Twinset wing for single, is it really that bad ? (Comparison to big jacket bcd)

[sea_ledford]

So you and your suit are about neutral at depth. The tank is the tank, you have to make up for that, but your 8.6kg of fixed weight seems high. That would be plate, one reg, and hardware like lights and such. Is that the dry weight, or the buoyancy? Heavy steel plate?

If you are regularly diving with a steel stage, I'd recommend just moving to doubles.

It also looks like you calculations are rounded up three times for a safety margin. Why do you think 17kg is too small? By your own numbers, you only need 16kg at 60m at the very beginning of the dive. You will have more positive buoyancy at any other point in the dive (assuming a wetsuit).

 

[Piotr_F]

So you and your suit are about neutral at depth. The tank is the tank, you have to make up for that, but your 8.6kg of fixed weight seems high. That would be plate, one reg, and hardware like lights and such. Is that the dry weight, or the buoyancy? Heavy steel plate?

If you are regularly diving with a steel stage, I'd recommend just moving to doubles.

It also looks like you calculations are rounded up three times for a safety margin. Why do you think 17kg is too small? By your own numbers, you only need 16kg at 60m at the very beginning of the dive. You will have more positive buoyancy at any other point in the dive (assuming a wetsuit).

Yeah, 8.6 kg is quite high, but that's mostly due to my camera gear and regulators built like a tank. Also, I’m a biologist and might have to carry around miscellaneous gear (e.g., a hammer and rebar). On deep dives, I don’t really carry that much gear, so I guess it's just another way of rounding up for safety…

As for the 17 kg wing, it's true that, theoretically, it could do the job, but what about emergencies? During my underwater training, I learned how to rescue an overweighted diver with an empty BCD or a BCD failure. In that situation, I don’t think I would say no to an extra 5 kg of lift. Do you think this approach is too cautious?

Most of the instructors around me use 20+ L jacket BCDs, so that’s kind of the standard for me.

 

[grantmac]

In an emergency those tools and camera are all droppable ballast. If you don't want to drop them it's not an emergency.
That said 60m on a single tank of what I'm presuming is air is foolish.

 

[divezonescuba]

This might help. It is an older video and I initially received a lot of hate on it. It is in the queue to be updated as I now use bungee laced thru the plate and wing loops to reduce the taco effect. The revised video is still in the planning stage.

If you have a larger wing such as the 45 pound Dive Rite REC and you do not address the tacoing issue, you can lose a significant amount of buoyancy control as others have stated. However, I would not dive a single tank with the 60 pound classic using this method as it is just too large.

The hate centered around the use of the wing loops. Some said that they could not stand the stress of using them this way. However, what little stress there is, is actually well distributed. I am still waiting to die using this method, ten or 12 years later.

If you find this video helpful, please subscribe.

 

[Chris-Wood]

I took a OMS bungee'd wing to Egypt last month. I had enough lift for most of the divers on the boat, but I didn't find it too large due to the bungees. For other divers bungees might lead to shunning from the dive team.

I very rarely dive a single tank, almost 99% manifold twins so for me, it depends if you can only have one wing.

 

[Piotr_F]

In an emergency those tools and camera are all droppable ballast. If you don't want to drop them it's not an emergency.
That said 60m on a single tank of what I'm presuming is air is foolish.

Very good point. Still, emergency response behavior is a weird thing. I fear that my instinctive reaction would be to use my BCD to get more lift and rescue my buddy rather than unclip the bolt snap and dump my gear.

You’re probably right about deep air diving; however, those depths are only accessible to properly trained divers.

 

[Piotr_F]

This might help. It is an older video and I initially received a lot of hate on it. It is in the queue to be updated as I now use bungee laced thru the plate and wing loops to reduce the taco effect. The revised video is still in the planning stage.

If you have a larger wing such as the 45 pound Dive Rite REC and you do not address the tacoing issue, you can lose a significant amount of buoyancy control as others have stated. However, I would not dive a single tank with the 60 pound classic using this method as it is just too large.

The hate centered around the use of the wing loops. Some said that they could not stand the stress of using them this way. However, what little stress there is, is actually well distributed. I am still waiting to die using this method, ten or 12 years later.

If you find this video helpful, please subscribe.

Take you for sharing this, I am looking forward to the update. Maybe you could include a DIY tutorial to add this bungie/velctro tape setup to a plain wing without bungies ?

 

[inquis]

Yeah, I'm confused by the "fixed weight" you listed as well. (In spite of that text, they should be buoyancies, not dry weights.) A 3 kg dry backplate, for example, would have a buoyancy of about -2.6 kg. Also, the camera gear should be about neutral in the water. You can measure negative buoyancy directly with a luggage scale and a large bucket/trashcan/hot tub/pool/lake. For things like wetsuits, put it in a bag/pillowcase with enough weight to sink it, then measure that with & without the suit, with the difference being the suit buoyancy.

 

[Piotr_F]

Yeah, I'm confused by the "fixed weight" you listed as well. (In spite of that text, they should be buoyancies, not dry weights.) A 3 kg dry backplate, for example, would have a buoyancy of about -2.6 kg. Also, the camera gear should be about neutral in the water. You can measure negative buoyancy directly with a luggage scale and a large bucket/trashcan/hot tub/pool/lake. For things like wetsuits, put it in a bag/pillowcase with enough weight to sink it, then measure that with & without the suit, with the difference being the suit buoyancy.

Yeah I now how to do that and the difference between dry weight and buoyancy (don't have such a massive bucket nor a luggage scale tho so maybe my eyeballing is a little of). I recon that my camera setup is not great. It is an heavy metal one but have not done anything to make neutral yet...

 

[sea_ledford]

Yeah, 8.6 kg is quite high, but that's mostly due to my camera gear and regulators built like a tank. Also, I’m a biologist and might have to carry around miscellaneous gear (e.g., a hammer and rebar). On deep dives, I don’t really carry that much gear, so I guess it's just another way of rounding up for safety…

As for the 17 kg wing, it's true that, theoretically, it could do the job, but what about emergencies? During my underwater training, I learned how to rescue an overweighted diver with an empty BCD or a BCD failure. In that situation, I don’t think I would say no to an extra 5 kg of lift. Do you think this approach is too cautious?

Most of the instructors around me use 20+ L jacket BCDs, so that’s kind of the standard for me.

You don't want to include sampling gear in your calculations. It should be light enough that it doesn't matter that much (tape measures and quadrats), or heavy enough that you use (or at least have access to) a lift bag (Hammers, chisles, pneumatic tools, etc). Plus you can always drop it if needed. I always tell my dive buddies and fellow researchers that if they seem me with my camera dangling from its tether, I need help. It means I have decided that whatever issue I'm dealing with is more important than a $15k camera.

Rescuing an overweighted diver requires ditching weights or rethinking your system (team, equipment, procedures, etc). Dual bladder wings are sometimes the best sub-optimal option.

The issue isn't that your approach is too cautious, it is that you being too cautious in your thinking is making you less safe.

Appropriately sized tanks/wing combo and a drysuit sound like what you need honestly. Doing working dives to 60m on air with not ideal equipment sounds like a terrible place to be. You should be having some safety talks with your team/PI/DSO. As a DSO, I would never approve that as a plan.