Bottle Choices for Tech

[Micheal]

As I have progressed through my Tech Courses and divers, I have generally been diving with HP100 Doubles, and either AL40, AL80 or both for Deco and O2. My observations from watching other divers around, is the AL40 and AL80 seem to be pretty standard bottles this usage.

My question is why not HP80s? Do the AL80s trim out better, is it the extra buoyancy weight or what.

I am in the market for a few more bottles, and was originally going to get some HP80's. My daughter and random girls I meet are generally on the petite side, and I am 5'7". So the 5" shorter and 4 lbs lights HPs is preferred by the girls.

That said, the bottles will get 5x more use by me in a tech configuration.

 

[-JD-]

I imagine @Marie13 might see this anyway, but she is likely to be able to pass on some relevant experience on 80s vs 100s

 

[grantctobin]

As I have progressed through my Tech Courses and divers, I have generally been diving with HP100 Doubles, and either AL40, AL80 or both for Deco and O2. My observations from watching other divers around, is the AL40 and AL80 seem to be pretty standard bottles this usage.

My question is why not HP80s? Do the AL80s trim out better, is it the extra buoyancy weight or what.

I am in the market for a few more bottles, and was originally going to get some HP80's. My daughter and random girls I meet are generally on the petite side, and I am 5'7". So the 5" shorter and 4 lbs lights HPs is preferred by the girls.

That said, the bottles will get 5x more use by me in a tech configuration.

Stick with 80s and 40s. 80s full of O2/50%/32% are heavy enough and when breathed down can float out of the way or on a leash. No reason to carry cylinders that are 3kg more negative in water just to save yourself 1.5kg out of water.

This is assuming you’re asking about deco or stage cylinders. The height of HP80s as doubles tends to make them trim out poorly and they’re far too heavy for wetsuit diving.

 

[Marie13]

I imagine @Marie13 might see this anyway, but she is likely to be able to pass on some relevant experience on 80s vs 100s

I’m away from home as I was diving today in Ohio, but I’ll come back to this later.

 

[tbone1004]

@Micheal HP80's are far too negative when empty so they will throw your trim off in the roll direction and because they're so heavy would also have to be compensated into your lift requirements more significantly as well as weighting. HP80's are about 3lbs negative when empty vs an AL80 at +4.4, so that is almost an 8lb buoyancy shift when empty and every 80 would be a 10+lb brick strapped to your side. You couldn't compensate for that with just your body. I can see the appeal if you are short, but unfortunately you need stage/deco bottles to be as close to neutral as possible when full for them to behave and HP80's are about the most negative tanks you can buy today.

 

[OTF]

What tbone said, plus AL80s are dirt cheap and ubiquitous.

 

[Jeremy Williams]

It’s actually kinda strange that AL80s are not really all that great for what they get used for most of the time (i.e. single tank back mount) but they really are pretty great deco/bailout/stage cylinders. I didn’t even own one until I started tech diving. AL40s are so good on land that I wish I got to use them in the water more...

 

[Marie13]

I first thought this post was about using HP80s as backmount doubles. But for deco/stage bottles? Bad idea. Stick with AL80/AL40.

Get some HP80s for the shorter people in your life. They’re fab as single tanks for shorter people. Just don’t expect to use them as deco/stage bottles.

I can tell you they’re OK for SM. Not the best. My LP85s and 50s trim out much better.

 

[helodriver87]

HP80s are total garbage for any application outside of a handful of very specific uses (backmount tanks for very short/buoyant people). For deco bottles, it's all about the AL80s and 40s until you get to really long O2 stops. That's when LP95s and 108s become useful. But that's a pretty niche application. HP80s will never be ideal for that kind of stuff.

 

[rjack321]

5ft tall women diving single tanks are the lone subpopulation of divers reasonably well suited to hp80s.

They are virtually useless for taller people in any actual tech diving application