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David, ???? Are you saying that 104 cu. ft. air in a PST weighs LESS than 80 (or 77) cu. ft. in a Luxfer? Some new laws of physics must be out that I don't know about. A cu.ft. of air weighs approx. 0.0736 lbs. so I would say the Luxfer spec looks about right but the PST one can't be. --Rob -----Original Message----- From: David M. Thiesfeld [mailto:dthiesfeld@su*.ne*] Sent: 22-Feb-2001 8:58 PM To: Marv; Don Burke Cc: techdiver Subject: Re: DIHUL, was: Fins question Guys, One of the things I see missing from your discussion is how much the tanks buoyancy changes from full to empty. Look at the abyss tank chart and you will see the PST 104 has a change of 4.6 lbs vs. 5.9 lbs. for the Luxfer 80 (77), now double those numbers and look at the weight difference needed. http://www.abysmal.com/pages/features-cylinders.html Also from looking at this chart I'd say that the Luxfer 80's are going to start swinging positively buoyant closer to 2000 psi than 1100 psi. A doubles manifold may push it down some but not that much. DT > > > Don Burke wrote: > > > From: Marv <ajmarve@ba*.ne*> > > > >> ok > >> first, if you read Pauls post you should have been able to infer that he > >> was discussing the weight of the tanks on dry land. > > > > > > The _only_ place that is true is on dry land. > > um, ok? > > > > For a given gas capacity, a > > diver wearing aluminum tanks is a bit heavier on the boat since the > > displacement of the aluminum requires wearing more weight. > > > only if you breathe the tanks below approx 1100psi, the point at which > they swing positive. > > > > > > >> If you ever tried to lift a set of 104s and then right away move a set > >> of 80's, like i do when im filling in my garage, you would see the > >> difference between the two, > > > > > > That's comparing apples and watermelons. > > Thats what i was saying, that the tanks were different. So much so that > if dry land weight was a consideration, as Paul indicated in his > original post, then the 80s "beat" the 104's. i never mentioned steel > 80's and esp not hp 80s like the pst. There is no reason to bring them > into the discussion in fact because they swim horribly. you guys can > talk numbers all you want, try diving the tanks and then tell me about it. > > > I made up a set of AL 80s and I'm wearing 11# of lead (with a steel plate) > > with a wetsuit in fresh water. I haven't hit the ocean with these yet, so > > my calculation of 17# is approximate at best. As soon as I go dry, those > > tanks will become deco/stage/rec bottles. If I didn't already own the AL > > 80s, I certainly wouldn't have bought them. > > > > Those 104s are a pretty heavy item as steel tanks go. They weigh about the > > same as an OMS 125. > > > > Capt JT wears a set of 104s and more power to him. I haven't asked him what > > he like about them. > > I have a welder and a generator I can lift when I feel the need for a > > hernia. :) > > I think I'll go for 112s when I get to that. > > the 104 is a good choice for cave, where extra buoyancy is a minus. one > can manage to dive them in the ocean,but i dont see them as ideal in the > ocean. > > > The wall thickness on an aluminum tank is so much greater than that of a > > steel tank, the weight of the tank is more and the displacement is more. > > and in the water you have the wt of the valve, the gas, the reg to > consider, along w/ all you other gear. > > Marv > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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