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Scuba Forum / General / February 2004How Do You Calculate Weight For Singles VS Doubles
I'm going to be switching from diving HP steel singles to HP steel doubles. How do you roughly calculate how much weight would be need with the doubles. Presently I need about 26 pounds with a DUI drysuit and a single HP 100. Thanks, Bob >I'm going to be switching from diving HP steel singles to HP steel doubles. >How do you roughly calculate how much weight would be need with the doubles. >Presently I need about 26 pounds with a DUI drysuit and a single HP 100. >Thanks, Try this site: http://www.subaqua.co.uk/cgi-bin/cylinder-buoyancy.cgi?units=imperial There are various other programs around that do a similart thing. Obviously the key figure is the buoyancy when empty. (You need to be able to hold a stop when both cyclinders are nearly empty). You also need to be confident that your drysuit/bc will support you when the cylinders are full. Doubling up a typical UK 12.2 litre cylinder would mean ~1Kg extra on the weight belt and ~2.5Kg of lift to maintain the status quo. David > >I'm going to be switching from diving HP steel singles to HP steel doubles. > >How do you roughly calculate how much weight would be need with the doubles. [quoted text clipped - 12 lines] > Doubling up a typical UK 12.2 litre cylinder would mean ~1Kg extra on > the weight belt and ~2.5Kg of lift to maintain the status quo. This looks pretty simple to me. A steel HP 100 is a few lbs negative when it's empty. The manifold and bands add a bit more. Add the weight of the bands and manifold to the negative buoyancy of the tank when empty and subtract that from the total weight you normally carry. Don't forget to consider lift and, perhaps, backup lift. When full, twin 100s will require quite a bit of extra lift to be safe. If doubling up 12 liter cylinders mean extra weight, you must be doubling tanks that are buoyant when empty, i.e. aluminum. Steel tanks, at least all I know of, are negative when empty. Lee > If doubling up 12 liter cylinders mean extra weight, you must be doubling > tanks that are buoyant when empty, i.e. aluminum. Steel tanks, at least all > I know of, are negative when empty. > > Lee OMS (Faber) LP steel tanks are neutral when empty. > > If doubling up 12 liter cylinders mean extra weight, you must be doubling > > tanks that are buoyant when empty, i.e. aluminum. Steel tanks, at least [quoted text clipped - 4 lines] > > > OMS (Faber) LP steel tanks are neutral when empty. Point taken. I think, however, he said HP tanks. I could be wrong. Lee >I'm going to be switching from diving HP steel singles to HP steel doubles. >How do you roughly calculate how much weight would be need with the doubles. >Presently I need about 26 pounds with a DUI drysuit and a single HP 100. >Thanks, "Calculate" weight requirement the same way. Drain the tanks to 30psi. Gear up, sans weight belt. Hang 10 2-pound weights on a 6-foot of webbing (spaced about 6" or so apart and secured.) Get in the water, let the 20-pound "belt" carry you down to 10ft. Lay the webbing on the bottom and hold one end. Vent your wing and suit. How many "bricks" are off the bottom are how many "bricks" you need on your belt. Figuring weight by doing math always results in the wrong answer, since your body composition will vary... it MAY give you a fair starting point. --- Rich http://richlockyer.tripod.com/ > Drain the tanks to 30psi. Rich, mate, I sure hope you meant 300 psi.  SignatureMatt matt@gol.com >> Drain the tanks to 30psi. > >Rich, mate, I sure hope you meant 300 psi. Oops. --- Rich http://richlockyer.tripod.com/ |
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