Weighting for descent vs bottom

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@mi000ke I would not lower a tank to 100psi on a boat dive. My tank, my dive site no problem I might then. I still think handing 2 lbs to buddy or DM at the end of SS will tell you all you need to know.
 
Very interesting discussion, but it brings to mind the old saying "Measure with a micrometer, and cut with an ax." The concept of super accurate and precise weighting for a SS at 15' or some other depth might come into play if you are diving at your local spot and using all of your own gear, including weights. However, that degree of precision has little to do with the reality of doing dives across the world with a wide variety of different dive ops, as well as the variance in available weights and accuracy of the weights themselves. For example, I have commercially purchased 2, 3, 4, and 5 pound weights, plus a bunch of homemade ones, none of which weigh exactly as stamped. So, if I grab four 4# weights on the dive boat, depending on the variations in actual weight, I could easily be a pound or so over or under what I actually think I have. And then the dive boat may not have the exact poundage I really want, so wind up using a couple pounds more than I think is ideal. Personally, I have never had a problem carrying an extra 2-3 pounds, and far prefer that than to risk corking to the surface at a time and place that is not of my choosing.
 
Very interesting discussion, but it brings to mind the old saying "Measure with a micrometer, and cut with an ax." The concept of super accurate and precise weighting for a SS at 15' or some other depth might come into play if you are diving at your local spot and using all of your own gear, including weights. However, that degree of precision has little to do with the reality of doing dives across the world with a wide variety of different dive ops, as well as the variance in available weights and accuracy of the weights themselves. For example, I have commercially purchased 2, 3, 4, and 5 pound weights, plus a bunch of homemade ones, none of which weigh exactly as stamped. So, if I grab four 4# weights on the dive boat, depending on the variations in actual weight, I could easily be a pound or so over or under what I actually think I have. And then the dive boat may not have the exact poundage I really want, so wind up using a couple pounds more than I think is ideal. Personally, I have never had a problem carrying an extra 2-3 pounds, and far prefer that than to risk corking to the surface at a time and place that is not of my choosing.

Yup. I ended up diving for a week in Coz a couple of pounds heavier than really necessary because they didn't have any 1lb weights, which I would have needed to get to where I wanted. I could have moved weights around some to get the right total weight, but then my trim would have been screwed up. I opted to be a couple of pounds heavy, but in good trim, rather than the at the correct total weight, but with a messed-up trim.
 
*Most of the time I surface with more than 1,000 PSI on a dive (aluminum 80), so I need to take that into consideration about how I felt about the weighting on a particular dive. That's what, 2 pounds in an AL80? It's a small amount, but if I've diving with 4 pounds of lead (plus whatever weight from my regulator, fins, camera, etc.) and I felt fine in terms of buoyancy, should I actually be adding 2 pounds of lead to account for a lighter tank?

If you are at 15' at 1000# with an empty BC, then adding 2# for the rest of the air would work. This should be done using your basic kit. Then you should check the buoyancy of the camera, or any other dive specific gear that could be lost on a dive, a couple of pounds could be made up by breathing technique, but larger amounts cannot. So don't subtract the 10# hammer and chisel to liberate a porthole from your weightbelt because you might lose it and blow through the safety stop or worse yet, if needed, a deco stop.

A discussion among the converted is interesting, the people I worry about is typified by a diver I met on a boat that lost one of his weight pockets. I found it on the bottom and tried to see if it belonged to anyone on the boat, everyone said no. The next morning he found his pocket missing and came to me. He had a buoyancy problem which he adjusted for and made a proper safety stop, but couldn't figure out why he kept rolling to one side while going back to the boat. I gave back the pocket and told him to leave that weight on the boat and split the other pocket weight between the two and see how that worked. He may still have had too much weight but not by nearly as much.


Bob
 
If you are at 15' at 1000# with an empty BC, then adding 2# for the rest of the air would work. This should be done using your basic kit. Then you should check the buoyancy of the camera, or any other dive specific gear that could be lost on a dive, a couple of pounds could be made up by breathing technique, but larger amounts cannot. So don't subtract the 10# hammer and chisel to liberate a porthole from your weightbelt because you might lose it and blow through the safety stop or worse yet, if needed, a deco stop. Bob

I'm inclined to add up the total amount of the kit because it represents the total weight I need. I'm simply viewing it as, of the total weight I need for proper buoyancy, X amount comes from lead weights.

Btw, how would you define being overweighted? Is it a number (absolute or percentage) or it is the impact it has on the diving?
 
I'm inclined to add up the total amount of the kit because it represents the total weight I need. I'm simply viewing it as, of the total weight I need for proper buoyancy, X amount comes from lead weights.

Btw, how would you define being overweighted? Is it a number (absolute or percentage) or it is the impact it has on the diving?

In the big picture, it's the effect it has on your diving, but I personally think it's more of an effect of the actual amount, rather than a percentage. If you're 5 lb over-weight, you have to put approx. 5 pints of air into your BC to counteract it, no matter what percentage that is. And that 5 pints will expand to 10 pints (putting you 5 lb too buoyant) when you go up from 90 ft to 30 ft no matter what the percentage is.
 
I weight my self for the bottom because that's where you are the longest. I swim down so being light at the surface is NBD to me and I don't have problems at the safety stop. I also dive steel tanks to the weight swing to positive is less with an empty tank. The biggest thing is being comfortable on your dive, because it's your dive.
 
I weight my self for the bottom because that's where you are the longest. I swim down so being light at the surface is NBD to me and I don't have problems at the safety stop. I also dive steel tanks to the weight swing to positive is less with an empty tank. The biggest thing is being comfortable on your dive, because it's your dive.

While I agree with what you are saying, I cannot agree on the weight swing on a steel or aluminum tank. The weight of the air consumed is the same PROVIDED that the tank has the same content. :drunks:
 
True, I was meaning the swing into the positive side of neutral. An Al 80 is way positive and steels are closer to neutral @ the same psi. The way steels float may help.
 
I don't know where this talk about weighting for the safety stop at the end of the dive comes from. This means that the last 15 ft of every dive involve an uncontrolled ascent, which is something you want to avoid.

Of COURSE you want to be weighted right for the 15 ft stop but also at 10ft and 5ft or even 2ft. Cutting back on the couple of pounds of weight it takes to maintain control throughout the *entire* dive from surface to surface is like having breaks on your car that stop at some point AFTER the stop sign. Someone said above that the perfect weight was with 500# in the tank. What if the diver gets delayed and he has 300# in the tank? Cutting the margin so thin will mean that he will not be able to hold his safety stop if he has to use any of the reserve air he has...... think about what you're saying here.

Anyway, I think this is wrong thinking. Obviously we are dealing here with two different paradigms but I think the difference in how much weight you need to be in control all the way to the surface isn't worth the potential issues involved in making an uncontrolled ascent through the last 15ft of every dive. Seriously.

If you think about it, no technical diver on the planet would weight themselves to make an uncontrolled ascent over the last 15ft of every dive for obvious safety reasons so why are you recommending for recreational divers to do just that? It's bad advice if you ask me.

R..

I couldn't agree more. The above is what everyone should recommend for fellow divers regardless how they do it themselves. Also, more often than not my dives do not end with a static safety stop at 5 m and then a pop to the surface. They typically end with a gradual accent with a lot of time spent in the region 6 - 1 meter. I need to be weighted for that too.
 

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