kaylee_ann
crazy diver
Sometimes I can’t take a deep enough breath to inhale enough to become positively buoyant. It’s weird.
Ascent Question
- Thread starter bushcat
- Start date
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I would like to see you when you are diving. Many divers dive negatively buoyant without realizing it. They correct their depth constantly with their kicking. When you dive, occasionally stop all motion for a while to see what happens.
A second possibility is that you could be overweighted. If you have a lot of air in your BCD to compensate for the extra weight, then you have a very limited range in which your lungs can overcome that. When teaching OW classes, I would traditionally be about 4-6 pounds overweighted, and I could do a demonstration in which I would go from the bottom of a 12 foot pool to the surface and back to the bottom, using only my lungs to change depth. If I were instead practicing with my steel doubles, I could only do that for a few feet of depth change.
kaylee_ann
crazy diver
so for example when i get to about 15 feet i have to put air in my BC to be neutrally buoyant, or i start sinking pretty fast. i think it's because of the wetsuit compression. i will try to inhale, hold it, and nothing changes.
once i'm at a constant depth, i usually don't have buoyancy issues and can just inhale to ascend
(i might be confused)
Do you mean that when you ascend to 15 feet, you have to add air to the BCD? That means tw3o things:
- You dumped air too fast while ascending.
- You are overweighted. At the end of a single tank dive, you should be able to hold your safety stop comfortably with little air in the BCD.
kaylee_ann
crazy diver
No I was talking about when descending in order to regain neutral buoyancy, I have to add air to my BC, an inhale won’t work.
Okay, then, that is different.
When you descend, any air that is still in the BCD contracts, and your wetsuit is also compressed. The thicker the wetsuit, the more that happens. It is normal to have to add air to the BCD as you descend.
kaylee_ann
crazy diver
Yeah, sometimes I have to do it to begin my ascent
Keep in mind at the start of the dive you are negatively buoyant by about 5 lbs at the 15 ft safety stop depth *when perfectly weighted* due to the air you have yet to breath (assuming an AL80 tank). That's 2.3 liters of water you have to displace to be neutral (assuming you emptied the wing to descend). On average for women, the max inhale after a normal exhale is 2.4 liters. In other words, arguably right at your limit, and the common practice of weighting to be a couple lbs heavy (at the end of the dive) requires another liter, easily surpassing the lung capacity of many.
If you HAVE to do it, then you're not neutral before that. That said, a typical larger breath might add 3ish lbs of buoyancy. If neutral, you would start up, but hardly quickly. A blip on the inflator will certainly speed the process up.
You have two buttons on your inflator hose. Think of the button on the end--the one you use to bleed air out of your bc--as a brake pedal you can lightly tap from time to time to keep from ascending too quickly.*
To ascend, simply point your body toward the surface and start swimming. You don't have to bleed any air; just start kicking gently.
As you ascend, the air in your bc will expand, increasing your rate of ascent.
When this happens, tap the "brake pedal" lightly, bleeding off only enough air to slow your ascent to the desired rate, but not so much as to actually stop your upward movement.
Observe the results.
Repeat as necessary.
When you do reach the surface, fully inflate the bc.
Hope this helps.
---------------
*Think of the other button, the one located close to where the low pressure hose connects to the power inflator, as a brake pedal you can lightly tap from time to time to keep from descending too quickly and to keep from crashing into the bottom.
To ascend, simply point your body toward the surface and start swimming. You don't have to bleed any air; just start kicking gently.
As you ascend, the air in your bc will expand, increasing your rate of ascent.
When this happens, tap the "brake pedal" lightly, bleeding off only enough air to slow your ascent to the desired rate, but not so much as to actually stop your upward movement.
Observe the results.
Repeat as necessary.
When you do reach the surface, fully inflate the bc.
Hope this helps.
---------------
*Think of the other button, the one located close to where the low pressure hose connects to the power inflator, as a brake pedal you can lightly tap from time to time to keep from descending too quickly and to keep from crashing into the bottom.
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