steel aluminum tank

[seiff]

I am posting this here because I want the DIR perspective on this one, and I want insight from more thoughtful divers; I clicked "Has this been asked before" and the responses to the other posts were, well...they didn't really hit the spot, let's say. Someone even said that steel is lighter than Aluminum. Not even gonna go there, let's get to my concern.

George Irvine, in his article on DIR equipment on gue.com says "steel tanks should never be used without a drysuit." To start, I understand this concept. However, here in SoCal, as you guys know, we wear 7mm suits with hoods, and with aluminum tanks will require anywhere from 20-30 pounds of lead, which is a ridiculous amount of weight. With a HP100 steel, most people here take down 14lbs, which still seems like plenty to ditch and become neutral for an ESA (at deeper depths (100ft+) this is not true, I know, because the wetsuit compresses SO much that you could not swim-up your rig even after ditching).

Ok, so what do you DIR'ers have to say? What safety aspects have I overlooked that makes open water rigs with single steel tanks a safety liability? The recreational dive community hails steel tanks as the solution to bouyancy issues, but GUE says "NEVER USE THEM WITH WETSUITS" so there is obviously some thought process that I have not heard. -tadd

P.S. The other reason I post this here is because I want to be involved in DIR diving and want to build a safe rig.

 

[Robert Phillips]

George was most likely referring to steel doubles, as that is his paradigm.
When GI is discussing diving, it usually concerns the dives he is doing and not recreational diving. This difference causes the most confusion and angst as recreational divers read his posts and think that he is talking about recreational diving when he is not.

 

[Soggy]

First, welcome to SB and the DIR forum.

Second, this topic has been discussed ad nauseum in this forum fairly recently. I suggest you start with http://www.scubaboard.com/search.php

You have to look at the spirit of the rule. The point here is to have a rig that is as balanced as possible (a truly "balanced rig" is a pipe dream as gas has weight, so you can never be particularly neutral, especially in doubles). If you can comfortably swim up your configuration with full tanks from the depths that you are diving, you are fine. The problem with steel tanks and a wetsuit is that when your 7mm wetsuit compresses at depth, you can lose upwards of 10-15 lbs of buoyancy. Add to that 12-20 lbs of gas in a set of steel doubles plus the negative buoyancy of the tanks themselves and you will be incredibly negative unless you suffer from HFS syndrome.

This being said, ordinarily, this will not be a problem with single tanks since it is easy to properly weight yourself and still be able to swim the rig up.

Your friend is right, a steel tank, cft for cft will be lighter on dry land than a comparable aluminum tank. A HP80 is lighter than an Al80. A LP72 is substantially lighter than an Al80. This is because the walls are much thinner on a steel tank than an aluminum tank. Steel tanks are also physically smaller than aluminum tanks, thus have a higher density and are more negatively buoyant.

On a side note, a drysuit is, in general, a much better solution than a thick wetsuit since you don't have to compensate for the loss in buoyancy in your suit and you are evenly weighted regardless of depth.

Hope this helps. Please use the search feature to find more information on this topic.

 

[seiff]

Thanks for the responses. I know this is discussed alot but like I said I was trying to corner some DIR principles regarding this issue. I did read the post on the other part of the site.

When GI is discussing diving, it usually concerns the dives he is doing and not recreational diving. This difference causes the most confusion and angst as recreational divers read his posts and think that he is talking about recreational diving when he is not.

Sorry to be the "angst-ridden-rec-diver" (J/K). That makes sense, but he did say NEVER so I wanted some other opinions on that. I guess I was looking for something like "We have discussed this in the DIR community and even though you can argue either way we still say NEVER EVER use steel with a wetsuit. Period." or something concrete like that. Would you say that some leniencies may be made in a recreational situation?

Also, another thought I had...at a depth where neoprene compression is dangerous, like 130+ feet, one should probably not even be wearing a wetsuit anyway, right? That's getting into deep diving and a wetsuit is not safe equipment. Thanks again. -tadd

 

[SparticleBrane]

Neoprene compression is dangerous?
...what...?

 

[limeyx]

Thanks for the responses. I know this is discussed alot but like I said I was trying to corner some DIR principles regarding this issue. I did read the post on the other part of the site.



Sorry to be the "angst-ridden-rec-diver" (J/K). That makes sense, but he did say NEVER so I wanted some other opinions on that. I guess I was looking for something like "We have discussed this in the DIR community and even though you can argue either way we still say NEVER EVER use steel with a wetsuit. Period." or something concrete like that. Would you say that some leniencies may be made in a recreational situation?

Also, another thought I had...at a depth where neoprene compression is dangerous, like 130+ feet, one should probably not even be wearing a wetsuit anyway, right? That's getting into deep diving and a wetsuit is not safe equipment. Thanks again. -tadd

George says a lot of "never ever" or "always always" things, I think to make a point that they are really important, but you do have to take the context into account. Unfortunately a lot of what is or is not "DIR" is encoded in oral communications or fragmented writings, so there are sometimes inconsistencies, especially when principles have been refined or modified (which believe it or not, does happen

A wetsuit does compress with depth, so even if you are properly balanced, it will lose thermal characteristics as you get deeper. In warm waters, this might be OK, but in colder waters, you might get cold. I wouldn't say the wetsuit itself is dangerous, but the effects of the cold could be.

Ultimately, it's (mostly) up to the individual diver to decide what is "appropriate" warmth-wise for the exposures they are doing, *assuming* their rig is balanced.

The important points are
- Is your rig balanced (on the surface can you float, if your wing fails at the worst possible time, can you safely get to the surface without needing tricks like double-bladder wings and lift bags)
- For the worst-case exposures you are doing, are you going to be warm enough?

Thick wetsuits are (generally) not considered DIR simply because they compress a lot and make it hard to get a balanced rig -- so sometimes you really have to look a layer deeper and say "why" is a wetsuit not DIR or not recommended.

Some people will still cling to the "George said" or "It's written right here" but in reality it is very difficult to communicate a statement that is 100% accurate, so sometimes you have to look at the underlying reasoning.

 

[Charlie99]

Neoprene compression is dangerous?
...what...?

Yes it is.

As far as the "no steel tanks with wetsuits" edict, a strong argument could be made that thick wetsuits are the greater culprit than are steel tanks.

==================================================

The related question would be "Are thick wetsuits and aluminum tanks DIR?"

If one is wearing 7mm full suit + 7mm farmer john and needs lots of lead to compensate for that buoyancy, whether one has a steel tank or an aluminum tank, that diver will be very negative at depth. Yes, if he has aluminum tanks he can arrange to have weight that he can ditch at depth, but then he won't be able to control his ascent when shallow.

Charlie Allen

 

[seiff]

Yes, if he has aluminum tanks he can arrange to have weight that he can ditch at depth, but then he won't be able to control his ascent when shallow.

This is why I like my steel. AL's can swing from negative when full to positive when empty. This seems very counter intuitive to me as far as balancing one's equipment, and as a very beginning diver I had a few chances to experience that swing the hard way. There are some steel tanks (mostly LP's) that have this characteristic as well.

Charlie, I also like your statment that the wetsuit is the problem, not the tank. -tadd

 

[Soggy]

This is why I like my steel. AL's can swing from negative when full to positive when empty. This seems very counter intuitive to me as far as balancing one's equipment, and as a very beginning diver I had a few chances to experience that swing the hard way. There are some steel tanks (mostly LP's) that have this characteristic as well.

Charlie, I also like your statment that the wetsuit is the problem, not the tank. -tadd

All tanks have a buoyancy swing equal to the weight of the gas within the tank. For an aluminum 80 it is ~6 lbs. For a HP80, it's ~6 lbs. The only difference is that aluminum is more buoyant when empty, so you need to wear more weight to compensate. The swing is no different, however.

All LP tanks that I know of are negative or neutral when empty.

 

[Soggy]

If I dive that depth with my single steel HP100, and a 3mm suit in the Keys (a 3mm does not have significant compression that you can't still swim up the tank full, if need be), how is that dangerous,

It's not dangerous to use a single steel tank that you can swim up with a wetsuit.

and why should I wear a drysuit in 80+ degree water?

You wouldn't, unless you were using steel doubles, in which case you would need a drysuit. Alternatively, you could dive al stages with al doubles and the wetsuit and still be fine.

(Doubles, yeah... different story - still wouldn't wear a dry suit, rather a redundant bladder BC).

Double bladder BCs are not DIR. This is the DIR forum. If you would like to discuss double bladder BCs, please do so in the appropriate forum.