On using a small tank to increase bottom time and provide redundancy

[SouthernSharktoothDiver]

@NothingClever Streamlining, now there's a point I hadn't considered all that heavily. I intended to mount the pony to the side of the main tank, valve open, second stage in predive mode. Under that configuration, how bad of a drag should I expect. Like, ballpark. 10% worse? 50%? Double? Cause if it's 10% I'm not worried about that, but double would be quite an issue. As for the condition of my regs, they're currently in fine shape, but plenty of things can happen down there in the dark to screw up a regset. If, for example, a LP hose were to snag on a piece of sharp metal (like, say, a piece of tin roofing~I've found weirder down there) and cut open, I could be in quite a lot of trouble. For this reason (and others like it) I feel like redundancy is a good idea regardless of the state of my primary regset. As for why my post focused more on bottom time than redundancy, I've more or less already decided on redundancy, the question is do I use the pony as a range extension or not. However, I'm concerned about the streamlining issue, as I hadn't really considered it much. Further thoughts on that would be appreciated.

@Wibble My plan was to go with the backmount option, which prompts me to ask what is probably a stupid question: Why do I need to be able to reach the valve? If I cut it on before the dive, do I need to be able to cut it off later? It's not like an isolation manifold where it might drain another tank as well. I'm not disagreeing with you, I just legitimately don't know why I need to be able to cut the valve off.

 

[happy-diver]

Mate you don't need our advice/opinions, we need yours, to loosen up and enjoy ourselves, thanks in advance!

 

[LI-er]

This is pretty much par for SB

"Hey I have this great idea what you all think of it?"
"Yeah no not so great, there's a simpler better way"
"Well I have 10 dives now and I think its great so Imma do it anyway"
"Carry on"

"I'm right!"
"No, I'M right!"
"You're wrong"
"No YOU'RE wrong"
"You're an &$%#"
"You're a BIGGER ^&*%!"
"You are no longer allowed to reply to this thread because of a TOS violation."

 

[MrChen]

@MrChen That is my goal. Based on my stated plan, do you feel I'm not doing so sufficiently, and if so, why?

Because extending your bottom time is different than practicing an ascent with your pony. The latter does not extend your bottom time.

 

[NothingClever]

I've more or less already decided on redundancy, the question is do I use the pony as a range extension or not.

I think you’ve already made up your mind on both topics.

Good luck with getting your “money’s worth” and your diving.

 

[KenE]

Why would you drain a full tank just to get a visual? Especially one that you might not even use for quite some time? Leave it filled, don't worry about an expired viz or hydro until it's time to refill it. Unless of course there will be an issue with an upcoming weeklong livaboard trip or whatever.

I have been fortunate not to need to use my pony for a couple years. The regulator testing draws it down ever so gradually that eventually I need it refilled and it is likely out of viz at that point. To keep the post simple I did not explain why I get the viz on the pony or how often.

 

[NorCalDM]

If you are using the pony as part of your gas planning to extend your bottom time you no longer have redundancy. All you are doing is adding more equipment and complications. Sell the tanks you have and get a bigger ones, keep the pony and treat it as such.

 

[chrisjur]

If you are using the pony as part of your gas planning to extend your bottom time you no longer have redundancy. All you are doing is adding more equipment and complications. Sell the tanks you have and get a bigger ones, keep the pony and treat it as such.

I was so tired of this thread, but this pretty much sums up the issue in the most concise and accurate fashion.

 

[LI-er]

If you are using the pony as part of your gas planning to extend your bottom time you no longer have redundancy. All you are doing is adding more equipment and complications. Sell the tanks you have and get a bigger ones, keep the pony and treat it as such.

Not necessarily true. As I stated I consider the gas in my 19 or 30 cf pony to be my reserve during most of the dive, which allows me to drain my main tank lower and thus prolong the dive. I have redundancy during most of the dive, until I'm below the "typical recommended reserve" in my main tank. At which point, I still have some redundancy but the remaining air supply between both tanks would be tight if there was a catastrophic loss of gas from one of the tanks. At that point in the dive I'm generally close to the upline or near the boat or exit point, I'm certainly not nose deep inside a wreck.

So my dive planning means "redundancy during most of the dive" + "dive extension using the pony as reserve" during the last 10 minutes or so when I'm near the exit point.

As far as adding equipment and complications? We're talking another cylinder and regulator and computer.

According to your logic, divers shouldn't use rebreathers or carry more than one tank at any time because it's too complicated.

 

[Tom_Ivan]

If you are using the pony as part of your gas planning to extend your bottom time you no longer have redundancy. All you are doing is adding more equipment and complications. Sell the tanks you have and get a bigger ones, keep the pony and treat it as such.

This is incorrect.

If you have two gas sources then you have redundancy. Having a cylinder partially drained doesn't somhow eliminate the usefullness of the remaining gas.