Doubles Wing Recommendation

[Nick_Radov]

Completely disagree. Ditchable weight shouldn't even be a thing in technical diving. That's an open water concept that's taught to beginner recreational divers (so they can get to the surface ASAP), just like "never hold your breath" and so on.

You are giving terrible, dangerous advice. The best practices for ocean technical diving were worked out over 20 years ago and extensively discussed on the old Techdiver mailing list by WKPP divers and their associates. See the links I provided above. Let's learn from the mistakes of others rather than endlessly going over the same old arguments.

Do not use negatively buoyant double steel tanks when diving in a wetsuit. There is never any valid reason for a sport divers to do so. There are always better options. Let's get clear on the basics and stop making excuses.

 

[boriss]

Eh I think in another few years of your technical diving career you’ll look back on this post and realize you’re a little far right of center. A pair of AL80s (or a third as a bottom stage) are more than adequate for what most people are doing in open ocean for decompression diving. If they’re not, then your exposure is long enough that you’ll probably want a drysuit.

My experience is limited for sure, but my knowledge is based on those way more experienced as well. I see lots of tech dives here (including plenty of people being trained) and HP100 are the norm. Some people prefer LP85's.

Our decompression was in 88F waters. I don't want a drysuit. Not for local conditions.

Until then, you have less than 218cf of gas in your HP100s, though I’d love to see the how you came up with 218. To continue the semantics, you in the rig you show pictures of from your ANDP class last week have ditchable weight right? It might not look like it at first sight, but your AL72s count as ditchable.

If you count my AL72 as ditchable weight, then let's add to that my flash lights, reels, etc. That's not their purpose though, they aren't brought with me for ballast.

As far as how to compute the gas, I actually made a mistake, calculated at 3700psi. It's 210cuft at 3600psi.

Do you dive with your second inflator connected? And do you think in an out of control descent you could connect that inflator quickly enough to stabilize yourself at a depth?

Never connected and you shouldn't be descending uncontrollably. However, that does bring up a good point and I'll ponder on it. Thanks!

 

[grantctobin]

you shouldn't be descending uncontrollably. However, that does bring up a good point and I'll ponder on it. Thanks!

You go to jump and grab the granny line intending to wait for the rest of the team on the morning and oops, the primary bladder elbow disconnects from the wing and poof, goodbye surface. The likelihood of all of these things coming together, especially over a bottomless wall, isn’t that high, but can’t be totally discounted. Sure, someone could manually inflate their second bladder, but most people can’t do that while equalizing while being in a good headspace to unfucc the situation.

There’s a few people that can comfortably kick up a set of full nitrox 85s (let’s say a mid level competitive cyclist like @kensuf), but I wish it was less the norm in S Florida, as most people can’t sustain that exertion. A light trimix 21/35 or 18/45 in 85s also lightens the load to the point where it could be considered balanced in a wetsuit. It’s when people start moving towards heavier cylinders that I grow more apprehensive.

As a last point, it’s pretty easy for me (and others) to get cold during decompression in 80+ degree water in a wetsuit over the course of a long week of 4-6hr of dive time per day.

 

[crofrog]

There’s a few people that can comfortably kick up a set of full nitrox 85s (let’s say a mid level competitive cyclist like @kensuf), but I wish it was less the norm in S Florida, as most people can’t sustain that exertion. A light trimix 21/35 or 18/45 in 85s also lightens the load to the point where it could be considered balanced in a wetsuit. It’s when people start moving towards heavier cylinders that I grow more apprehensive.

It depends on the LP85's. Faber LP85's are -3.8lb @ 2640psi with a valve and 2.32 empty, at 3500 psi they should be ~ -5.7lb.

A luxfer s80 is similar were as a luxfer 80 is about -1.5

 

[boriss]

You go to jump and grab the granny line intending to wait for the rest of the team on the morning and oops, the primary bladder elbow disconnects from the wing and poof, goodbye surface. The likelihood of all of these things coming together, especially over a bottomless wall, isn’t that high, but can’t be totally discounted. Sure, someone could manually inflate their second bladder, but most people can’t do that while equalizing while being in a good headspace to unfucc the situation.

There’s a few people that can comfortably kick up a set of full nitrox 85s (let’s say a mid level competitive cyclist like @kensuf), but I wish it was less the norm in S Florida, as most people can’t sustain that exertion. A light trimix 21/35 or 18/45 in 85s also lightens the load to the point where it could be considered balanced in a wetsuit. It’s when people start moving towards heavier cylinders that I grow more apprehensive.

As a last point, it’s pretty easy for me (and others) to get cold during decompression in 80+ degree water in a wetsuit over the course of a long week of 4-6hr of dive time per day.

I've had no issue kicking to stay up before, even with all the weight. It's not fun, but doable. In which case I'd have to kick and inflate. It gets easier with every breath. It is what it is.

I think the situation you bring up is possible, but so are many others. If we take them all down the inevitable rabbit hole, we may as well stay home. Here's an example: let's say you take Alu80 doubles but then need an additional Alu80 and at least an Alu40 (deco) to do the same dive. Now you're task loaded, dealing with more bottles, you can accidentally breathe the wrong gas. We obviously train not to do that, but you get the point. It has happened that people breathed the wrong gas. In addition, if you're going into an overhead environment it's also more gear that can hold you up or get you stuck or you can bump and damage, etc.

I'm more worried about something happening at depth and then not being able to come back up or be able to control that ascent while doing mandatory decompression. Where I dive there's always a bottom and that's my target. I still don't discount your points and I will keep them in mind for sure.

My longest dive so far is 80 minutes... I know not what these 4-6 hour dives you speak of. Maybe in a cave, but not allowed on a charter boat here, unless there's an issue, obviously.

 

[kensuf]

Never connected and you shouldn't be descending uncontrollably. However, that does bring up a good point and I'll ponder on it. Thanks!

You should never have both power inflators connected. Period. Do not think that is what @grantctobin was advocating, he wasn't.

 

[rddvet]

There's alot of dumb in this thread (coming from only a small % of those in the thread).

 

[Roy_W]

Don't dive in a wetsuit with heavy (negative) steel doubles in the first place. Why would anyone take that risk? It's just totally pointless and unnecessary.

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).

I understand that most emergency situations should be covered but what are the chances of wing failure. Modern wings are pretty damned sturdy..
Would a dry suit actually be enough to bring 2 * 10 ltrs tanks to the surface from 36m ( 110 feet)? 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.

I am seriously interested in understanding more.

 

[digitalMechanic]

The reason a drysuit is considered safer with heavy tanks is not because it can act as a flotation device, but because unlike a wetsuit, its buoyancy doesn't change with depth.

A 7mm wetsuit may be very buoyant at the surface, but once you are at 30m, it has compressed so much that it can lose as much as 80% of its buoyancy. A drysuit on the other hand, does not compress. Therefore, it is easier to achieve a balanced rig with a drysuit.

I recommend watching this video to learn more

 

[Roy_W]

The reason a drysuit is considered safer with heavy tanks is not because it can act as a flotation device, but because unlike a wetsuit, its buoyancy doesn't change with depth.

A 7mm wetsuit may be very buoyant at the surface, but once you are at 30m, it has compressed so much that it can lose as much as 80% of its buoyancy. A drysuit on the other hand, does not compress. Therefore, it is easier to achieve a balanced rig with a drysuit.

I recommend watching this video to learn more

Yes I fully understand the problem with wet suit compression but what difference would this make compared to a dry suit after a Wing/Bladder failure.

If I have understood the statement from Nick_Radov, he is stating that whilst wearing a wetsuit we would not be able to surface with our tanks should our Wing/Bladder fail.

If such were the case, is Nick therefore stating that if we had been wearing a dry suit we would have been able to return to the surface ?

Hence my immediate thought : Is a dry suit, on it's own, capable of bringing a diver back to surface with his tanks. Obviously due to the fact that a dry suit can be inflated.