halcyon eclipse for doubles?

[cool_hardware52]

That's not true.

The buoyancy swing on (standard) double AL80s ranges from -2.8 to +8.8 in salt water - maybe shifted a little more to the negative side when you add bands and a manifold. Lightweight steels, on the other hand (including Faber, original "Genesis" tanks made by PST, and the newer E7s) are about neutral when empty, and will be much more negative (as compared to AL80s) when full. Their buoyancy characteristics are closer to NB80s, which makes them a less desirable choice for divers in wetsuits (as discussed in this recent thread).

A lightweight steel cylinder might be marginally acceptable for wetsuit diving in a single tank rig (depending on other factors), but there is no way I would double them up unless I was diving dry.

I don't think we are to far apart in our thinking.

I routinely use faber lp 85's that are almost neutral when empty, and about 6 lbs neg when full. If I have 6lbs in a weight belt and ~3 lbs in a can light. I start the dive about 5-6lbs. negative. This represents about 1/2 the gas I might breathe. Assume the worse case senario, i.e. total buoyancy failure at early in the dive. Ditch my belt and can light and I need to swim up only about 7-8 lbs, and that's assuming I'm at 165 or deeper. At ~165 a neo wetsuit is at zero bouyancy, if I'm shallower my suits still somewhat positive, meaning I need to swim up less, and I'll be positive when I get to the surface.

Clearly this won't work with PST 104's that are ~11.5 neg each when full, but that's not my point. My point is to understand the total weighting picture.

There are fabers sold in the UK that are both lighter, and higher working pressure than the steels sold in the US. These will be positive when empty.

On this, we agree - the critical issue is one of the "balanced rig", which is why it's important to check these things before committing to a purchase.

Lightweight steels, + ditchable ballast is really no different than Lightweight Al's + ditchable ballast. The question is can you swim up the rig early in the dive after ditching, and will you able to stay at the surface after you get there. If you have little or no ditchable when using the lightest steels, then AL80's are a better choice. If you do have enough then where's the problem?

Tobin

 

[BarryNL]

agreed. Steel doubles + wet suit is not DIR. The wetsuit looses bouancy when going deeper, and that might result in non-neutral rig. You should be able to swim up if your wing fails (apart from having backup bouancy).

Surely this prevents ever using steel doubles? They would be at least 25lbs negative I would think or at least 30lbs with a steel backplate. I can't imagine swimming that up.

Are steel doubles (12s or greater) a possible DIR option?

Edit: Ah, I see this has been covered. So, lightweight steels are a must for doubles then?

 

[BarryNL]

40 pound explorer or evolve would be fine.
there are also plenty of other wing manufacturers out there too.
I have not had such good experience with Halcyon wings and might look elsewhere next time I buy

I have to admit, having looked at their stuff up against other brands it doesn't seem to be that great. I was going to get an Eclipse backplate/wing but ending up buying a DIR Zone which was a couple of hundred euros cheaper and certainly looks a lot tougher. The inflation valve also has a much nicer, progressive feel to it than the Halcyon 'precison' inflator.

I also have a Halcyon DSMB which has only been used half a dozen times and already the boltsnap doesn't close properly and the inflation valve is starting to leak.

Overall, their stuff is probably OK, but there seems to be better, cheaper stuff from the competition.

 

[DIR-Atlanta]

Are steel doubles (12s or greater) a possible DIR option?

Only with a drysuit.

So, lightweight steels are a must for doubles then?

That' s an incomplete (and possibly misleading) conclusion. If you are diving dry, then you can pretty much use whatever you want, for either singles or doubles. If you are diving wet, then you mostly want to concentrate on Aluminum cylinders (and particularly so if you are using doubles).

I just did a quick check, but could not locate any buoyancy characteristics for 10L or 12L aluminum cylinders. Just based on dimensions, a 10L aluminum appears to be roughly equivalent to a Luxfer S072, so I would guess the buoyancy characteristics would be similar (-1.4 to 3.8lbs, which is about the same as an S080). The 12L cylinders appear to be roughly equivalent to Luxfer S092s, which would be too negative for wetsuit diving.

So my guess is that the "preferred" Aluminum cylinder for wetsuit diving in Europe would be the 10L (if we have any European divers who can jump in here and confirm or deny that, then I'd appreciate it).

 

[El Orans]

So my guess is that the "preferred" Aluminum cylinder for wetsuit diving in Europe would be the 10L (if we have any European divers who can jump in here and confirm or deny that, then I'd appreciate it).

Wetsuit, Eclipse #30, single steel 10 or 12L. Works like a charm.

 

[wb416]

I was wondering if I could use my eclipse 40lb. wing on a set of doubles? I heard that some people were doing this. Also, if I were to get a evolve wing would I need the 40 or 60 lb. wing? I am currently diving with a 130 hp tank and the 40 lb. eclipse wing which gives me plenty of lift when i'm on the surface. (I am 6 ft. 160-170 lbs.)

I have used a 36# Pioneer on Double 80's before, and although it "worked", it was definitely sub-optimal. It didn't feel right. Air shifts around allot more since the wing wasn't big enough to wrap up around the tank.

So... my recommendation is to go with the correct wing and use an Explorer (or equiv).

 

[cerich]

That's not true.

The buoyancy swing on (standard) double AL80s ranges from -2.8 to +8.8 in salt water - maybe shifted a little more to the negative side when you add bands and a manifold. Lightweight steels, on the other hand (including Faber, original "Genesis" tanks made by PST, and the newer E7s) are about neutral when empty, and will be much more negative (as compared to AL80s) when full. Their buoyancy characteristics are closer to NB80s, which makes them a less desirable choice for divers in wetsuits (as discussed in this recent thread).

A lightweight steel cylinder might be marginally acceptable for wetsuit diving in a single tank rig (depending on other factors), but there is no way I would double them up unless I was diving dry.


On this, we agree - the critical issue is one of the "balanced rig", which is why it's important to check these things before committing to a purchase.

NO, that's not true . A luxfer cylinder (standard 80) goes from -1.4 full to +3.4 with 500 psi. So in doubles -2.8 full and +6.8 at 500 psi (not including bands, manifold) (You had this correct) Worthington LP85 steel cylinders you can see in doubles as little as -12 and neutral empty (not including bands and manifold). I suggest that you can swim 12lbs up from any depth wet(although in reality it will be less than 12lbs anyway). In fact many folks will use a v weight with the double 80's to trim and weight correctly. With the LP85's you can ditch the v weight and the trim is sweet, better than double alum. 80's.

That being said MOST steel cylinders I would not dive doubled wet.

The cool aide is sweet but the mind is sweeter....

I agree 100% the critical issue is a balanced rig, with some small amount of steel tanks that can be achieved wet.

I know this goes againts the mantra that you suscribe to, but if you get a chance dive some doubled 85's wet, you may find yourself thinking they are the better way to go.

 

[DIR-Atlanta]

Lightweight steels, + ditchable ballast is really no different than Lightweight Al's + ditchable ballast. The question is can you swim up the rig early in the dive after ditching, and will you able to stay at the surface after you get there.

Personally, I believe that's a bit of an over-simplification (although your point about being able to swim the rig up is "spot on"). I do not necessarily agree that "Lightweight steels, + ditchable ballast is really no different than Lightweight Al's + ditchable ballast." I think it depends entirely on the parameters of the dive.

So just to clarify - I am not saying that "steel tanks are OK in a wetsuit". In fact, I am saying the opposite of that. I believe unequivocally that if you are diving doubles in a wetsuit, then you should be using standard AL80s (Luxfer S080s or equivalent), and that if you are using double steels, then you should be diving dry.

The point where things gets sticky with this is when you are talking about a single tank rig. Whenever I have this discussion with someone, I always have this mental image of a guy wearing a wetsuit with a SS backplate and weighted STA, but claiming that his setup is "DIR" because he is using an Aluminum cylinder. That clearly is an example of a person who does not understand the relevant issues.

Buoyancy-wise however, there is very little difference between (for example) SS B/P + unweighted STA + AL80, versus AL B/P + weighted STA + AL80, versus AL B/P + unweighted STA + steel. In fact, I have used all three of these combinations on shallow (< 100 feet) OW dives in a wetsuit, and in all cases I was able to swim the rig up easily from depth.

However, there are a lot of advantages to standardizing on the AL80 for your single tank rig - it is simply a much more versatile (and cheaper!) tank. You can use it as a single, or as a stage bottle, or doubled up. Most steel tanks cannot be used this way, so if you start out with a steel single, then you often wind up with an "orphan" tank that is dedicated to one specific purpose. Just consider your own example - an OMS 85 may work fine in a single tank rig for wetsuit diving or doubled up for drysuit diving, but it won't work as a stage bottle.

Furthermore, most places rent AL80s by default, so if you are weighted for that type of tank anyway, then it takes a lot of the guesswork out when you travel somewhere and have to rent (or borrow) someone else's tank. Face it - it's a lot easier to transport a weighted STA than a steel tank.

Regarding your anecdote about 165 foot dives while using an OMS 85 - no offense intended, but that is something I would personally never do. At that depth I would be on a light trimix, and in doubles (AL80s if wet, steels if dry). I pretty much try to restrict my single tank diving to a max depth of 100-110 feet.

 

[cool_hardware52]

Regarding your anecdote about 165 foot dives while using an OMS 85 - no offense intended, but that is something I would personally never do. At that depth I would be on a light trimix, and in doubles (AL80s if wet, steels if dry). I pretty much try to restrict my single tank diving to a max depth of 100-110 feet.

Where did I say I'd ever be at 165 on a single LP85 on air? I mentioned 165 only to point out that above that depth neoprene is still somewhat buoyant.


Tobin

 

[cerich]

Where did I say I'd ever be at 165 on a single LP85 on air? I mentioned 165 only to point out that above that depth neoprene is still somewhat buoyant.

Tobin

Hey Tobin,

I feel we may have to stop the debate. From the GUE DIR camp there is no acceptable method to dive double steel while wet. Single steel "maybe". Well in a 7mm semi dry I'm quite happy to dive a single 130....

The overall concept of the GUE DIR point of view on this is sound, good advice. But like every rule there are exceptions. Thing is that exceptions are frowned upon to ardent followers so thus are dismissed out of hand. I personally chalk this up to lack of experience.

As far as alum 80's being more versitile, sure....when was the last time you broke down double 80's to make stages out of them???? :huh: They are cheaper.

Best,

Chris