BC and tank for cold waters

[Royan]

Hi, I'm writing here for advice in a new BC and tank combination, in order to improve my buoyancy and comfort, and I'm also open for suggestions if I'm moving the right way with this equipment change.
Currently I do recreational diving in Chile within 52-55 ºF all year, salt water, wearing a Dive Rite 901 drysuit, thick and bulky Mares undersuit, jacket style Cressi Aquaride BCD, thick neoprene boots/hood/gloves. I use recreational Cressi Master T10 regulators, DIN valve, with single AL80 tank, filled with 200 bar typical. These AL80 are mostly the only type of air cylinder the dive centers rent to us, so I have dove with these configuration for many years. In Chile, a good amount of sealife is past 20 meters (away from spearfishing), so I do a lot of deep dives (25-40 meters). I have good air consumption and keep an acceptable well controlled buoyancy.
With this configuration, I need 14kg of total lead weight ballast, in order to keep a 5mt/3min safety stop with the AL80 tank at the 50bar gas reserve. I know I am somewhat floaty, and I have tried to improve this over the years, but 14kg is the least I can go down for now.
Last weekend I went diving to a different dive center wich rented me a steel Faber HP80 short tank, and it was a very positive experience. It cuted me 3kg of lead weight off my pockets, so I went down with 11kg in total, and I still felt more negative than with AL80. I could inflate my drysuit with more aire so I was warm and comfortable. The tank was totally fine on my back, and I didn't have any balance nor buoyancy problems underwater.
I came out of the water convinced to buy one of these steel tanks, but the guy at the LDS commented me that I would also want to change my BCD to a wing/backplate type, wich will improve my trim and can cut down even more ballast if using a stainless steel backplate. The thing is, while the HP80 cylinder is light and comfortable to carry, and give me apparently enough gas for my dives, it is too short for the mayority of wing bladders I'm seeing over the internet. In concret, I'm looking for the DGX Wing package, wich has got good reviews here, but its bladder is a tad tall. I'm 173cm / 5'8" tall by the way.

I will greatly appreciate any advice and suggestion regarding this dive gear change for me. I'm sorry if it was a so long post, I tried to resume

 

[inquis]

Consider HP100 instead of HP80. If going to 30-40 m, I'd want the extra gas, just in case.

Also, with your height, I think the position would be better than that of the HP80. If you have the HP80 tank valve where you can reach it while diving (which is mandatory in my opinion), does the tank bottom even reach the bench if you sit down?)

 

[Brett Hatch]

Are your local dive shops able to fill to around 3500 psi / 240 bar? If so, I agree that it sounds like you are looking for an HP100 steel tank. If you can dive an AL80 with your current wing, then you can dive an HP100. My main dive buddy is 5'7" or so, and HP100 is a fine height for him, and a fine height for me at 6'0".

HP100 buoyancy is about .5 kg lighter than the HP80, and holds 25% more gas. It is about the same height as most AL80's (maybe 1-2cm shorter, but people usually put a plastic boot on the bottom which is 1-2cm tall). HP80 is about 12cm shorter than AL80/HP100, as you found out. Downside of the HP100 is that it weighs about 3kg more than the HP80 when empty, and the 20 cu ft extra gas weighs another 1kg or so. So, call it 4kg total heavier than the HP80 to carry on dry land.

Is there anywhere you could rent an HP100 for a dive, to see if you like the weight and the height? Or, any local divers who might lend you one for the day?

Edit to add: I would not recommend buying an HP80 and a wing, just so that you can dive the 80. Because I think you are more likely to like the HP100 better, which should work fine with your current BC. I do prefer a backplate+wing over a jacket BC, but buying one for the sole purpose of diving an HP80 sounds like overkill.

 

[undrwater]

Cressi Aquaride BCD,

If you change to a more neutrally buoyant bcd, you can drop even more weight.

 

[Marie13]

Steel 80s are fabulous tanks. I dived them back when I did single tank.

 

[runsongas]

steel plate, weighted sta, hp100 will shave nearly 8kg off what you currently run

 

[Royan]

If you have the HP80 tank valve where you can reach it while diving (which is mandatory in my opinion), does the tank bottom even reach the bench if you sit down?)

can't remember the exact position, but while underwater I felt the bottom of the tank just at the middle of my butt

Are your local dive shops able to fill to around 3500 psi / 240 bar?

yes, while some of them tend to fill only 200bar (dives here are short anyway), I'm almost sure they all CAN fill to 230+. My LDS do so

Is there anywhere you could rent an HP100 for a dive

I will ask to dive centers and known divers around. Definitely a worth try

 

[Royan]

I do prefer a backplate+wing over a jacket BC, but buying one for the sole purpose of diving an HP80 sounds like overkill

my idea of switching to wing/bp was to improve trim and feel less bulky underwater too

If you change to a more neutrally buoyant bcd, you can drop even more weight.

you mean wing/bp is more negative than jacket bcd?

steel plate, weighted sta, hp100 will shave nearly 8kg off what you currently run

that sounds great, it will let me with almost only the weights in my belt (6kg)

you are helping me a lot, thanks!

 

[undrwater]

you mean wing/bp is more negative than jacket bcd?

All that foam cushion on the straps of the jacket are buoyant. Backplate / wing can come with cushioned straps, but generally aren't. Add the negative plate, and there you go.

 

[stuartv]

Yes, a back plate and wing is going to be more negatively buoyant than a jacket BCD. A fair bit more negative.

An HP100 is still slightly shorter than an AL80.

"I don't like having all this extra gas" - said no person ever.

Don't buy an HP80. Get an HP100 (or two). I dive with women much smaller than you are, who use HP100s with no problems at all. On deep dives, the extra gas won't matter, as you'll run out of NDL first anyway. On shallow dives, where NDLs are very long, the extra gas will allow you to do even longer dives, if you wish and are able.

You already saw that changing to a steel tank allows you to take a good chunk of lead off your rig.

If you also switch to a steel back plate and wing, you'll be able to take off another good chunk. Adding a weighted STA takes off another chunk (or, really, just moves it to your spine area).