with the amount of air in my lungs - deep breath sends me up and exhaling sends me down.

I started a thread on this issue a while back - asking the question: Should you weight for easy descent at the beginning of a dive or for neutral buoyancy with empty BCD at the end of dive safety stop?

Weighting for descent vs bottom

I now use the least amount of weight that will allow me to duck dive down and still hold neutral buoyancy at 15' safety stop with an empty BDC. I was able to go from 16# to 12# . The greater effort to descend is worth it for the much better control I have over buoyancy for the rest of the dive. I also tried this weight in a 8' salt water pool and was able to hold my depth at 2' above bottom with no problem. I often will float a few feet below the surface while waiting for others to board the boat at the end of a dive, so this weight seems to work well through the entire dive, and I guess that's what you want.

 

[lowviz]

We have worked to reduce the amount of weight we carry, and find it much easier to control buoyancy at depth. ...//...

On our last diving trip we did two dives at very shallow depths, less then 20', and one dive where the last 20 minutes was at less than 20'. We found ourselves having to work hard to avoid popping up at the end of the dives when our tanks were nearly depleted. ...

You didn't say if you were diving a wetsuit.

A wetsuit will compress at depth. So if you did your weight check after a deeper dive, it will be a bit less buoyant during that check. Add a couple of pounds.

"A pint is a pound". (roughly) one or two pints of air in your wing vs. a completely empty wing is no big deal.

 

[stephen1254]

Both my wife and I use a 5MM full suit in 83 degree salt water - we have Florida blood! At 175 pounds, I've reduced my weight from 20 pounds to 14 pounds. At 125 pounds, my wife has reduced her weight from 14 pounds to 8 pounds. We have both found that getting into the water first and allowing our suits to saturate while waiting for the rest of our group eases our descent.

I'm still wondering, however, about my original question. While I agree that less weight makes it easier to control buoyancy at deeper depths, when the dive depth ranges from 15' to 20' that control over buoyancy would seem to be less of an issue; even with more weight there would be only a little more air in the BC, and that air can be slowly vented as we consume air in the tank. I suppose the only way to know for sure is to experiment.

 

[lowviz]

...//... While I agree that less weight makes it easier to control buoyancy at deeper depths, when the dive depth ranges from 15' to 20' that control over buoyancy would seem to be less of an issue; ...

No, it is more.

The relative pressure change is what matters as that is what causes an equivalent change in the gas volume in your BC.

33' to the surface is a change of 2 ATA down to 1 ATA. 50% difference from 'depth'.

133' to 100' is a change of 5 ATA to 4 ATA, still 1 ATA difference, but now only 20% from 'depth'.