doubles in DIR diving wet....

[Derek S]

wow, wow, wow....thank you all for your posts, they are very informative but let me add my comment and forgive me if my lack of diving experience (70 dives) let me say something wrong.

I now dive a steel HP 100 and I can swim it up fine with my wing deflated so I don't anticipate problems with double AL80's.

It looks like the main but not only issue with doubles is the isolator that might be closed when filled. If the blender does a mistake when filling doubles we can assume that he can do the same mistake with single tanks mostly when using exotic gases so besides analyzing the tanks and keep an eye on the filling process the problem is the same with single and doubles....right? I always analyze my tank at the shop and sometimes again before the dive so that should cover me.

I understand that doubles are more complex but I believe that they offer a degree of safety that offset the added "danger"....right?

I am all about trainning so what class would you recommend for doubles?....is ther a class for doubles?

Thank you again for all this info, very interesting

Basically it boils down to some people not watching and/or analyzing their tanks before strapping them on. Most people check them no problem, but it only takes once....

I don't care if my wife was the one to fill them, I WILL analyze both tanks every time before I dive.

And as far as it happening with singles...Since there is only one tank and no manifold, there is a less of a chance for problems, but if someone is getting their tank filled at a place that uses PP blending, that always is a possibility..

Moral of the story? Always analyze your tanks.

I too have 2 steel HP 100s. I assume yours is a PST. At the start of the dive, you're going to be 12lbs negative. I don't know about you, but I wouldn't want to find out the hard way that you couldn't swim them up.

You're in Miami, close enough to quite a few GUE instructors and DIR minded-divers. Contact a GUE instructor and voice your thoughts/concerns.

 

[Jasonmh]

Not if you are doing anything deep.

Way to take a post out of context. Look at the quote I was responding to. The OP asked if it was non-dir to use double AL80s, the answer is no, there is nothing inherintly not DIR about using AL80s.

 

[rainman_02]

no, galvanized are the way to go, but I was following the perceived issues with steel versus aluminum. myopic opinions continue to plague this issue...

What's myopic?

If someone in a wetsuit can swim up a full set of double steel tanks with no other buoyancy and the rig is balanced I can't see why it wouldn't be DIR. But, if they can't swim up the weight, then it can't be DIR.

 

[aue-mike]

Way to take a post out of context. Look at the quote I was responding to. The OP asked if it was non-dir to use double AL80s, the answer is no, there is nothing inherintly not DIR about using AL80s.

Please forgive me for taking your post out of context.

 

[aue-mike]

What's myopic?

If someone in a wetsuit can swim up a full set of double steel tanks with no other buoyancy and the rig is balanced I can't see why it wouldn't be DIR. But, if they can't swim up the weight, then it can't be DIR.

Myopic in the sense most don't look at the complete suite of issues when touting double AL80s (supposedly DIR) when touting them over steel doubles (apparently DIW).

And "balance" is an inappropriate term that has generally been misused in this discussion.

 

[SparticleBrane]

Enlighten us about the complete suite of issues, then?

 

[TSandM]

A "balanced" rig is defined as one where the diver can swim the rig up from depth in the event of a wing failure, but can also hold a stop with 500 psi or less in the tanks. The prescription is that, if you cannot create a "balanced" rig with the tanks you are using, you need redundant buoyancy and/or ditchable weight. Therefore, large steel doubles are not recommended with thick wetsuits, because the loss of buoyancy of the suit at depth, plus the large negative buoyancy of the full tanks, means that, if you have a wing failure at the beginning of the dive at depth, you may not be able to get back to the surface.

Al80s will obligate almost everybody to carry some weight, if they are using any exposure protection at all. Therefore, you can create ditchable weight if you need it to be able to swim the rig up from depth.

My dive buddy dives doubled 130s. He is horribly negative when they are full; there is no way I could swim those tanks up from depth, and I don't know if he's ever tried to do it. But he also dives a drysuit, which is redundant buoyancy.

I think it is well worth thinking about these things when you head into the water.

 

[ekewaka]

One of the basic principles that the DIR philosophy follows is that, if you don't need it, don't take it with you. If your diving will primarily be above 100 fsw, non-overhead, non-decompression diving, you don't need doubles.

Are you suggesting that my first cave or deco dive should also be my first doubles dive?

 

[SparticleBrane]

Unfortunately, this is an issue I have with DIR.
While I might not "need" doubles on my dives I do, I enjoy using them. I also think that if you're going to regularly use doubles for deco/overhead diving, diving them regularly is a good idea to make sure you keep the skills current. Using doubles when they're absolutely needed is just plain silly.

 

[ekewaka]

Why is this in the DIR forum? A lot of people have said that doubles are dangerous because some idiot could fill them with the isolator closed, and then you could breath the wrong gas if you don't analyze it. This shouldn't be a problem because we always analyze our gas before we dive. Am I correct, or is it now DIR to dive without analyzing?