Pony bottle 19 vs 30 cf, and clipped on left side of BP/W ?

[Roger Hobden]

What are the pros and cons of diving with a 19 cf vs 30 cf pony bottle ?
What would be the "average" duration of each size ?
The cost of either one is practically the same here in Canada.

If your setup is backplate/ wing, would the left side D-ring be the best place to clip it ?
Is it possible to partially mitigate the effect of having an extra load on one side with trim weights on the other ?

(Some divers will probably say that pony bottles and BP/W don't mix well, so we might possibly be throwing DIR out the window, unless I'm wrong. )

Edit: Please note I spelled "poney" as we would do when writing in the french language.

 

[tbone1004]

al40's actually carry better than either a 19 or a 30 since they are less negative when full. Better to have and not need, than to need and not have. If carrying the big one is easier than the small ones, why bother with the small ones?

I like to use 100ft as an "easy" math number for rock bottom calculations since it's 4ata. 5 minute conflict resolution at 1cfm is 20cf right off the bat. Add in 4 minutes for ascent, which averages to 2ata*1cfm*4mins=8cf, add in a 5 minute safety/deco stop which is 1cfm*2ata*5min=10cf, and you're at 38cf. Is it worst case and heavily padded? yes, but more air never hurt anyone, and there is no downside to the al40 when slinging.

slung on the left side is best, though I would add a loop bungee to the plate so you can sidemount that one bottle instead of just letting it dangle.
If you dive with an AL40 you won't need to counter any weight. If you wear a belt though, I'd probably bias 2lbs heavy on the right side.

Pony bottles are not DIR compliant as they are not necessary within the principals of DIR.

 

[Compressor]

If your setup is backplate/ wing, would the left side D-ring be the best place to clip it ?

Yes; The 40 cu ft gets clips to left chest D-ring and the bottom to the left hip one.
Agree with TBone about usefulness of AL40.

 

[Roger Hobden]

al40's actually carry better than either a 19 or a 30 since they are less negative when full. Better to have and not need, than to need and not have. If carrying the big one is easier than the small ones, why bother with the small ones?

Great advice: i went to the website of the distributer, and indeed this information is plain to see.

Very cool ! Many thanks !

 

[RyanT]

To follow up on @tbone1004's point. When I first started tech diving a few years ago, I was kind of freaked out about the prospect of slinging a 40 cf tank. I seriously thought the thing was long, super unweildy and a bit intimidating. It only took me a couple of dives, however, to figure out that they work really well in the water and almost become unnoticeable.

 

[Roger Hobden]

Yes; The 40 cu ft gets clips to left chest D-ring and the bottom to the right hip one.

So it would be in diagonal in front of the trunk of the diver ?
Is there a place on the Internet where In can locate a photo of this ?
it would seem to be in the way of my arms and access to cutting tools worn on the belt.

 

[Compressor]

No; it would go under the left arm. Since the tank is a bit positively buoyant, it will find it way under the left arm pit.
I'll look for a picture for you and post.

 

[Compressor]

Look here for the picture. I would post but image is copyrighted.

 

[dberry]

Yes; The 40 cu ft gets clips to left chest D-ring and the bottom to the right hip one.
Agree with TBone about usefulness of AL40.

Interesting... I was taught to clip to the left shoulder and left hip (not the right hip). I don't see how the latter wouldn't cross your body.

 

[Compressor]

Interesting... I was taught to clip to the left shoulder and left hip (not the right hip). I don't see how the latter wouldn't cross your body.

Thanks for picking up my error. I did mean left and left. Corrected my post above.