Pony Bottle

[Teller]

I want to get a redundant air source an I have decided to get a pony bottle. Right now I dive well within the rec limits but I know someday I want to get into deco diving. What would be a good size pony tank to buy that I can use later as a deco tank.

 

[texdiveguy]

Well that is a great question with plenty of correct answers.

For me I would think a basic Al40 would handle O2 and other EAN mixes for shorter decos.

For longer deco or repeated deco dives there is nothing better than an Al80.

"I have done most of my diving in low vis lakes ....... " your best statement.

In looking through your SB bio page I see you have good basic experience and good quality eqpt., keep it up!

 

[RJP]

What would be a good size pony tank to buy that I can use later as a deco tank.

40cf. Plenty for now, and the right size for deco gas if/when you step up.

 

[Trace Malinowski]

Get a 40.

 

[islanduni]

That's not a pony bottle, that's a whole surface supplied air system! How deep do you want to go? 300ft?

 

[David_57]

Luxfer 40 is the way to go they trim out nice.

 

[Trace Malinowski]

If we assume that many recreational divers descend to the maximum depth recommended for sport diving which is 130 feet, and if we assume that a diver doing such dives may be exploring shipwrecks in which he or she can become entangled on the exterior (nevermind entering without proper training and equipment), and assuming that diver would like time to be able to solve problems on the bottom as well as complete a safety or emergency deco stop, this a V-Planner ascent and gas plan for a 10 minute dive to 130 feet.

V-Planner 3.86 by Ross Hemingway,
VPM code by Erik C. Baker.
Decompression model: VPM - B/E

DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = Nominal
Dec to 130ft (2) Air 50ft/min descent.
Level 130ft 7:24 (10) Air 1.04 ppO2, 130ft ead
Asc to 20ft (13) Air -30ft/min ascent.
Stop at 20ft 0:20 (14) Air 0.34 ppO2, 20ft ead
Stop at 10ft 2:00 (16) Air 0.27 ppO2, 10ft ead
Surface (16) Air -30ft/min ascent.

Off gassing starts at 69.5ft
OTU's this dive: 11
CNS Total: 4.0%
41.5 cu ft Air
41.5 cu ft TOTAL
DIVE PLAN COMPLETE

An AL40 will handle an ascent from 130 with a small safety factor. It is the smallest sized bottle preferred by most technical divers because of its ride and buoyancy characteristics when carried as a stage - especially Luxfer as David said. I'd recommend that a 40 pony be "stage" carried if the diver's rig can properly accommodate it.

 

[Thalassamania]

I concur, a 40 makes the most sense.

 

[kanonfodr]

I use a Luxfer AL40 as my pony, stage rigged and attached to my Hog Rig. Works great and gives me plenty of bailout gas for my diving, and I like the future expandability options it allows (stage/deco).

Peace,
Greg

 

[dumpsterDiver]

I disagree with the advice so far. Your question is the problem. It is like someone saying that they want to be able to do 250 foot scuba dives sometime in the future so what size double tanks should I buy now for my first scuba lesson?

A 40 might be fine for a stage bottle for technical diving, but it is way, too big and heavy to drag around on most recreational dives. I know lots of people that have 30 cu-ft tanks but they are such a pain they won't use them on a 110 ft dive. They get left on the boat or in the garage.

For no-deco, recreational diving, I prefer a SMALL, pony, one that will get me from the bottom to the surface and maybe give me a couple minutes of time to hang at 15 feet. For this type of diving, you only need a 13 or 19 cu-ft bottle. You need to balance safety with inconvenience, or otherwise you would be carrying an 80 cu-ft pony bottle clipped off to the shoulder, which MUST be safer right?


You need to do the math on your own breathing rate, your expected ascent rate, if you want any reserve to handle problems on the bottom or do you assume an immediate ascent should your have a total failure of your scuba unit.

Get a small pony bottle now and a bigger one later. If you get into technical diving in the future, the cost of another stage bottle is NOTHING.

Today i was diving solo in about 95 feet, I was carrying a 6 cu-ft tank, which for me, is enough to get me from the bottom to the top and this tiny tank has no noticable drag and the weight with a reg is like 5-6 lbs, I guess.