FIXXERVI6 once bubbled...
ok.... how about double aluminum 100's, just about the same bouancy as 80's.
would a 45# wing be good enough for double 100's and an aluminum back blate?
Okay, I'm a little late to this thread and everything else has pretty much been covered with lots of pretty formulas and calculations to back it up.
One thing that I think has been neglected is dissimilar tank turn pressures. What does that have to do with anything? EVERYTHING!
If you are planning to dive strictly recreational limits then double just about anything is probably overkill. You could easily overstay NDL's even with nitrox with a large enough capacity of gas.
If you are planning on doing tech diving, then you will be doing some sort of overhead environment, whether it be cave, wreck, or simply an obligatory deco ceiling. Regardless, O/E diving demands that you set a gas turnpoint for your dive.
Even if you have the biggest baddest set of tanks out there, and the other person(s) on your team have puny twin 72 setups, then
you will still be turning the dive based on the smallest supply of gas
Example: You have twin 120's (240 cft) your buddy has twin 80's (160 cft) and we are assuming tanks are filled to working pressure. Rule of thirds is minimum for O/E diving, so basing off the smallest size(160/3) equals roughly 53 cft. So the first one of you to use 53 cft will be calling the dive and all of that extra gas in your tanks will be of virtually no use.
If that is the direction you are headed in, it makes more sense to think of gear selection like this as a team so it simplifies the dive planning.
And if you are heading to Florida, it is fairly easy to rent doubles there in common sizes.
Spectre once bubbled...
Hmm.. never heard of _that_ method. How many dives have you logged on that theory? It seems a bit aggressive to me, as the original 120 rule was in the old navy tables, designed for divers in impeccible shape with chambers close by.
It's been around for a while. I *believe* its the method that GUE teaches as a way of keeping track of NDL on the fly. Perhaps MHK could enlighten us on the accuracy of this statement?
I've done numerous dives based on this theory now. Keep in mind that it's based on
max depth and it's really most effective in the 50-100' range. Exceeding the table limits incurs a deco obligation of roughly one to one.
For most recreational divers, I think this is good information to know in case of a Charlie Foxtrot with their computers. I wouldn't advise it as the sole method of dive planning without some deeper understanding of decompression mechanics.
Karl_in_Calif once bubbled...
Spectre, if you need to lose weight fast, try this:
Breakfast: 1 hard boiled egg, one glass OJ, one slice dry toast.
Lunch: 2 slices bread, one lettuce leaf, one sliced tomato, one glass lowfat milk.
Dinner: one half cup cottage cheese, pepper, garlic salt, one glass apple juice.
Do that for about a month, and you will be packing argon into your drysuit during deco hangs as well ! 
Water temps has nothing to do with it. But for the record, our water temps vary from 40^F to 60^F seasonally. And that is warm, compared to the Pacific Northwest.
Water temp has nothing to do with it???? What does weight have to do with it? Weight is
not a good indicator of body fat, and body fat is what aids in thermal insulation. Of course you dont
need a lot of protection unless the water temp requires it.
Planning the dive with proper exposure protection, which includes undergarments would seem to be much more critical than weight.
I'd like to see what someone from the PNW thinks about this statement.
Unky Pug? Are you reading?
