How much weight to use

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blue steal

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Not sure if this is the forum to post in, but here goes.
I need a bit of advice on how much weight to use.
I have been diving "cold" water with an AL80 and using 24lb on a weight belt or weight intergrated BCD.
I am buying a HP100 steel tank and wanted to know where to start.
Stats show the AL80 is -1.4 full and +3.5 when empty(500psi?).
The HP100 is -10 full and -2.5 empty.
so, I'm thinking about 8 lbs less to a 16lb weight belt.
Also would like to use those tank cam bands weight pouches from XS suba to trim out better, maybe 2-6lbs. there and further decrease the weight on the belt.
Any advice would be appreciated...........thanks
 
...I would start by using 4 - 6 lbs less weight, see how that goes, then on the next dive lighten up by 2 lbs as needed.....it's better to be a little overweighted and gradually cut back than be underweighted and not be able to hold a safety stop. Trim pouches have their place, but watch out for non-ditchable weight that can be a problem in an emergency.
 
Not sure if this is the forum to post in, but here goes.
I need a bit of advice on how much weight to use.
I have been diving "cold" water with an AL80 and using 24lb on a weight belt or weight intergrated BCD.
I am buying a HP100 steel tank and wanted to know where to start.
Stats show the AL80 is -1.4 full and +3.5 when empty(500psi?).

Yes, at 500 PSI, although they usually quote it as +3.4 at that pressure, assuming this is a Luxfer. It's +4.4 empty. Figure the Worthington HP100 will be -3.5 at 500 PSI.

The HP100 is -10 full and -2.5 empty.
so, I'm thinking about 8 lbs less to a 16lb weight belt.

No, because it's the weight when they're near empty that matters, not that when they're full. The larger tank has a greater difference in buoyancy between full and empty than the smaller one, so you'll find you sink much easier at the start of the dive. Figure the difference in buoyancy at the safety stop at ~7 lb (-3.5 to +3.4). Eight lb. less will probably be excessive, unless you're normally a bit overweighted and can afford to drop the weight in any case. I'd start with 6 lb. less and adjust it downwards 1 lb at a time.

Unfortunately, it's pretty tough to make 1 lb. changes symmetrically owing to the lack of .5 lb. weights. About all you can do is use 1 lb. ankle weights attached to your valve or something similar, unless you have a weight belt with an odd number of pockets. However, having 1 lb. extra on one side probably won't be a big deal if you even notice it, but try it for yourself and see.

Also would like to use those tank cam bands weight pouches from XS suba to trim out better, maybe 2-6lbs. there and further decrease the weight on the belt.
Any advice would be appreciated...........thanks

If you're diving dry in cold water, I'd recommend putting all your weight on the cambands (or in trim pockets on the BC) - I use a 6 lb. S/S BP/W with 4 lb. (Asahi HP100) or 8 lb. (OMS LP112) of lead in camband pockets. If you're diving wet then I'd try splitting your weight 50/50 between the belt (or weight integration) and pockets - you shouldn't split it more than 75/25, and less of a spread is better. If the BC you're using has two cambands instead of one, you can also experiment with and adjust your trim by putting the pockets on either the top or bottom band. Just make sure to locate the pockets as close to the BC bladder (and your back) as you can get them.

Guy
 
I have been diving "cold" water with an AL80 and using 24lb on a weight belt or weight intergrated BCD.
I am buying a HP100 steel tank and wanted to know where to start.
Stats show the AL80 is -1.4 full and +3.5 when empty(500psi?).
The HP100 is -10 full and -2.5 empty.
so, I'm thinking about 8 lbs less to a 16lb weight belt.
According to the TechDivingLimited.com website, the Luxfer 80 tank is +4.4 lbs. empty.
The tank specs indicate that you should be taking off 6.9 lbs. of lead when you switch from AL80 to HP100.
Simple math. It's the difference between the buoyancy specs when empty: (-2.5) - (+4.4) = -6.9 lbs.
As Guy Alcala states above, it's difficult to work with odd amounts of weight due to symmetry. Take off either 6 or 8 lbs. I'd recommend erring on the heavy side (so initially try taking off 6 lbs.).
Keep in mind that the published buoyancy specs of a particular tank may not be entirely accurate.
Also would like to use those tank cam bands weight pouches from XS suba to trim out better, maybe 2-6lbs. there and further decrease the weight on the belt.
Go ahead and get the XS Scuba weight pouches. I use 'em and they work great with my BP/W. How much weight you should shift from your waist/belt to the weight pouches depends on your specific body type and gear configuration. It's very much a trial-and-error process. Start off with small weights (2 lbs.) in each weight pocket and adjust until everything's just right. Good luck!
 
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I'd start off by removing 6#.

Looking at the empty buoyancy of the two tanks you listed, the delta is 6#. When comparing different tanks trying to figure out what, look at the end value. You need to be weighted properly to hold you SS.

SS back plates are 5-6#. Get a couple of the XS pockets for the cam bands and stick 3# on each side of the tank and see how that does.

Effectively you've removed 12# off your weight belt. Not too shabby!
 
I did exactly that - went from AL80 to HP100 - a year ago. You will be 8 lbs more negative with a full tank and 6 lbs more negative at 500 psi. If your weighting is controlled by your safety stop as mine is, then you can take 6 lbs of lead off your ballast.

I then switched my BCD for a SS BP/W and dropped another 8-10 lbs. of lead.
 
Thanks for the good tips.
I think I will start with 6 lb off the belt.
Then get the XS scuba trim pouches and try 3lb on each side for 6 lb.
The Belt will then have 12lb.
Now for another twist.....................
I'm going to stop renting the BC and make the purchase to a SS DSS Hog rig in another month or so. Question now is how much more weight can I take off? I think the DSS SS plate is 6 lbs.
I understand I need some ditchable weight, so I'll keep my weight belt.
 
...I would start by using 4 - 6 lbs less weight, see how that goes, then on the next dive lighten up by 2 lbs as needed.....it's better to be a little overweighted and gradually cut back than be underweighted and not be able to hold a safety stop. Trim pouches have their place, but watch out for non-ditchable weight that can be a problem in an emergency.
What he said...that's what I did.

I did exactly that - went from AL80 to HP100 - a year ago. You will be 8 lbs more negative with a full tank and 6 lbs more negative at 500 psi. If your weighting is controlled by your safety stop as mine is, then you can take 6 lbs of lead off your ballast.

I then switched my BCD for a SS BP/W and dropped another 8-10 lbs. of lead.

Ditto again. I dive with a total of 14 less lbs now when in the same exposure protection.
 
Thanks for the good tips.
I think I will start with 6 lb off the belt.
Then get the XS scuba trim pouches and try 3lb on each side for 6 lb.
The Belt will then have 12lb.
Now for another twist.....................
I'm going to stop renting the BC and make the purchase to a SS DSS Hog rig in another month or so. Question now is how much more weight can I take off? I think the DSS SS plate is 6 lbs.
I understand I need some ditchable weight, so I'll keep my weight belt.

Maybe a pound or two.

The 6# that you will be putting into those two neat little pouches is basically simulating having a 6# SS BP on now. With that said, typical BC's tend to be normally buoyant. Take your BC and try to sink it next time. It won't. There will be a couple of less pounds that you need to sink your BC.

If you get a STA for your rig, assuming you're diving singles, that is another pound or two that can come off your belt.

As you noted, you want some ditchable weight.
 
I am a big fan of the XS Scuba pouches.......

3 lbs per pouch is a good amount, 4 is the max......

I think they are rated for 5 lbs but that really fills them up......

If you need more weight high up then the 1 or 2 lb ankle weights around the tank neck seem to work well for adjusting trim.......

Hope this helps......M
 

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