Spare Air

[DaFireMedic]

I think it depends on the assumptions you want to make as you plan your redundant air use. Do you assume you will spend a minute or 2 at depth breathing your pony while trying to remedy the problem? How much increase in SAC do you assume as you deal with your problem? What rate of ascent do you assume? How many rest stops? How long? If you go with all very conservative (safe) assumptions, it's not hard to work out a requirement for more than 13 or 19 cu ft.

Good points, thank you. I have practiced ascents from 100' with the 13' bottle, using a 30' per minute rate to be familiar with what it would allow me for a safety stop, etc. and I had a surprising amount of air left after a 5 minute stop at 15', even while attempting to simulate a faster breathing rate during ascent. But thats a good point about additional time at depth dealing with the problem. I will do some additional evaluation to take these points into account. I am pretty conservative with my planning, but I also tend toward the minimalist side with regards to equipment. Whether or not I will switch to a larger bottle, I don't know. But I can use the info to plan my dives/emergency plan accordingly. RIDIVER was kind enough to send me a SAC spreadsheet to assist with the SAC rate stuff. Thanks to all.

 

[Sideband]

I don't know of any reason other then personal choice for recommending bottles that large. I use 30cuft pony. I don't use it for dive I am doing less then 80 feet unless i am diving with students and only then dive it when I am taking the stu's deeper then 60 feet. I have really good air consumption so the pony is more for their use then mine.

If I find any supporting documentation that puts in black and white the criteria you listed I will let you know.

You need enough reserve gas to get both you and your buddy to the surface in the event of a failure (or two). Figuring a stressed SAC of 1cft/min for both of you, at 80' it will take a little over 35cft of air for both of you to make a deep stop, safety stop and the ascent with one minute at depth to get things under control. For 40' it comes to a hair over 17cft of air needed.
I got these numbers from the Rock Bottom spreadsheet that was made available in another thread a while back.

Joe

 

[redacted]

You need enough reserve gas to get both you and your buddy to the surface in the event of a failure (or two).
Joe

When I carry a pony, it is intended just for me; not for any buddy. It is carried for solo diving or to give me options independent of a buddy otherwise.

But it is an intesting idea. Does this mean you should add an octo to the pony? And should your buddy carry a similiar sized pony? Also with an octo?

 

[RIDIVER501]

You need enough reserve gas to get both you and your buddy to the surface in the event of a failure (or two). Figuring a stressed SAC of 1cft/min for both of you, at 80' it will take a little over 35cft of air for both of you to make a deep stop, safety stop and the ascent with one minute at depth to get things under control. For 40' it comes to a hair over 17cft of air needed.
I got these numbers from the Rock Bottom spreadsheet that was made available in another thread a while back.

Joe

Says who? if my air supply is intact and my buddies isn't then there is enough air for the both of us. me in my primary and the buddy on my pony.
Assuming your proposed excessive SAC rate. of 1, a 30 cuft pony will last 9 minutes at 80 feet 18 minutes at 20 feet.
80-160 sec transit time we'll say round it to 3 minutes for argument sake. so well assume worst case scenario transiting to 20 feet and keep a full on burn of air. so 3 mins to get to 20 feet burns 1/3 of the air supply.
By the time I hit 20 feet it still has 2/3 air supply which is now burning at the 20 consumption rate so when it hits the 20 foot stop the pony now has 12 minutes of air remaining. 3 minute safety stop at 20 feet. now it has 9 minutes of air. say we take a full minute to get to the surface now it has 8 minutes left. minus your minute to "get things under control" still plenty of air in a 30.
In actuality it would have more air remaining because the burn rate on the bottle would decrease on the transit as we got shallower as I am sure the anxiety level would drop thus the sac rate would drop which would further increase the duration of the air supply.

 

[Nobby]

Nobody goes out and intends on getting in car accidents either but they happen.


I can't resist on this one, so when I run low on air I will then out of air then I am in an OOA situation?? I see, Thanks for shedding light on that one.


But it evolved into one.


Funny a pony looks like the regular tank I use. the reg system looks like the regular reg I use. Humm where did I get that specialized training..ummm in my basic open water course. How to set up my gear. how to use it...tough one use of an alternate air souce skill..... now spare air....doesn't look like anything I was exposed to in basic OW course. used like a alternate air source, covered in basic OW. How to fill it. humm that becomes my responsibility not the LDS's...ok need to be trained on that. How the componets fit togeter and how to turn it on. didn't get that in basic OW.

So your point is invalid. you get all the training for how to use and set up a pony on basic OW minus how to attach it to yourself or primary unit. Spare air can and should require additional training especially if the spare air user is one of those pesky entry level divers having trouble with those 3 hoses of theirs. (see your comment below)


As a safety officer from my naval days that is incorrect there are always patterns that can be traced back to recreate the cause of an accident/incident. those patterns usually also have tell tale signs that if one is vigilant they can see and identify those signs to halt the pattern and avoid disaster. that is where that whole preventative measure thing comes in handy from the rescue diver course.

I am an instructor. I dive routinely with a pony. more for my students sake them my own. when I am diving for fun I rarely take a pony if I am diving less then 80 feet. deeper then 80 on a fun dive I do have the pony.


Not going to slide off on a training tangent here.

enough said here. one point we agree on


redundant already answered above. not sure what oggin is but I will assume it's water in some shape or form.

You and your Navy days and you don't know what oggin is? It's Jack (sailor) speak for the sea.

I've had enough of this horse s&*$. Agree to disagree and leave it at that, we can all find flaws in each other's arguments and it is becoming a pitched battle of wits, and that is not what this forum is intended for. Truce, no hard feelings?

 

[RIDIVER501]

Agreed,
but 16 years in the Nav never heard that term... Must be a Uk thing

 

[Lil' Irish Temper]

I wonder what would happen if you shot a SpareAir?

Maybe this thread would die.


It just really sucks that this thread has spiraled out of control that someone with a real Snorkeling / Freediving question is being buried by this thread, that has nothing to do with freediving anymore.

bikeflip22, and kjd2121, I hope people notice your Snorkeling post/question's and more can add their 2 cents

 

[Kim]

I wonder what would happen if you shot a SpareAir?

Fizzzzzzzzzzzzzzzzzz.................

 

[RIDIVER501]

Using the suggested 1cuft per min burn rate suggestion and comparing volumes of spare air, 30cuft pony and 40cuft pony.
check out the spread sheet and the associated chart.
it does assume constant depth but has some interesting base line info.
all three units will last longer then the number for the depth the ascent is started from, but look how low Spare air is. At that sac rate it only last 3 minutes at the surface.

 

[Nobby]

I wonder what would happen if you shot a SpareAir?

Maybe this thread would die.


It just really sucks that this thread has spiraled out of control that someone with a real Snorkeling / Freediving question is being buried by this thread, that has nothing to do with freediving anymore.

bikeflip22, and kjd2121, I hope people notice your Snorkeling post/question's and more can add their 2 cents

Oooooh I don't think so. The original question was addressed and answered with a unanimous NO, DON'T DO IT! The original poster never attempted to come back to the forum, not because it hijacked as this didn't happen, but prob because he got the answer, or as some suggest was just trolling around. His question was answered and that was the end of the thread.