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On Sat, 23 Oct 1999, Dave Sutton wrote: > >Double Fabers (neutral empty) with about 100cf of air: 7.8 pounds > >Manifold: 2 pounds > >Bands: 1 pound > >Regulators: 3 pounds > >Aluminum backplate: 1 pound > > About right. > > >Add another 7.8 pounds with full cylinders at 200cf. > > Nope. You doubled the air weight. You included it to begin with at the > top. No. I did not. 0.078 pounds per cubic foot. If you start with 200cf, that's almost 16 pounds of gas. Use half of it, you end the dive with almost 8 pounds. Nothing doubled. > >You start your dive at about -23 pounds MINIMUM, all of it to be > >compensated for with your drysuit. > > Nope. For starters you are off by doubling the air weight. You are wrong there. > Plus, most of it is already compensated by the air in the microscopic > threads of thinsulate insulation. The freemoving air in the suit is > quite small. The thinsulate retains bouyancy even when saturated with > water. I threw my undies in the pool and waited a week (so, it was an > old set of DUI stuff that stank from sitting unwashed for a > week.....). It still floated high and dry. (Still stank, too.....) How much of your buoyancy is inherent in the undergarment, then? > >I've tried using my drysuit this way, and found the amount of gas in the > >suit too large to manage. My neck seal kept burping ... so I use my BC. I > >do know it works well enough to get my backside to the surface, though, if > >my BC fails. > > Well, I believe that the added complexity of the need to manage two > inflation systems is not worth it. C'mon, this is not complex. It was reflexive after a couple dozen dives. And I don't have an extra-large bubble in my suit, which you must, to compensate for the breathing gas used. > Are you wearing -any- weight? Yup. SS backplate plus 8 pound V-weight. I'm weighted so if my cylinders are dead empty, I can still get neutral. I prefer the V-weight to a weight belt for trim reasons. With both a BC and drysuit, I'm not concerned about having ditchable weight. > I need about 14 pounds plus my tools to be negative with all of the > air evacuated from my suit. If you are having a burping issue (no > beans on the boat, please...) and are wearing any lead, you are > off on the wrong track. Don't think so. Can't shed any lead, since then in an OOA I woulld be unable to maintain my stops. Latex neck seal is plenty dry, thank you, but not so tight that it strangles me. I keep just enough gas in my suit to not get squeezed, and I'm plenty warm. The BC gets the rest. > Bottom line: My suit is -nearly- empty at the beginning of the dive > and is even less empty as I use gas. I'll assume you meant "less full" as you consume gas. You must be changing your buoyancy by an amount equal to the weight of breathing gas used. 100cf of air is 7.8 pounds. That represents a bubble about the volume of a gallon of water. Hardly "nearly empty". Furthermore, if your suit is very close to empty at the end of a dive with 1/2 to 2/3 of your gas supply remaining, you are at risk of being unable to maintain deco stops if you consume or loose the balance of your gas supply. > What sort of drysuit and undies are you using? That may be the missing > link here. The majority of my bouyancy, like I said, is in air trapped > in the insulation. Might be your issue too, maybe you should change > yer shorts ;-) I have two suits, DUI CF200 and Andy's Trilam. Andy's Undies, US100 and US200 depending on water temperature. Mostly dive the CF200 and US200 in New Jersey these days. You haven't said anything yet that would lead me to think I need to change anything. -- Art Greenberg artg@ec*.ne* -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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