To weight or not to weight

[dkktsunami]

This weight stuff is so confusing. I have friends that only put wts in their BC and that scares me.

How does weighting relate to the amount of air in you BC before you start diving. Two of my friends have an ongoing feud. One swears your BCD should be totally empty of any air when you first enter the water, the other insists that your BCD should have a little air. Our instructer never addressed this issue. I have never joined the discussion. What do most folks do?

If your BCD is initially empty then you would need less weights.

You need enough weight to keep youself submerged at the end of the dive - if you have used most of your available air you will be appox. 5 pounds lighter. The proper method of doing a weight check is at the end of a dive, at 10 feet of depth, with an empty bc and 500 psi in your tank. The correct amount of weight is the least amount that will allow you to hold this position without bobbing to the surface. If you are too heavy you will sink, too light, float to the surface. The reason for this technique is to keep the weight that you dive with to an absolute minimum (this ultimately affects the amount of work you do, your buoyancy and probably trim, and your air consumption rate). It is, however, necessary to have just enough weight to complete your safety stop. Over time, and with experience and practice, you will likely be able to reduce the minimum amount of weight you carry as you learn to control your shallow depth with "shallow" breathing for a few minutes. When you determine the correct weight, record this figure along with thermal protection and other gear. Every time you change what you are wearing in terms of mils or weight, it will affect your buoyancy. Keep records.

 

[paddler3d]

This weight stuff is so confusing. I have friends that only put wts in their BC and that scares me.

How does weighting relate to the amount of air in you BC before you start diving. Two of my friends have an ongoing feud. One swears your BCD should be totally empty of any air when you first enter the water, the other insists that your BCD should have a little air. Our instructer never addressed this issue. I have never joined the discussion. What do most folks do?

If your BCD is initially empty then you would need less weights.

Sort of hitting at this backward.

You are properly weighted when you are close to 500psi in your tanks, no air in your BC and when you hold your breath, your float at eye level to the water.

To run this in reverse, look at the buoyancy characteristics of your tank. For example, a Catalina AL80 is -1.6#s full and +2.8#s full. That is a swing of 4.4#s.

With a full tank, no air in your BC and holding your breath, figure out your weighting so that you float at eye level. Add 4-5#s to compensate for the swing of the tank from the beginning to the end of the dive.

 

[TheScubaBOB]

This weight stuff is so confusing. I have friends that only put wts in their BC and that scares me.

How does weighting relate to the amount of air in you BC before you start diving. Two of my friends have an ongoing feud. One swears your BCD should be totally empty of any air when you first enter the water, the other insists that your BCD should have a little air. Our instructer never addressed this issue. I have never joined the discussion. What do most folks do?

If your BCD is initially empty then you would need less weights.

You've received as good answer from dkktsunami regarding how to be weighted.

To directly answer your question about air in the BC, when you begin your descent you should dump ALL of the air from your BC. Then as you descend slowly add air to your BC so that when you reach your desired depth you are neutrally buoyant.

In truth, properly weighted for the end of the dive means you're slightly overweighted at the beginning.

 

[LollyO]

5) Finally, KNOW HOW TO DUMP YOUR WEIGHT. Practice it. It kills me to read how often divers make it to the surface but because they can't or don't remember to dump their weight they end up drowning.
.

How many divers die each year because they didnt dump their weights?

Where can your regularly practice dumping your weights? Do you regularly practice this in a swimming pool?

thanks,

 

[LollyO]

Get the body trimmed out.

.

What is your definition of trimmed out?
thanks,

 

[iztok]

This weight stuff is so confusing. I have friends that only put wts in their BC and that scares me.

How does weighting relate to the amount of air in you BC before you start diving. Two of my friends have an ongoing feud. One swears your BCD should be totally empty of any air when you first enter the water, the other insists that your BCD should have a little air. Our instructer never addressed this issue. I have never joined the discussion. What do most folks do?

If your BCD is initially empty then you would need less weights.

You need to do the weighting with an empty tank you are diving (500psi for example). At this point your BC should be pretty much empty at 15ft and you should be neutral. This is what I was always told is good weighting.

Now if the above is the case then when you do your first decent your tank will have 3000+ psi in it and be heavier. So while properly weighted and buoyant you should have some air in BC at 15 ft to compensate for additional weight.

 

[Bubbletrubble]

Great discussion with good info on weighting concerns...

To run this in reverse, look at the buoyancy characteristics of your tank. For example, a Catalina AL80 is -1.6#s full and +2.8#s full. That is a swing of 4.4#s.

@paddler3d: At least two sources on the Internet show different specs for a Catalina S80 aluminum tank.
Huron Scuba: Full = -1.8 lbs. , Empty = +4.0 lbs.
TechDivingLimited: Full = -1.8 lbs. , Empty = +4.0 lbs.
(all buoyancy specs quoted include tank valve)
These specs indicate a 5.8 lb. swing from full to empty.

@BettyRubble: All other gear and conditions (water density) being equal, if you want to see how much more/less lead you will need with a new tank, you can simply calculate it from an online tank specs chart. I've used the following 2 sources: TechDivingLimited and Huron Scuba.
Hope you find this info useful.

 

[Bubbletrubble]

What is your definition of trimmed out?
thanks,

@LollyO:
"Trimmed out" means your torso + upper legs are horizontal in the water.
Here's one of many YouTube videos that shows proper horizontal trim.
As mentioned previously, proper trim + streamlined rig minimizes drag when moving through the water.

 

[BettyRubble]

How many divers die each year because they didnt dump their weights?

Where can your regularly practice dumping your weights? Do you regularly practice this in a swimming pool?

thanks,

Being the goober that I am, I practice in my living room. My getup has a slightly different release mechanism (I'm in a Zena) so I walked around in it for a couple of days practicing dumping.

Pools are good too, or on the shallow side of a dive site maybe? Talk with your instructor for recommendations for your local dive site.

Oh and you asked about how many divers die for not dumping weight - I don't know the statistics but I read of 3 accounts recently where the diver made it to the surface but didn't dump the weight and ended up panicing and drowning. ONe guy was fine a the surface, dumped his gear to get up on his boat easier, but not the belt . somehow lost grip and sank - his buddy found him at the bottom with his weight belt on and his lobster bag still attached to his weight belt.

 

[Bubbletrubble]

This weight stuff is so confusing. I have friends that only put wts in their BC and that scares me.

I don't know if this should really "scare" you. You might want to discuss with them the merits of splitting up their weight, though.

How does weighting relate to the amount of air in you BC before you start diving. Two of my friends have an ongoing feud. One swears your BCD should be totally empty of any air when you first enter the water, the other insists that your BCD should have a little air. Our instructer never addressed this issue. I have never joined the discussion. What do most folks do?

I hope that I'm not reading too much into your post, but I would like to clarify something:
For the purposes of doing a weight check, your BCD should have no air in it.
For the purposes of entering the water at the beginning of a dive, I generally inflate my BCD enough to establish positive buoyancy. Most of the time I'll just inflate it fully (usually by blowing into the oral inflator). The only exception to this is when I'm diving off of a boat in current and the dive plan requires an immediate descent...then I'll enter the water negatively buoyant.