Weighting for Neutral Buoyancy

[wetb4igetinthewater]

What is a good quick practical way to make sure I am perfectly weighted? I've struggled a bit with this particularly because we sometimes rent BCs or wetsuits on vacation. I've done the bob in the ocean level with eyes/top of head, and found it lacking. Calculators don't work because I don't have access to inherent buoyancy specs for rental gear. I try to be within 1 lbs over weighted because it's easier to mitigate than being slightly under weighted in an emergency.

In theory I aim to be neutrally buoyant with 0.00 psi in the tank at 15-20 ft, BC empty. In practice it's kind of difficult to achieve because, up to this point, I always end dives with at least 500 psi, usually closer to 1,000 psi. What is the typical inherent buoyancy of an AL80 at 0.00 psi and 1,000 psi?

This might interest you: Teaching Neutrally Buoyant and Trimmed: How to weight properly, Part 3 - SDI | TDI | ERDI | PFI

 

[Blackcrusader]

I like to be a couple of kilos over weighted. Sometimes better when in swirls when trying to take photos or video. Also for when I see other divers underweighted at end of dives. Always better to be carrying more weight which you have a BCD to compensate for than being under weighted.

 

[gqllc007]

You might want to not under think your over weighting either, just saying. It can be dangerous especially if a significant portion of it cannot be jettisoned. N

All of it could have been jettisoned in equal amounts so I was covered just fine...my point was I can handle being weighted just right too being grossly overweighted...underweighted is the worst

 

[Nemrod]

And I guess my point, though not well made, is that it is a bad idea to count on a BC to counter being grossly overweighted and in particular if much of the weight is not jettisonable (or even if it is). I did not specifically quote you though your post contained the gist of my concern so I did use your words. IMO, it is bad technique to purposely or knowingly overweight and then use the BC to compensate routinely. I see divers so overweighted that their wings are nearly full at depth when their suits compress. I know it is not easy, especially with bigger people and heavy exposure suits and adding on very negative steel tanks. Yes, you will have some air in your wing unless maybe you are in a drysuit. But the less, the better. N

 

[gqllc007]

And I guess my point, though not well made, is that it is a bad idea to count on a BC to counter being grossly overweighted and in particular if much of the weight is not jettisonable (or even if it is). I did not specifically quote you though your post contained the gist of my concern so I did use your words. IMO, it is bad technique to purposely or knowingly overweight and then use the BC to compensate routinely. I see divers so overweighted that their wings are nearly full at depth when their suits compress. I know it is not easy, especially with bigger people and heavy exposure suits and adding on very negative steel tanks. Yes, you will have some air in your wing unless maybe you are in a drysuit. But the less, the better. N

I agree...The issue I had was isolated to the one DM giving me 16 pounds instead of 8 pounds. I didn't even realize the mistake till I was back on the boat and once I replayed in my head what occurred I realized what happened. The dive went fine without any issues....Otherwise I am ok with around 2 pounds overweight so I can do my photography

 

[scrane]

The ideal and the goal is to have enough weight to maintain your safety stop with little or no air in your BC. At this weight you should easily be able to descend at the beginning of the dive and continue your dive with minimal air in your BC which is subject to expansion and contraction due to depth.
I have seen many new divers floundering on the surface unable to descend due to being underweighted. So take your dive master's advice and start out a little heavy and see how it goes at your safety stop.

 

[Nemrod]

I agree...The issue I had was isolated to the one DM giving me 16 pounds instead of 8 pounds. I didn't even realize the mistake till I was back on the boat and once I replayed in my head what occurred I realized what happened. The dive went fine without any issues....Otherwise I am ok with around 2 pounds overweight so I can do my photography

Yes sir, I really just borrowed your words without intent to single you out. I know you are a good diver and would not taco your wing! .

I may have been 19 or 20yo and I think I may have weighed 150 pounds, no exposure suit, nothing but a t shirt and swim suit. I was on a boat in Key West. The DM asked if everybody had a weight belt and that everybody NEEDED a weight belt and I raised my hand that I therefore needed one because he said so. So the DM came over and looked at me, fiddled around in the weight bin and produced me a belt, I put it on. All I had for a BC was a Dacor SeaChute with maybe 12 pounds of lift in the BC bladder plus another 15 in the CO2 section. Predictably I jumped in and went straight to the bottom. No problem I thought, it had a fancy power inflator, I inflated the BC until it burped and I was still glued to the bottom. In a little while I decided to fire the CO2 cartridge and reluctantly gravity let me go and buoyancy won out, barely. I had enough lead for three people. I took off the belt and dived without. Not everyone NEEDS a weight belt .

So I been there right with you . Gotta watch them DMs!

James

 

[boulderjohn]

Yes sir, I really just borrowed your words without intent to single you out. I know you are a good diver and would not taco your wing! .

I may have been 19 or 20yo and I think I may have weighed 150 pounds, no exposure suit, nothing but a t shirt and swim suit. I was on a boat in Key West. The DM asked if everybody had a weight belt and that everybody NEEDED a weight belt and I raised my hand that I therefore needed one because he said so. So the DM came over and looked at me, fiddled around in the weight bin and produced me a belt, I put it on. All I had for a BC was a Dacor SeaChute with maybe 12 pounds of lift in the BC bladder plus another 15 in the CO2 section. Predictably I jumped in and went straight to the bottom. No problem I thought, it had a fancy power inflator, I inflated the BC until it burped and I was still glued to the bottom. In a little while I decided to fire the CO2 cartridge and reluctantly gravity let me go and buoyancy won out, barely. I had enough lead for three people. I took off the belt and dived without. Not everyone NEEDS a weight belt .

A technical diving instructor I know told me a very similar story. He was an absolute beginner, barely knew what he was doing. The DM gave him a weight belt with about 3 times as much weight as he needed. The buckle did not work correctly, so he tied the belt in a knot. When they went in, he plunged to the bottom and laid there, pinned to the sand. There was some sort of chaos going on around (I can't remember exactly), and he said he watched the chaos for a while before realizing he had better do something about his own situation. He could not move. He could not untie the knot in the weight belt. I don't remember how he said he finally made it to the surface, but I do know it was a close call.

I was working on my Assistant Instructor certification in Key Largo, and I saw something that is etched forever in my memory. A young woman who was part of another group was literally crawling on the sand, her integrated weight pockets bulging with lead, with a look on her face that clearly said "I hate, hate, hate, hate this! If I ever get to the surface, I am never going to dive again." I vowed then that no student of mine would ever be like that.

 

[BlueTrin]

What is a good quick practical way to make sure I am perfectly weighted? I've struggled a bit with this particularly because we sometimes rent BCs or wetsuits on vacation. I've done the bob in the ocean level with eyes/top of head, and found it lacking. Calculators don't work because I don't have access to inherent buoyancy specs for rental gear. I try to be within 1 lbs over weighted because it's easier to mitigate than being slightly under weighted in an emergency.

In theory I aim to be neutrally buoyant with 0.00 psi in the tank at 15-20 ft, BC empty. In practice it's kind of difficult to achieve because, up to this point, I always end dives with at least 500 psi, usually closer to 1,000 psi. What is the typical inherent buoyancy of an AL80 at 0.00 psi and 1,000 psi?

If you do a series of dives with the same equipment, you can, before the dive, ask the guide/Divemaster (or an experienced buddy) to do a weight check at the end of the first dive if it is in a safe place to do so.

When you finish a dive try to write down in you log the following information:
* the equipment you had including the type and thickness of the exposure suit
* how much lead you had
* if it was fresh or sea water.

Once you have logged how much weight you need with many configurations, you should be able to approximate the right weight using the previous log entries, but unless you have done a weight check (with a particular configuration) it’s probably safer to be a little bit heavier than lighter (but not grossly overweighted)

 

[The Chairman]

There's a mismatch of terms here. You don't weight for neutral buoyancy. You should weight to acheive a balanced rig, as much as possible. A balanced rig makes being neutral quite easy. However, it's not always possible, and in that case, you should have redundant buoyancy.