AL100 for deco bottle and/or sidemount?

[stuartv]

I've been looking for a pair of AL80s to use as a deco bottles and, eventually, warm water sidemount bottles.

I found a pair of Luxfer AL100s locally for cheap. I have not bought them.

The buoyancy specs say +2.8 when empty. That's a little more negative than an AL80, but still positive. That seems like a good thing for a deco bottle or a warm water SM bottle.

They are heavy, on the surface, but I don't care about that. My normal tanks are double HP120s, so a single AL100 is going to seem light.

But, I really don't have any feel for whether the 8" diameter will be hugely worse than 7.25" as a slung deco bottle, or it will be a small increment worse.

So, that's the Internet Diver analysis. What is the Real Diver analysis?

Would these AL100s be good as a deco bottle?

Would they be good as sidemount cylinders in warm water?

Should I just keep looking for AL80s? It's obvious an AL80 would be fine as a deco cylinder. But, I'm a little concerned that a pair of AL80s will be small for me to use in SM. And a pair of steel 100s might be too negative when I'm diving in warm water.

TIA for any wisdom you choose to share!

 

[Diver0001]

Would these AL100s be good as a deco bottle?

I have two of these that I use as deco bottles. I asked this same question on SB and was told (mostly by people who don't use them) that they were not suitable as stages. I bought them anyway because I figured I could use them as singles if they didn't work out as stages.

Up to now I'm satisfied with them. As compared to smaller bottles they feel a little awkward until you get the rigging dialed in. I'll save you some time: the trick is to keep the tail clip short. When they're full they're heavy carrying in and out of the water for shore entries. That's the main thing I find awkward about them. Diving with them is fine.

R..

 

[Superlyte27]

It's a terrible tank for everything. You'll hate it. I'm not kidding.

It's heavy and wide. So it provides a little more gas than an 80, but more drag to move it through the water, so you gain nothing.

For deco, it's going to be seriously negative most of the time. That's no fun either.

 

[victorzamora]

It's a terrible tank for everything. You'll hate it. I'm not kidding.

I was told this multiple times and I was sure people were overreacting. Then I dove one a few times. They weren't wrong.

I'm not a hater of 8" tanks, I've been diving 8" tanks almost exclusively for quite a while now. Those AL100s are just absolutely no fun.

 

[stuartv]

Okay, thanks @Diver0001 for your perspective, but I think I'm going to bow to the majority and just keep looking for AL80s.

As I thought about it more, I figured that deco bottles are normally intended to never drop below half full. So, in the case of an AL100, that would mean it would start out around 5# negative and never be neutral at any point. That definitely does not sound as nice as an AL80 that starts out only around 1.5 - 2# negative and ends up neutral or a little positive. I'm talking here about having it slung on one side as a deco bottle.

Having an 8" cylinder hanging off my left side D-rings, that is 5# negative does seem like it could be noticeably more annoying than a 7.25" cylinder that is much less negative.

Thanks for the input to all of you!

 

[Diver0001]

Having an 8" cylinder hanging off my left side D-rings, that is 5# negative does seem like it could be noticeably more annoying than a 7.25" cylinder that is much less negative.

You know, I think if I were to buy new cylinders now that I would probably go for AL-80s too. I bought these ones more as an experiment than anything else because we bought 6 of them dirt cheap from someone eager to dump them.

As for how negative they are. I know everyone says that they are heavy and awkward but my impression is that most people who don't like them don't use them and probably never have. This is the same in all gear discussions. People with little to no experience with something are often the most critical of whatever it is, from regulators to flippers to ... you name it. even deco tanks.

The one thing I don't like about these tanks is how heavy they are above water. The 100s are noticeably bigger when slung but strangely I don't find them noticeably more negative or any harder to handle after you get the rigging sorted out.

In any event they don't slow me down or throw me out of balance so I don't feel motivated to change it all again but if I'm honest I think 80s are just as good and they're smaller and lighter, more "optimal" for deco bottles. On that same thought, if you're not doing a lot of deco then a 7l (50cf) bottle is just fine too and they're virtually invisible to you as a diver.

R..

 

[sea_ledford]

I have Al100's that are perfect for the diving a lot of my team is doing. Either as doubles or a single back gas, they are my preferred tanks for work. I should say that we are doing deep, 100-130', NDL limit dives on partially removed rigs in the Gulf. The bottom is anywhere from 160 to 400+ feet, and there is nothing between about 85' and the surface. Most divers can get away with using an 80 for those dives, but the reserve margins are cutting it pretty thin, and are no where even close to the 1/3's I would like. The 100's bring them back with pretty close to 1000 psi. But I prefer thinner margins than strapping a 10+ lb negative tank on people wearing 3mm suits (or less) in effectively bottomless water.

Same with the doubles, to get much more in the way of larger gas supplies, I'm looking at very negative steels which are a no-go in my book for our open water conditions. I have a few doubled hp119's that I would never jump off a boat with, but they are fine for caves.

As a stage bottle though? I wouldn't use them. If you need that much gas, you would probably do better to have multiple tanks with different mixes in them.

-Chris

 

[cburgert]

Leave all that behind and just dive a single 80. It's a simple set up and can be done solo. You can even use a back flotation bcd and no need for a sidemount.

 

[decompression]

On the deco bottle front, its a bit unorthodox to use bottles much bigger than the standard AL40, certainly at the AN/DP level. I'm sure when you've cut your tables and see the gas required for 30 mins of deco at 70' or 20' that 40 Cuft is plenty.
Now for stage bottles, again the AL80's are the go to cylinder, if you need more capacity then you might be better off with 2 stages (independent sources) than 1 large cylinder.

 

[stuartv]

As a stage bottle though? I wouldn't use them. If you need that much gas, you would probably do better to have multiple tanks with different mixes in them.

-Chris

On the deco bottle front, its a bit unorthodox to use bottles much bigger than the standard AL40, certainly at the AN/DP level. I'm sure when you've cut your tables and see the gas required for 30 mins of deco at 70' or 20' that 40 Cuft is plenty.

My training is to plan to only use 1/2 my deco gas, keeping the other half for my buddy, in case he loses his deco gas. So, using an AL40 only gives me 20 cu-ft to work with.

I'm planning for diving the Oriskany in a couple of months. When I plan what kind of bottom time I could do with double 120s, the deco is working out that 20 cu-ft is not quite enough. At least, not if I use the deco mix that gives me the shortest overall run time (EAN70). If I were go go with 100%, then 20 cu-ft would be enough, but my total run time would be longer.

Thus why I have been looking for a couple of 80s. But I have also been thinking of trying side mount sometime in the not too distant future. I thought possibly AL100s would be better as sidemount tanks in warm water than using HP100s - since the AL100s are not as negative. That made me think that maybe a pair of cheap AL100s would be good for double duty as a deco gas cylinder and a pair of them for my main tanks in side mount.

I reckon I'll just keep looking for a pair of AL80s and, probably, when I get around to trying sidemount, I'll just use the pair of HP100s that I have. Or maybe the pair of AL80s.