View Full Version : Meg ADV Query



Major Clanger
06-06-12, 09:25 PM
As my diving on this wonderful unit progresses, more questions pop up outside of training. Training standard was to turn on the adv and leave it on. However, as I tighten up on things, am finding this increasingly wasteful. Due to only having 80 bar of dil for my last dive, I chose to turn off the adv on reaching the bottom and was able to leave it off for the remainder of the dive, apart from two manual quick squirts. For a 30m dive I "only" used 30 bar of dil in an hour. Do the majority turn off their adv, including for deeper dives beyond the 30 metre range? Interested in what strategies people may use. Where practical I intend to turn it off but am wondering about the pitfalls of that.

The Duck
06-06-12, 10:20 PM
Whilst not diving a Meg (Inspo Classic), I use the flow-stop to isolate the DIL when I reach the bottom. If needed I use the manual add to top up the loop if I drop down deeper.

(However note: I am new at CCR!)

megangel1
07-06-12, 04:43 AM
I dive a meg ... guess the name gives it away?

I was taught to isolate the ADV after descent. Now I use a BOV and rarely have it on at all, DIL add via BOV.

philsiswick
07-06-12, 06:52 AM
I'm not sure why isolating your ADV would reduce your dil usage? Surely, you need the dil you need to keep the loop at whatever volume you want as you descend?

On the Inspo, I was taught to isolate the dil on the bottom and I did that for a while as my dil usage settled down into the 'normal' range. I also used dil for the wing, although I use my drysuit for buoyancy. During that time, my wife did her Mod 1 with another instructor and was strongly discouraged from isolating dil (in fact, he suggested taking the flowstop off completely) - I was persuaded by the arguments, stopped isolating and found no change to my dil usage. I learned to anticipate when the ADV was going to fire and manually adding, or feathering the ADV to pull in the gas I needed.

The JJ has no flowstop - the ADV is also your dil MAV. There was no increase in my dil usage when I moved over to it and I've found that, just like with the Inspo, I can anticipate the ADV and feather it as I want.

No criticism - just intrigued. Most units don't seem to have an ADV isolation option and my experience says there is no benefit (for dil usage at least) for doing so, so is there something different about the Meg?

Timw
07-06-12, 07:56 AM
I isolate the dil before I ascend as I was taught.
I do it because I nearly always use a hypoxia dil and this way it becomes a conscious decision to add dil if I over- vent the loop on the ascent. It doesn't affect dil usage at all. I probably use as much dil for the wing as for the loop. I want the flow stop there to isolate the adv if it leaks. If it does, I still want access to the dil for the wing so turning off at the cylinder would be a pain in the ass. I can add my deep bail out as dil via the MAV.

megangel1
07-06-12, 12:48 PM
It more likely that DIL is being used for suit or wing inflation. On a standard ( if there is such a thing ) Meg, the wing is normally fed from the on-board DIL. I guess the shut-off is therefore present to allow one to isolate the ADV and still be able to use DIL for wing/suit inflation?

I can not say that my DIL usage varies noticably whether I add via BOV or via ADV (the ADV is the on-board DIL MAV on a meg as opposed to the off-board MAV TimW mentioned above) nor if I dive with it isolated or not.

I drive my dry suit from a seperate source anyway but do use the 1st stage as a manifold as per Dave Sutton style setup. Having the isolation is therefore nice as I can still use my primary wing inflator as well as the BOV if the ADV fails open.

As buoyancy control improves, DIL usage normally decreases. The (un)concious add/vent from the wing probably has a much bigger impact on DIL usage.

Major Clanger
07-06-12, 05:07 PM
I guess a lot of it is to do with my current level of experience and honing the anticipatory skills. With the adv off, I think that i became more focused on maintaining a constant depth, in a manner I hadn't with it on, and so vented less.

windymiller
07-06-12, 07:06 PM
I was taught to switch off the adv when I reached the bottom...The meg adv is very sensitive due to its plunger design and I presume thats why every single one has a flow stop fitted

taylojonyd
07-06-12, 07:46 PM
...

Major Clanger
07-06-12, 07:59 PM
so is there something different about the Meg?

The meg doesn't have manual dil addition, other than hitting the adv, so similar to the jj. Increasingly I think that with the adv being so sensitive, it's my changes of depth and subsequent venting that I think is at fault. 30 bar on an hour's dive at 30m was very good for me, whereas previoulsy it was closer to 70.

What would others expect ball park for a similar dive based on 3 litre cylinders, wing control for bouyancy and suit inflate off the bailout to take off squeeze? Maybe it's me using the wing for control off the dil, whereas I get the feeling most may use the suit with seperate bottle, that's loading dil usage.

PeterVICEG
08-06-12, 05:34 AM
Geez, I have no intuitive sense of what a bar is as we are all psi over here. All I know is that a year ago I barelled through the dil, and now I can get several hours or several dives out of one 19 cubic foot tank.

I turn my adv off at the bottom. If I want some I turn it on and then off. I find it easier to maintain min loop volume with the adv off.

Peter

Major Clanger
08-06-12, 06:56 AM
Vice versa here, our thoughts are a mix of imperial and metric. IIRC 200 bar is approx 3000psi.

Major Clanger
09-06-12, 04:58 PM
Two dives today both with adv shut off. DIL and O2 usage down a lot on usual levels.