double tank weighting issue?

[Flightlead]

Well, honestly I'm going to continue to stay away from a weight belt. I admit I'm nowhere near as experienced or knowledgeable as most of the participants in this discussion, but since there doesn't seem to be a clear advantage either way I'm gonna permanently ditch my weight belt. It is practically impossible to wear with my doubles, gets in the way, slips, screws up my trim, is uncomfortable, and frankly, I think its dangerous.

I did have an idea though, I used to work for a company that made space batteries. one design was a single pressure vessel about 3x the size of a football. Now, if I could rig up a pump I could use that as an adjustable ballast tank. can't figure out how to attach diving planes to my backplate though

 

[Thalassamania]

Well, honestly I'm going to continue to stay away from a weight belt. I admit I'm nowhere near as experienced or knowledgeable as most of the participants in this discussion, but since there doesn't seem to be a clear advantage either way I'm gonna permanently ditch my weight belt. It is practically impossible to wear with my doubles, gets in the way, slips, screws up my trim, is uncomfortable, and frankly, I think its dangerous.

Actually I think that you'll find it will help your trim. But that's your choice.

I did have an idea though, I used to work for a company that made space batteries. one design was a single pressure vessel about 3x the size of a football. Now, if I could rig up a pump I could use that as an adjustable ballast tank. can't figure out how to attach diving planes to my backplate though

We tested out a buoyancy control cylinder that our shop built for a small ROV. We were not actually planning on using if for diving, but it was kind of fun. It was a cylinder with a piston in it that could be moved up and down by an electric motor to change buoyancy. There was a "stay here" button that once pushed would cause the cylinder to alter buoyancy and attempt to maintain constant pressure on it's transducer. It was kind of fun to play with, but the mechanical system was too slow and the lag made it constantly overshoot its depth and then turn around and overshoot it the other way.

 

[Flightlead]

Actually I think that you'll find it will help your trim. But that's your choice.

well, I find a weight belt hurts my trip as it puts the weight around my hips and makes me feet heavy. without a weight belt, with the center of mass/center of lift aligned, I can easily maintain a flat trim

We tested out a buoyancy control cylinder that our shop built for a small ROV. We were not actually planning on using if for diving, but it was kind of fun.

I was only joking about that part

 

[Thalassamania]

well, I find a weight belt hurts my trip as it puts the weight around my hips and makes me feet heavy. without a weight belt, with the center of mass/center of lift aligned, I can easily maintain a flat trim

I guess a piece of it is what you are used to. I like to be able to adjust my trim on the fly and with a weight belt I can push it up a little or pull it down a bit and that has a huge effect.

I was only joking about that part

I know you were, but sometimes even the things you joke about come true.

 

[Papa_Bear]

Well, honestly I'm going to continue to stay away from a weight belt. I admit I'm nowhere near as experienced or knowledgeable as most of the participants in this discussion, but since there doesn't seem to be a clear advantage either way I'm gonna permanently ditch my weight belt. It is practically impossible to wear with my doubles, gets in the way, slips, screws up my trim, is uncomfortable, and frankly, I think its dangerous.

I did have an idea though, I used to work for a company that made space batteries. one design was a single pressure vessel about 3x the size of a football. Now, if I could rig up a pump I could use that as an adjustable ballast tank. can't figure out how to attach diving planes to my backplate though

May I ask why you need a wight belt with doubles? They are usually heavy enough not to need a belt?!!! So what is going on with your set up? You shouldn't have to wear one! Did I miss something?

 

[nereas]

Thanks everyone for all your info, da aquamaster, if I find that I need to add weight I can simply switch to my SS backplate, but the way it is set up now is right on with the Al backplate, Im going to do some more practise in the pool to make sure Thanks

If you are going to dive with all non-ditchable weight, then you should have 2 methods of buoyancy, in case you need it. When diving with your 3mm suit, this means you should have a double-bladder wing. You can get these from Oxycheq easily enough.

When diving with your drysuit, this can serve as your backup buoyancy. Not great, but better than no backup.

If your leg(s) cramp, then you won't be able to swim anything up. Thus swimming-up, although a popular myth among some agencies, is a dangerous recourse in the absence of a real backup buoyancy system.

Those above who have joked about ditchable weight are joking with the Grim Reaper, and he is laughing too.

 

[nereas]

May I ask why you need a wight belt with doubles? They are usually heavy enough not to need a belt?!!! So what is going on with your set up? You shouldn't have to wear one! Did I miss something?

Yes, indeed, you have missed plenty.

Gas weighs about 0.08 lbs per cubic foot. As you exhale, you lose this ballast from your tank(s) during the dive.

Your non-ditchable weight would ideally make you neutral (not buoyant) in the water at the beginning of your dive. And your weight belt would provide the added ballast to make you neutral at the end of your dive, when your tanks are lighter.

Thus at any point in your dive you could ensure neutral or slightly positive buoyancy by dropping your belt if absolutely necessary, if an NDL dive, or else allow you to establish positive buoyancy at the surface at the end of your dive.

That is what you are missing.

But feel free to dive negatively buoyant with all non-ditchable weight. Be advised that you are gambling with the Grim Reaper, in that case.

 

[JeffG]

They are usually heavy enough not to need a belt?!!! So what is going on with your set up?

Weight is not the same as buoyancy.

You shouldn't have to wear one! Did I miss something?

Yes. You need to get out more.

 

[TSandM]

May I ask why you need a wight belt with doubles? They are usually heavy enough not to need a belt?!!! So what is going on with your set up? You shouldn't have to wear one! Did I miss something?

This is very individual. For me, using double LP85s and the undergarments required to keep me warm in 42 degree water, I'm carrying 26 pounds of lead to be neutral at 5' with 300 psi, which is where I weight myself. And this has been checked, so I'm not overweighted.

 

[Papa_Bear]

If you are wearing doubles you obviously need a BCD to control your trim, but you don't need wights that are detachable depending on the kind of diving you will do! Wights are for one thing and one thing only to sink the rubber! If you can dive without wights you will have a better dive! Longer dives as well! A BCD is not required, but nether is a motor in your car if your at the top of the hill! But getting back up the other side could be a challenge? Every diver should strive to use as little wight as possible!

Are you doing a dry suit? With my 7mm and twin 105's I don't need any and I am not skinny! Under garments would indicate Dry suit and over coming air and bulk in the suit, I would never talk to you about density! But 26lbs with doubles is a lot of wight! Good luck with that! I wouldn't want to trek the trails in all that!