Spare air

[muddiver]

Agreed. ANYTHING is better than nothing if you really do have to get the heck out of dodge. But when you can plan on purchasing something like the O.P., then it makes sense to work out the math, and make an informed decision.

After looking at their page, the spare air is 1.7 cuft, and the big boy is 3cuft. I'd challenge anyone I know to do a clean ascent from 99ft with a 1.7 cuft bottle, nevermind the safety stop.

I agree with you. Plan your dive, dive your plan. And the cost of a SpareAir is really not worth the it.

It would be nice to actually see an intagation of the bailout consumption to depth table.

 

[ClayJar]

Just as an aside, people keep throwing "calculus" in here. While it's true that you find the formula using calculus, what you end up with doesn't need calculus at all.

1. Find the time for the ascent (excluding stops) by dividing the depth by the ascent rate.
2. Find the average depth for the ascent (excluding stops) by dividing the start depth by two. (It's the simple arithmetic average.)
3. Calculate the air consumption for the ascent (excluding stops) by using the ascent time at the average depth of the ascent.
4. Calculate the air consumption of each stop individually.
5. Add the ascent and stop(s) together.

So, for example, ascending from 90' with a half-depth deep stop for one minute and a 3-minute safety stop would be:

• 3 minutes at 45' for the ascent
• 1 minute at 45' for the deep stop
• 3 minutes at 15' for the safety stop

Doing the math, I get:

Gas Consumed = SAC * (4min * (1+45'/33') + 3 min * (1 + 15'/33')) = SAC * 13.82


If you want to do the ascent in phases, that's fine, too. Just find the average depth for each phase (start plus end, divided by two) and the ascent for that phase (depth difference divided by ascent rate). If you use multiple ascent rates, you'd just do each ascent rate's section separately.

 

[Alex777]

Ah! I see we have another Spare Air thread, off and running, developing legs of its own. I wonder if we should just set up a Spare Air Forum?

 

[trucker girl]

More to the point. If one is so sloppy in dive planning as to depend on this contraption then they probably shouldn't be diving.

Really.

If you'd like, I can bring mine to the M&G for you to try out. I'm not diving, so I probably won't kill you with it... I'll bring my snorkel, too.

 

[Scotttyd]

 

[Sideband]

Your right I should not have been diving.

Also the research station I was working out of should not have 72 cu cylinders that look darn near like AL 80's. I know I can do that dive on a 80 cu cylinder with plenty of gas to spare. But at 5:00 am the cylinders all look the same.

Since it was a search dive it was not deemed necessary to use more cylinders or go to a surface supplied spread. that might have prevented the OOA situation as well.

But, my point is that having a redundant breathing gas supply is better than no backup. Even if all you plan to do is "blow N go".

Your first answer, "because I was not paying attention to my gas supply", sounds more likely. Just how much longer would you have had at 130' with that extra 5 cuft of air in an 80? 2 whole minutes? Maybe? How could you do that dive on an 80 and have plenty of gas to spare if you aren't paying attention?
I don't mean to pick on your posts, but this excuse is lame and doesn't even make sense.

 

[LiteHedded]

monitor your gas
monitor your gas
monitor your gas
monitor your gas
dive with good buddies =)

 

[Randy43068]

And you are here reading the thread and posting in it. What's your point?

What's your point?

 

[Randy43068]

If you'd like, I can bring mine to the M&G for you to try out. I'm not diving, so I probably won't kill you with it... I'll bring my snorkel, too.

No thank you, I really don't need either. But I appreciate your thoughtful offer and your kindness.

 

[Randy43068]

Exactly!!