Weight Systems - DIR point of view

[dbulmer]

Thanks - what would happen if suit flooded/wing loss with deco obligation? You'd dump the ali stages presumably? Or no deco but an argon cylinder was being carried?

 

[Wreck Junkie]

What kind of wetsuit are you wearing? What kind of drysuit will you have? I dropped a couple of pounds going from a thick wetsuit to a trilam drysuit.

Scubapro 5 mm plus 2 mmm overjacket. will have bare trilam.

 

[mindGrabber]

???

Every DIR diver I know uses steel tanks ...

... Bob (Grateful Diver)

So every DIR diver you know have to be cave-diver

One of the key points of DIR system is "balanced rig".

It means that diver should be able to maintain 10’ stop with tanks close to empty (500 psi) and with empty BC devices (I mean both wings and dry suit).

In a worse scenario you are making blue water dive, you are at the end of your bottom time and you are suddenly getting catastrophic gas loss. So you have zero in your tanks and you can’t inflate both wings and dry suit. You have some deco obligations, you are breathing buddy’s gas and you have to ascend and not forget to maintain all you deco stops.

With steel doubles in such conditions you’ll get constant negative weight and I hardly believe that correct exit can be done.

 

[Soggy]

With steel doubles in such conditions you’ll get constant negative weight and I hardly believe that correct exit can be done.

See, that's the flaw in the logic....

First of all, the issue is at the *beginning* of a dive where you are overweighted by 20+ lbs...you need to be able to swim *that* up. Anyone can swim up a set of empty tanks.

Secondly, most people who use double Al80s with a drysuit also use an 11 lb v-weight to counteract the inherent buoyancy of the Al80s. That v-weight is not ditchable, thus it might as well be made out of the same material your tanks are....the fact that it is a separate piece of lead is 100% irrelevant.

Let's *critically* examine this rather than accepting what is being told to us.

Aluminum 80 configuration:
Aluminum tanks (empty) = +4 x 2 = +8
Bands & Manifold ( estimate) = -3
SS Backplate = -6
V-weight = -11
Total = -12 lbs


Steel 130 configuration:
Steel 130s (empty) = -2.5 x 2 = -5
Bands & manifold (estimate) = -3
SS Backplate = -6
Total = -14 lbs



As you can see, the empty negative weight is the approximately the same between the two sets of tanks. However, if you add the *gas* into the situation, Al80s have 12 lbs of gas and E8-130s have 20 lbs. This means that the steel configuration is now much much more negatively buoyant, but that has *nothing* to do with the material the tank is made of and *everything* to do with the amount of gas carried on the back.

Nobody said you have to always fill your tanks to the brim, either. I frequently fill my tanks to 2400 psi or so simply because there is no need for all the extra gas. This brings my total rig buoyancy very close to a set of Al80s.

I won't even mention the fact that, with empty double 130s, I need 6 lbs of weight on a belt to stay down (in salt water), so obviously with empty tanks, it's an easy swim, and with full tanks, not a hard one.

 

[ScubaDadMiami]

The idea is not to be able to swim up full tanks with both a wing and drysuit failure.

Steels are perfectly acceptable to dive in the ocean if the diver uses a drysuit. In that case, where there is a wing failure, the diver can use the drysuit to get neutral for the ascent. What is not acceptable is using heavily negative steels while not having some sort of wing backup (such as the drysuit).

Where the diver is using a wetsuit, that is when the diver should be using aluminums. In that case, the diver is not nearly so negative and will be able to swim up the tanks.

 

[ScubaDadMiami]

My options thus are two:

Either add the other weight pouch to the right side and trim both MC pouches to suit the new weight requirements.

Or wear a separate weight belt.

It all depends on your trim. Some people use a heavier plate or use a V-weight; some go with a weight belt.

To my knowledge, there is no problem with using weight pockets. Even Halcyon manufactures them: http://www.halcyon.net/mc/acb.shtml.

 

[MXGratefulDiver]

So every DIR diver you know have to be cave-diver

Actually, we don't have caves in Puget Sound. Occasionally, people head off to Akumel or Florida, but for the most part we're what you would call "open ocean" divers.

One of the key points of DIR system is "balanced rig".

It means that diver should be able to maintain 10’ stop with tanks close to empty (500 psi) and with empty BC devices (I mean both wings and dry suit).

In a worse scenario you are making blue water dive, you are at the end of your bottom time and you are suddenly getting catastrophic gas loss. So you have zero in your tanks and you can’t inflate both wings and dry suit. You have some deco obligations, you are breathing buddy’s gas and you have to ascend and not forget to maintain all you deco stops.

With steel doubles in such conditions you’ll get constant negative weight and I hardly believe that correct exit can be done.

Well, I see it done all the time. My double rig is steel E8-119's. Now, granted I'm not very experienced with them yet, but I have been able to hold a 10-foot stop with just 250 psi in them ... while Uncle Pug was breathing off my primary second-stage.

By far the most popular rig out here is double steel 104's ... and some of those guys can hang at 10 feet forever, it seems. Had one pull an OOA drill on me at 8 feet once, just for yuks and giggles ...

... Bob (Grateful Diver)

 

[mindGrabber]

Secondly, most people who use double Al80s with a drysuit also use an 11 lb v-weight to counteract the inherent buoyancy of the Al80s. That v-weight is not ditchable, thus it might as well be made out of the same material your tanks are....the fact that it is a separate piece of lead is 100% irrelevant.

Let's *critically* examine this rather than accepting what is being told to us.

Aluminum 80 configuration:
Aluminum tanks (empty) = +4 x 2 = +8
Bands & Manifold ( estimate) = -3
SS Backplate = -6
V-weight = -11
Total = -12 lbs

Steel 130 configuration:
Steel 130s (empty) = -2.5 x 2 = -5
Bands & manifold (estimate) = -3
SS Backplate = -6
Total = -14 lbs

In described rig configuration the difference is not so big - 12 lbs against - 14 lbs of negative buoyancy.

The point is that I simply don’t sure that I’ll be able to maintain long deco-stop (let’s say 30 minutes on 10’) in both cases. May be I can but firstly I have to run such kind of simulation in a pool

Another point is that I’m diving a bit another rig configuration. I’m not using v-weights. My typical configuration for dry-suit is AL 80 doubles with manifold, SS backplate, 2-4 lbs attached directly to doubles, 12 lbs weight-belt, 3 lbs light canister.

Playing with your numbers I’ll get 3 to 5 lbs of negative buoyancy with my rig against 14 lbs of negative buoyancy with steel doubles. 10 lbs of difference is more than enough to motivate myself use AL doubles.

 

[Soggy]

The idea is not to be able to swim up full tanks with both a wing and drysuit failure.

Actually, that is exactly the idea. You may want to discuss this in more detail with your local GUE instructor.

 

[Soggy]

Playing with your numbers I’ll get 3 to 5 lbs of negative buoyancy with my rig against 14 lbs of negative buoyancy with steel doubles. 10 lbs of difference is more than enough to motivate myself use AL doubles.

Using a weight belt vs. v-weight lends credibility to this argument, but most people I've seen argue steel vs aluminum (with drysuit) are using v-weights.

I'll just accept the fact that I can swim my double 130s up in the ocean and that a *complete* drysuit AND *complete* wing failure is about as likely as pigs flying.