6.9 vs 7.25 vs 8.0

[Nemrod]

Those are the common tank diameters approximate. Yes, I have a Faber 85 steel that is more like 7.1 but ya know how it goes. My question, Phoenix aside for the moment, has anybody noticed any real breathing difference--same regulator and same approximate up/down positon. In other words, do you notice the regulator harder to breath with the larger diameter tanks?

Now, the Phoenix, being longer sits on a 7.25 or even 8.0 tank like a standard RAM/DA sits on a steel 72 of 6.9 diameter. Do you gjuys notice any real difference?

One of the reasons I bring this up is it is a pain in the rear to constantly be adjusting my harness cambands for different size tanks. I am thinking to standardize. I could use my aluminum 80s with 7.25 and also get a couple of lightweight 65s also 7.25 diamter. I have never been an air hog and a 63 can get me into deco in some cases. It would certainly entertain me and my wife on shallower divres to 60ish feet. Dives to 100 feet, use an aluminum 80 and dives over 100 feet--well---that is another story.

Nemrod

[capn_tucker]

Well, I've tried my Phoenix with 72s, 80s and 100s, and it works great with all of them. I use the 100s most often as they are 3300psi tanks, and I'm the king of air hogs. With an 80 I'm always the first one back in the boat. And I wouldn't have any kind of bottom time with a 72 unless they're twin 72s (which I'll soon be going to exclusively, as I'm getting a really hard time from the dive shops with the aluminum 100s; they're the "infamous" pre-88 type)..

[Bryan]

I'll get a few rocks thrown my way.....As soon as I figure out what J valve will work with these cylinders I'm going to use them almost all the time. The size is just a little larger than a AL 50 and I know it weighs more so I would not need a weight belt most of the time...Brittnee has one I have used it a few times and I think they are great.

http://www.bluesteelllc.com/products.htm

I'm talking about the FX80DVB

[1969ivan1]

WHAT! Next you are going to be wearing a bcd with 40 d rings and pink tusa fins? What are you going to do for a harness?
Allan and I used our old 72s and hung with all the modern divers in the st lawrence...................no problem. It may have helped on one dive when I jumped in with my doubled 72s pumped to 3000 by Moe Hunt's dive shoppe . I guess Moe's wife was distracted by my bedroom eyes? I am glad the burst disks held .

[luis]

I'll get a few rocks thrown my way.....As soon as I figure out what J valve will work with these cylinders I'm going to use them almost all the time. The size is just a little larger than a AL 50 and I know it weighs more so I would not need a weight belt most of the time...Brittnee has one I have used it a few times and I think they are great.

http://www.bluesteelllc.com/products.htm

I'm talking about the FX80DVB

Keep in mind that a 300 psi reserve in a 72 will give you about 8.6 cu ft of reserve. With a steel 80 (at 3442 psi) the 300 psi reserve will be a bit less than 7 cu ft.

If you are going to get a reserve, I always liked the Scubapro DCAR valve.

Those are nice tanks. Christine has a couple of them. They look like little bombs.

[Nemrod]

I have used those high pressure steels and I just don't like them. I find them very heavy feeling in the water and trim me head down. I much prefer Faber's LP and multi pressure cylinders. Their steel LP 85 is a good cylinder and robust enough to pump to 3,000 at which point you got yourself some air there guy. I just don't like the HP steels, maybe I will change my mind someday. They dive like a have a lead ingot right behind my head, they don't seem to fit in a SeaHunt harness and require trickery to get them low on a BP/wing, don't fit in my Voit SnugPack, so it is.


I am thinking that a Phoenix should position with a 7.25 tank and breath the same as a RAM on a 6.9 tank, the longer body should negate the extra water column?

Nemrod

[luis]

I am thinking that a Phoenix should position with a 7.25 tank and breath the same as a RAM on a 6.9 tank, the longer body should negate the extra water column?

Nemrod

Well the difference in radius is

(7.25" - 6.9") / 2 = 0.175 inches.

The Phoenix is approximately 0.78 inches longer that the original RAM so it would be closer to your back on either tank.

I hope this helps.


I haven’t notice any difference in performance using a steel 72 or an aluminum 80, but as a human I don’t think I am that well calibrated. That is why I tend to rely on instruments.

Also when I was diving my Phoenix with an Aluminum 80 I was in Bonaire…everything just performed better down there…just a shorty, minimal use of a BC, etc. etc.



Oh one more thing… my new theory in regulator performance and human perception is that we do the work with our lungs, but the pressure sensor is in our ears. Therefore, when it comes to perception is the elevation difference (water column) between the regulator diaphragm and the ears that matter, not to the lungs.

IMHO the difference in water column to the lungs matter for actual work, but not for perceived effort. But this is just a preliminary theory based on many conversations with others, my limited knowledge of physiology, and other observations.

[BSea]

The new worthington LP 85 is also 7.25. That's what I have. As you said, you can put 3000 in them, and you end up with almost 100.