MichaelMc
Working toward Cenotes
What available small sidemount tanks do people like? Roughly ’AL63/80 + redundancy’ for 40’ - 80'. Most discussions seem to be of larger tanks, LP85+, which is more than I want to walk to the water every dive. Two of X, Y, and Z is always a good answer, but which would you get 4 of if you also had big tanks.
Survey has: tank, diameter, empty buoyancy, and neutral land weight. I left a broader than maybe suited tank range, but may be missing tanks. The small HP tanks seem too small.
In this sidemount diving, not pony, forum:
* LP50 stand out as sweet,
* Steel 72 are common, are a lot of gas, and some say pushed steel’s limits,
* AL40 get a serviceable nod.
AL40s are favored in non-side discussions of big ponys, with barely a mention of LP50s. But LP50s get play as CCR bailouts, if cave filled. Realizing that pony tanks spend their dives full, while side mount tanks go toward their reserves, and have different trim expectations.
Size: The redundancy sort of pushes to the 80 or 100 total gas range, depending on if a single 63 would have worked.
Heavy/Light: I understand there are separate views on best, based on heavy, HP, tanks or light tanks. And that can dictate rig differences with rear rails or light tank repositioning. I carry a lot of lead, but am happy not using my tanks as ballast.
Fills: I’m not in cave country, yet a top shop rented me an LP85 at 2950 PSI, saying ‘its fine’ when I raised an eyebrow. I’d rather avoiding full cave fills. I’m not sure the available small tank options are broad enough for the difference to matter in the selection.
Thanks,
Michael
Me: I dive Monterey single BP/W with a 20/10 wetsuit, normally AL63 when others have AL80, often next to a fill station. 120+ dives. Seated top of shoulder 25”, 5’9, 140 lb., 30” waist.
My Plan: I want to move to side for redundancy, fun, travel. I’m starting side mounting a pony off my plate with loop bungee. My plan is two LP50s. Then migrate to a sidemount rig. Then get two LP85s. LP50/85 mix and match seems to cover many dive lengths, with maybe ultimately LP50s as accelerated deco. I want to try side enough that I don’t plan on stopping at the pony state. 100’ is deep enough for me without Helium and a rebreather, and 60-80’ is fun enough. I help teach advanced single backmount students in the 30-40' range, under NAUI/AAUS.
Some prior threads: 2017: Best Tanks?, 2016: Tank choices, or just screwing around!!, 2016: Sidemount Tanks Options, 2012: What are Your Favorite Side Mount Tanks?, 2010: "Best" Tanks for Sidemount, and Why?,
Some specs for reference, or correction.
Scuba Cylinders | Metal Impact w/o valve? (Metal Impact / Worthington)
Blue Steel Scuba - Cylinder Specs salt w/o valve. M71: 3300 PSI, FX71 3442 PSI
Tank buoyancy numbers w/ valve
Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan w/ valve
Survey has: tank, diameter, empty buoyancy, and neutral land weight. I left a broader than maybe suited tank range, but may be missing tanks. The small HP tanks seem too small.
In this sidemount diving, not pony, forum:
* LP50 stand out as sweet,
* Steel 72 are common, are a lot of gas, and some say pushed steel’s limits,
* AL40 get a serviceable nod.
AL40s are favored in non-side discussions of big ponys, with barely a mention of LP50s. But LP50s get play as CCR bailouts, if cave filled. Realizing that pony tanks spend their dives full, while side mount tanks go toward their reserves, and have different trim expectations.
Even when an AL30 may be more appropriate due to gas planning or something even smaller, we just grab the 40 because of how easily they carry. Same with why we use AL80's for stages even though LP72's are better in terms of size:weight:capacity on land, the al80's handle better in the water so we use them. Same reason no one uses al63's or 50's. You go straight to an al40, and if that isn't big enough, straight to an al80 *unless you were lucky enough to be able to grab a bunch of the AL72's when they were available that are even nicer*
Size: The redundancy sort of pushes to the 80 or 100 total gas range, depending on if a single 63 would have worked.
Heavy/Light: I understand there are separate views on best, based on heavy, HP, tanks or light tanks. And that can dictate rig differences with rear rails or light tank repositioning. I carry a lot of lead, but am happy not using my tanks as ballast.
Fills: I’m not in cave country, yet a top shop rented me an LP85 at 2950 PSI, saying ‘its fine’ when I raised an eyebrow. I’d rather avoiding full cave fills. I’m not sure the available small tank options are broad enough for the difference to matter in the selection.
Thanks,
Michael
Me: I dive Monterey single BP/W with a 20/10 wetsuit, normally AL63 when others have AL80, often next to a fill station. 120+ dives. Seated top of shoulder 25”, 5’9, 140 lb., 30” waist.
My Plan: I want to move to side for redundancy, fun, travel. I’m starting side mounting a pony off my plate with loop bungee. My plan is two LP50s. Then migrate to a sidemount rig. Then get two LP85s. LP50/85 mix and match seems to cover many dive lengths, with maybe ultimately LP50s as accelerated deco. I want to try side enough that I don’t plan on stopping at the pony state. 100’ is deep enough for me without Helium and a rebreather, and 60-80’ is fun enough. I help teach advanced single backmount students in the 30-40' range, under NAUI/AAUS.
Some prior threads: 2017: Best Tanks?, 2016: Tank choices, or just screwing around!!, 2016: Sidemount Tanks Options, 2012: What are Your Favorite Side Mount Tanks?, 2010: "Best" Tanks for Sidemount, and Why?,
Some specs for reference, or correction.
Code:
Vol Diam Len. Full / Empty Wt. N.Wt.
AL S30 M.I. 30.0/4.3 5.25 19.5 -1.5 / 0.4 12.25 12.65
AL S40 M.I. 40.0/5.7 5.25 24.6 -0.7 / 3.0 15.30 18.30 *
AL S50 M.I. 48.4/6.9 6.9 19.0 -2.5 / 0.8 21.3 22.1
AL S63 M.I. 63.0/9.0 7.25 21.9 -2.4 / 2.5 26.9 29.4
Code:
LP27 Faber 27/ 4 5.46 14.43 -3.0 / -1.1 11.7 10.6
LP45 Faber 45/ 7 5.51 23.0 -2.7 / 0.6 17.6 18.2
LP50 Faber 50/ 7.8 5.51 25.2 -2.4 / 1.2 18.9 20.1 *
M71 Faber 71/ 9 6.84 20.47 -4.4 / 0.9 28.7 29.6
FX71 Faber 71/ 9 6.73 21.26 -7.0 / -1.4 24.7 23.3
Code:
S72 various 71/ 6.9 25.1 -5.4 / 0 26 26 *
Code:
AL72 luxfer 69.6/ 6.9 26 -1.6 / 3.6 28.4 32.0
Code:
LP85 Faber 85/13 7.01 26.0 -3.8 / 2.3 31.2 33.5
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