Planning a dive trip in a few months and wondering what I should do, bear with me. Twinsets or Stage/Pony Cylinder

[HenryUK]

I am planning a dive trip in a few months and wondering what I should do, bear with me.

I plan on diving to a maximum of 40m using 28% Nitrox with NO deco (using PPO2 1.4).

I have dived to 40m on a few occasions using 12L steel tanks (both air and Nitrox) filled to 220bar and typically get out of the water with 70-90bar (between 9min and 15min bottom time depending on gas mix & average depth).

At first (when I knew no better) I relied on being close to the DM in case of an out air situation, but I know that I regularly surface with more air than the DM and think I should be taking extra precautions.

Getting to my question, bearing in mind I am not planning to go into deco, would you suggest I am better off:

1. Diving twinsets for peace of mind (not because of air consumption but the possibility of failure) and redundancy
2. Diving 12L singles (or 15L but consumption isn’t my concern) and carrying a stage/pony cylinder

As I have mentioned, I am not planning for deco, but I want to avoid a situation where kit failure (free flow or other issue) could lead to an out of air situation without any redundant air source available.

The pro’s and con’s I can see to each of these are:

Twinset pros:

1. Ample air supply
2. Redundancy in the event of failure

Twinset cons:

1. Cost to hire and fill tanks
2. Cost of training to learn shut downs etc.

Carrying stage/Pony cylinder:

Pros:

1. Limited additional cost (as I don’t plan on using it I only need to rent the tank and fill it once/*twice)
2. Limited additional training, ej. shut downs etc. (*I’d do some shallow dives to get used to the setup and switching regulators before diving to 40m)

Con’s:

1. Buoyancy and trim issues

I think twinsets would be the better option; but considering the additional cost, the fact I am comfortable with my air consumption and that I am NOT planning on going into deco, perhaps taking a stage/pony cylinder could be the better option.

I should also mention that I have recently started diving dry, which in itself is taking some getting used to (although I hope to get at least 20 dives in my drysuit before I go away, so hoping I’ll be used to it by then) and wonder if carrying a stage/pony cylinder could throw off my buoyancy and trim just as I’ve started getting used to my drysuit.

Any and all thoughts and suggestions welcome… I have even considered an advanced Nitrox/deco course - but as I am not planning a deco dive I think, at this stage, that would be unnecessary (if I was planning a deco dive, after having had proper training, I would only do so using twinsets and stages as necessary).

Looking forward to hearing your thoughts.

 

[Marie13]

First question: where will you be diving?

 

[HenryUK]

First question: where will you be diving?

Malta (well Gozo actually) in the Mediterranean… the actual site is The Hephaestus wreck…

 

[BoltSnap]

Diving 12L singles (or 15L but consumption isn’t my concern) and carrying a stage/pony cylinder

I'd probably pick this option based on your facts.

 

[HenryUK]

I'd probably pick this option based on your facts.

Interesting and I appreciate your feedback…

 

[Marie13]

Malta (well Gozo actually) in the Mediterranean… the actual site is The Hephaestus wreck…

Have you dived twins before? It’s not really clear if you have. Just sling an aluminum 40cft for a pony bottle. For emergency use, not as a stage to extend dive. That’s the simplest thing to do.

 

[-JD-]

To further expand on @Marie13 's question: Where do you see yourself diving "frequently" in the future?

If it includes warm-water tourist-dominated destinations, twinsets may be hard to (practically) impossible to obtain. You can usually get a pony filled if you bring one and there is an overnight before diving to send it out to the fill-station - rentals up to AL40s are less common. You can (almost) always rent an extra AL80.



Both twinsets and stage/pony likely require changing/updating/adding to your gear, but differently.

If it is only for emergency redundancy, A pony will be the easiest, least-expensive, and most flexible - there is a decent chance that you may be able to use or modify your existing BC kit. If you want to backmount twins, you are in for at least a new wing if you are diving an otherwise compatible backplate (type) rig.

If you need/want a little more air for the dive, but mostly redundancy, Independent doubles (No manifold, No bands) can work by renting an extra tank across a 2-tank trip, but that is a more complex setup because kit and training is going to be rare to DIY.

Regardless you will need an extra regulator set.

 

[HenryUK]

Have you dived twins before? It’s not really clear if you have. Just sling an aluminum 40cft for a pony bottle. For emergency use, not as a stage to extend dive. That’s the simplest thing to do.

Thanks and sorry for not being clear in my original post… no, I have never dived twins or carried a pony bottle… I was only asking about ’in an emergency situation’ and wouldn’t be looking to use the additional gas to extend the dive, only in case of an emergency…

 

[HenryUK]

To further expand on @Marie13 's question: Where do you see yourself diving "frequently" in the future?

If it includes warm-water tourist-dominated destinations, twinsets may be hard to (practically) impossible to obtain. You can usually get a pony filled if you bring one and there is an overnight before diving to send it out to the fill-station - rentals up to AL40s are less common. You can (almost) always rent an extra AL80.



Both twinsets and stage/pony likely require changing/updating/adding to your gear, but differently.

If it is only for emergency redundancy, A pony will be the easiest, least-expensive, and most flexible - there is a decent chance that you may be able to use or modify your existing BC kit. If you want to backmount twins, you are in for at least a new wing if you are diving an otherwise compatible backplate (type) rig.

If you need/want a little more air for the dive, but mostly redundancy, Independent doubles (No manifold, No bands) can work by renting an extra tank across a 2-tank trip, but that is a more complex setup because kit and training is going to be rare to DIY.

Regardless you will need an extra regulator set.

Thanks for your reply.

I have only really done ‘holiday/warm water‘ diving but am now getting into UK/Cold water diving. I try to use dive centres that offer technical diving (so twinsets are typically available, they just cost more) as I’ve found the quality/experience of the DM’s to generally be superior. I plan to learn how to use twinsets in future, but wondered if I should do it before this trip (seems it could be unnecessary and certainly costly).

It would only be used in an emergency situation (sorry if i caused confusion using pony and stage interchangeably). I dive a BP/W set-up so wouldn’t have an issues attaching a redundant air source (concerns over trim/buoyancy/entanglement however), but i would definitely need a doubles wing and regulator set-up.

Thanks again for your reply

 

[MichaelMc]

Slinging a 30 or 40 off your PB/W should be easy at a tech place. Sidemounting it will make it more compact, like a normal sling but tucked into the shoulder a bit with a bungee loop coming off the top side of the plate/back.

For future tech, small doubles are nice as an intro. Also you can dive any double as isolated doubles if you are not up on valve drills yet. I'd wait till after this trip.