30 cf or 40 cf Pony Bottle for Tech diving?

[tndash]

Hello all, I am interested in getting a pony bottle and since I am relatively new and don’t know much about tech diving, I wanted a few opinions. I have read ALL posts on pony bottles vs spare air and narrowed it down to the two in the title (specifically Luxfer) and have read that the 40cf would be the better buy for tech diving. The following specs are from Luxfer:



AL-13 13.2 CF 3000 PSI -1.7 LBS -0.9 LBS 6.0 LBS 4.40" 13.1"
AL-19 19.9 CF 3000 PSI -1.4 LBS -0.1 LBS 8.2 LBS 4.40" 18.6"
AL-30 30.0 CF 3000 PSI -1.0 LBS +0.8 LBS 11.6 LBS 4.90" 21.9"
AL-40 40.0 CF 3000 PSI -0.7 LBS +1.8 LBS 15.3 LBS 5.25" 24.6"

I would prefer the smaller bottle (30cf), but have not read any comments on wheter or not it would be acceptable for tech diving.

I have only read that the 40cf bottle would be a good pony bottle to use on recreational dives that can also be used when tech diving. Can someone please give me their opinions and let me know if a 30cf bottle would suffice for tech diving? Thanks all

 

[Rainer]

For O2, 30cf is fine for most dives. For 50%, it would not suffice for 30 minutes at 150' (with any reserve; well, at least not for me). A 40 is probably better, especially as relates to resale value. In any case, with <50 dives, you're probably a few years away from this mattering, and in that span, the cost of a single bottle will be pretty meaningless...

 

[rjack321]

Luxfer's are not really available anymore. Get a hymark, they are functionally the same.

You will need a 6 or 14cf bottle for argon
And at least one AL40 deco bottle
And possibly an AL30 deco bottle if you have access to a booster for O2.

Oh and another couple years worth of dives...

 

[Steve SDI/TDI HQ]

You failed to specify what you intent to use this additional bottle for, and what exactly you mean by technical diving.

If this bottle is for contingency gas, then a thirty MAY suffice; however, if at ANY time you intend to use it to carry decompression gas, a 40 is the minimum size you need to consider.

All that said, you need to talk (face to face not on the internet) with an instructor who is actively teaching and diving the sort of dives you wish to one day do.

 

[tk trekers]

Luxfer's are not really available anymore. Get a hymark, they are functionally the same.

You will need a 6 or 14cf bottle for argon
And at least one AL40 deco bottle
And possibly an AL30 deco bottle if you have access to a booster for O2.

Oh and another couple years worth of dives...

According to XS Scuba's website, Luxfer's are available. I know Scuba Toys carries a lot of XS Scuba gear, I only see Catalina 40's listed on their site but you could always call them & check.

 

[Colliam7]

I would prefer the smaller bottle (30cf), but have not read any comments on wheter or not it would be acceptable for tech diving. I have only read that the 40cf bottle would be a good pony bottle to use on recreational dives that can also be used when tech diving. Can someone please give me their opinions and let me know if a 30cf bottle would suffice for tech diving?

The specific answer to your question - 30s are fine for tech diving. I have two 30s and a 40 that I use as deco bottles, and as pony bottles on recreational dives. As Rainer said, you would probably use them primarily as 100% O2 bottles, rather than 50% bottles. I have also used a 30cf to carry mixes that I wanted to transiently use on ascent (such as 35/25), and I have also used them to supplement backgas. Having said that, I would recommend a 40 over a 30 in your situation. I don't find the difference in size to matter in terms of carrying the bottle (a 40 is just as comfortable as a 30), and I do find there are deco dives where the 30 pushes my ability to dive within thirds. I bought the 40 new, a number of years back, to use as a pony, planning to eventually use it as a deco bottle. I later got the 30s used as part of a package purchase with two sets of double 80s. If I were buying a new bottle today, I would still go for a 40. But, if you go with a 30, you can certainly use it for deco diving in the future.

 

[DevonDiver]

You failed to specify what you intent to use this additional bottle for, and what exactly you mean by technical diving.

In any case, with <50 dives, you're probably a few years away from this mattering, and in that span, the cost of a single bottle will be pretty meaningless...

Oh and another couple years worth of dives...

Guys, I get the impression (as he states in the OP) that he doesn't know...which is why he is asking. I also get the impression that he has no intention of doing tech diving anytime soon.

However, you can't blame the guy for wanting to plan ahead and purchase kit that will continue to be relevant as his diving progresses.

All that said, you need to talk (face to face not on the internet) with an instructor who is actively teaching and diving the sort of dives you wish to one day do.

Steve hit the nail on the head with this one. There is no substitute for first-hand knowledge. That said, this forum does exist the the sharing on knowledge....

For the OP...

As a recreational diver, the size of redundant cylinder you require is going to be dictated by two things.... your air consumption and your dive depths. It only has to deal with ascent and, at most, a safety stop.

To cover all contingencies, most recreational divers opt for a cylinder of around 3L capacity. This will give you an abundance of air for an emergency ascent, whilst not being so large that it will significantly add task loading, effort or annoyance to your diving.

As a technical diver, you will use appropriately sized cylinders to contain specific decompression gasses for your ascent. However, the ascent is much slower and you would be performing decompression stops of much longer duration than a safety stop. Consequently, the cylinders needed are much larger (and more bulky). They would, generally, be complete over-kill if used as emergency ascent/redundancy bottles for recreational dives.

It is relatively hard to balance the two, greatly differing, requirements without making a compromise in one area or the other.

Before making a decision, do some research on gas planning. Calculate your Surface Air Consumption (SAC) and use this to extrapolate your current air requirements with a redundancy/emergency ascent bottle. That should be your primary focus.

When the time comes for tech diving, you may be able to utilise that bottle as a deco stage...and having a smaller bottle will give you some options for relatively light deco dives. Chances are, however, that you will have to invest in several more generously sized cylinders at that point.

Given your relatively small experience...and the looong time frame until you are ready for tech training, my best advice is... START SAVING YOUR MONEY NOW

 

[rjack321]

According to XS Scuba's website, Luxfer's are available. I know Scuba Toys carries a lot of XS Scuba gear, I only see Catalina 40's listed on their site but you could always call them & check.

Currently, Luxfer's are "available" in extremely limited quantities and prices are high. There's no need to limit oneself to Luxfer's. The hymark/cyltechs are fine tanks and even Catalina's are really not that big a deal.

If I needed any more 40s I'd look on craig's list for used Luxfers or hymark for a new one.

 

[tndash]

You all have been great. Thanks so much. Devon is quite right, I am not sure of what I would like to venture into (but cave diving is high on my list). I am looking ahead to use what I buy now for the future. So far, it appears to be a trade off.

I could buy a 30(for slightly less bulk) but MAY be limited in the future for deco dives.

I could buy a 40 now, which could easly fit my needs for a deco bottle, but would be carrying more bulk up to that point, which is some time away.

Rainer-thx for the resale value comment-didn&#8217;t think of that.

Colliam-thx

 

[Doc Harry]

If you are planning to go down the tech route, I would not recommend a pony bottle.

A stage bottle would be more appropriate.

Many do not like the manner in which the Catalina cylinders hang, too butt heavy. Luxfer seems to be the preferred stage bottle. The Hymark 40 has characteristics similar to Luxfer 40 and has received good reviews.

All of my 40-cubic foot stages are Luxfer and I have not tried the Catalina or Hymark myself.