Which sidemount AL80 brand?

[Tim Clark Diving]

I’ve been trying different aluminum 80 cylinder brands for sidemount and have been surprised with how different they are. I have three Al 80s that I have been playing with. XS Scuba S80s turn positive at around 2000 psi and are very positive at the end of the dive. Luxford s80s are negative during the entire dive but are close to neutral at the end. Catalina C80s are also negative during most of the dive. I think I like the XS the most since it doesn’t pull down on my rig but wanted to get others opinions. Is there any reason to go with any particular brand for sidemount? I dive in warm water with no wetsuit. Thanks!

 

[gmerick]

If you practice managing tank buoyancy by moving the lower boltsnap attachment your concern would not be an issue.
I start out the dive with my AL80's on a d-ring located on the point of my hip. (when walking in for a shore dive, I use the same d-ring for the TOP boltsnap until I get into chest deep water). I immediately relocate the lower boltsnap further to the rear so the base of the tank is in line with my hip. As the dive progresses, that lower boltsnap moves forward to maintain tank position. At the end of the dive, depending on tank pressure and tank buoyancy, it can be attached 2 inches from my buckle. To end the dive, I again move the boltsnap to the rigid d-ring at the point of my hip to make climbing the ladder issue free. Some divers use a sliding d-ring to aid relocating the attachment. I prefer to have a heavy 1.5" rubber o-ring on my belt on either side of the rigid d-ring. It's easy to slide the rubber ring to wherever it is needed at the time.
The above works equally well for Catalina S80's or for steel Faber 117's.

 

[Tim Clark Diving]

Thanks for the advice on moving the lower connection location. I currently have a lower and upper connection that I move between, so that isn't really the issue. This may be getting into the weeds more than most people do, but I am playing around with brands of Al80 cylinders and their buoyancy characteristics. It also may be a personal choice based on individual needs. I found this thread:

Updated SCUBA tank specifications list -- in PDF and spreadsheet

Hello! I have wasted my entire d1ay re-working a SCUBA tank specifications list. I've been working with the Huron Scuba list for *years*, but I'm suspicious of the information: where did it come from? Also, it includes a lot of junk I've never seen in real life, as well as tanks that no one...

scubaboard.com

It has a great table of cylinder specs. However, reading the numbers and diving the cylinders gave me different impressions. The Catalina and Luxford cylinders were heavier in the water than I expected, and didn't get very positive at the end. The XS was very positive. I was wondering if people found they have a preference on brand/buoyancy characteristics. I haven't for deco cylinders, but it is pretty obvious I need to match brands to balance out my sidemount rig. I have more brands at work so I may just try different ones and see what works for me. I do a lot of photography so the positive buoyancy of the XC cylinders may be a benefit since it keeps the cylinders off the reef. However, I am interested in hearing what others think and why they chose a particular brand of AL80s for sidemount.

 

[grantmac]

I like tanks that are either negative throughout, or go rather positive.
The exception are LP72 but because I like their other characteristics.
I use sliding rings (SumpUK).

 

[halocline]

Thanks for the advice on moving the lower connection location. I currently have a lower and upper connection that I move between, so that isn't really the issue. This may be getting into the weeds more than most people do, but I am playing around with brands of Al80 cylinders and their buoyancy characteristics. It also may be a personal choice based on individual needs. I found this thread:

Updated SCUBA tank specifications list -- in PDF and spreadsheet

Hello! I have wasted my entire d1ay re-working a SCUBA tank specifications list. I've been working with the Huron Scuba list for *years*, but I'm suspicious of the information: where did it come from? Also, it includes a lot of junk I've never seen in real life, as well as tanks that no one...

scubaboard.com

It has a great table of cylinder specs. However, reading the numbers and diving the cylinders gave me different impressions. The Catalina and Luxford cylinders were heavier in the water than I expected, and didn't get very positive at the end. The XS was very positive. I was wondering if people found they have a preference on brand/buoyancy characteristics. I haven't for deco cylinders, but it is pretty obvious I need to match brands to balance out my sidemount rig. I have more brands at work so I may just try different ones and see what works for me. I do a lot of photography so the positive buoyancy of the XC cylinders may be a benefit since it keeps the cylinders off the reef. However, I am interested in hearing what others think and why they chose a particular brand of AL80s for sidemount.

You can look up the specs, but it looks like the XS scuba tank is made by Metal Impact and has similar buoyancy specs as Catalina, about 4 lbs positive empty. Luxfer tanks are a bit more positive, 4.4 lbs empty. I don’t know if that’s with or without a valve, which obviously makes a big difference.

I have Catalinas at home, and I use Luxfers in MX. I don’t notice that much difference, the Luxfers are a little more butt-light but not much. You might have had the so-called neutral AL80s which are much heavier.

 

[inquis]

Luxfer tanks are a bit more positive, 4.4 lbs empty. I don’t know if that’s with or without a valve, which obviously makes a big difference.

I'd say that's with a valve (and seawater, FWIW). I've measured my Luxfer at +2.25 lb (ocean) / +1.4 lb (fresh) with a regulator and DIR rigging.

 

[halocline]

Here’s a thread where someone posted tanks specs from the manufacturer, with valve.

Updated SCUBA tank specifications list -- in PDF and spreadsheet

Hello! I have wasted my entire day re-working a SCUBA tank specifications list. I've been working with the Huron Scuba list for *years*, but I'm suspicious of the information: where did it come from? Also, it includes a lot of junk I've never seen in real life, as well as tanks that no one...

scubaboard.com

According to that, Metal impact tanks are a full pound less positive empty than Luxfer, but only .1 pounds more negative when full. Since they hold the same amount of gas, this is clearly impossible. My guess is that the actual buoyancy specs, measured with identical valves in the same water, are going to be very close, and the fact that the OP experienced them as being very different is due to something else. It’s very easy to ‘feel’ more light or heavy on a particular dive even with the same gear, especially as a new diver or someone with a new configuration. With SM, subtle differences in trim, placement of the lower attachment, etc.. can make a big difference in how things feel.

 

[Tim Clark Diving]

Thanks halocline. I figured out what was going on. I have the Luxfer S080N cylinder. I didn’t realize they made a neutral and a regular S080. The luxfer S080N has very similar buoyancy characteristics as the Catalina C80 that I was using. I’ve found I really don’t like either one for SM. The metal impact behaved much nicer in the water. I will be avoiding the neutral cylinders in the future. They really pull down on my sides. I much prefer the more positively buoyant metal impact. Based on the specs, I’m guessing I would also like the standard Catalina and luxfer S80s. Will see what I can find in the local shops.

 

[halocline]

Thanks halocline. I figured out what was going on. I have the Luxfer S080N cylinder. I didn’t realize they made a neutral and a regular S080. The luxfer S080N has very similar buoyancy characteristics as the Catalina C80 that I was using. I’ve found I really don’t like either one for SM. The metal impact behaved much nicer in the water. I will be avoiding the neutral cylinders in the future. They really pull down on my sides. I much prefer the more positively buoyant metal impact. Based on the specs, I’m guessing I would also like the standard Catalina and luxfer S80s. Will see what I can find in the local shops.

Glad you figured it out. Most of the time in MX (and elsewhere, I suspect) rental tanks are Luxfers, probably because they were the most common tanks. So if you're going to learn sidemount at home but also rent AL80s for SM, it's not a bad idea to stick with Luxfers, if you can even them any more. I see at divegearexpress that 'thunderbird' tanks have replaced Metal Impact, which apparently replaced Luxfer, who stopped making AL80s a couple of years ago.

The luxfer/metal impact/thunderbird tanks (assuming they are one and the same) are generally slightly preferred over Catalina as stages because they are thought to ride a little better. My guess is that many divers who express that opinion are using steel main tanks and like the additional bump in buoyancy. My experience diving AL80s in SM, with a stage, is that there isn't much practical difference. I will say that the typical scenario near the end of a long dive with a near empty stage and SM tanks with around 1000 PSI is that I'm going to be butt-light despite my best efforts, maybe it's a little less annoying with Catalinas. So there are the two sides of the coin.