Neutrally Buoyant Al 80's

[gr8ful divr]

Anyone have any experience with neutrally buoyant Al 80's? What are the advantages/disadvantages. As I build a collection of tanks (many of which will be dedicated for certain gas mixes) is there reasons for/against getting neutrally buoyant tanks?

Looking for DIR perspective which is why this is posted here and not under the tanks forum. Posted some clarifying remarks below. Thanks.

 

[ronbeau]

Anyone have any experience with neutrally buoyant Al 80's? What are the advantages/disadvantages. As I build a collection of tanks (many of which will be dedicated for certain gas mixes) is there reasons for/against getting neutrally buoyant tanks?

Another option to overcome aluminum tank buoyancy issue is the "Tank Buoyancy Compensator" from Dive Innovations.

http://www.diveinnovations.com/index.html

It is effectively a tank boot with a ditch-able 5 pound weight.

I just bought 2 for my AL 80s. It appears to be well made. I bought it at LeisurePro.
I have not yet used in in an actual dive (just came in this week). I will be using labor day weekend. I also have a ScubaPro KnightHawk BC. This will put the weight in the back and add stability when on the surface.

 

[AaronR103]

Hey man. I asked this same thing a few days ago. http://www.scubaboard.com/showthread.php?t=140479

The conclusion I came to out of all of it was that the weight seems to be added either at the bottom, bringing your head up, or at the top, driving your head down, either way it seems like it would be messing with your trim.

A

 

[gr8ful divr]

Thanks Aaron. I guess we are thinking alike. Rather than trim issues, I was more concerned with whether there were any advantages/disadvantages to having neutrally buoyant AL80's as I progress to longer and longer dives. Once I get steel tanks I would want to use these AL80's as stage bottles as Brett suggested in our other forum. I have seen posts where GI mentions floating empty stage bottles to the surface during decompression rather than carrying them. Obviously this wouldn't be possible with neutrally buoyant tanks. Just wondering if there are other less obvious advantages/disadvantages to neutrally buoyant AL80's. Are there any DIR divers using them? If so, in what capacity?

 

[donacheson]

... I have seen posts where GI mentions floating empty stage bottles to the surface during decompression rather than carrying them. Obviously this wouldn't be possible with neutrally buoyant tanks. ...

Without reading GI's posts, will Al80's float (when near empty) with valves and with regs attached?

 

[JeffG]

Once I get steel tanks I would want to use these AL80's as stage bottles as Brett suggested in our other forum.

Then you don't want those tanks. Just get the regular luxfer AL80's.

 

[JeffG]

Without reading GI's posts, will Al80's float (when near empty) with valves and with regs attached?

Yes

 

[lamont]

Without reading GI's posts, will Al80's float (when near empty) with valves and with regs attached?

definitely.

 

[DIR-Atlanta]

I guess we are thinking alike. Rather than trim issues, I was more concerned with whether there were any advantages/disadvantages to having neutrally buoyant AL80's as I progress to longer and longer dives.

No advantages that I can see, and several disadvantages - the buoyancy characteristics of the NB80s are much closer to those of steel tanks than to the traditional S080s, so the issue of "balanced rig" comes into play. If you are diving wet, then using NB80s (particularly as doubles) may cause problems with being too negative at depth.

And as JeffG pointed out, if your goal is to use the 80s as stage bottles after you move on to steel doubles, then you definitely don't want the NB80s for that. Negatively buoyant stage bottles are a big no-no - they mess up your trim and hang below your body line. The standard S080s are just about perfect with respect to buoyancy, so that is what you should start with now - that way you don't have to re-purchase later as your diving progresses.

 

[lamont]

No advantages that I can see, and several disadvantages - the buoyancy characteristics of the NB80s are much closer to those of steel tanks than to the traditional S080s, so the issue of "balanced rig" comes into play. If you are diving wet, then using NB80s (particularly as doubles) may cause problems with being too negative at depth.

And as JeffG pointed out, if your goal is to use the 80s as stage bottles after you move on to steel doubles, then you definitely don't want the NB80s for that. Negatively buoyant stage bottles are a big no-no - they mess up your trim and hang below your body line. The standard S080s are just about perfect with respect to buoyancy, so that is what you should start with now - that way you don't have to re-purchase later as your diving progresses.

OTOH, i've been thinking about a set of double al80s to compliment my existing steel doubles and the neutral 80s would be cheaper than double LP80s or double HP100 steel tanks, and I wouldn't need some obscenely big v-weight to get them down like i would with the standard double al80s...