Doubles Wing Recommendation

[inquis]

Is a dry suit, on it's own, capable of bringing a diver back to surface with his tanks.

Easily when not overweighted. The non-reserve air in your double 10/232s weighs about 5 kg. The drysuit needs to uniformly expand by about 3mm. (It won't, of course, but hopefully that's illustrative of the ease.)

 

[Roy_W]

Easily when not overweighted. The non-reserve air in your double 10/232s weighs about 5 kg.

Therefore my buddy, with a 23Kg ( 55 Lbs) wing, should also be capable of bringing me up without too much effort using his wing?

( I agree that one should be self reliant where possible but that is also one of the main reason for not diving alone))

 

[inquis]

Therefore my buddy, with a 23Kg ( 55 Lbs) wing, should also be capable of bringing me up without too much effort using his wing?

Dunno, is he/she overweighted?

Just kidding. Yes, I'm sure they could, but you should be able to swim up 5 kg on your own. You can hold onto then on the surface while waiting for the boat.

 

[Roy_W]

Just kidding. Yes, I'm sure they could, but you should be able to swim up 5 kg on your own. You can hold onto then on the surface while waiting for the boat.

I agree and this is why I don't understand the statement that one should never dive negative doubles in a wetsuit..

 

[inquis]

whilst wearing a wetsuit we would not be able to surface with our tanks should our Wing/Bladder fail.

Do the math. 5 kg for air. Perhaps 10 kg for 7mm wetsuit in salt water? I know I couldn't swim up 15 kg.

The message is redundant buoyancy is a must. If that's a really reliable buddy, lift bag, redundant bladder, or a smarter overall choice (drysuit or AL tanks+ditchable weight) is your call.

 

[inquis]

one should never dive negative doubles in a wetsuit..

Not to speak for @Nick_Radov , but buddy separation can happen. Deploying a lift bag while trying to kick against 15 kg on a wall dive with no bottom is... tough. (The 5 kg figure was when in a drysuit.)

A blown wing should be an irritation, not a life-threatening emergency.

 

[Roy_W]

I must admit that I don't believe I have ever seen anyone that I know dive with a redundant buoyancy system.. other than their buddy.

* Most of the guys in Dry Suits wear a harness style weight belt , so not ditchable.
* I have never seen anyone with a double bladder system.
* And no one ever talks about this issue, therefore I will have to bring it up at the next club dive.

Interesting topic.

 

[L13]

I must admit that I don't believe I have ever seen anyone that I know dive with a redundant buoyancy system.. other than their buddy.

* Most of the guys in Dry Suits wear a harness style weight belt , so not ditchable.
* I have never seen anyone with a double bladder system.
* And no one ever talks about this issue, therefore I will have to bring it up at the next club dive.

Interesting topic.

Everyone diving a dry suit with a BC has a redundant buoyancy system. Most tech divers I know have a third buoyancy system when diving dry (their normal second when diving wet, they always carry at least a lift bag or SMB).

 

[Nick_Radov]

I am not a very experienced diver, around 170 dives and in my club, there must be around 70% of people diving wet suits and doubles, myself included, we all have steel tanks.. At our local site the max depth is around 36m ( 110 feet) and I have never heard anyone mention this situation, nor have I never seen anyone with a secondary bladder and yet there are some very experienced divers, rebreathers, trimix guys etc - with 1000 of dives, and even 1 dive professional ( the rebreathers and trimix guys are almost always in dry suits though - it's cold here, they dive deeper/longer but elsewhere).

You will find that experience in terms of years or number of dives means very little. There are divers who have done thousands of dives over decades but somehow managed to learn nothing, or (even worse) all the wrong things. Just because divers have been getting away with something doesn't necessarily make it a good idea. It's best to go back to first principles and analyze what really makes sense.

I understand that most emergency situations should be covered but what are the chances of wing failure. Modern wings are pretty damned sturdy..

Yes, modern wings are pretty sturdy. The most common failure I've seen is for the rear dump valve to break or stick open (jammed with debris). That will prevent it from holding gas, although if you stay sort of vertical you can keep a little gas in the top part. I've also heard of cases where the corrugated hose pulled off the elbow fitting.

Would a dry suit actually be enough to bring 2 * 10 ltrs tanks to the surface from 36m ( 110 feet)?

Those 10 liter double tanks will only ever have a maximum of about 5 kg / 10 lbs of gas (or even less with a helium mix). A drysuit isn't exactly a flotation device, but anyone can swim 10 lbs up to the surface. Once you're at the surface you can ditch your weights if necessary to keep your head above water.

I don't use any extra lead, I am relatively balanced already with the tanks. My wetsuit is a recent 7mm , a neoprene t-shirt, heavy boots and 5 mm gloves and hood. ( Waiting on a dry suit arriving in November). From what I understand a dry-suit should not be considered as a flotation device.

Well, there's your problem. If you're diving in open water with no ditchable weight, then you don't actually have a balanced rig. You should have enough ditchable weight so that you can at least get neutral on the surface with full tanks and a failed wing. That might mean switching to more positively buoyant tanks, or switching from a steel to carbon fiber backplate. I've seen a trend of ocean divers going with no ditchable weight out of a desire to be "slick"; this stems from being unclear on the basics and not thinking things through.

The real problem with those 7 mm wetsuits is that they compress away to nothing at depth and lose almost all their buoyancy. So, if you have a wing failure at the beginning of a dive when your back tanks are at their most negative then you may struggle to swim your rig up from maximum depth until the neoprene expands. That said, 10 liter doubles are small enough that in practice you might be able to get away with it. The real concern is with larger steel tanks which hold much more gas (extra weight) and are more negative even when empty.

BAUE George Irvine Lecture

 

[Nick_Radov]

Therefore my buddy, with a 23Kg ( 55 Lbs) wing, should also be capable of bringing me up without too much effort using his wing?

You've got to be kidding. That's the kind of thing that sounds good on the Internet and will turn into a complete CF while you're trying to manage an emergency during a real dive. The most likely outcome is that you and your buddy lose your grip on each other in the middle of the ascent, and then you go plummeting back towards the bottom (hope you're not on a vertical wall) while your buddy (with an over-inflated wing) rockets to the surface.

Every diver on the team needs to have a balanced rig and manage their own buoyancy at all times. It's smart to dive with a buddy, but you can't rely on a buddy for redundant buoyancy. Keep it simple instead of trying to introduce convolutions to address problems that shouldn't exist in the first place or are purely the result of not buying the correct gear. (There is a procedure for rescuing an unconscious diver by kind of riding them up, and using their wing for both of you, but that's a separate issue and not really relevant here.)