Optimal Pony Bottle Size for Failure at 100ft?

[sod kamus]

Optimal Pony Bottle Size for Failure at 100ft?

I dive with a 19 cu ft. I've drilled with it and at 100' it will give me about 10 minutes of air. Some self-proclaimed "experts" say that's too small, and I'm better off without it. My logic is, if I'm in a situation where I need to switch to the pony, I'm coming home now, so that's all I need to reach the surface from 100'. My pony is a get-to-the-surface bottle, not a bottom-time-extender bottle or a deco bottle.

I'm just not the guy whose going to drag a 30 or 40 cu ft bottle around on a recreational dive with me. At 100" or less, I just don't need 20 minutes of air to "get home" in an emergency. At 100', the surface is less than 4 minutes away at a safe ascent rate. From 100' I can surface, and do a safety stop on my pony during drills. I figure in a "real" emergency situation that safety stop air would be used up by increased breathing rate, so I obviously would skip the safety stop in a real OOA emergency.

Dragging a 30 or 40 cu ft deco bottle around as a pony bottle for recreational diving is like using a .30-06 for squirrel hunting IMO. But to each his own.

 

[MidOH]

How big are you?

I can use an Al40 as a pony, and use it to extend the dive. It slings just as easy.

Al80 rentals are a bit weak.

 

[Rogerdiv]

Switch to doubles for redundancy, or an H-valve on a higher capacity single tank. My 40 pony is filled with 50% O2, for deco purposes, or a shallow emergency.

 

[MidOH]

But then the Scuba police will say:
You need a manifold, dry suit, tech training, rubber fins, waffles, and a drill instructor.

Nothing wrong with a big pony for Rec+ dives.

50% is handy. An MOD of 60-70' would still be redundancy on most of my dives.

 

[jborg]

 

[coldwaterglutton]

You might get by with a 19 for 100 feet, but why not just go to a 40 (or 30) on the theory you may want to dive deeper and don't want to get another bottle?

 

[34109411]

Optimal Pony Bottle Size for Failure at 100ft?

I dive with a 19 cu ft. I've drilled with it and at 100' it will give me about 10 minutes of air. Some self-proclaimed "experts" say that's too small, and I'm better off without it. My logic is, if I'm in a situation where I need to switch to the pony, I'm coming home now, so that's all I need to reach the surface from 100'. My pony is a get-to-the-surface bottle, not a bottom-time-extender bottle or a deco bottle.

I'm just not the guy whose going to drag a 30 or 40 cu ft bottle around on a recreational dive with me. At 100" or less, I just don't need 20 minutes of air to "get home" in an emergency. At 100', the surface is less than 4 minutes away at a safe ascent rate. From 100' I can surface, and do a safety stop on my pony during drills. I figure in a "real" emergency situation that safety stop air would be used up by increased breathing rate, so I obviously would skip the safety stop in a real OOA emergency.

Dragging a 30 or 40 cu ft deco bottle around as a pony bottle for recreational diving is like using a .30-06 for squirrel hunting IMO. But to each his own.

take into account that in a emergency/stress situation your air consumption will increase. I do carry a 30 CF i barely notice it.

Be safe

 

[johndiver999]

Optimal Pony Bottle Size for Failure at 100ft?

I dive with a 19 cu ft. I've drilled with it and at 100' it will give me about 10 minutes of air. Some self-proclaimed "experts" say that's too small, and I'm better off without it. My logic is, if I'm in a situation where I need to switch to the pony, I'm coming home now, so that's all I need to reach the surface from 100'. My pony is a get-to-the-surface bottle, not a bottom-time-extender bottle or a deco bottle.

I'm just not the guy whose going to drag a 30 or 40 cu ft bottle around on a recreational dive with me. At 100" or less, I just don't need 20 minutes of air to "get home" in an emergency. At 100', the surface is less than 4 minutes away at a safe ascent rate. From 100' I can surface, and do a safety stop on my pony during drills. I figure in a "real" emergency situation that safety stop air would be used up by increased breathing rate, so I obviously would skip the safety stop in a real OOA emergency.

Dragging a 30 or 40 cu ft deco bottle around as a pony bottle for recreational diving is like using a .30-06 for squirrel hunting IMO. But to each his own.

If you know you can not calm down doing a leisurely 3- minute ascent, then perhaps you should take a larger pony, so you can do the safety stop.

I'm comfortable with a 6 cu-ft at that depth.

 

[scubadada]

...I'm comfortable with a 6 cu-ft at that depth.

A direct ascent from 100 ft at 30 ft/min at twice my average RMV would take me 6 cu ft. I'm quite sure I could do that ascent on a 6 cu ft pony also. However, when I carry a pony, it is 19 cu ft.

 

[rx7diver]

Optimal Pony Bottle Size for Failure at 100ft?

... I'm just not the guy whose going to drag a 30 or 40 cu ft bottle around on a recreational dive with me. At 100" or less, I just don't need 20 minutes of air to "get home" in an emergency. At 100', the surface is less than 4 minutes away at a safe ascent rate. From 100' I can surface, and do a safety stop on my pony during drills. I figure in a "real" emergency situation that safety stop air would be used up by increased breathing rate, so I obviously would skip the safety stop in a real OOA emergency.

Dragging a 30 or 40 cu ft deco bottle around as a pony bottle for recreational diving is like using a .30-06 for squirrel hunting IMO. But to each his own.

@sod kamus,

The earlier (?) version of Luxfer Al 30 was noticeably smaller (a bit shorter, but more important here, narrower) than the current version. See my post #43 in the old thread Al 30 or Al 40 for pics. You owe it to yourself to track down and try one of these.

IIRC, I wrote up and posted an example here a long time ago that suggests that an Al 30 is sufficient for returning from a 100 fsw recreational dive at maximum NDL (using Navy Tables, IIRC), returning the way you came.

ETA: Here's my old thread: Gas Planning Example

rx7diver