roakey once bubbled...
Let's do the math with my 104 setup. I'm diving dry, in fresh water, and all my weight is in the backplate/cylinder combination. Backplate: -6 pounds. Full 104s: about -15 each in fresh water or -30 total. Manifold, call it -2. 6+30+2 = 38 pounds.
Though not a huge margin, the 45 is just fine...
Ok, already coverd the equipment floating on it's own. Higher out of the water? You're calling for almost DOUBLE the lift required? Are we talking about floating ourselves higher out of the water, or if diving trimix are we talking becoming a dirigible and flying back to shore?
Note the requirement for lift is DECREASED with 72s versus 104s, by, taking a SWAG, about 5 pounds, even if all your weight is on the BP. This should make the 45 pound lift wing have plenty of extra for floating you higher in the water without going overboard.
So, if a 45 pound lift wing can float a dual 72 kit with room to spare, it can just as easily float you in a flooded drysuit as well, don't you agree? (and if not, why not?)
An average human head weighs 15 lbs (above water - where most divers want it when on the surface.). So by your own calculations and with no lift coming from a flooded drysuit, 45 lbs of lift is no longer fine and you are breathing through a snorkel at the surface.
From experience, with a flooded dry suit and 45 lbs of lift with a pair of full steel 72's your chin will almost but not quite be out of the water, you will be breathing either the snorkle or a reg and you will be dumping your weights to get yourself farther above the waves lapping you in the face.
Even with an intact dry suit, if you add the weight of your neck, the tops of your shoulders, a inch or two of your chest, the regs (which you left out of your calculations), valves or manifold, and the tops of the tanks then yes, you will find you do in fact need the extra 30 lbs of lift to get you significantly farther out of the water.
It probably is not a concern in a spring, but even when nothing goes wrong in open water with wind, waves, etc. getting comfortably above water is not only nice but at times essential if you are having to wait on the surface for the rest of the divers to enter the water. I have seen a lot of under lifted divers winded from a short stay on a rough surface before they ever got under water, and it is not great to have to recover from the entry when you need to be focused on the start of the dive.
I will agree that 45 lbs is minimally adequate with twin 72's under ideal conditions as I dove with doubles and a 45 lb wing in the mid-eighties. But I also always dove a 7mm wetsuit at the time, so I could always count on a substantial portion of lift coming from it at the surface.
Calculation aside, actually doing it is far more instructive. I chose to go with a wing with more lift as it offerred more support on the surface and had very little downside when under the water. A picture is worth a thousand words and I wish I had a picture of the same diver at the surface with 45 lbs of lift and with 75 lbs of lift just to show the difference.
And as for the "I didn't have my moderator hat on" excuse, I was taught to lead by example and the leading didn't stop just because I was off duty. I think the same should apply here.
If not then everyone would be free to say "Eat me" when ever someone made them mad and would then not have to worry about being disciplined for it because guess what , they just didn't have their freindly polite and courteous forum visitor hat on at the time. It's hard to fault someone else for being rude when you set the example by being rude. In the end it costs you your credibility as a moderator.
