Extra Lead

[MikeFerrara]

While I agree that all divers should learn early on about optinal weighting, and try to be at their ppb at all times, the sad reality of open water classes is that even if a student understands weights, how they work, how much should be worn, they're still wearing unfamiliar gear, they're still nervous, they're still getting used to breathing underwater and what that does to buoyancy.
It took me time to get my weighting down correctly, and that was after 20-30 dives, trying different setups, and even now, it changes depending on how I'm feeling, what I'm wearing, so to try to rush students into the same realm is more dangerous. I for one would rather have a student slightly bouncing on the bottom than jetting to the top as they learn about their gear inflation.

If a student doesn't have a better handle on it than that, I don't want him on the bottom. A diver has a greater chance of an uncontrolled ascent if they're over weighted. It's true that a divers weight needs will change some as technique improves but, IMO, they should be pretty good before ever leaving the pool. BC is one of the first skills that needs to be mastered rather than one of the last.

I see a lot of lead every weekend helping classes, and some students wear almost 3x the weight I wear (and I'm not a small guy), its just part of open water.

This is the sad truth but it doesn't have to be that way. The sad truth is that most classes don't really teach buoyancy control at all but rather leave the student to hopfully learn it on their own later.

I did it once as a student, I'll bet most divers did.

Me too. And once I gained a little more experience I was determined to do things different with my students.

A student knowing about optimal weighting and a student being able to perform with it are too vastly different and temporally-segregated things. If anything, rushing students to perform under conditions they are not used to is even more dangerous than a student wearing a few more pounds. Having a student descend slowly to the bottom - even if as a result of a few extra pounds in their pockets - is paid back triplefold by a comfortable, excited student underwater.

What's dangerous is plastering students to the bottom so they can kneel and clear a mask. That is forcing students to perform under conditions they aren't used to. On the other hand if they better master buoyancy control in a shallow controled environment (like a pool) they can comfortably clear that mask while neutral and horizontal (while diving) like the rest of us do.

 

[mweitz]

Certainly there is a happy medium. If you look at the wording of my original post, I am not talking about weighting during the OW class. What I am referring to specifically is mostly the "discussion" of weighting, how to properly figure it and why it is important.

I currently use about 22#. I'm 5'10, 200#, Xcel 9/7/6 with an E7-120. I was told to use 10% of my bodyweight plus 12# (32#). I started with 30, and would still be there if I hadn't found this board. BTW, I was sinking like a ROCK with 30#. When I went back to my LDS to go over weighting again, I was told not to use less than 26#.

Mark

 

[Chuck Tribolet]

The rules of thumb are for a starting point only. Slowly
reduce the amount of weight you need until you can hold
your 15' stop with NO air in your BC, 300 PSI, and no
kicking.

If you want to experiment in a freshwater pool, get it right,
then take the weight of the entire system (diver, all gear
including lead) and multiply by .0256. Add that much
lead and you will be right on in saltwater. That's not a
rule of thumb, that's physics. Typical saltwater is 2.56%
more dense than fresh water. Red Sea is slightly denser
but not enough to matter.

 

[Brian Gilpin]

The rules of thumb are for a starting point only. Slowly
reduce the amount of weight you need until you can hold
your 15' stop with NO air in your BC, 300 PSI, and no
kicking.

True but this needs to be done at the end of the dive with about 500 lbs in tank not at the begininning with a full tank.

If you want to experiment in a freshwater pool, get it right,
then take the weight of the entire system (diver, all gear
including lead) and multiply by .0256. Add that much
lead and you will be right on in saltwater. That's not a
rule of thumb, that's physics. Typical saltwater is 2.56%
more dense than fresh water. Red Sea is slightly denser
but not enough to matter.

Lead is subject to the exact weight of predictable physics every time. Human behaviour is a different thing. Weighting someone in the warm calm waters of a pool is appropriate. Next you adjust as Chuck indicates.Now put this same person with the adjusted weight in a small surge and 52 degree water and many will not sink. And I am assuming here that they are initially overweighted by the amount of air in their tank.If you watch them closely you will see that their body is doing all sorts of different things to keep them from sinking.They even kick upwards and then tell you they cannot get down.Almost always they dont even know they are doing it!

Imagine you have weighted everyone correctly and once you have entered the water three of your five students cannot sink. How much extra weight can one instructor carry? Go through this a few times and see what you do. My only beef is that sometime in the course when the student is more comfortable this needs to be corrected and it seldom is.

 

[MikeFerrara]

True but this needs to be done at the end of the dive with about 500 lbs in tank not at the begininning with a full tank.

No problem doing it with a full tank. Just get nuetral and then add a few pounds...we know what a the buoyancy shift of the tank will be...right?

Lead is subject to the exact weight of predictable physics every time. Human behaviour is a different thing. Weighting someone in the warm calm waters of a pool is appropriate. Next you adjust as Chuck indicates.Now put this same person with the adjusted weight in a small surge and 52 degree water and many will not sink. And I am assuming here that they are initially overweighted by the amount of air in their tank.If you watch them closely you will see that their body is doing all sorts of different things to keep them from sinking.They even kick upwards and then tell you they cannot get down.Almost always they dont even know they are doing it!

If they don't want to go down or don't know how...I'd rather they didn't.

Imagine you have weighted everyone correctly and once you have entered the water three of your five students cannot sink. How much extra weight can one instructor carry? Go through this a few times and see what you do. My only beef is that sometime in the course when the student is more comfortable this needs to be corrected and it seldom is.

Well, I can tell you what I did. I made them learn to descend before we started OW dive 1.

If they're weighted right...and they know how to descend...they must go down right?

The answer to flailing hands and feet is to stop flailing the hands and feet...not to add more weight.

That's like saying you need a bigger engine in your car because it don't go fast enough with the emergency brake locked on...just take the brake off.

Doc, it hurts when I do this...and doc says...well don't do it.

As my daughter would say..."well NO DUUUHHHH!"

 

[Ishie]

I was diving way overweighted. I'm 5'3, 155# with two piece 7 mm wetsuit. Started with 26# but went to 24 by my last cert dive.

When our instructor noticed our problems getting down (Jim had the same problem), he made some suggestions that really came in handy. I noticed that even crossing my legs so I wouldn't inadvertantly fin up (which I did at the very beginning), I was still having trouble initially getting down. He pointed out that we were probably getting so excited before a dive and anticipating going down that we were breathing in too deeply as we tried to descend, filling our lungs and of course, going up.

We've worked on it and are doing pretty well. I stopped using 24 after hitting the bottom of Lover's one day like a piano. Right now I'm at 20. I still feel a bit heavy in the beginning of a dive. I've tried 18 with success for the first three quarters of the dive, but the minute the AL80 gets a little low, I start having some trouble staying down when I'm between 5-12 feet. Jim's problem is worse since he uses more air than I do, so his tanks get lighter.

This last weekend (and what a horrid weekend it was), I felt very overweighted on a night dive because I had swapped out my 80 for a steel 72 I rented without adjusted my weight. Whoops. I like the steel, and I want to replace my tank with a high pressure 80 in the long run, but it takes some getting used to, including problems with rolling.

 

[MikeFerrara]

I was diving way overweighted. I'm 5'3, 155# with two piece 7 mm wetsuit. Started with 26# but went to 24 by my last cert dive.

When our instructor noticed our problems getting down (Jim had the same problem), he made some suggestions that really came in handy. I noticed that even crossing my legs so I wouldn't inadvertantly fin up (which I did at the very beginning), I was still having trouble initially getting down. He pointed out that we were probably getting so excited before a dive and anticipating going down that we were breathing in too deeply as we tried to descend, filling our lungs and of course, going up.

We've worked on it and are doing pretty well. I stopped using 24 after hitting the bottom of Lover's one day like a piano. Right now I'm at 20. I still feel a bit heavy in the beginning of a dive. I've tried 18 with success for the first three quarters of the dive, but the minute the AL80 gets a little low, I start having some trouble staying down when I'm between 5-12 feet. Jim's problem is worse since he uses more air than I do, so his tanks get lighter.

This last weekend (and what a horrid weekend it was), I felt very overweighted on a night dive because I had swapped out my 80 for a steel 72 I rented without adjusted my weight. Whoops. I like the steel, and I want to replace my tank with a high pressure 80 in the long run, but it takes some getting used to, including problems with rolling.

Even perfectly weighted you will be heavy in the beginning by the weight of the air in the tank (about 6 pounds for an 80 cu ft tank).

As you noticed, if you take off too much you'll have trouble at the end of the dive. You need to be careful here because if you're in a heavy wet suit you may be fine at depth where the suit has lost much of it's buoyancy due to compression. As you ascend, though, and the suit expands and becomes more buoyant you'll shoot to the surface. Not good.

You need to be correctly weighted for a near empty tank.

 

[CALI68]

What Mark has yet to mention is that He and Jason (Darkpup) were helping at least one person with 40lbs of weight!!!!! That's deplorable! Physics, rules of thumb or otherwise...that's just stupid. Why not just tie an anchor to the Diver?

 

[Ishie]

Even perfectly weighted you will be heavy in the beginning by the weight of the air in the tank (about 6 pounds for an 80 cu ft tank)...
You need to be correctly weighted for a near empty tank.

I knew about adjustments for the beginning of the dive. Haven't used a steel tank since my eighth dive or so (now at 48) and I was surprised by how much of a difference there was when I swapped my AL80 out with the steel 72.

Thanks!

 

[coreypenrose]

I knew a Monterey diver who dove with a 40 lb weight belt and 20 lbs in his BC...