Dual vs Single bladder wings

[Scubee]

When i went onto twinset diving, I thought long and hard about which wing to go for. I am aware that a significant number of incidents happen in relation to the difficulty in establishing postive buoyancy at the surface and took this into account when making my decision. I acted on advice and bought a dual bladder wing (Diverite Superwing 2). I have to say that i really liked it.

I went off to the dive show, and found the Frog Bargain. i had read about my drysuit supposedly providing redundant buoyancy, so i should be OK with a single bladder wing. Other advice was that a single bladder wing was the right thing to have. For me, the cost was worth 'giving it a go'.

I got the wing in February, i think it was and dived with it on several occasions. Nothing special, but no complaints either. Then I went to Swanage. I sat out of one of the boat dives, to accompany a nervous diver under the pier. He had had a bad experience on the Kyarra that morning, and needed a bit of confidence building. I wouldn't normally do a 4m dive with the twins, but hey ho, in for a penny!

We got in, swam out to the start of the pier and descended. Within a minute or so, I lost him (yes, the viz was that bad!) and surfaced (he was there!). I tried to fill the wing, ony to find that my low pressure inflator stuck open and was fizzing air out all over the place, and I couldn't get buoyant. I have no idea why, but i couldn't orally inflate the wing either at that point. No problem, i thought... shove air into the dry suit - that'll keep you afloat. I shoved air in but before I could relax and stop finning, the neck seal vented - Drysuit full.

OK,.... I am in about 4m of water under Swanage pier, and I can't stay afloat. Marvellous (but not really life threatening). So we descended again and remained under to navigate our way back to a position where i could stand, problem over. Luckily, i had shedloads of air and i was in shallow water. If the wing had failed that morning, I would have been in 30m of water and not so easy a situation to resolve.

I learned that day that my drysuit is not sufficient redundant buoyancy for a 12l twinset, SS backplate and no other kit in a situation where my wing fails.

I had the inflator looked at, and it is perfectly fine now- an o ring had failed. However, i won't dive with that wing again - back to the dual bladder Diverite.

[simonsticky]

You don't go on to mention that same weekend that you were talking on your mobile to a friend on the pier whilst you whilst you ate & drank at the tea stall. Waving to identify yourself.

Everyone else sitting there was waving to her too
(Nice work.)

Put a string on your tailgate yet?

Nice to meet you

s

[Mark Chase]

Originally Posted by Scubee

When i went onto twinset diving, I thought long and hard about which wing to go for. I am aware that a significant number of incidents happen in relation to the difficulty in establishing postive buoyancy at the surface and took this into account when making my decision. I acted on advice and bought a dual bladder wing (Diverite Superwing 2). I have to say that i really liked it.

I went off to the dive show, and found the Frog Bargain. i had read about my drysuit supposedly providing redundant buoyancy, so i should be OK with a single bladder wing. Other advice was that a single bladder wing was the right thing to have. For me, the cost was worth 'giving it a go'.

I got the wing in February, i think it was and dived with it on several occasions. Nothing special, but no complaints either. Then I went to Swanage. I sat out of one of the boat dives, to accompany a nervous diver under the pier. He had had a bad experience on the Kyarra that morning, and needed a bit of confidence building. I wouldn't normally do a 4m dive with the twins, but hey ho, in for a penny!

We got in, swam out to the start of the pier and descended. Within a minute or so, I lost him (yes, the viz was that bad!) and surfaced (he was there!). I tried to fill the wing, ony to find that my low pressure inflator stuck open and was fizzing air out all over the place, and I couldn't get buoyant. I have no idea why, but i couldn't orally inflate the wing either at that point. No problem, i thought... shove air into the dry suit - that'll keep you afloat. I shoved air in but before I could relax and stop finning, the neck seal vented - Drysuit full.

OK,.... I am in about 4m of water under Swanage pier, and I can't stay afloat. Marvellous (but not really life threatening). So we descended again and remained under to navigate our way back to a position where i could stand, problem over. Luckily, i had shedloads of air and i was in shallow water. If the wing had failed that morning, I would have been in 30m of water and not so easy a situation to resolve.

I learned that day that my drysuit is not sufficient redundant buoyancy for a 12l twinset, SS backplate and no other kit in a situation where my wing fails.

I had the inflator looked at, and it is perfectly fine now- an o ring had failed. However, i won't dive with that wing again - back to the dual bladder Diverite.

Good ish point, but your going to take some flack for it.

With just a twin set there is no way you should have had a problem using your dry suit for buoyancy control. What your admitting to is being overweighted in the first place.

The suit should theoretically only be compensating for the weight of gas in your cylinders.

However a dry suit is not supposed to lift you head and shoulders out of the water like a big wing can. If thats what you were expecting the fair point the duel bladder wing is definitely a plus.

My view is, if your diving multi tanks in a wet suit then a duel wing is a must have. The usual reasons put forward to not to have a duel wing are rubbish.

ATB

Mark Chase

[Scubee]

Originally Posted by simonsticky

You don't go on to mention that same weekend that you were talking on your mobile to a friend on the pier whilst you whilst you ate & drank at the tea stall. Waving to identify yourself.

Everyone else sitting there was waving to her too
(Nice work.)

Put a string on your tailgate yet?

Nice to meet you

s

Oh, that was sooooooo funny!

Nice to meet you too!

Originally Posted by Mark Chase

Good ish point, but your going to take some flack for it.

With just a twin set there is no way you should have had a problem using your dry suit for buoyancy control. What your admitting to is being overweighted in the first place.

The suit should theoretically only be compensating for the weight of gas in your cylinders.

'Taking flack' for it isn't really the purpose of the thread, or this sub forum. This area is supposed to be to pass on incidents which taught us something about diving. This taught me that I don't want to use a single bladder wing.

Maybe, I was overweighted at that point. I had 4kg, which is what i need to hold a 6m stop at the end of a dive with diddly squat air in my tanks. TBH, if I had thought about it, I didn't need that much, because I had about 100 bar in the twins ad could probably have left some behind. However, the considerations when you are about to do a 4m dive are very different to when you are about to do a 40m dive. I could have taken a couple of kilos off the harness but didn't. Don't we all start a dive overweighted, to compensate for the air you will use?

[Colin Marriott]

Originally Posted by Scubee

. . . 'Taking flack' for it isn't really the purpose of the thread, or this sub forum. This area is supposed to be to pass on incidents which taught us something about diving.

Shame it's not taught you to check your equipment before you get into the water



ColinM

[Scubee]

Originally Posted by Colin Marriott

Shame it's not taught you to check your equipment before you get into the water



ColinM

Did I say I hadn't? Nope. I have no idea when the thing failed. I swam out to the entry point - with air in the wing. It didn't get in there by magic.

[Garf]

Unfortunately, I tend to agree from Mark. You didn;'t learn that drysuit is insufficient buoyancy for a a twinset - it should be more than ample.

We regularly practice failed wing ascents using the drysuit. Apart from being more difficult to hold stops (though not being as familiar with the practice) it should be no real drama.

The tendancy to overweight can be tempting, but it just causes so many problems, and exposes you to risks, that it's really not worth it.

What leassons can be learnt from this -

1. Overweighting can cause small problems to evolve into large problems,
2. Weight checks should be done often.
3. We should, IMHO, be correctly weighted with virtually empty cylinders. Not 30 bar. Not 50 bar. But next to nothing. If we are having to breathe our cylinders down to nothing because of a problem, the last thing we want is to lose control of buoyancy then as well. If you do your weight checks with 50 bar, then you might as well consider the last 50 bar unbreatheable.

[Scubee]

Originally Posted by Garf

Unfortunately, I tend to agree from Mark. What you learnt was not that a drysuit is insufficient buoyancy for a a twinset - it should be more than ample.

What you learnt is that if you are overweighted, which it sounds like you almost certainly were, a drysuit may then be insufficent redundant buoyancy.

We regularly practice failed wing ascents using the drysuit. Apart from being more difficult to hold stops (though not being as familiar with the practice) it should be no real drama.

Yep, It should be. However, in this case it wasn't. I have done weight check after weight check and still come up with the same result. If i want to be able to hold a stop with near empty tanks, i need 2kg in fresh, therefore, in theory, 4kg in salt.

[MattS]

Well I use 4Kg with twin 12s and I would not say I am overweighted. I am weighted so that I can holf a stop at 3m with 50bar. That should equate to holding a stop slightly deeper with slightly less gas. I virtually always end up completeing the final stops with nothing in the wing so am struggling to see what the issue with that might be.

I have a dual bladder wing having bought it for an exped diving 50m to 60m in a 3mm wetsuit. Maybe it is not optimal for UK diving but it is perfectly adequate. In the UK the additional inflator is stowed disconnected out the way but could be crosspatched from my DS inflate with a bit of effort. Personally I think having it connected permanently could cause more problems than it might solve (weeping inflate hoses, inadvertantly hitting the inflate while doing something else). In the situation of a failed wing and struggling for surface buoyancy I can dump the 4KGs, dump stages, inflate a lift bag or DSMB and dump the set if needs be.

YMMV

[Clare Gledhill]

Those who point out that to be correctly weighted we need to be neutral when our tanks are nearing empty are of course correct.

However, staying down is only one part of the equation. We also have to consider any loss of buoyancy during the dive (from compression of neoprene in our suits etc. when we are at depth) If we lose our main source of buoyancy (a wing failure) at the start of a dive we may still have a full gas load (and perhaps the burden of a compressed suit which took lead to sink it at the start of the dive but now provides less lift until we can return to the shallows). We need to be able to get up again.

It is not enough to say that a drysuit will act as redundant buoyancy. It depends on the sort of suit, the undergarments chosen etc. With my regular kit in Florida, no added weight and a fully inflated 60lb wing I can barely get my head out of the water on the surface - a change of kit configuration sorted this out. Remember it is total weight v total buoyancy - both must be balanced.

A suit should be able to handle the weight of the gas in twin 12s though - I've done it a few times to check and it is managable, although slightly unpleasant if you are not used to it. A large amount of gas in a drysuit is very unstable - and has to be managed carefully as the bubble will move to the highest point. Going vertical will allow gas to burp out of the neck seal as one board member on this thread found. If a large amount of lift is required in an emergency it is best to look at moving some of the weight to a form which is ditchable in such circumstances.

So - double bladders. You already have two sources of buoyancy to manage - your suit and your wing - and two inflators that could fail. Most who choose to dive a second bladder on their wing do not dive it connected as this would add a third potential failure - but prepare to connect it in case of problem. I see no need for this in a carefully weighted kit set up - especially with a drysuit - but your own view may differ.