What is the best size tanks for sidemount?

[tbone1004]

The best size is the size that provides enough gas for the dive that's been planned. That might be a single AL80, or four HP100's, or whatever.

don't do four steel tanks....

I have "intervals" for my primary tanks. I only dive aluminum if I have to fly somewhere, so this is steel-centric
LP50's cave filled are roughly 130cf
LP50's and one stage are roughly 200cf
If I need more than that, I go to HP120's which are 240cf
Pair of those with a stage are roughly 300cf
If I need more than that I go to LP121's which are also roughly 300cf and will have stages with that

 

[The Chairman]

If I need more than that I go to LP121's which are also roughly 300cf and will have stages with that

Cave filled? More like 360. Add an 80 and you can go on vacation in that cave.

 

[tbone1004]

Cave filled? More like 360. Add an 80 and you can go on vacation in that cave.

faber calls the 3442 19L as 149cf which is 155 at cave fill vs 165 if you run 121*3600/2640, so I treat them as 150's.

pre-CCR, the "normal" dives I was doing was a pair of 121's and 2 stages. We were in there for a while

 

[The Chairman]

Ah. My LP 120s are not + rated. 2400 =>3600 means 180/per. Not that I would ever allow my tanks to be "cave filled".

 

[tbone1004]

Ah. My LP 120s are not + rated. 2400 =>3600 means 180/per. Not that I would ever allow my tanks to be "cave filled".

who built them where they weren't + rated from the factory? Only aware of PST's and Fabers, both of which had + ratings. OMS called them 125's, but they're still the same 19L bottles. 121*3600/2640=165/1.065 *compressibility at 3600psi* is 155. That is the same as the FX149's as well which already have compressibility factored in since they're 3442's

 

[The Chairman]

I don't remember who made them. I'll be out in the workshop rebuilding breather regs this afternoon, so I'll check. Pretty sure they aren't plus rated. I call them my water heaters.

 

[tbone1004]

I don't remember who made them. I'll be out in the workshop rebuilding breather regs this afternoon, so I'll check. Pretty sure they aren't plus rated. I call them my water heaters.

if they aren't, the only think I can think of is a Heiser 120 but that's 3190psi and those things are bricks. Anything at 2400 should be built to the 3aa standard and will have the 10+ overfill allowed.

 

[stretchthepenn]

I have the same question as the OP, so I'mma chime in with my requirements and see what y'all have to say. I'm looking for steel tanks in particular; I'm...

• 6'4" tall, about 220 lbs
• typically wearing either a 5mm wetsuit with a 3mm hooded vest OR a shellsuit with either a 200g or 400g undergarment
• doing dives compatible with the PADI Tec 40 class, looking to continue onto dives matching the Tec 45 and Tec 50 classes
• mostly doing OW dives, perhaps some wrecks, but not going into caves anytime soon
• looking for modern tanks with 3/4 threads

 

[tbone1004]

@stretchthepenn HP120's or maybe 100's. That's the "go-to" with the choice of 100's/120's based mainly on height.
I'm 6'3", 32" inseam and these are PST HP120's. Faber FX120's are an inch and a half longer, so FX100's may be better.

Do you have any tanks now?

 

[Scuba_Aaron]

I use my steel lp50's when in a wetsuit and steel lp85's in a drysuit. The weighting is almost perfect.