Sidemount stage/deco bottle question.

[Aquabot]

I'm fairly new to sidemount but well read and recently had a question pop I to my head that I forgot to ask my instructor. During my course I asked my instructor about caring stages/deco bottles, at which point he explained the technique he used. I remember him telling me that that for every tank added you would need to add 2lbs to counter the weight of the valves and maintain trim.

Now my question is this:
When you go and doff the stage/deco bottles wouldnt the extra weight throw off your trim or am I just over thinking it?

I realize that moving the weight from the body to the tanks with camband is a possibility, but I personally don't like that. I have not had a chance to get into the water with my extra bottles and experiment yet.

 

[tbone1004]

I've never had to add weights to counter stage bottles.... Did 5 stage dives last week with no issue. It does effect your trim slightly in the beginning but once you breathe it down it balances out fine, but with most rigs you can just pack some more air on that side of the wing and counter it or just adjust your body positioning for the first 5-10 minutes.

In cave diving you drop the bottles so the weight would be a major pain, in open water I might maybe think about it, but that's all it would be since the deco bottle would be on the right and would counter the stage on the left. Keep in mind, DIR divers put everything on the left without trim weights, and as soon as you breathe the bottle down, the al80 will start floating which makes the trim weight counterproductive since it would throw you pretty hard to the other side. No offense to your instructor, but it doesn't sound like he really knows what is going on....

 

[Aquabot]

I've never had to add weights to counter stage bottles.... Did 5 stage dives last week with no issue. It does effect your trim slightly in the beginning but once you breathe it down it balances out fine, but with most rigs you can just pack some more air on that side of the wing and counter it or just adjust your body positioning for the first 5-10 minutes.

In cave diving you drop the bottles so the weight would be a major pain, in open water I might maybe think about it, but that's all it would be since the deco bottle would be on the right and would counter the stage on the left. Keep in mind, DIR divers put everything on the left without trim weights, and as soon as you breathe the bottle down, the al80 will start floating which makes the trim weight counterproductive since it would throw you pretty hard to the other side. No offense to your instructor, but it doesn't sound like he really knows what is going on....

Thanks tbone1004 for your response . I can say that he does know what he is doing with out a doubt lol. The course was for just basic open water side mount and we did not go into detail about it as it wasn't a focus within the course, was just a curiosity on my part.

He did let me take one of his cylinders during the final dive tho just to see what it felt like and I definitely went head down (see photo of me with the extra bottle). I do intend on asking him the same question I asked here to see what his response is.

After I donned the extra tank it was everything I could do to not go head down.

 

[tbone1004]

well you look fine in that picture trim wise but think of the math, also I was thinking you meant putting it on the other side of your body to counter roll, not pitch, either way though, not needed.

Valve+first stage=2lbs
AL80's, at least luxfers which are preferred stages, are 4.4lbs positive when empty, 1.4lbs negative when full. So to put a 2lb trim weight to counter the head of the bottle for roll, you will go farther out of roll stability as the tank gets breathed down because you'll go from 1.4lbs heavy on the left, to 4.4lbs heavy on the right when the tank is empty, not good.

As far as pitch stability you have a few different options. First one would be to get the tank as far down your body as possible. with first stages behind your arm pits it is pretty much a nonissue as sidemounting with steel tanks tends to put you foot heavy anyway, top mounting stages helps dramatically with this btw. The other option is to use 2" SS cam bands which are about 1lb negative and when clipped to your weight belt will help to pull the weight back a bit, but the biggest thing is to get the bottles pulled as far down as possible. The razor guys tend to keep their stages pretty far forward, which is fine, but you can usually counter that by pulling your arms in, extending your feet slightly, or just arching your back a bit more.

 

[Aquabot]

well you look fine in that picture trim wise but think of the math, also I was thinking you meant putting it on the other side of your body to counter roll, not pitch, either way though, not needed.

Valve+first stage=2lbs
AL80's, at least luxfers which are preferred stages, are 4.4lbs positive when empty, 1.4lbs negative when full. So to put a 2lb trim weight to counter the head of the bottle for roll, you will go farther out of roll stability as the tank gets breathed down because you'll go from 1.4lbs heavy on the left, to 4.4lbs heavy on the right when the tank is empty, not good.

As far as pitch stability you have a few different options. First one would be to get the tank as far down your body as possible. with first stages behind your arm pits it is pretty much a nonissue as sidemounting with steel tanks tends to put you foot heavy anyway, top mounting stages helps dramatically with this btw. The other option is to use 2" SS cam bands which are about 1lb negative and when clipped to your weight belt will help to pull the weight back a bit, but the biggest thing is to get the bottles pulled as far down as possible. The razor guys tend to keep their stages pretty far forward, which is fine, but you can usually counter that by pulling your arms in, extending your feet slightly, or just arching your back a bit more.

Thanks again tbone. Yea I reckon I could have explained it a little better lol.