AL80 v AL100 (Luxfer) @ 200bar

[llyamah]

Hi all. I know there have been similar threads about this in the past but I can't work this out.

I'm currently diving in tropical conditions. No wetsuit and a BP+W. Tank choices at my dive shop (only one I can visit) are AL80 and AL100. The dive school (only one I go to) fills all tanks to 200bar (is this the same as 2000psi)? This seems to be standard wherever I dive on holiday.

So far because I'm a bit heavy on air I am diving the AL100. However, everyone else is diving the AL80s.

My question. Will it make much difference to dive time of I dropped to the AL80? I read somewhere that the AL100 will only make a difference if it is filled to 3300psi.

 

[Blackcrusader]

Hi all. I know there have been similar threads about this in the past but I can't work this out. I'm currently diving in tropical conditions. No wetsuit and a BP+W. Tank choices at my dive shop (only one I can visit) are AL80 and AL100. The dive school (only one I go to) fills all tanks to 200bar (is this the same as 2000psi)? This seems to be standard wherever I dive on holiday. So far because I'm a bit heavy on air I am diving the AL100. However, everyone else is diving the AL80s.
My question. Will it make much difference to dive time of I dropped to the AL80? I read somewhere that the AL100 will only make a difference if it is filled to 3300psi.

Firstly 200 bar is around 3000 psi. Using an AL100 will mean a change in weights and some people find that don't benefit right away as they are not used to a heavier, thicker tank, and the extra drag. I dive in Asia so in shorts and T shirt and AL80 is common at most dive centers. Some will have larger tanks. Dive times depend on your sac rate, depth, whether or not you dive into currents or with a current and how relaxed you are. Obviously an AL100 has more volume and with 200 bar you get the benefit of the increased volume therefor longer dive times than on an AL80.

I usually do 30 - 50 dives each 2 - 3 week vacation. If you can do 3 dives a day for five days at the end of the 15 dives you should be able to improve your air consumption with better diving skills you can pick up from experienced divers. You did not list certificate level but with say less than 30 dives Open Water? If I am diving with a group of open water divers with an AL80 and do a 50 - 60 minute dive to max 20m or 65 feet I would often end the dive with 120 bar 1740 psi or more.

PS I'm 6'1 and weigh 300 pounds. Being a large chap some people think I will be having shorter dive times.

 

[GF99/99]

My question. Will it make much difference to dive time of I dropped to the AL80? I read somewhere that the AL100 will only make a difference if it is filled to 3300psi.

To answer your question first we need to know how much gas your using out of the s100? if your surfacing with 100 bar then no switching to an s80 still not make any difference in your dive time and it would beneficial to switch to the s80 since its smaller lighter tank. Now if your surfacing with 50 bar then yes the s100 is helping in your favor by giving you more gas.

For reference a:
s100 filled to 200bar has a capacity of 2640 liters of gas
s80 filled to 200bar has a capacity of 2220 liters of gas

Basically an s100 will give you about 20% more gas than an s80.

 

[Superlyte27]

The AL100 is thicker and heavier than an AL80. Even if everything else was exactly the same, you have an extra inch in drag, and more weight that your bcd has to offset, which is more drag. I would bet you an AL80 that you can do the exact same dive on an AL80 as you can in an AL100

 

[Blackcrusader]

The AL100 is thicker and heavier than an AL80. Even if everything else was exactly the same, you have an extra inch in drag, and more weight that your bcd has to offset, which is more drag. I would bet you an AL80 that you can do the exact same dive on an AL80 as you can in an AL100

Yes as I wrote when people use an AL100 and are used to an AL80 the extra weight and drag often does not get them longer dive times until they learn how to dive with the AL100. The increase in air volume is offset by the divers inability to cope with the extra weight and drag and also tank placement in the BCD. I need to have my tank placed in a different position than an AL80 to get the weight right for my buoyancy and trim.

 

[scubadada]

I did the same calculations that @marsh9077 did, but in imperial units (sorry). I get the same answer, a little less than 20% more gas with the AL100.

With the AL100, you will be able to dive with about 2 kg less weight. If you have an average gas consumption, around 14.2 L/min, you will get just under 10 min more dive time at 20 meters. If you have a lower gas consumption, you will get more time, higher consumption, less time. You'll have to decide if that is significant for you. It may make a difference to you if you are diving air, less NDL time, or nitrox, more NDL time.

I've never dived an AL100, can't comment on dive characteristics

 

[Blackcrusader]

I've never dived an AL100, can't comment on dive characteristics

I own an AL100 and it's at a dive center I dive with. It stays there. I bought it to reduce the weights needed on a weight belt or in inserts. So for recreational diving it will actually not help a lot of new divers as they will consume more air due to the extra drag. I can really feel the difference when I go back to an AL80 it's like someone took a parachute off my back and so much easier with an AL 80 if you need to swim fast. Again diving techniques are what the OP needs not a bigger tank. I've lent my tank to other divers and they come back disappointed their dive time was not changed as they are not used to using it.

Just slapping on an AL100 will actually not help the person become a better diver and with a high sac rate they won't get longer dive times. On the other hand I have a lot of dives on my AL100, it's good to have the extra air for any emergency. I also have an extremely good SAC rate of around 8l/min or less so when I do those deep dives on a single tank whether it be an AL80 or AL100 can do those two hour dives at shallower depths.

 

[NAM001]

The AL100 I used on one occasion was heavy compared to the al80. the al80 buoyancy was +4 to -2 and the al 100 was -1 to-9. very similar to my lp steels.
for sake of argument a bar is 15 psi.

 

[Nathan Doty]

Get a steel hp100. You'll have a smaller tank with less weight, which will keep your consumption down, and you'll still have the capacity. Or get a steel hp80, and have a TINY tank with a little less air.

When I was diving on 72's I usually had about the same air left as others on their aluminum 80's. I switched to 100's and I can probably do 2 dives without switching. Well could, I haven't been in the water in a while... In any case on air my bottom time is the limiter,not air supply. And I'm switching to nitrox...