Mailing List Archive Mailing List Archive
At last a more or less sane answer. Yes air is air and if you breath 6 pounds of air you will be six pounds more buoyant. Yes you need more lead with aluminum tanks than with steel to be properly weighted for a dive. On the other hand, a aluminum tank + the extra lead may be less total weight on your back for a simple recreational dive on the local reef. A steel 95 may be heavier in total than an aluminum 80 plus the extra lead to achieve the same starting buoyancy. Dick In message <330A7D6E.6BDE@ut*.ed*> Jeff Kell writes: > Once again we seem to be flogging the greasy spot in the road where the > horse used to be... > > "Buoyancy" refers to whether you are lighter or heavier than water. If > you are lighter than water, you displace a volume of water equal to your > mass. If you are heavier than water, you displace a volume of water > equal to your volume. Remember Archimedes? > > If you're negative, it doesn't matter much if it's a pound or a hundred, > you'll sink. If you're positive, similar analogy but you float. > > To dive, you must be negative. With [most if not all] steels you are > negative empty or full; with [some if not all] aluminums you can be > positive when empty. The weight of the "air" is fixed. You want to be > slightly negative with an empty tank and empty BC; with Al this takes > more weight than steel [generally speaking]. So you carry more lead > for Al or less for steel; big deal. That figures on your finishing > weighting requirements. HP/LP low/high capacity tanks only increase > the difference in weighting between full/empty, independent of tanks. > But since Al is generally positive, it takes more weight to offset the > buoyancy characteristics to start with than steel which may have you > more or less negative to start with. > > Yeah, they are generalizations, and I'm sure some nit-picking is to > follow. But air is air, not that much magic involved other than Al > takes more weight to offset the *initial* empty positive buoyancy. > After that, all sides are essentially equal for a given volume of gas > at any pressure. > > Jeff Kell <jeff-kell@ut*.ed*> > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send list subscription requests to `techdiver-request@aquanaut.com'. ------------- Dick Barker dickb@es*.co* http://www.eskimo.com/~dickb/ Are you qualified to join OFDA? http://www.eskimo.com/~dickb/ofda.html San Juan Isl Dive Charter? http://www.eskimo.com/~dickb/starfire.html -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send list subscription 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]