Making a single bladder wing work....

[bottlefish]

As far as I understand it, GUE equipment allows for a single bladdered wing, using a dry suit as the backup bouyancy method in case of primary failure.

I'm intrigued as to how this can work in practice. No problem if the diver is just diving a twin set, however if they are taking on something a little more aggressive, I can't see how the dry suit would provide sufficient bouyancy to work as a backup.

For instance, to complete an 80 metre dive, 25 minutes, I'd be looking to use twin 12 steels on my back, with three ali 80's for travel and deco.

Given that I want to be weighted to allow for neutral bouyancy when my tanks are near empty, I also need to provide bouyancy for this rig at the start of the dive when the tanks are full, an increase of around 15 kilos.

So, that would mean displacing 15 litres of air with my dry suit, if my wing were to fail towards the beginning of the dive.... that seems like an awful lot to try and get into a dry suit!

Am I missing something?

Cheers

Stu

[Lanny]

Originally Posted by bottlefish

As far as I understand it, GUE equipment allows for a single bladdered wing, using a dry suit as the backup bouyancy method in case of primary failure.

I'm intrigued as to how this can work in practice. No problem if the diver is just diving a twin set, however if they are taking on something a little more aggressive, I can't see how the dry suit would provide sufficient bouyancy to work as a backup.

For instance, to complete an 80 metre dive, 25 minutes, I'd be looking to use twin 12 steels on my back, with three ali 80's for travel and deco.

Given that I want to be weighted to allow for neutral bouyancy when my tanks are near empty, I also need to provide bouyancy for this rig at the start of the dive when the tanks are full, an increase of around 15 kilos.

So, that would mean displacing 15 litres of air with my dry suit, if my wing were to fail towards the beginning of the dive.... that seems like an awful lot to try and get into a dry suit!

Am I missing something?

Cheers

Stu

Hi Stu,

15kg seems a bit of an over-estimation - each Al80 will be about 1kg negative when full, and your steels will be 2-4kg negative each, depending on who makes them. Total negative weight about 6-11kg.

If the worst happens and you lose all buoyancy right at the beginning of a dive, you have the option of ditching your stages and/or canister light, before you even consider your DSMB/liftbag or other members of the team.

I have dived with 4 AL80 stages with twin Al80 backgas and a wetsuit (i.e. no redundant buoyancy source) and was happy that my rig was sufficently balanced that I could swim it up in the event of a failure, albeit with the possibility of ditching stages. (And I had a Scooter )

I am sure someone more qualified than I will be along in a minute to give you a fuller answer, but that is how I see it.

[neilh]

Originally Posted by bottlefish

So, that would mean displacing 15 litres of air with my dry suit, if my wing were to fail towards the beginning of the dive.... that seems like an awful lot to try and get into a dry suit!

If it fails at the start of the dive you could ditch your stages or hand some/all of them off to your team.

[bottlefish]

Thanks for the answer... to expand the example a little bit...

Steel 12's tend to go from around 3 kilos neg when full to neutral when empty, so that gives a total potential bouyancy change of 6 kilos for a twin set.

Ali 80's tend to go from around 0.5 kilo neg when full to 2 kilo pos when empty, so a potential bouyancy change of 7.5 kilos for all three tanks.

So that's a total potential bouyancy change of 13 kilos (using specs from a variety of web sites, and yep, the initial guess at 15k was a bit high)

My logic (if the term applies )

You need to be weighted to allow yourself to maintain neutral bouyancy when fully rigged and tanks are at near empty (in case the brown stuff hit the fan), i.e. you need to allow for that total 13k shift in bouyancy.

Taking the worst case example, if you were to have a bouyancy failure at the start of your ascent, you would have consumed around half the gas in the twins, so you would have gained 3 k lift. That still leaves 10 k neg that your bouyancy needs to cope with. You still need to complete all of your ascent and deco, so handing off gear is not a great idea (plus, in my mind, the more you breath down the tanks, the more lift they give you).

Still seems a lot to try and gain from a dry suit, or even worse, swim up from 80 metres if you're in wet. Ditching gear, using a lift bag, team members etc are all options...

But (and of course, this was were this was heading), surely having a dual bladder wing resolves this with minimal negative impact, means the diver can complete such a dive with minimal fuss or task loading?

Just trying to get my ducks in order before Brian flogs my CD wing from under my nose

[londonsean69]

I believe that if you were doing a dive that required 3 gasses (stage plus 3 deco gasses) the general opinion is you would be better in a drysuit, as you would be in the water for a while, even with higher water temperatures.

There is a similar thread on Direxplorers.

[bottlefish]

Originally Posted by londonsean69

I believe that if you were doing a dive that required 3 gasses (stage plus 3 deco gasses) the general opinion is you would be better in a drysuit, as you would be in the water for a while, even with higher water temperatures.

There is a similar thread on Direxplorers.

That was my original question, expecting a dry suit to provide 10 kilos of lift seems a little excessive...

[neilh]

Originally Posted by bottlefish

Taking the worst case example, if you were to have a bouyancy failure at the start of your ascent

Hehe - ah, but now you've changed when the failure occurs
In this case if your 3 ali80s include a bottom stage then I guess you would have used enough of it to get it positive (not sure here as I'm not tech2) so as you say it'll be providing some additional lift. You can always hand off bottles or send them up the SMB line if you're getting too much lift.

Also your wing will probably hold at least some gas and that gas is going to expand as you ascend, so you may not need to completely replace the wing with suit gas.

Originally Posted by bottlefish

or even worse, swim up from 80 metres if you're in wet.

Which is why you may consider alternatives to a wetsuit for that kind of dive

[londonsean69]

Originally Posted by bottlefish

That was my original question, expecting a dry suit to provide 10 kilos of lift seems a little excessive...

But it doesn't have to provide 10 kilos, you could use a combination of handing stages etc off, and the drysuit, plus you can 'probably' keep some air in the wing.

I think it was Claire who's inflator came off in her hand at the start of a T2 dive, and all was good till she went vertical to hand stuff off

Found it

Descending for dive 2, I put some gas in my wing and had bubbles come out from under my arm. Must have hit one of the two stage regs there I figured – so did it again. Bubbles again. I looked down and the whole inflator had come off the corrugated hose – bugger.

So this is time to test the balanced rig then. Twin 12s with 150 bar, Pro 14 and three stage bottles – all full. I was OK actually as I made my way back to the surface horizontal until I went vertical – which was a big mistake as the water pressure vented the wing – despite my attempts to prevent this by folding the top of the hose over. I sank down a meter or so but with Al, Frase, Jarrod and Andy Kerslake around there was no big deal. Before any time at all had past, all my stages had been handed off to Al, Jarrod and Andy got me over to the side and out of the water and the wing was fixed.

[bottlefish]

Originally Posted by neilh

Hehe - ah, but now you've changed when the failure occurs

Yeah, sorry 'bout that

Originally Posted by neilh

In this case if your 3 ali80s include a bottom stage then I guess you would have used enough of it to get it positive (not sure here as I'm not tech2) so as you say it'll be providing some additional lift. You can always hand off bottles or send them up the SMB line if you're getting too much lift.

None of my stages/slings would be suitable for that depth, I'd be on back gas until around 50 metres.... so all stages would be full.

Originally Posted by neilh

Also your wing will probably hold at least some gas and that gas is going to expand as you ascend, so you may not need to completely replace the wing with suit gas.

Yep, true, although I hate the idea of "may not", would much rather dive with wills and wonts, makes it much easier to keep my mum happy

Originally Posted by neilh

Which is why you may consider alternatives to a wetsuit for that kind of dive

Brought in the wet suit in response to another answer, it'd have to be a pretty toasty bath to see my languishing on deco for that long in a wet suit

[Garf]

Originally Posted by bottlefish

Yeah, sorry 'bout that


None of my stages/slings would be suitable for that depth, I'd be on back gas until around 50 metres.... so all stages would be full.

I thought you wanted a DIR answer. We'd have breathed down the bottom stage first. We'd also have a team of people literally holding on to us, removing and reattaching bottles where necessary. you don't have to lift it all yourself, that's what the people with working wings are for.