Luxfer S100 as bottom stage...

[Mark1982]

Hi,
is there anyone who can tell me how does an aluminium Luxfer S100 cylinder behave as bottle stage?

As "behaviour" I mean how it lies during the dive, how simple is moving it, ...
( For example, talking about S80 cylinders, a Luxfer S80 behaves better than a Catalina one )


I'm going to buy a Luxfer S80 to use it as bottom stage, but I've also thought S100 as valuable alternative (thanks to the 20 cuft bigger inner volume - I don't care about operative pressure because I can refill any cylinder @ max 200 bar and no more).

In term of dimensions, a S100 is roughly a S80 with a 2 cm bigger diameter... not so much!
But I never seen a S100 in my life and most of all I don't know how it acts underwater while is becoming empty...

Notice that I'll clip this bottom stage in the right shoulder D-ring in addition to the S80 with EAN50...


Thanks anticipately,
bye bye,
Marco

 

[rjack321]

Don't do it. 2cm larger diameter is huge/bulky and S100s are the dreadful tanks + stupidly positive. Worst buoyancy characteristics EVER.

 

[NAM001]

Unless someone else makes an al 100 i dove one and was no diffferent than my lp95. I did not breath t down though. Probably to 1000 and surfaed.

 

[Mark1982]

Thank You both for your replies!
As I've thought, bigger diameter could be a seious problem if I use a S100 as bottle stage...

About buoyancy... I trust You when You say that S100s are really positive, but at the same time I'm confued looking at Luxfer S100 specifications (maybe because I'm looking at a new type of S100) ...

Take a look at L6X® Luxfer web page : the "Salt Water buyoancy (empty)" column says that a S80 ( with a +1,9 kg buoyancy ) is more positive than a S100 ( with its +1,3 kg buoyancy )...

I'm confused...

 

[parzdiver]

Hi,
is there anyone who can tell me how does an aluminium Luxfer S100 cylinder behave as bottle stage?

As "behaviour" I mean how it lies during the dive, how simple is moving it, ...
( For example, talking about S80 cylinders, a Luxfer S80 behaves better than a Catalina one )


I'm going to buy a Luxfer S80 to use it as bottom stage, but I've also thought S100 as valuable alternative (thanks to the 20 cuft bigger inner volume - I don't care about operative pressure because I can refill any cylinder @ max 200 bar and no more).

The statement highlighted will eliminate the S100 - it is rated at 3300 PSI. So you'd be at about 90% capacity.

I have handled the Al100's and they are big and bulky and heavy (dry weight). If you are looking for alternatives to the AL80, hop into the Side Mount forums, there are a lot of good discussions about what tanks are best for slinging.

 

[rjack321]

What backgas tanks are you diving?

 

[Mark1982]

Thanks for suggesting me the Sidempount forum... it's a good idea!


About refill pressure, sorry, I've been a bit hasty...
If I want it, I can find a refill-center able to refill my bottom stage at 220 bar... and I surely have to do it if I plan a demanding dive!
In this case a S100 (with its 228 bar operative pressure) would be better than a S80, which has 207 bar as operative pressure.
But S100, even at 200 bar, can allow me to do demanding dives too (more than what an S80 could do).
My interest in S100 is not in the higher operative pressure, but in the bigger volume without an excessive increase of outer dimension compared to S80s.

I'm interested most of all at S100s behaviour and their distribution of weight/mass underwater... (not a matter if they are heavy outside).

The new S100s Luxfer seem to be heavier than S80s underwater... and maybe it could be a good thing...
In particular, doing some approximative calculus, a S80 with valve and regulator would be neutral in salt water when it reaches 110-115 bar of a 18/50 gas mix... then it becomes more and more positive...
A S100 would become neutral at 45 bar of 18/50 gas mix: it sounds better...
But these are mere calculus...


I actually dive with a 12+12 steel twin set for back gas + s80 for EAN50 + s40 for oxygen.
I would use the bottom stage for extending bottom time in nomoxic trimix dives (and a S80 would be surely ok for this), but I'll also do hypoxic dives next year... so, in addition to another s80 ( 35/30 deco gas ), I will need a big bottom stage for hypoxic demanding dives where other divers usually use a 18+18 liters steel twin set (and often they shift to a 20+20 twin set becasue 18+18 is a bit limiting)...

 

[rjack321]

I don't think you need another 80 for 35/30 deco gas. We use 40s for our deepest mix (35/25) because you aren't going to be spending as much time that deep in the deco profile anyway.

I do think you need tanks bigger than 12L for hypoxic deco dives. I use the equilvalent of 16L or 18L + a S80 stage and its plenty for me. Once you have this many tanks you need a scooter honestly... I don't think you'll be happy substituting an S100 for larger doubles, get the larger doubles.

 

[ajduplessis]

I have no experience with S100 cylinders but know they are "fatter" and heavier. Deeper dives (300ft/100m) generally requires 3xS80 (1 bailout, 2 deep stages) and 1x S40 with 100 or 70% final deco. On a dive like this real estate under on your arms is already very restrictive, thus would not suggest S100 as even less space will be available.

As already mentioned rather increase your back-gas to 15 or 18l cylinders. I use 15's and find them good enough.

 

[PfcAJ]

You don't want heavier deco bottles or stages. It's awful. More drag, more mass to move around, more bulk, generally not good.