Recreation diver:pony bottle?

[Jibeho]

Check out this link, It helped me out alot in deciding that I wanted to get a pony bottle. (which I am still yet to do). And deciding on its size.

http://www.scubanaked.com/pony.html

EDIT: The chart on the link is assuming a half foot acent rate WITHOUT safety stop

Again another chart assuming a 30fpm assent rate. Let me ask this if your at a cook out and your buddy is having a heart attack and you dial 911. Will the rescue squad stop at all red lights and do the speed limit on their response? I hope not.

Same deal I was trained years ago that the proper assent rate was 60fpm. Over the years this has changed to 60fpm till 60fsw then 30fpm to your stop. Most will quote 30fpm for the total assent. If your out of air will you be stopping at those red lights?

 

[grazie42]

Perhaps the point is that if you´re going to plan for an emergency, why not make it a plan that gets you out of the water in comfort and ease rather than in a "mad dash" for the surface? The reason that makes you go for the pony in the first place may also be entanglement so that the 1 minute (if any) that you calculate using at depth may end up being very inadequate.

I think the point everyone is trying to make is to think about what kind of failiures you want your pony to be able to get you out of and what data that realistically represent your specific circumstances. THEN decide the size you need to handle those failiures. And of course to keep up with anything that changes the data you´re using in your model or the failiures you want to survive.

It´s all about risk vs reward but please make sure that the things that you want to be survivable with the help of your pony, really are. I´m sometimes surprised by people who decide that "sometimes **** happens" (ie I want my pony "just in case") and consider that reason enough to get a pony but then balk at sizes when faced with calculations for some of the specific **** that may happen...

ymmv

 

[rongoodman]

If that ambulance doesn't stop at red lights and somebody gets hurt, they're going to pay, heart attack or not. If they exceed the speed limit and cause an accident, same thing.

 

[fire_diver]

Again another chart assuming a 30fpm assent rate. Let me ask this if your at a cook out and your buddy is having a heart attack and you dial 911. Will the rescue squad stop at all red lights and do the speed limit on their response? I hope not.

Same deal I was trained years ago that the proper assent rate was 60fpm. Over the years this has changed to 60fpm till 60fsw then 30fpm to your stop. Most will quote 30fpm for the total assent. If your out of air will you be stopping at those red lights?

If I go OOA for some strange reason, then yes, I will be going 30fpm or slower. And stopping at all the stop lights, and probably a few yellows too. Because I will have my pony with me, and more than enough emergency air to make that safe, slow ascent.

FD

 

[dhampton82]

Again another chart assuming a 30fpm assent rate. Let me ask this if your at a cook out and your buddy is having a heart attack and you dial 911. Will the rescue squad stop at all red lights and do the speed limit on their response? I hope not.

Same deal I was trained years ago that the proper assent rate was 60fpm. Over the years this has changed to 60fpm till 60fsw then 30fpm to your stop. Most will quote 30fpm for the total assent. If your out of air will you be stopping at those red lights?

Yes, the chart is assuming a 30fpm ascent rate, would you rather use a chart that assumes a 80 fpm ascent rate? And then use said chart to choose your tank? Then in an OOA situation find out that you ascendded only at 50 fpm and ran out of air at 20 ft.....with no saftey stop?

Point being, the chart is being conservative. if the chart says that you have "X" amount of time to ascend at 30 fpm, and you actually ascend at 50 fpm, you will still have the required amount of air for your ascent.

 

[lamont]

Again another chart assuming a 30fpm assent rate. Let me ask this if your at a cook out and your buddy is having a heart attack and you dial 911. Will the rescue squad stop at all red lights and do the speed limit on their response? I hope not.

Same deal I was trained years ago that the proper assent rate was 60fpm. Over the years this has changed to 60fpm till 60fsw then 30fpm to your stop. Most will quote 30fpm for the total assent. If your out of air will you be stopping at those red lights?

If you've got a 20 minute deco ceiling will you be planning on 'running the red lights' and getting bent to snot, or will you plan your gas so that you don't get hurt even if one or two gas loss issues occur? Every training agency I'm aware of teaches that you have contingency gas so that you don't blow your stops just because one regulator had an issue. Why should it be considered acceptable in recreational diving to put yourself at risk by doing a 60-80 fpm direct ascent from 100+ fsw because you couldn't be bothered to learn how to solve problems underwater?

In a recreational setting it is pathetically easy to ensure that you can do a 30 fpm ascent and hit your stops -- quit arguing that recreational divers should put themselves at added risk of getting bent just because they aren't supposed to take diving seriously enough to avoid that risk...

 

[Doc Intrepid]

Again another chart assuming a 30fpm assent rate. Let me ask this if your at a cook out and your buddy is having a heart attack and you dial 911. Will the rescue squad stop at all red lights and do the speed limit on their response? I hope not.

Same deal I was trained years ago that the proper assent rate was 60fpm. Over the years this has changed to 60fpm till 60fsw then 30fpm to your stop. Most will quote 30fpm for the total assent. If your out of air will you be stopping at those red lights?

The decision will be based on how deep you were diving, for how long.

Generally divers tend to run out of gas (or have related "issues") toward the end of their dives. They may have been wherever they were for quite a few minutes, depending on where they're diving, following some DM, etc.

As Lamont noted, if you're carrying a bailout bottle with a capacity sufficient to allow you to surface unstressed and unbent, then it makes sense to provide for adequate gas to allow a 30 fpm ascent rate.

Things have changed since all divers were taught the 60 fpm ascent rate, and in particular a broader understanding has emerged regarding seed bubble formation, fast and slow compartments with respect to ongassing and offgassing, and related datapoints regarding how DCI occurs.

If you're planning for safety anyway, it makes sense to take these elements into consideration in your planning. If you're carrying a bailout bottle to begin with, it should provide for a safe ascent (e.g 30 fpm) from whatever depth you were at (to include 130 fsw for recreational divers) for whatever time you were there.

Regards,

Doc

 

[Jibeho]

If you've got a 20 minute deco ceiling will you be planning on 'running the red lights' and getting bent to snot, or will you plan your gas so that you don't get hurt even if one or two gas loss issues occur? Every training agency I'm aware of teaches that you have contingency gas so that you don't blow your stops just because one regulator had an issue. Why should it be considered acceptable in recreational diving to put yourself at risk by doing a 60-80 fpm direct ascent from 100+ fsw because you couldn't be bothered to learn how to solve problems underwater?

In a recreational setting it is pathetically easy to ensure that you can do a 30 fpm ascent and hit your stops -- quit arguing that recreational divers should put themselves at added risk of getting bent just because they aren't supposed to take diving seriously enough to avoid that risk...

Thanks for the advice.

I'm purely a 25-50 dive a year recreational diver. I find myself diving alone more then your average person. I have practiced using my pony. I'm not worried about running out of gas due to my neglect ( I would assume your would call this poor gas management)? What I worry about is the 0ne in a million failed regulator. I have never been in deco land the closest was about 4 min. Most time my NDL is well in the double figures. I feel that if that 1:1,000,000 hits I will go to my pony, do a 360 looking for someone to motion that I'm going up and make a controlled assent in the 45-60fpm range. If I have gas left I would hang at 15 a few.

Now take the above and assume I did not pack my pony. the 1:1,000,000 happens. My buddy is facing away from me up current 20 feet away looking for a bug. My bad for not being joined at the hip. Also my bad for more then likely giving my wife an early insurance pay out.

I feel there is a balance of to little and to much for a diver like me. To little would be a 6cf to much would be anything larger then a 19cf. I have had a measure of my stressed SAC it was .87. My daily SAC is .45-.48. I feel that in my neck of the woods allowing for the assent that I can live with a 13cf is right for me. Much larger and I would start to 2ndn guess whether I want to lug it around.

 

[Jibeho]

The decision will be based on how deep you were diving, for how long.

Generally divers tend to run out of gas (or have related "issues") toward the end of their dives. They may have been wherever they were for quite a few minutes, depending on where they're diving, following some DM, etc.

As Lamont noted, if you're carrying a bailout bottle with a capacity sufficient to allow you to surface unstressed and unbent, then it makes sense to provide for adequate gas to allow a 30 fpm ascent rate.

Things have changed since all divers were taught the 60 fpm ascent rate, and in particular a broader understanding has emerged regarding seed bubble formation, fast and slow compartments with respect to ongassing and offgassing, and related datapoints regarding how DCI occurs.

If you're planning for safety anyway, it makes sense to take these elements into consideration in your planning. If you're carrying a bailout bottle to begin with, it should provide for a safe ascent (e.g 30 fpm) from whatever depth you were at (to include 130 fsw for recreational divers) for whatever time you were there.

Regards,

Doc

Thanks Doc, and again good advice.

I dive 100s most of the group I dive with are using 80s. I tend to end my dives in the 1,000 to 1,200 PSI range then the others are near 500 in their 80s. Like I told Lamont I carry the pony for the 1:1,000,000 equipment failure.

Cheers

 

[lamont]

I feel there is a balance of to little and to much for a diver like me. To little would be a 6cf to much would be anything larger then a 19cf. I have had a measure of my stressed SAC it was .87. My daily SAC is .45-.48. I feel that in my neck of the woods allowing for the assent that I can live with a 13cf is right for me. Much larger and I would start to 2ndn guess whether I want to lug it around.

Well, you just completely backed off and now agree just about precisely with the green areas of the chart that you were critiqueing... ( 13 cu ft min down to 66 fsw and 19 cu ft min at 100 fsw)