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Scott, you either leave double the amount of gas it normally takes you to scooter ( i.e., drop safeties for each diver at each stage drop) assuming you are prepared to tow each other, or you merely put in the amount of gas it takes each diver to swim, which you will have to figure based on where you can see the line swimming from. Obviously, the best bet is to be able to pull across the floor, even though it is deeper. We have to go with the double the scootering gas method, and pick up full safeties , leaving the partial stages, as there is no swimming out of Leon Sinks, but then we also have a strict towing protocol and always tow backup scooters, and we never toast one scooter completely, but leave enough juice to get back to the last one we dropped if the current one fails. At 85 feet, you can get pretty liberal , but if it were me, I would invest in two more Makos. Propulsion ( speed ) is everything in a bad situation. From: ScottBonis@ao*.co* <ScottBonis@ao*.co*> To: cavers@cavers.com <cavers@cavers.com> Date: Monday, July 17, 2000 11:30 PM Subject: Cave dive planning with scooter >Hi Group, > >I have come across a question for which I would really appreciate some help >from those on the list who are experienced in planning cave dives using >scooters. And I believe that there are probably some of the most >knowledgeable scooter divers in the world on this list. The question deals >with how many safety cylinders I need to stage in a cave and how close to >each other they need to be. > >For our particular situation I can give the following information, and if in >the future this information should change, I can adapt the answers we >determine here now. I am purposely using conservative numbers because, as I >have said in the past, I have this wide yellow streak running down the center >of my back when I'm diving in an unfamiliar overhead situation. And >exploring our "New Little Cave" in Belize, when we're more than a half mile >in, is such a situation. > >The following figures might be typical to use. > >Scooters: (2) Oceanic Mako's running @ 2 mph with an 80 min. burn time. >Divers: Both divers with RMV's of 0.6 cu.ft./min. swimming @ 0.5 mph >and 0.4 cu.ft./min. riding >Back tanks: Double 85's filled to 3100 psi. yielding 200 cu.ft. >Drop Tanks: 80 cu.ft. aluminum's pumped to 3300 psi. >Cave: Drops rapidly and runs fairly horizontal @ 70 - 85 ft., lets >say no current for now. >Deco gas: Oxygen tanks can easily be staged at the cave entrance. > >The scooter cave dive planning rules with which I am familiar require >assuming both scooters die at the point of deepest penetration, requiring a >swimming exit. And subsequently the dive becomes a typical cave dive, so I >must have enough gas for both myself and my buddy to exit. The planning for >this, should it be felt that this is the correct approach, is straightforward. > >But if we have staged tanks as we plan to, they might be, say, 1,500 ft. >apart. And I'm interested in opinions as to how many tanks need to be at >each station. I assume our planning would be such that we could get to the >first set of tanks with 1/2 of our back gas remaining, but then do we need to >have 2 or three tanks waiting? And at each station along the way >subsequently, do we need 2 or three tanks? Or has it been found acceptable >to consider our remaining back gas to be enough of a safety factor in case >there is a problem with one of the drop tanks. (Seems reasonable to me, but >I'm just checking.) I feel that I can't plan on our support divers, being >cave students I certified about a year ago, penetrating much deeper than 1/4 >mile into the cave. And since this is not a supported project, most of the >money I can spare has gone into buying the two Mako's, so I can't afford any >more right now. > >My guess, from the GPS readings of the cenotes with which we are familiar, is >that we probably will not need to penetrate more than 1.5 to 2 miles before >we come out another entrance. But as this is only what I assume (which can >easily make an ASS of U and ME), I'd like to get my contingency planning in >order. I realize that the deeper penetrations, if necessary, may necessitate >additional planning to accommodate the scooters' burn times. > >So any thoughts on planning this type of dive would be gratefully >appreciated. I figure that there is probably more experience with scooter >usage in cave diving on this list then just about any other place with which >I am familiar. Thanks a bunch for your time. > >Take care and safe diving, Scott >
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