Mailing List Archive Mailing List Archive
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? Well, if I have a piece of equipment that is only a handling problem in my garage, I build a fixture for it. I don't base what I wear in the water on how it handles on the beach. I also don't lug around stuff I don't need, wet or dry. > > 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. A common misconception. The diver is trimmed as a total package (unless we are talking about stage bottles). I must weigh one pound for every 27 cubic inches my entire rig, including my body, displaces. It matters not whether the tanks are full of gas, at 29 inches of vacuum or half full of mouse milk. The weight can be anywhere, although I prefer a CG a bit above my waist and that is what I set up for. A Luxfer aluminum 80 displaces 37 pounds of seawater. An OMS steel 85 displaces 31 pounds of seawater. Getting that AL 80 underwater means 37# needs to be somewhere in my rig. Getting the steel 85 underwater means 31# needs to be somewhere in my rig. The 80 weighs about 35 and the 85 weighs about 31, so shifting from aluminum to steel means I remove two pounds from elsewhere in the rig. That means I weigh 6 pounds less on the boat per tank. Double these figures for double tanks. If there is 80 cu ft of gas in the tank, it weighs the same no matter which tank it is in. Since all the other equipment displaces the same amount of water and weighs the same in either case, it falls out of the equation. > >> 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. That post never made it to techdiver. When the discussion got here, it was "AL 80 is the ultimate tank." It isn't. If you're negative and have done everything else to try to fix it, going to aluminum is a good idea since it increases your non-compressing displacement. (Yeah, I know the tank flexes under pressure, but not enough to amount to anything). If you are carrying lead you want to eliminate, steel is a better way to go. That doesn't mean you strap a K bottle on your back, which I think is your point. There are smaller steel tanks than the 104. You might even look at 66s. I've used both aluminum and steel and the difference in overall weight for gas capacity is impressive. That doesn't mean double 125s make any sense at all for me. There is a _reason_ you don't see aluminum tanks in sizes above 100. The weighting gets silly. If your point is that an AL 80 is easier to deal with than a steel 104, I agree. It just didn't get to the techdiver list that way. > 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. I'm never going to poke my nose into a cave, so I'll take your word for it. I can't see myself ever owning a set of 104s. My body composition makes 112s make more sense. > > 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. All of which is the same for steel or aluminum, so it falls out of the equation. One pound for every 27 cubic inches. It's not just a good idea, it's the law. Don Burke Chesapeake, Virginia Shop online without a credit card http://www.rocketcash.com RocketCash, a NetZero subsidiary -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]