What pony size?

[kwinter]

As for your "go back and learn how to dive" comment....no but you could use a refresher course in social skills

That's pretty damn arrogant of you. I gotta go with Frank on this one. You're the guy that said you could accidentally end up with a deco obligation. First, we don't dive by accident. Second, if a few minutes of deco would cause you to run out of back gas, you failed to plan that as well. A pony or independent gas source is not related to deco.

 

[flots am]

Been thinking for a while about a redundant air source. I'm thinking either 19 or 30cu ft. What are advantages (other than less/more air) disadvanatges if any?

You need to calculate that for yourself based on your stressed RMV, your maximum planned depth, and your ascent rate.

I know a girl who could get from 130' to the surface on a 19 and still have enough left for a short dive. I know a guy who would use more than a 19 before he realized that something was wrong.

Nobody else can answer this question for you. You have to do it yourself. You might need a 13. Or a 19. Or a 45. Nobody can tell you.

flots.

 

[Only halcyon]

Well said!! However I am a huge advocate of every diver waking up to the notion of being 100% selfsuficient. Correct, a well planned dive should not require a pony, shall we remove car airbags if we plan our drive? Variables are something we plan to avoid but arise in every sport. Deciding how big your safety net needs to be is of personal preferance based on 'what, where, how', how much air do you need to survive an absolute worst case scenario? That number is as different as a fingerprint. I feel good intent, lazy execution.

 

[drrich2]

To follow up some of what others said. I mainly use a pony when I solo dive a local quarry. I use a 30 cf. I like to turn the valve on to pressure my reg. on the pony, then turn it back off unless needed. Idea is to prevent water getting in through the 2'nd stage (it's a piston reg.; seems like I read somewhere it's good to keep it pressurized when rinsing, or to avoid having the 1'rst stage lower than the 2'nd; I could be wrong, but it's what I do). So every dive the pressure in my tank drops. Since a fill at our LDS will probably cost the same as a regular tank ($7, or a punch on my air fill card), and I don't have to have the full 30 cf to be comfy with it for the dives & conditions I'm doing, this saves a bit of money.

But I sling mine & don't plan to take it on plane trips. And I'm a big guy with a SAC (around 0.65 cf/min., give or take) that's maybe decent but not great.

As for deco., which I'm not trained in & haven't run into yet, I figure if I accidentally got into it, I'd catch it quickly, have a brief obligation, and 'follow the computer's' advice on what depth to go to & how long to wait.

Having to skip deco. to reach the surface without an OOA situation is conceivable, but should be highly unlikely.

Richard.

 

[GrumpyOldGuy]

I ended up with 3 pony bottles, 6, 13 and 30.
The 13 is my go to pony, small enough to be used all the time, big enough to be a real help.
You can make endless calculations on the ideal size. If you are not in deco, any size can be the right size, you just adjust your ascent to match.
If you travel, the 6 and 13 are the practical sizes to pack. The 6 is pushing the envelope, best for dives under 70', so the 13 wins.
I drill with them so I know they are big enough to get the job done and regular drills insure my SAC rate will not spike just because I ran OOA.

 

[waterpirate]

I think that the size of the bottle is directly related to how you carry it, depth, intent of use. I have never met anyone who ever complained that the bail out bottle was to big after a emergancy ascent using it. If your bc allows you to sling a bottle, the 40 is a natural choice. If your bc is not conducive to slinging a bottle it boils down to mounting. The mounting style will prompt alot of discussion on orientation, valve position, spg, ect.

No matter what you end up with, practice and comfort are key. I was on a charter 3 weeks ago when another team had a member free flow his primary. Due to the divers lack of practice, comfort, and execution of his back up he wound up on his buddies long hose. His buddy as well as the rest of us gave him alot of grief. Not for the lack of reg maintanace but for being not able to self deploy his backup.

hope this helps you sort it out.
Eric

 

[scubadada]

SDI, in the Solo Diving Manual, suggests a pony of 1/3 of your primary gas volume. This would translate into a 30 or 40 cu ft tank for singles diving.

I am a traveling diver and dive AL 80s and steel 100s nearly all of the time. I don't generally go below recreational limits and generally dive NDL with occasional short deco obligations in the range of a safety stop. I sling a 19 cu ft pony. I made this choice based on the volume of gas it would take me to ascend from 130 feet with a minute at depth, normal ascent rate, and 3 minute SS, at twice my usual SRMV. Of course, without the minute at depth and/or without the safety stop, the volume required would be less.

As pointed out, this is a personal decision.

 

[Jim-SAR]

I use a back mounted 30. For me, it's not about what's easiest to carry, or the minimum to get to the surface. As a public safety diver I simply like to have options for whatever I might encounter even if me and my friends are just diving for fun. I can appreciate the calculations to determine minimum requirements.

Diving around wrecks, there's a higher chance for entanglements/snags and we like to have options in case we need to spend some extra time helping our buddy. Even with the rule of 1/3's for my primary tank, if I know I have a 30 pony, I'll stay longer to effect a rescue. It's more about what "could happen" than what you "plan" on happening for me.


Sent from my iPhone using Tapatalk

 

[GrumpyOldGuy]

I....... I have never met anyone who ever complained that the bail out bottle was to big after a emergancy ascent using it.................

Although I agree with many points on your post, this part is weak logic for a couple of reasons,
1) You are only looking a divers used their pony in an emergency, that should be close to zero unless you dive with a bunch of bozo's, in which case their opinion is worthless.
2) Your are ignoring the divers who have a pony, but left it topside because is was too big / cumbersome, they will NEVER report anything about using the pony in an emergency.

 

[diverrex]

You"re 50!!!

I find a 13 to be adequate but you need to keep it full. I also have a 19 and even if the pressure drops over a few days of diving, it is still more than enough from any recreational depth. The 13 travels a bit better.

This is one of the reasons I switched from a 13 to a 19. Just a little drop in pressure in the 13 and then the volume of air left starts to be borderline. I don't notice any difference with a 19 attached to my tank than the 13.

19 & 30 won't fit in rack, got it. As for your "go back and learn how to dive" comment....no but you could use a refresher course in social skills

He said he knew it would sound snooty but didn't mean it that way. And I took his "you" to not necessarily mean directly personal to the OP but to anyone that thought that way, and I'd tend to agree with that sentiment.