Thick Wetsuits and Aluminum Tank -- DIR?

[Charlie99]

Having read yet another "are steel tanks and wetsuits DIR?" thread, I figured it was time to ask the related question ---

Is it DIR to have a thick wetsuit (7mm full + 7mm farmer john for example) with a single 80cu ft or 100 cu ft aluminum tank?

How about with AL80 doubles?

It has always seemed to me that the real culprit in the steel tanks + wetsuits situation is the wetsuit, not the tank.

Thanks in advance,

Charlie Allen

 

[Kendall Raine]

It has always seemed to me that the real culprit in the steel tanks + wetsuits situation is the wetsuit, not the tank.

Thanks in advance,

Charlie Allen

Completely agree. The argument has nothing to do with wet steel or dry steel, per se. That's an oversimplification that owes it's origin to the objection of using double steel tanks wet. It really comes down to a ditchable versus non-ditchable weight analysis. That has to do with static and dynamic buoyancy and are you set up to deal with a BC failure given the gas delta, wetsuit compression and empty weight of the tanks. There is a point where the static and dynamic weight of steel tanks makes using them wet a hazard, but the devil is in the numbers.

To those who would tell me it's more dangerous to use an AA 72 wet than an AL 80 wet I say check your math.

 

[limeyx]

Completely agree. The argument has nothing to do with wet steel or dry steel, per se. That's an oversimplification that owes it's origin to the objection of using double steel tanks wet. It really comes down to a ditchable versus non-ditchable weight analysis. That has to do with static and dynamic buoyancy and are you set up to deal with a BC failure given the gas delta, wetsuit compression and empty weight of the tanks. There is a point where the static and dynamic weight of steel tanks makes using them wet a hazard, but the devil is in the numbers.

To those who would tell me it's more dangerous to use an AA 72 wet than an AL 80 wet I say check your math.

Agreed. Also, whenever I hear about someone using such a thick wetsuit, I think they are somehow trying to "circumvent" thermal issues by simply adding thickness (of wetsuit rather than moving to a drysuit, which might be a better choice if it's cold enough to really need 14MM of wetsuit.

 

[limeyx]

Having read yet another "are steel tanks and wetsuits DIR?" thread, I figured it was time to ask the related question ---

Is it DIR to have a thick wetsuit (7mm full + 7mm farmer john for example) with a single 80cu ft or 100 cu ft aluminum tank?

How about with AL80 doubles?

It has always seemed to me that the real culprit in the steel tanks + wetsuits situation is the wetsuit, not the tank.

Thanks in advance,

Charlie Allen

As Kendall says, it's really a simplification of "can you dive a balanced rig," coupled with the fact that a wetsuit cannot function as secondary buoyancy like a drysuit can.

With thin wetsuits, and AL80s, I believe people are diving AL plates with no extra weight.
If that's the case, then going to steels will probably make the diver 3-4 pounds more negative for each tank, so 6 to 8 pounds more to swim up in an emergency.

 

[TSandM]

We were told in Fundies that heavy wetsuits are not a good idea for deep (>100 fsw) diving, period, because of the tremendous buoyancy swings.

 

[Charlie99]

We were told in Fundies that heavy wetsuits are not a good idea for deep (>100 fsw) diving, period, because of the tremendous buoyancy swings.

So why do so many repeatedly say "Wetsuits + steel tanks are not DIR", but so few will say or post "Thick wetsuits are not DIR"?

 

[boomx5]

So why do so many repeatedly say "Wetsuits + steel tanks are not DIR", but so few will say or post "Thick wetsuits are not DIR"?

Because they are quick to quote GI3 without giving a well reasoned answer as Kendall gave. Though I agree with the premise, it's more about diving a balanced rig instead of adhearing to a broad generalization. It's kind of the same thing as saying, "we don't do 2 hours dives in the ocean". While it may be true for some applications, you can't paint all ocean diving with the same broad brush.

 

[TSandM]

Also, doubled steel tanks with THIN wetsuits may be a bad idea, because the rig may be too negative to be balanced because the wetsuit has so LITTLE buoyancy. So, in fact, it may be difficult to find any combination where a wetsuit and doubled steel tanks is an optimal solution.

 

[RTodd]

So why do so many repeatedly say "Wetsuits + steel tanks are not DIR", but so few will say or post "Thick wetsuits are not DIR"?

Thick wetsuits are not DIR.

I was going to qualify that but can't actually think of any real exceptions right now. New divers learning the basics in colder water diving shallow is hard to get away from. Plus, using a 5mm or one piece 7mm in Akumal where you are diving shallow and using AL doubles is acceptable. But a drysuit is still a better choice in those applications. Colder water and/ or deep, drysuit.

 

[limeyx]

So why do so many repeatedly say "Wetsuits + steel tanks are not DIR", but so few will say or post "Thick wetsuits are not DIR"?

You wont find me saying thick wetsuits are not DIR because sometimes I dive one.
If that makes me "non DIR" then I dont really give a crap.

I use a 7MM wetsuit with a single steel tank usually for beach diving to 40 or so feet. Also, almost always if I am only doing a single dive, or if the entrance is too rocky for my drysuit.

More than one dive in a 7MM at 59F will make me hypothermic (yeah,I am a wimp) so I dont do it.

I dive caves (77F) in a drysuit. I froze my butt off in hawaii in a 3MM in 79F water.

It's really about (for me)
- exposure -- how cold am I going to get in the worst case?
- can I swim my rig up.

if I can do both of those in a "thick" wetsuit, then it's not such an issue.
That said, for deeper dives I generally will take a drysuit even in warm water (although I haven't done much warm-water deeper diving)