It all affects your weighting, exposure protection, cylinders, fresh or salt water etc. I won't chime in about how much weight you should use as it is different for everybody. Keep it as evenly distributed as possible as you don't want all of it on your waist. I keep a chart of my configurations and the weight I use for each including if it is a new or old wetsuit and fresh or salt water. Most of it I remember but if it has been awhile for a certain configuration I just look it up and done.
Weight distribution with changing gear configurations
- Thread starter Cthippo
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@Cthippo , you said that you completely emptied your BCD with a near-empty tank today, what did that do to your buoyancy? I would expect you to still be quite negative, which would imply that you can still drop more weight, as others in the thread have suggested. But if you were neutral, and your BC was totally empty, then you have found the right amount of lead
As for the cylinder question: yes, you most definitely should adjust your weighting when you switch from one tank to another. @tmassey compiled a detailed list of the specs of many common tanks, it's available in the second post of this thread: Updated SCUBA tank specifications list -- in PDF and spreadsheet
The relevant column is the second-to-last one, which is the buoyancy of the tank when empty. Typical Catalina AL80's are +4.1 lb, and typical Faber LP95's are +1.69 lb, so you should be able to dive the LP95 with about 2 lbs less lead, all else being equal. Note that it's important to compare the empty tank buoyancy here, not the full tank buoyancy, because it's the end-of-dive buoyancy that is relevant.
As for the cylinder question: yes, you most definitely should adjust your weighting when you switch from one tank to another. @tmassey compiled a detailed list of the specs of many common tanks, it's available in the second post of this thread: Updated SCUBA tank specifications list -- in PDF and spreadsheet
The relevant column is the second-to-last one, which is the buoyancy of the tank when empty. Typical Catalina AL80's are +4.1 lb, and typical Faber LP95's are +1.69 lb, so you should be able to dive the LP95 with about 2 lbs less lead, all else being equal. Note that it's important to compare the empty tank buoyancy here, not the full tank buoyancy, because it's the end-of-dive buoyancy that is relevant.
You need to be careful using that list for this purpose. It is based on manufacturer specs and some manufacturers list the buoyancy spec including a valve while others do not. For example Faber does not include the buoyancy of the valve in its listing. With a valve, it's actually around 1lb negative.
That's why I prefer the Huron Scuba list at SCUBA Cylinder Specifications – Huron Scuba, Snorkel & Adventure Travel Inc. PADI 5 star IDC in Ann Arbor, MI for this kind of thing.
Yes, I do.
With an aluminum 80 in saltwater I carry 12 pounds of weight in my 3/2 suits (generally with a 3mm vest and rash guard under). I carry 4 to 6 pounds of it in cam band pouches. The remainder is carried in two QR (quick dump) pouches on my waist belt. This balances well and I can get buoyant on the surface if needed by dumping that 6 or 8 pounds in the QR belt pouches. If I am using my LP steels I do not need weight in the cam band pouches, they are empty. I do not mind being very slightly buoyant at the end of a dive as long as I can hold my stop. A few weeks ago I must have lost a 3 pounds weight out of my QR pouches. I got to my stop and kept having to swim down. I had been indulging myself with large size DQ Blizzards during the trip and figured, dang, I am fat! I was so relieved when I got back on the the deck and noted I had lost a weight, ohhhh, okay
. I celebrated with yet another Blizzard, yum!James
What is the buoyancy of your rig without tank and weights?Yes, I do.
With an aluminum 80 in saltwater I carry 12 pounds of weight in my 3/2 suits (generally with a 3mm vest and rash guard under). I carry 4 to 6 pounds of it in cam band pouches. The remainder is carried in two QR (quick dump) pouches on my waist belt. This balances well and I can get buoyant on the surface if needed by dumping that 6 or 8 pounds in the QR belt pouches. If I am using my LP steels I do not need weight in the cam band pouches, they are empty. I do not mind being very slightly buoyant at the end of a dive as long as I can hold my stop. A few weeks ago I must have lost a 3 pounds weight out of my QR pouches. I got to my stop and kept having to swim down. I had been indulging myself with large size DQ Blizzards during the trip and figured, dang, I am fat! I was so relieved when I got back on the the deck and noted I had lost a weight, ohhhh, okay
James
Good question, really, I do not know. These are my two usual rigs and I weight the same for either:
The VDH 22# wing and plate on the left I notice tends to sink in the rinse tank and the Oxy 18# wing and plate tends to float in the rinse tank. They are both fairly transparent to the rest of what is going on, that being exposure protection and cylinder. I have a steel plate on an Oxy 30# wing. If I use it with an aluminum 80 it dives much like the two rigs above do on a steel tank, no cam band weights needed.
My wife has a VDH plate and 18# VDH wing, she is a little bitty thing but I set her up with 14 pounds (split between cam bands and QR pouches) I think with an aluminum 80. I can probably do with 10 (with the aforementioned equipment) but have grown to like a couple of extra pounds for stability in surge and current.
Sorry I could not be more specific, we are all different but I suspect the OP needs to get in the pool and play with weighting. I have to swim down, especially for the first dive of the day, until the air gets out of my suit and crushes a bit and I see other divers venting and sinking downward feet first, maybe I should change my saying to swim down, swim around, float back up!
James
Interesting setup with the octo on a breakaway necklace bungee. Does it normally run under your arm? Also, why the crossed straps on the VDH plate - is that set up for an actual double hose reg?
FWIW, the density of fatty tissues is around .9 g/cc and non-fatty tissues (primarily muscle and bone) is 1.1. It looks like you'd sink unless you were 50% fat, but you need to add in the approximately 5 pounds lift from the air left in our lungs even after an exhale.
This is the key. Even if all our equipment matches, we won't have the same weight needs. The buoyancy of naked people can easily vary 10 pounds, more for the really obese.
FWIW, the density of fatty tissues is around .9 g/cc and non-fatty tissues (primarily muscle and bone) is 1.1. It looks like you'd sink unless you were 50% fat, but you need to add in the approximately 5 pounds lift from the air left in our lungs even after an exhale.
I found playing with the weight locations can help you stay level in the water. like four me the 8 pounds I use when diving in my 3mill I found putting 4 in the back upper weight bags by the tank help me counter act the fact my fins like to sink. The best advice I can give is spend a day in 30 feet of water trying out different amounts of weight and the location of them. keep in mind gloves and hood also change how much you need.
broncobowsher
Contributor
I find it difficult to get weighting right as you get in the water. My trick is to get close and at the end of the dive, dive again. Just as you are getting out of the water get neutral just below the surface. Don't add any air and get out of the water. Now look at the wing/BC and see how much air is actually in it. There should be very little. If there is a lot of air, you have too much lead. A pint's a pound. How many pints of excess air are in there.
If you can sink right away when you get in the water, you are likely too heavy. I know it takes a minute or two for water to get into my wetsuit, as the water gets in the air gets out. A shorty is pretty quick, full suit with hooded vest, not so quick. Even a drysuit as the excess air migrates to the exhaust valve.
If you can sink right away when you get in the water, you are likely too heavy. I know it takes a minute or two for water to get into my wetsuit, as the water gets in the air gets out. A shorty is pretty quick, full suit with hooded vest, not so quick. Even a drysuit as the excess air migrates to the exhaust valve.
I'm surprised nobody has brought up @rsingler 's thread in the knowledge base:
scubaboard.com
Once you isolate the factors of your gear, it's been spot on for me when I have gear changes, fresh/saltwater changes, or any combination.
Respectfully,
James
Info - Optimal Buoyancy Computer
The Optimal Buoyancy Computer A tool to help nail buoyancy and improve safety, before you splash 1) How much lead should I carry with my new wetsuit? 2) How big a wing should I buy? 3) Will my BCD support my lead, both at the surface and when my wetsuit is compressed at depth? 4) Will my BCD...
Respectfully,
James
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