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Sorry for the WOB but a few people have asked me to elaborate
on just what I meant when I said you can dive safely without
a manifold. Since there has been interest I thought that it
might be worth posting my replies to the general list.
D Drake said "otherwise explain yourself". I'm not sure if he
meant me, but here goes:
Pete asked how I set up my gear for independents,
Hmm my exact configuration?? OK,
I use twin CIG 95 cuft alloy cylinders, I don't know if you can get them
in the states, but they are *slightly* negative when full and *slightly*
positive when empty. That's why I selected them, they were at the
time the largest cylinder I could get that was neutrally bouyant. I
wanted that so that if I wanted to ditch them and enter a wreck with
a lighter setup I could do it without a large change in bouyancy.
They have 300 bar DIN valves, and as soon as I get my act together I'll
blank off the burst disks. They are held to a diverite back plate by
stainless steel bands and the cylinders are turned slightly so that the
hoses from the 1st stages come across without major bends in them.
All the hoses from the right cross over to the left and come over the
left shoulder, but the hp hose comes down behind and under my left arm
where it is clipped of onto my harness.
The opposite is done with my left cylinder, except that the backup BC
hose goes down behind my left shoulder to where the backup BC inflator
is clipped off to the back plate behind me (with a rubber loop that I
can pull away). The back up BC hose has a backup timeing device and
depth gauge cabletied to the large hose.
Both the SPG's are tactile or "stem" types that can be read in total
siltout.
The hoses for the regulators (one per 1st stage, no Occy as such) are
the short type as they are neater, and I almost never (<1/year) dive
as a part of a buddy team.
I have the hose for the dry suit inflator and the backup bc coming off
one cylinder and the primary bc off the other, so that if there is
a failure of a cylinder I don't loose both the primary bc *and* the
drysuit at the same time.
I have two diverite wings.
I have a spare mask in a diverite pocket, along with a safety sausage,
which I can attach to a reel and send up by itself, or use to signal
on the surface (I don't know how well that will work, I haven't had to
use it yet)
The O2 cylinder (4 litre, 200 bar) is usually clipped to my right side
at belt level on the wiast strap of the harness. The 2m (standard
length) hose from the AirDive O2 reg is retained on the cylinder itself
by innertube bands. The mouthpiece is stuck in one of those plastic
holders intended for an Occy, to prevent filling it with crap, and
free flows. I also sometimes chest mount it as I'm experimenting to
find out which I like best. I use a Large locking "D" carebiner (sp?)
that is easy to use in akward spots, and when the screwgate is done up
it can't come undone, *or* trap line. You have to unscrew the gate
first.
I usually have an alloy valve protector that I made out of some scrap
alloy channel running over the whole lot of hoses and such.
I wear a neoprene drysuit, with polypropelyene (sp?) underwear, and
a lycra suit between the underwear and the suit.
I have a very small knife, which I sharpen with the roughest file I
can find. It sits in a tiny scabbard that goes on my harness waist
belt behind the O2 clips. I have a reel clipped to my chest on the
right. I use double buckle weight belt, and I put my harness on *over*
my weights (my instructor would just die!).
Oh yeah, and I have the cheapest fins you can buy, because my beloved
jetfins with the spring straps don't fit over my drysuit booties. ;(
When I plan the dive, I calculate all the air that will be required for
the ascent and deco. I must leave the bottom when both cylinders reach
the point that they have just this amount of air left. Eg if I work
out that the ascent and deco require 25 cuft (1/4 of a cylinder) then
I leave with more than 1/4 left in *both* cylinders. If I work out that
it will take 50 cuft then I leave with more than 1/2 in both cylinders.
(or when my planned bottom time runs out of course)
I write my DrX air/O2 tables on both my hands with a laundry marker. I
write on both runtime and stop time so that any transcription errors are
self catching.
If my O2 fails I can deco on air by the Aladin Pro on my left wrist.
(I may need to dip into both cylinders for this, but consider that
for this to be a problem, I would have to lose both my O2, one of my
air cylinders, and not be able to find the anchor line, which has
surface supplied air at 3, 6 and 9 m)
I think I've covered most of my thoughts that went into planning my
air diving setup. *Please* let me know if you can see any holes in
my planning. I'd hate to get caught by surprise.
Oh BTW most of my air diving is between 40 and 65 metres, and that
is what this is for, but I've done a couple of shallow dives (27 m)
with this setup and it seemed quite good.
Cheers Jason :)
Gary asked;
Jason, Yoe mentioned that the divers you knew that used
manifolds have since removed them. I'm curious as to the
reason why? Did they experience trouble with the manifold
itself or they just prefer independent cylinders?
Gary
I haven't got a manifold so I can't really comment with any exactness,
but from memory this is what guys who don't use them anymore have said.
"I don't like the fact that it is *possible* however unlikely that
you could loose your *entire* gas supply in one go"
"You can't seperate them, so you have to carry them both around
when you want fills and such, so it is really heavy" This guy had
twin 150's so being able to carry them around one at a time really meant
something.
"I sometimes want different gasses in each tank and you can't do that
with a manifold"
"I don't think that you could close off that centre valve fast enough.
You think, if one reg blows a hose, then you have lost that cylinder
even if the centre valve is shut. My poseidon can empty a full cylinder
in well under a minute, imagine a hose blowout! At least with
independents you *know* that you have two seperate supplies, either one
of which will get you back safely"
"have you ever seen a burst disk go, the whole thing is empty before you
know what is happening"
"I want to sell it so I can buy a couple of steel 100's"
"Its bloody useless"
"It takes too long to change it over to sidemounts and back again"
"If I get rid of this I save [some number I can't remember] of O'rings,
so there is far less to go wrong" I don't think he had ever had one
fail, I haven't heard of any failing out here at all.
I think that most of the guys who have bought one have done so because
the american tech training agencies have pushed them. When they get
out into the real world, of Ozzie divers, they find that they didn't
need them and that they offered no safety improvement. What works,
works, but do you need what it does?
Oh BTW I heard through the grapevine that a local diver had a
close shave when he was diving with a manifold. Seems that he had
trouble reaching the centre valve, so he closed it, intending to
open it again and decant across, later in the dive. The dive turned
out to be unexpectedly difficult and at 110 m (360ft) his primary supply
ran out. He was *thrilled* to find that he couldn't open the centre
valve underwater, and that the valve for his backup reg was turned off.
On the spur of the moment he invented a hand signal which means "if you
happen to have a spare moment could you come over and turn on my gas?"
which amazingly enough was understood by the guy who happened to be
there at the time. Lucky ;)
Of course if he had been diving independents, then he would have
switched regs *ages* before the supply ran out. (part of diving with
independents is that you have to change regs before the gas in the
first supply reaches the point where it wouldn't get you back)
Cheers Jason :)
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