Steel 72 Doubles

[rhlee]

I think the whole "balanced rig" thing is a bit overdone.

260cf of air/32 weighs over 20lbs. That means you're starting the dive 20lbs overweighted (compared to the end of the dive), which, nominally means you have 20lbs of additional lift in your wing. Aside from dynamic instability issues up the ying yang, if you lose that lift, you've got to find some way to find yourself to the surface.

If you're fit and can swim up 10lbs yourself, that leaves 10lbs to deal with, which means ~10lbs ditchable. Maybe that's doable, maybe it's not. Myself, I wear no weight belt, so this rig would not balance for me. In either case, it's awfully heavy and is heavily constraining where you can move weight around. And starting the dive with 20+lbs of lift in your wing seems awfully unstable to me...

(And before anyone says this isn't a DIR answer this is exactly what we came up with on my DIR-F ).

oh, well, in that case....

 

[rhlee]

i trim out great with my 130 with 32 in them not all bouts will let you take 3 sets of dubs are even 2 sets or stages ect.

read more carefully, I suggested 1 set of doubles + stage -or- 3 sets of doubles FOR 2 divers.

 

[lamont]

260cf of air/32 weighs over 20lbs. That means you're starting the dive 20lbs overweighted (compared to the end of the dive), which, nominally means you have 20lbs of additional lift in your wing. Aside from dynamic instability issues up the ying yang, if you lose that lift, you've got to find some way to find yourself to the surface.

If you're fit and can swim up 10lbs yourself, that leaves 10lbs to deal with, which means ~10lbs ditchable. Maybe that's doable, maybe it's not. Myself, I wear no weight belt, so this rig would not balance for me. In either case, it's awfully heavy and is heavily constraining where you can move weight around. And starting the dive with 20+lbs of lift in your wing seems awfully unstable to me...



oh, well, in that case....

I tried swimming up double-130s with EAN32 and with no gas in the wing and no air added to my drysuit and i could do it. Once I got off the bottom, staying in place required quite a bit of effort -- about like treading water in a pool for me (I'm not one of the people that float easily in freshwater) -- but it was doable at least for a short period of time. Trying to deco that way would suck.

I also tried using only suit inflation to simulate a complete wing failure, and while it sucked and there was probably a risk of a drysuit neck blowout if you went vertical, but as an emergency procedure you could complete a deco that way in a pinch.

Steel 72 doubles are also perfectly DIR provided that you don't compromise your gas plan.

 

[alwaingold]

As Rob pointed out, it is the weight of the gas that counts.

Some people on this thread don't seem to get it. If you are neutral at the end of the dive, with nearly empty tanks, and an empty wing, then at the beginning of the dive, you will be heavy by the weight of the gas in the tanks. It doesn't matter if N cuft of gas are in Al tanks or steel tanks -- the gas weighs the same thing, and the buoyancy shift will be the same. But the choice of Al tanks vs. steel tanks does affect your options for weight distribution. As Rob pointed out, if you are properly weighted in steel tanks without a belt, then balancing a rig with a 20 lb buoyancy shift may be a problem.

Lamont points out that he can swim up 20 pounds of weight in a pool. Congratulations. It doesn't matter what he can swim up; it matters what the guy wearing the tanks can swim up. I think 10 lbs is used as a rule of thumb limit in Fundies, but what really matters is what you personally can do (which you could find out by trying it in a pool).

260cf of air/32 weighs over 20lbs...

 

[BarryNL]

As Rob pointed out, it is the weight of the gas that counts.

Some people on this thread don't seem to get it. If you are neutral at the end of the dive, with nearly empty tanks, and an empty wing, then at the beginning of the dive, you will be heavy by the weight of the gas in the tanks. It doesn't matter if N cuft of gas are in Al tanks or steel tanks -- the gas weighs the same thing, and the buoyancy shift will be the same.

That misses the compressibility of the wetsuit issue. You need to be able to be neutral at the end of the dive with empty tanks at 3m, this means you will be overweighted at the start of the dive (when you hit bottom) by the weight of the gas plus the buoyancy loss from your wetsuit. That's the weight you either have to swim up or ditch.

 

[onfloat]

That misses the compressibility of the wetsuit issue. You need to be able to be neutral at the end of the dive with empty tanks at 3m, this means you will be overweighted at the start of the dive (when you hit bottom) by the weight of the gas plus the buoyancy loss from your wetsuit. That's the weight you either have to swim up or ditch.

Bingo!!

 

[pengwe]

I think if I ended up in a situation where I couldn't swim up my rig, I might ask my buddy for a lift. But then, I have ditchable weight, so maybe I would give them my weight belt, and they could give it back to me later in the ascent. Do people foresee problems with that?

 

[amascuba]

I think if I ended up in a situation where I couldn't swim up my rig, I might ask my buddy for a lift. But then, I have ditchable weight, so maybe I would give them my weight belt, and they could give it back to me later in the ascent. Do people foresee problems with that?

Think about this for a second. You're in a situation where you need to make an ascent ASAP, your wing is not functional, and you can not swim your rig up; You're going to take the time to unfasten your harness to remove the crotch strap, take off your weight belt, hand it to your buddy, loop your crotch strap back through your waste belt, and refasten your harness. Sounds time consuming and convoluted to me.

 

[Gombessa]

You're going to take the time to unfasten your harness to remove the crotch strap, take off your weight belt, hand it to your buddy, loop your crotch strap back through your waste belt, and refasten your harness. Sounds time consuming and convoluted to me.

Doesn't ditching the weight involve exactly the same steps as outlined above? Once the decision is made to lose the belt, I wouldn't even think about handing it off, but I'm not sure where the extra convolution is coming from in the above.

 

[amascuba]

Doesn't ditching the weight involve exactly the same steps as outlined above? Once the decision is made to lose the belt, I wouldn't even think about handing it off, but I'm not sure where the extra convolution is coming from in the above.

Part of the balanced rig is being able to swim the rig up from depth without the help of your wing. If you are unable to do that then redundant buoyancy is needed, hence the use of a drysuit. There should not be a need to drop weights at depth.