30 cf or 40 cf Pony Bottle for Tech diving?

[lowviz]

Don't know if you read this thread (http://www.scubaboard.com/forums/ba...ny-bottle-recreational-diving-need-input.html) during your searches, but worth scanning.

A 19 will do a lot within recreational limits and isn't cumbersome underwater. My opinion is that a 40 has too big of a "crutch" factor for new divers, meaning that you can pretty much forget gas management without that nagging voice in your head telling you that you should be paying better attention to your SPG and getting back with your minimum. So, if you really want to point yourself in the tech direction now, start by practicing gas management and sling a 19.

 

[dschonbrun]

Suggest you do some tech instruction and based on the equipment you use in the course, make a decision. Most instructional facilities I've worked with use 40cf sideslung bottles for basic tech training.

 

[HowardE]

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

Your comparison and contrast of Buoyancy properties and weight shouldn't be the deciding factor in this kind of choice. Really it's about RMV and how much gas you'll want to complete the dive.

That said; it's the capacity of the tank (stage bottle, pony bottle, slung bottle, whatever you want to call it) that is the deciding factor. For some people with very low SAC rates, a 30CF bottle is plenty for decompression for short deco dives. For most divers doing staged decompression, a 40CF is the bare bones minimum they would carry.

If you don't know your RMV under different conditions and levels of stress... then you're probably not ready to begin planning extended - decompression dives....

If you're just looking for a redundant air source, then any of the tanks you've listed are fine for recreational NDL type diving - as a bailout option.

 

[Meng_Tze]

Without knowing what your plans are for the future, I'd say go with the 40's as they are very universal and will do well as a pony, limited stage, deco bottle to start with.

 

[DA Aquamaster]

Over the long term, whichnis what ypu are asking, you will end up with a couple of different tanks for a few different purposes.

1) For a deco bottle with a high percentage deco mix (80% or 100%) there are three basic choices - an AL 30, an AL 40 or a (steel) LP 45.

Luxer AL 30's are about 1.2 lbs positive whne empty and AL 40's are about 2.2 lbs positive. When you add the deco reg, they are still slightly negative to just barely neutral but both have a tendency to float tail high either clipped on a line or clipped to you. An LP 45 will be neutral when empty and a bout 2 pounds negative with the reg - and floats a bit better in the water when low on gas.

A full Luxfer AL 30 with stage strap and deco reg will weigh 19 pounds, a full Luxfer AL 40 will weigh about 24 pounds in a similar configuration and while a full Faber LP 45 will weigh 25 pounds with the same stage strap and deco reg.

So the choice is the shorter, smaller diameter and lighter AL 30 or a longer, larger diamter and heavier AL 40 or LP 45 (the LP 45 is 2 inches shorter than the AL 40, but 5.5" in diameter rather than 5.25") depending on your preferences in terms of buoyancy traits and steel versus aluminum construction.

I dove with AL30's for years and if you have a decent SAC they offer enough gas for a couple short deco dives or one moderate deco dive. But I switched from AL 30's to LP 45's and eventually sold most of the 30's off as the 45 is more compatible with the longer run times I seem to be doing now.

I prefer their buoyancy traits and how they ride in the water, but the downside of the LP 45 is the cost as they run around $300-$350 when you can get an AL 40 for around $200.


2) The Luxfer AL 80 and Catalina S80's are virtually the default for a stage bottle used for bottom mix, travel gas, or a lower percentage deco mix used at deeper stops. They are cheap, readily available and carry fairly well as a stage unlike generally more negative steel tanks. They also have the normal AL tank trait of floating tail high when near empty.

The Catalina C80 however is neutral when empty and is generally regarded as being too negative for use as a stage.

As indicated above, the Hymark AL 80 is comparable to the Luxfer AL 80.

Hymark recently started making an AL 72 that is similar to the AL 80 in lenght but only 6.9" in diameter and slightly less positively buoyant. With a reg attached it is neutral and floats level in the water at about 500 psi and it makes an excellent stage, deco or bailout bottle with only 5 cu ft less capacity than an AL 80 (AL 80s only hold 7 cu ft.) and 3 pounds less weight. Sherwood Scuba recently became the distributor for them.

A full AL 80 with stage strap and reg will weigh about 43 pounds and a full AL 72 in an identical configuration will weight about 39 pounds.

---

Over the long term, it is hard to go wrong with an AL 80 and an AL40 or LP 45 and if you buy them used for a decent price you can get your money back out of them if you sell them. In the case of AL tanks stay away from anything older than about 1990 to avoid the testing issues and predjudices surrounding the older 6351-T6 alloy used by everyone except Catalina prior to about 1987-1990.

 

[tndash]

WOW-Thank you all- I appreciate everyones expertise and time taken in responding to my queries. DA- thx a bunch(I think the 80s will be too much for me initially).

 

[DryGear]

I have an AL30 and an AL40, the 40 is a couple inches longer but you truly cannot notice the difference between them when you are in the water.

If you are thinking of technical/cave diving down the road you will find the 40 far more useful as all of your dive buddies will be packing them, and if you are using an AL30 to their AL40's you will likely be limiting you & your buddy's dive plans as you can't carry as much deco gas (unless you are really out-perfoming their SAC rates).

 

[lowridersvt]

We seem to sell mostly 40's to rec divers looking for a bail out bottle. It should be able to bring you and your buddy from depth and hold a stop using buddy breathing of course .

As for a tech standpoint 30 are a little small for you and your buddy to share for your o2 stop so a 40 is your best bet if you plan to go the tech root

as for a hymark i dont know anything about them never got to try them but catalina 40's are way to heavy its like draging a brick about the same as a steel 45 great for caves but not open water .