Couple questions on a pony bottle for bail out

[mrdre]

.... and the fact that in an emergency even a 40 cuft bottle has questionable value at 100'....

Are you serious?!?!?! So breathing from buddy's 80 cft tank at the end of the dive is perfectly enough (according to the the rule of thirds, which many in OW don't follow - you are going to have 26 cf of gas), but 40 cf pony is NOT enough? I'm just curious how far you are ready to go with such absurd statements just to stick with "no pony" mantra? Would 60 cf pony be enough? )

 

[jadairiii]

40 cubic feet not enough to bail out from a NDL dive to 100 ft.!!! Why is it that some people have to take their diatribe against pony bottles to the point of absurdity?

Before you claim absurdity, do the math using a SAC of 2, that I took from Kwinter's post. Add in a couple of minutes on the bottom to "fix" a problem, 30 ft/min ascent and give this diver some safety stops then tell me what he has left in his 40.

Simple math, try it.

 

[grf88]

Before you claim absurdity, do the math using a SAC of 2, that I took from Kwinter's post. Add in a couple of minutes on the bottom to "fix" a problem, 30 ft/min ascent and give this diver some safety stops then tell me what he has left in his 40.

Simple math, try it.

Your claim was that most peoples SAC rate was such that 40 cu.ft. was not enough.

 

[jadairiii]

...according to the the rule of thirds, ...

I am serious, do the math.

Why would you dive thirds on a 100' reef dive? What any thinking diver should dive, on a non-tech reef dive, is just calculate the minimum gas you and a buddy would need to come off the bottom in an emergency then subtract that out of your total gas and then you have your usable amount with a built in back up. Only other planning would be if you have to come back to a fixed point or a drift dive.

 

[mrdre]

Before you claim absurdity, do the math using a SAC of 2, that I took from Kwinter's post. Add in a couple of minutes on the bottom to "fix" a problem, 30 ft/min ascent and give this diver some safety stops then tell me what he has left in his 40.

Simple math, try it.

Yes, I looked at his post, he said SAC 2 for VERY SHORT BURSTS... He said his SAC is 1 - and it's a very conservative estimate (he mentioned that too). So.. SAC 2 - very short burst to "fix" the problem (pull the reg from the pony and stick it to the mouth) and SAC 1 for the rest. Let's do the math.. try it.

 

[uncfnp]

deleted. Don't know why I let myself me drawn back in.

 

[Basking Ridge Diver]

If your SAC is 2.0 - Your Gonna Die! Either that or you have no business being at 100 feet.

That said - a 100 foot dive with a SAC rate of 2.0 and a safety stop at 20 feet for 3 mins puts you at 26.40 Cu Ft. I am not playing around when I have a serious issue at depth I am heading up as would most divers that know their SAC rate is 2.0... No Overhead and No Deco Obligation... but you need to seriously consider bringing that rate down...

 

[dumpsterDiver]

The DIR guy says a 40 cu-ft can't get a person to the surface from 100 feet, so what does that mean? That in order to get two people up from 100 feet, then you will need to reserve what... 90 cu-ft in the tank to get two people to the surface? So exactly how do these DIR people dive (or spearfish)? Do they carry 3 or 4 tanks or do 5 min bottom times?

 

[PfcAJ]

~40cuft is enough for 2 divers huffin' and puffin' to sort a problem at the bottom (about a minute) and do a min-deco ascent from 100ft while still huffin' and puffin'.

Its more than enough for 1 guy to switch off his RB or his broke/OOG OC rig and head to the surface from 100ft if its enough gas to bring TWO divers up.

Dat math.

If I were to dive solo (and I'm not inclined to do that) or dive a CCR at rec depths (I'm not inclined to do that either) a 40 is what I would take.

---------- Post added July 31st, 2014 at 05:45 PM ----------

The DIR guy says a 40 cu-ft can't get a person to the surface from 100 feet, so what does that mean? That in order to get two people up from 100 feet, then you will need to reserve what... 90 cu-ft in the tank to get two people to the surface? So exactly how do these DIR people dive (or spearfish)? Do they carry 3 or 4 tanks or do 5 min bottom times?

Beats me man. This thread is officially looney tunes .

 

[kwinter]

Navy Seals use a SAC rate of 2.5 and can't keep it going for that long. It is a ridiculously high rate for the working portion of a dive, and I mean really working your buns off. That isn't going to happen on a simple, NDL rec dive. The only way a SAC rate would get that high would be a full blown CO2 hit. That is also not gonna happen on a simple, NDL rec dive. And forget about taking a few minutes to solve a problem at depth. That is certainly not on the mind of the average rec diver once he has bailed out to his pony bottle.

And even if all this were not ludicrous, going from 110 feet to 20 feet at 30 fpm would take 3 minutes at an average depth of about 66 feet. So that's 3 ATA for 3 minutes at 2.0 SAC, or 18 cf. Then tack on a lower SAC of 1.0 for 3 minutes at 20 feet for an additional 4.8 cf. And before you start questioning the assumptions, answer these questions.

1. Why would you ascend at only 30 fpm if it was an emergency instead of the accepted 60 fpm? And yes, I would do it despite my PFO.
2. Why would you even stop at 20 feet for 3 minutes if you are still huffing and puffing at 2.0? Although you probably would have passed out by that time.
3. Why would you even think the ascent would be at a SAC of 2.0 if that is the rate of the working portion of a commercial dive?

I can do the calculations. Based on any realistic scenario, a 40 cf pony bottle is overkill. A 40 cf stage bottle or deco bottle or bailout bottle is a different animal. The OP was asking about getting a reg for his 19 cf pony bottle for recreational diving. The thread has taken many different turns since then.