Initial Descent...getting down

[traumadiver]

Alot of threads that I read in reference to bouyancy and descent deal with controlling your fast descent. My problem is a little bit different.
I have a problem with starting my descent. When I am at the surface I let all the air out of my BC, and exhale as much as I can, but I still stay at the surface. Most would say, you are not weighted down enough. When I do a bouyancy check prior to descent, it seems that I am weighted correctly, I float at eye level with my BC empty and a normal breath in my lungs.
I find my self having to start my descent in a head down, fin up configuration, stroking and finning downward until I hit about 10-12 ft. Then everything is A-ok. My bouyancy is nice and neutral and everything is really nice. Sometimes my buddy has to hold on to me to help me out.
I know that most of this problem has to do with my wetsuit compressing. I started having this problem when I started diving with a 5mm full wetsuit. It may also be because I am a skinny, tall man, although I thought only fat floated...!
I am hesitant to add more weight, just for my initial descent, because that would not help me at depth.
Is this normal? Should I be doing something different? Suggestions would be appreciated.
Thanks in advance

 

[Charlie99]

Assuming that you are properly weighted (see comments below) then your problem might be air trapped inside your wetsuit and BCD, or simply that it takes a while for water to saturate your wetsuit. If this is the problem, the symptom would be that on the second dive of the day, that you don't have trouble descending. This would be because your wetsuit is now saturated with water and is less buoyant. Same for any padding and fabric on your BCD. If this is your problem there isn't much you can do other than bobbing around for a couple of minutes before your dive or adding a couple of pounds to compensate.

----------- are you really properly weighted ??? -----------------

If you end the dive with a near empty tank, can you easily do a safety stop at 10 or 15'; and can you do a controlled, slow ascent to the surface after that ?

It's OK if you need to breathe shallowly during the last few feet of the ascent after your safety stop, but you should be able to control and stop your ascent even when just 5 feet down and a near empty tank.

If you can do the above then you are properly weighted. The pre-dive eye level with full tank is just a crude check.


Charlie

 

[dkktsunami]

A couple of comments: before descending make certain that air is not trapped in wet suit. I get vertical on the surface and pull out on waist belt to release any air trapped in legs. Also a new or seldomly used wet suit needs a little convincing. And buoyancy check needs to be done with a tank that is nearly empty (500 psi) at ten or 15 feet. The air you breathe from a 80 cu.ft. tank weighs a little less than 6 lbs. In other words you need to be about 4 - 6 lbs "heavy" at the beginning of the dive to have enough weight at the end of the dive to maintain a safety stop without popping to the surface.

 

[300bar]

When I do a bouyancy check prior to descent, it seems that I am weighted correctly, I float at eye level with my BC empty and a normal breath in my lungs.

But prior to your dive,your tank is full.It should be done with a near empty tank.

Hope it helps.

 

[CMAN]

A couple of questions first. When you do your bouyancy check at the surface and you exale ALL of your breath do you begin to sink? If not you need more weight. Next, when you are at the end of your dive and assending from your safty stop can you stop at 5 feet and hold there? If not you need more weight, if you can then my guess is you have air trapped in your suit that escapes during the dive.

 

[gsk3]

Add more weight. Try a pound or so. If you're underweighted at the beginning of a dive, you'll be really underweighted when you try to hold your safety stop. The air in your take weighs something.

 

[spectrum]

But prior to your dive,your tank is full.It should be done with a near empty tank.

Hope it helps.

Bingo!

For reference...

Remember to set your weight so that you bob vertically at eye level at the end of your dive with an empty BC, an average breath, your feet still (crossed) and about 500 PSI in your cylinder. A deep breath should get your mask out of the water and a deep exhale should sink your mask. Do all of this while breathing from your regulator. The end of the dive is the defining moment for your weight requirement and you want just enough to let you stay down in the shallows with a light cylinder.

You can make the same test pre-dive with a full cylinder and add 5 pounds to compensate for the buoyancy gain you will experience as you breathe the tank down. Be sure to repeat at the end since you are apt to have some stowaway buoyancy (trapped air) in your gear early in the dive. You are safer being two pounds heavy than 2 pounds light.

Starting the dive will also entail making sure you are 100% vented and are relaxed. Those factors combined with correct weighting and the 5+ pounds of expendable weight in the form of compressed air should get you on your way down. Some BCs are notorious for holding air in padding panels and in that case doing a bit of a duck dive to start the process is not a crime.

You do not want to do a duck dive to overcome a truly under weighted condition since that will leave you dangerously buoyant at the end of the dive.

Pete

 

[InTheDrink]

It could be your breathing. If you are ok on your safety stop (i.e. not struggling to stay down), then you are not under weighted. If you are breathing quickly it can making getting down harder. If you can focus on relaxing your breathing then it will make it much easier. Relax, get breathing under control, then big, slow, long exhale.

However, if you're struggling to stay down on your safety stop then you are likely under weighted.

This is my experience at least.

 

[String]

But prior to your dive,your tank is full.It should be done with a near empty tank.

Hope it helps.

Or just factor in the weight of gas and add that to the figure.

I dont like the eye level thing anyway - far better to remove weight, empty BC/suit and have someone hand you lead until you JUST start to sink.

 

[don Francisco]

The eye level floating bouyancy test is only a rough test to approximate correct weighting. Fine tune your weighting by following the advice given above. (neutral bouyancy, 15' empty BC, empty tank) But if in doubt, an extra pound or two won't adversly affect your diving.

Besides weighting there may be other subtle causes of your problem. First, as has been pointed out , burp your wetsuit by pulling the neck open at the surface. You may not fully emptying your BC - be sure that your posture is such that the inflator hose port is at the very top of the BC so you don't trap any air above it You also may be finning unconciously propelling yourself upwards and undoing your efforts to sink.

Lastly, you may not be completely emptying your lungs. You're probably a bit nervous at the beginning of your dive and not really emptying your lungs when you exhale. Most folks almost never truly empty their lungs anyway. Try this experiment as you read this - exhale, then after you think you're done exhale a bit more without inhaling first, odds are you squeezed some more air out, do it again to squeeze the last bit out. Practice fully exhaling until you know how to truly empty your lungs on the surface, so you'll be able to do it in the water.

Now for the descent, put it all together, burp your wetsuit and relax a momment. Don't worry about the dive, instead think about the pretty fishes you'll be seeing. Check that your feet are also relaxed and you're not finning and take a few deep breaths with full exhales to get mentally prepared.

When you're ready, simultaneously empty your BC and your lungs and you should begin to drop. Do not inhale until there's a few feet of water above you, and then only a small sip. You can resume breathing normally at a depth of 5 feet or so.

One other thing you can try is to fin up lifting your body out of the water slightly before you begin the descent. This will add some downward momentum to help start the descent, but don't do it so hard that you undo your efforts to empty your lungs.

Final thought - Ideal weighting is what works for you. If a few extra pounds at this stage of your dive experience helps you manage descent and safety stops better, add them. You can always shed them later when your skills improve and you're more comfortable.