View Full Version : Best way to send down extra gas.
Ok so we carry O2 because someone might need it and we also
carry spare cylinders with regs "just in case".
So please dont say that it shouldnt happen, because good deco
divers dont run out of gas ............
Yellow blob up the Orange DSMB means send me some gas.
So what's the best way of sending it down?
Everybody has a favorite suggestion from just chuck it in,
to use a slightly weighted BC and attach to DSMB line with
buddy line, leaving a 2m gap between descending cylinder and
divers heads.
I know most methods, just want to know what would be considered
the best.
Anybody got any other suggestions?
TerryH
Will Swift
21-06-2004, 12:47
Anybody got any other suggestions?
Send down a safety diver with it - it may cheer up the diver to see a friendly face.
:=Anybody got any other suggestions?
Send down a safety diver with it - it may cheer up the diver to see a friendly face.
Scenario 1. 12 divers in the water and only the skipper/boat
handler up top. Cant send a diver down then.
Scenario 2. 10 divers in the water and only a buddy pair on
board. Do both go in or just one, leaving a solo on board.
I know this may be a bit anal, but it's an addition to our
risk assessment and so we need all possible parameters worked
out.
Rgds
TerryH
Ben Field
21-06-2004, 15:37
The most common method I've seen prepared (not used I'd like to add) is a aqualung on 6-9mtrs of rope and a barrel/buoy on top, commonly filled with 80%.
Although this has several problems-
It doesn't account much for depth, how does a diver a 12mtrs get help? How does a diver a 6mtrs use a tank on 9mtrs of line?
Obviously the "best" solution would be a buddy pair to go down with gas to donate (by reg or stage bottle) to the diver, and to assist with deco, DSMB etc during extended/difficult decompression... in fact this is what is done on deep dives even if things are going well- the Britannic expeditions for example.
I think the best coverall plan is a stage type bottle with clips on that the diver can take and add to his kit (rather than leave hanging on the line) it should have two 2nd stages, at least one inflator hose and an SPG.
Preferably it should include a notepad on the line which the skipper/DM will retrieve after you have recieved the bottle
so you can tell them whats happened/how long you'll be :)
As to the bottles contents? I'm not sure.... thoughts?
Chris Cherrington
22-06-2004, 10:38
The most common method I've seen prepared (not used I'd like to add) is a aqualung on 6-9mtrs of rope and a barrel/buoy on top, commonly filled with 80%.
Why is the barrel/bouy filled with 80% ???
Chris
The most common method I've seen prepared (not used I'd like to add) is a aqualung on 6-9mtrs of rope and a barrel/buoy on top, commonly filled with 80%.
Although this has several problems-
It doesn't account much for depth, how does a diver a 12mtrs get help?
The idea is that you will make it to your gas switch / shallow stop on your reserve, or using a buddies donated reserve. The shallow stop is the long one where you are most likely to run out of gas. You signal the boat that your low on gas as soon as practical so they can prepare the drop tank and have it waiting to meet the diver during his ascent. If things are that bad that you can't make your shallow stop normally, well you have the choice to speed the ascent and blow or half stops deeper than the drop tank rope. If you are switching gas you may not know you have a problem until the switch is attempted, in which case you signal and wait at the drop tank rope depth.
How does a diver a 6mtrs use a tank on 9mtrs of line?
Haul the tank up or descend 3m.
I think the best coverall plan is a stage type bottle with clips on that the diver can take and add to his kit (rather than leave hanging on the line)
Not sure I like the idea of the drop tank being removed from the line. It is securely fastened, so why risk it going to the bottom of the sea by unfastening it. I think you would be better getting the OOA diver to abandon their own DSMB and clip onto the drop line, that way the boat knows where the drop tank is and the divers using it.
As to the bottles contents? I'm not sure.... thoughts?
The drop tank mix wants to be appropriate for the dive plan with a similar or higher FO2 than the deco schedule requires. The rope length is generally the MOD of the gas or the nearest shallower deco stop to it. For simple air diving, 50% is possibly a better choice for a drop tank.
Scenario 2. 10 divers in the water and only a buddy pair on
board. Do both go in or just one, leaving a solo on board.
Terry, I think the ban is on solo divers under water - not waiting on the boat ;-)
If the marshal is that anal, the safety diver could always claim to be using the DSMB line as a tether and hence solo diving legitimately for the time it takes to reach the striken pair.
Everybody has a favorite suggestion from just chuck it in,
to use a slightly weighted BC and attach to DSMB line with
buddy line, leaving a 2m gap between descending cylinder and
divers heads.
What is the point of the BC? Just attach a 2m jump line to the drop tank. A clip on the far end of the line is slid down the divers DSMB line and the tank lowered away from the divers. When the jump line arrives the divers transfer to the drop line and use it as a deco station.
Chris Cherrington
22-06-2004, 14:26
:=I think the best coverall plan is a stage type bottle with clips on that the diver can take and add to his kit (rather than leave hanging on the line)
Not sure I like the idea of the drop tank being removed from the line. It is securely fastened, so why risk it going to the bottom of the sea by unfastening it. I think you would be better getting the OOA diver to abandon their own DSMB and clip onto the drop line, that way the boat knows where the drop tank is and the divers using it.
I have a (serious this time) suggestion. (Although I still want to know why to put mix in the bouy).
Suspend your spare tank and reg at 9m. (Assuming you need to stop at this depth from the dive profile). Place snap clips on the rope at 6 and 3 meters so the whole tank/reg assembly can be pulled up to those depths and then clipped off - without detaching from the line.
That way unless the rope snaps you cannot lose the tank. If the clip breaks I guess it might scare the crap out you as the tank descends, but I doubt the likelhood of this - more likely as you say Matt to drop the tank.
Chris
PS I too would suggest EAN50 as the best compromise.
What is the point of the BC? Just attach a 2m jump line to the drop tank. A clip on the far end of the line is slid down the divers DSMB line and the tank lowered away from the divers. When the jump line arrives the divers transfer to the drop line and use it as a deco station.
Point is that we aready have it as a flotation device with
D-rings etc. and a way to attach a cylinder. Plus it can be
used for rescue by a now empty twinsetted diver.
Best compromise I have so far is to create a hoola hoop
effort which is thrown lifebuoy style over the DSMB. The cylinder is then thrown over and a round buoy as per trapeze
unravels as the hoop sinks.
This adds a brake to the cylinder on the descent and still lets
it stop at 6m. The dievers U/w get hit by the hoop and drag
line towards them.
Discuss.
TerryH
If the marshal is that anal, the safety diver could always claim to be using the DSMB line as a tether and hence solo diving legitimately for the time it takes to reach the striken pair.
Who says anything about the Marshal.
There are two divers underwater who have gone over the plan
thus asking for air. We CANT rely on a diver as part of any
rescue as .......
a) We dont know if there are any divers on board. or
b) We dont know what state the rescue diver is in (deco/air
wise).
As the numbers onboard increase then yes that may be an option,
but at this stage we MUST assume nil diver help.
TerryH
Nigel Hewitt
22-06-2004, 15:01
I have a (serious this time) suggestion. (Although I still want to know why to put mix in the bouy).
Because no serious diver uses air for anything other than the tyres on the truck. I've been on enough boats where the only fill for our DSMBi crack bottles for second dive has been argon, trimix or rich nitrox.
Suspend your spare tank and reg at 9m. (Assuming you need to stop at this depth from the dive profile). Place snap clips on the rope at 6 and 3 meters so the whole tank/reg assembly can be pulled up to those depths and then clipped off - without detaching from the line.
PS I too would suggest EAN50 as the best compromise.
I'd go for 6m. You wouldn't be crying for a drop tank to do deeper stops because they are too short. Who spends much time at 9m? Breath off your buddy or what reserves you have. The problem is that if you have had a free-flow you do not have enough gas for the shallow (ie long) stop. Since this is BSAC I'm not going to recommend 100% but use something good and rich as they might be ascending on back-gas and missing a deep switch. 50% is too lean especially if they are on a lot of helium. Anyhow having a bottle of rich mix is a good back up for the O2 set.
Ben Field
22-06-2004, 15:09
> Not sure I like the idea of the drop tank being removed from > the line. It is securely fastened, so why risk it going to
> the bottom of the sea by unfastening it.
Obviously I meant them to have common sense too... :)
You would clip it to yourself before disconnecting the upline I think? or even as you suggest leave it attached, I don't think abandoning your DSMB is wise, its bound to confuse matters.
BEN
Ben Field
22-06-2004, 15:13
> Why is the barrel/bouy filled with 80% ???
Chris? I'm surprised you even ask?
Assuming you have your barrel O2 clean? (see other thread about O2 cleaning/service interval of HSE approved barrels, I still maintain annually is sufficent, bl**dy CE regulations, tut tut)
Then 80% is the obvious choice...
BEN
:)
Nigel Hewitt
22-06-2004, 15:17
Best compromise I have so far is to create a hoola hoop effort which is thrown lifebuoy style over the DSMB. The cylinder is then thrown over and a round buoy as per trapeze unravels as the hoop sinks.
I'm not sure I have the picture....
Is it:
Hoop with rope to drop tank.
Separate rope from drop tank to float.
Hoop is weighted to sink itself and rope.
So:
Throw hoop with tank on boat so you can pull it back and start again if you miss. Once the hoop is round the DSMB the tank goes over the side with its float.
That works for me but am I changing the idea?
nigelH
Because no serious diver uses air for anything other than the tyres on the truck.
Nigel where have you been? The current trend is to fill tyres with pure nitrogen
<a href="http://www.merityre.co.uk/why_nitrogen.htm" >http://www.merityre.co.uk/why_nitrogen.htm</a>
john kendall
22-06-2004, 16:48
:=Best compromise I have so far is to create a hoola hoop effort which is thrown lifebuoy style over the DSMB. The cylinder is then thrown over and a round buoy as per trapeze unravels as the hoop sinks.
I'm not sure I have the picture....
Is it:
Hoop with rope to drop tank.
Separate rope from drop tank to float.
Hoop is weighted to sink itself and rope.
So:
Throw hoop with tank on boat so you can pull it back and start again if you miss. Once the hoop is round the DSMB the tank goes over the side with its float.
That works for me but am I changing the idea?
That's the theory. And in fact the practice as well. It is the only way we in CUUEG have managed to actually get a drop tank to divers with any regularity (We have spent a long long time playing with this, and practise it whenever we can)
John
Chris Cherrington
22-06-2004, 17:45
:=Because no serious diver uses air for anything other than the tyres on the truck.
Nigel where have you been? The current trend is to fill tyres with pure nitrogen
http://www.merityre.co.uk/why_nitrogen.htm
Mmmm...
That would bugger up James Bond when he did that breathing from a tyre underwater thing in whichever film it was..
Chris
:=
:=:=Best compromise I have so far is to create a hoola hoop effort which is thrown lifebuoy style over the DSMB. The cylinder is then thrown over and a round buoy as per trapeze unravels as the hoop sinks.
:=
:=I'm not sure I have the picture....
:=
:=Is it:
:=Hoop with rope to drop tank.
:=Separate rope from drop tank to float.
:=Hoop is weighted to sink itself and rope.
:=
:=So:
:=Throw hoop with tank on boat so you can pull it back and start again if you miss. Once the hoop is round the DSMB the tank goes over the side with its float.
:=
:=That works for me but am I changing the idea?
That's the theory. And in fact the practice as well. It is the only way we in CUUEG have managed to actually get a drop tank to divers with any regularity (We have spent a long long time playing with this, and practise it whenever we can)
Yep many thanks to John and CUUEG for the idea.
The only addition I can think of (which may/may not work) is
a line wrapped around a round buoy so it deploys as per a
trapeze barrel.
That should slow the cylinder down just enough to stop it
wacking someone on the head making matters worse.
TerryH
john kendall
22-06-2004, 19:13
:=:=
:=:=:=Best compromise I have so far is to create a hoola hoop effort which is thrown lifebuoy style over the DSMB. The cylinder is then thrown over and a round buoy as per trapeze unravels as the hoop sinks.
:=:=
:=:=I'm not sure I have the picture....
:=:=
:=:=Is it:
:=:=Hoop with rope to drop tank.
:=:=Separate rope from drop tank to float.
:=:=Hoop is weighted to sink itself and rope.
:=:=
:=:=So:
:=:=Throw hoop with tank on boat so you can pull it back and start again if you miss. Once the hoop is round the DSMB the tank goes over the side with its float.
:=:=
:=:=That works for me but am I changing the idea?
:=
:=That's the theory. And in fact the practice as well. It is the only way we in CUUEG have managed to actually get a drop tank to divers with any regularity (We have spent a long long time playing with this, and practise it whenever we can)
:=
Yep many thanks to John and CUUEG for the idea.
The only addition I can think of (which may/may not work) is
a line wrapped around a round buoy so it deploys as per a
trapeze barrel.
That should slow the cylinder down just enough to stop it
wacking someone on the head making matters worse.
What we do is have the line stowed between to bits of inner tube on the cylinder. This will then pull free as the cylinder is deployed.
You could also just lower the cylinder down by hand with the rope.
Depending on what size/type of cylinder you use this works quite well, certainly with an AL7 it is great, maybe a bit quick with a Steel 12.
HTH
John
Ok this is what we are going with.
Square made out of tube with bungy in centre (like flags).
Attached to cylinder with 6m of line. Another 6m goes onto
buoy.
Yellow signal goes up.
Lasso the DSMB with the square, throw/drop the cylinder away
from the DSMB. Chuck in the Buoy.
The square sinks and hits the divers and at the same time
the cylinder sinks and stops at 6m when the buoyline gets
taught.
Divers pull the line attached to the square and retrieve the
gas.
If the square gets snagged then the pendulum effect on the cylinder will bring it to the divers anyway + it is still
supported by the buoy.
TerryH
Nigel Hewitt
23-06-2004, 09:41
>>Because no serious diver uses air for anything other than the tyres on the truck.
>Nigel where have you been? The current trend is to fill tyres with pure nitrogen
Wooo. Well with this little toy (yes that is a dry suit nipple in it) I've got myslf and friends out of all sorts of trouble but we've ended up with all sorts of stuff in the tyres.
Admittedly it was usually just to get us to solid enough ground to jack the car - what is it with dive site car parks and huge nails?
Wooo. Well with this little toy
Are there any diving toys you don't have? ;-)
Nigel Hewitt
23-06-2004, 11:43
>>Wooo. Well with this little toy
>Are there any diving toys you don't have? ;-)
Probably. But I did just have to upgrade the car to carry all the rubbish I haul around as it is so if you spot any please don't tell me. That one was a fiver on ebay and a rummage round in the tool box so it was no big deal. It has more than paid for itself in saved angst since then.
nigelH
iainmsmith
23-06-2004, 13:30
Ok this is what we are going with.
Square made out of tube with bungy in centre (like flags).
Attached to cylinder with 6m of line. Another 6m goes onto
buoy.
Yellow signal goes up.
Lasso the DSMB with the square, throw/drop the cylinder away
from the DSMB. Chuck in the Buoy.
The square sinks and hits the divers and at the same time
the cylinder sinks and stops at 6m when the buoyline gets
taught.
Divers pull the line attached to the square and retrieve the
gas.
If the square gets snagged then the pendulum effect on the cylinder will bring it to the divers anyway + it is still
supported by the buoy.
Sounds remarkably familiar! :)
Just make sure that your square is big enough to go over two DSMBs lying flat on the surface. (I think I posted this somewhere, but can't find it, so it may have got lost in the
e-ether)
We keep a red and a yellow DSMB attached to the drop bottle so that once the receiving divers have sorted their lives out, they can send a red to indicate that all is now well (reducing the stress on the surface party who are wondering what sort of hell is breaking loose beneath them) but also giving them the chance to indicate that they need further help (ie need a pair of divers down to sort them out)
Iain
> Not sure I like the idea of the drop tank being removed from > the line. It is securely fastened, so why risk it going to
> the bottom of the sea by unfastening it.
Obviously I meant them to have common sense too...
Aha. But you just know Mr Murphy will come visit if you leave the door open for him.
You would clip it to yourself before disconnecting the upline I think? or even as you suggest leave it attached
Leave it on the line...you know it makes sense.
, I don't think abandoning your DSMB is wise, its bound to confuse matters.
If you abandon the DSMB the worse that will happen is it drifts off down tide and can be retrieved in slow time - or the cox runs over it! A DSMB line in close proximity to the drop line is asking for entanglement IMO.
I am obviously missing something here.
It all sounds remakably complicated to me! What exactly is wrong with clipping a line onto the DSMB line, after all the Yellow DSMB managed to come up the line so a carabineer is very likely to slide down.
What I am picturing is the drop tank with a decent buoy attached, with possibly a spare reel or buddy line for the jump line. Approach the divers DSMB, check for a slate and clip on the far end of the jump line. Lower the tank carefully away from the divers (why throw it). The jump line reaches the divers, they transfer to the dropline, jobs a good un! You only need what you are likely to find on a dive boat (drop tank, buff and reel) and no one has to play hoopla - knowing my luck the hoop would go straight over my head :-)
I am obviously missing something here.
Picture this:- You're on a boat with a high freeboard, some I've been on have been between 6 and 10 foot. All your divers are in the water so you are the only one in the boat. How do you attach a carabeenier to the line making sure it is below the yellow blob attachment so it does not snag?
:=
:=I am obviously missing something here.
Picture this:- You're on a boat with a high freeboard, some I've been on have been between 6 and 10 foot. All your divers are in the water so you are the only one in the boat. How do you attach a carabeenier to the line making sure it is below the yellow blob attachment so it does not snag?
Only way I can think of is pull it up with a boathook, which means your divers have:
1. A good chance of being pulled up with it.
2. The DSMB gets ripped off taking away the divers point
of ref etc.
3. The divers are now forced to let go while the reel goes
up 2m and they now have to deploy another blob. Meanwhile the
spare gas is droping down onto a reel which is now drifting away from the divers with the tide.
If you could clip on or near sea level, then fine a clip would
work, but we are working on the premise that all divers are
in the water and the only one available to do this lot is the
skipper. That means a boothook.
TerryH
iainmsmith
23-06-2004, 17:46
It all sounds remakably complicated to me!
It's not - the procedure is: Lassoo the DSMB, throw the tank overboard, throw the buoy overboard. Await confirmation that the divers have got the gas.
It also works, unlike every other method that we tried.(including methods not dissimilar to the one you suggest)
What exactly is wrong with clipping a line onto the DSMB line, after all the Yellow DSMB managed to come up the line so a carabineer is very likely to slide down.
Unless the boat crew, in the heat of the moment, clip the carabiner to the line above the yellow DSMB. At which point your gas is going precisely nowhere. It's also much harder to do from a larger boat which might have a freeboard of a couple of metres (especially if your skipper is the only person left on the boat.
What I am picturing is the drop tank with a decent buoy attached, with possibly a spare reel or buddy line for the jump line. Approach the divers DSMB, check for a slate and clip on the far end of the jump line. Lower the tank carefully away from the divers (why throw it?).
Speed.
The jump line reaches the divers, they transfer to the dropline, jobs a good un! You only need what you are likely to find on a dive boat (drop tank, buff and reel)
Admittedly, our drop bottle is job-specific kit that we take on board with us. I'm not keen on the idea of people having to improvise in critical situations when pre-planned, pre-rigged kit can be carried.
Iain
Philip Smith
24-06-2004, 08:13
Mmmm...
That would bugger up James Bond when he did that breathing from a tyre underwater thing in whichever film it was..
The Spy Who Gassed Me?
Andy Wade
26-06-2004, 22:53
will swift
03-07-2004, 19:04
:=If the marshal is that anal, the safety diver could always claim to be using the DSMB line as a tether and hence solo diving legitimately for the time it takes to reach the striken pair.
Who says anything about the Marshal.
There are two divers underwater who have gone over the plan
thus asking for air. We CANT rely on a diver as part of any
rescue as .......
a) We dont know if there are any divers on board. or
b) We dont know what state the rescue diver is in (deco/air
wise).
As the numbers onboard increase then yes that may be an option,
but at this stage we MUST assume nil diver help.
TerryH
Hi Terry,
Your thread didn't put any restrictions or assumptions on the methods to be offered.
I still think sending divers down is the best, obviously on a club dive that is limited, and I know the arguments about putting more divers into a risky situation, but if the diver put up the DSMB then they must have regained enough composure to be of a limited risk.
I think the hooped solution looks like a good one and I'm keen to see that performed and have a go myself.
Safe Diving
Wills.
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