85m air dive

[tracydr]

Someone mentioned that free divers go deeper than this, so what's the big deal. I should have included the quote. Sorry

 

[tracydr]

So you want him to try to set a deep air record instead?



I've done deeper dives on air with a single tank (and pony), no deco gas, solo and without anyone else'e knowledge on the boat. I consider it a stupid stunt, but everbody is different.

Remember: People are diving deeper than this while freediving!

My biggest questions are; Why the need for over 90 lbs lift in the BC? Why does it appear that second stages are hanging down in the photo? Why does it appear that both stage bottles are in front and deployed at the same time?

This is where the free diving comment got started. Sorry about not making myself clear.

 

[Blackwood]

Someone mentioned that free divers go deeper than this, so what's the big deal. I should have included the quote. Sorry

It's not a big deal, it just seemed to come out of nowhere (hard to follow a thread this long).

 

[Tortuga68]

The "what's the big deal?" bit was part of the quote, not tracy's addition

Assuming the backgas tanks were Al you only had about 18 pounds of gas. Adding a couple pounds for the shorty wetsuit gives you 20 pounds. A 30 pound wing would have been enough for the dive

Don't see many people diving doubles with 30# wings, why is that?

Can you elaborate on this please? More detail on the math would be good. The twins are AL80s as you assumed

 

[ianr33]

The reason nobody dives doubles with 30# wings is that as far as I know,nobody makes them.
However,I do have a a 40# halcyon doubles wing . Have done loads of dives with this using Al 80 doubles, an 80 deco tank and a 40 deco tank. It works fine.

As regards the math: 80 cu ft of air/nitrox weighs around 6 pounds. With double 80s and 2, 40 cu ft deco tanks you have a total of 240 cu ft of gas, that weighs 18 pounds.
You will also need some lift to compensate for the loss of wetsuit buoyancy at depth. With a thin shorty thats only going to be 2 or 3 pounds.

So,if you are just neutral on the surface with empty tanks, you will be around 18 pounds negative on the surface with full tanks. 20 pounds negative at depth with full tanks and a totally compressed wetsuit.
A 40 pound wing would be just enough to support 2 divers at the start of the dive.

The above assumes of course you are correctly weighted.

 

[Tortuga68]

Thanks for the reply. But what about ss backplate, manifold, tank bands, 4 sets of regs, xl jet fins with spring straps etc? Obviously if you've used a 40 then it's sufficient lift for the gear you mentioned, but I'm struggling to come up with 30# as the answer to the equation. I imagine there's a reason why no one - that I know of - makes doubles wings <40#

 

[lamont]

Thanks for the reply. But what about ss backplate, manifold, tank bands, 4 sets of regs, xl jet fins with spring straps etc? Obviously if you've used a 40 then it's sufficient lift for the gear you mentioned, but I'm struggling to come up with 30# as the answer to the equation. I imagine there's a reason why no one - that I know of - makes doubles wings <40#

Only way that you need to compensate for that is if you've got just about zero wetsuit bouyancy.

Since the least I've ever used for exposure protection is a 5mm, then the inherently buoyancy of the wetsuit compensates for manifold, bands, regs, etc. If you can get neutral with no air in your wing and nearly no gas in your tanks, then all you have to worry about is the buoyancy swing of the suit at depth and the buoyancy swing of the gas.

 

[ianr33]

Provided you are neutral on the surface with empty tanks the weight of a backplate etc doesn't matter.

Sure a backplate and regs etc weighs quite a bit,but offset that with your inherent buoyancy in seawater,plus the buoyancy of the wetsuit plus 4.4 pounds for each empty Al80 and 2.2 pounds for each 40 and you should be able to get neutral.

I know that with Al doubles in seawater,when wearing a 3mm wetsuit I need around 10 pounds of weight. Normally use a 6lb steel plate and 4 pounds on my waist. Any less than that and I start struggling to stay down when the tanks are near empty

 

[lamont]

It also reduces air shift and has the side effect of making venting easier

The tighter you've got the bungees and the easier it makes venting, the more gas you'll lose if you have a problem with the wing integrity.

 

[Tortuga68]

I understand the principle of being neutral with empty tanks; but in practice, I usually have ~100 bar in the twins and 50+ bar in each stage by the end of my 6m stop

And what I need to be able to do is trim out at 75m plus with up to 180 bar in the twins and over 100 bar in each stage, while wearing a 3mm shorty; I'm still not seeing how 30# is going to let me do that, let alone pull up my buddy from that depth if it should be required

In a 3mm shorty I can get down and hold stops comfortably without any extra weight under the above conditions; with my 5mm hooded shorty (which I used on the 85m dive) I need a single weight, which I cable-tie to my tank bands/manifold

If you can show me the math that says 30# will work, please do