Creed
Pro Diver
Posts: 189
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Post by Creed on Nov 6, 2005 12:09:50 GMT -8
I suppose people on a budget have to do with what they got as they begin vintage diving. In that case, the cheapest thing to do is simply to have the 80 filled to 2250 or so instead of 3000.
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Post by SeaRat on Nov 6, 2005 16:36:15 GMT -8
"You might not want to use that tank at 3000 PSI with the DW Mistral, it can damage the reg." Yeah, I caught that too but there was a thread some time back and I guess some people have tried it. The bad thing is that Mistral seats are rare and expensive. I just got a brand new one to save for a rainy day. I think much use at 3000 psi would damage the seat. I would not put my Mistral to that abuse anyway... I think it is diffucult to imagine how someone not from the vintage era could/would be mislead by "modern" diving practice and training and how much actual misinformation exists out there. I have in my hand an old Skindiver from 63 where there is a Nemrod adv. and the copy reads , "C'mon in... the water is fine". The lady has a wonderful looking wet suit and a strange looking single hose with a J valved tank. The fellow has a double hose also on a J valve tank. If I had to guess I think the picture was taken at Alexander Springs Fla. They have no BCs, no MaeWests no nothing. I can see their J rods and their simple tank harness, this is like a time warp---the way it was. I notice he has no weight belt and she has a weight belt slung low on her hips. Has anyone noticed that nowadays people wear the weight belt cinched up under their arm pits very nearly? When I use a weight belt I leave it so loose it barely is prevented from falling off my hips so that it sits below my tank waist strap. I suppose in the pre BC era the loss of a belt was no big deal because you did not have the super SeaKinght supercharged 25 D ring 75 lb lift BC engulfing your person that would rocket you to the surface. The contrasts are amazing.James Nemrod, when we lost our weight belt, we simply swam down and retrieved it; in those days, 1) I was thinner;) and 2) we carried a lot less weight. I used about 16 pounds in fresh water and 22 pounds in salt water in the 1960s and 1970s. We were good enough swimmers that we could get down pretty easily once we got our fins underwater. Weight belts now are being worn under the scuba harness too. That means that they cannot be dropped in an emergency until the scuba come off. A careful reading of Bernie Chowdhury's book, The Last Dive will show that Chris and Chrissy Rouse were unable to ditch any of their equipment during their emergency, and these guys had to be hauled up over the ladder of The Seeker fully geared, which made their recovery very difficult. Chrissie was pulled on board with all his gear on, but Chris was unconscious at the time. Here's the description form the book of the attempt to get Chris Rouse on board: If you haven't read this book, it is very instructive of the technical diving community. John
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Post by seakrakken on Nov 7, 2005 0:25:08 GMT -8
Isn't this the same group of divers that think it's a great idea to wrap a hose around your neck? I guess I shouldn't criticize, I've dabbled in closed circuit homebuilt O2 rebreathers and think it's the neatest thing since sliced cheese ;D
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Post by nemrod on Nov 7, 2005 11:18:21 GMT -8
Yes, they have a madness to their method or is it a method to their madness? In any case their methods do make some sense to a point. The methods and equipment they use is all about redundancy and reducing failure points and streamlining and does it surprise anyone that this methodolgy grew and evolved in the early cave diving community. In the early mid 70s I went to college at Valdosta State in Valdosta Ga. This is on the northern limits of cave country. I quickly fell into this group and began cave diving with very primitive gear. The roots of what is now called DIR fast became "the right way" and to this day it remains much the same with some minor changes. Obviously there are new sorts of equipment and all that but still DIR divers rely on the tables and don't use computers in their purest form. The long 7 foot hose is specifically used to allow a diver to breath from his buddys tank in narrow passage ways where he must trail or lead and also allows the diver to remove gear and still keep the second stage. There are various ways of stowing the long hose but regardless it is still a cave diving technique and while not dangeous in open water it is not needed. These guys do not vary their set up other than going from double to singles etc--they always dive the same configuration and methods. They are all about team diving and are exactly the opposite of solo divers. Most of the DIR group are just regular guys but their is a core group of fanatics for lack of a better word who think their way is the only way and obviously that cannot be true--here. Here is an example beyond the long hose, the spg must be on a 19-22 inch hose, the reglators must be able to be taken apart underwater, the knife must be small and be worn on the left waist strap, the equipment must be black, tanks must be natural finished and have no stickers on them (lol) and it goes on and on even to the exact position and design of D rings. All this info is readily available on the net and of course some of us were familiar with the earlier versions since we were there. Cave diving is dangerous, it can be fun and requires disipline and is very equipment oriented which is what may attract many cave divers secretly but I no longer cave dive. I still think back several times I should have died. I think back the bodies I saw being pulled out while we were camped near Genny when it was just in the middle of the woods and I have no desire to go back into them again. James
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frank
Regular Diver
Posts: 12
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Post by frank on Nov 7, 2005 17:36:55 GMT -8
SeaRat gave us a quote from "The Complete Manual of Scuba Diving" by A.P. Balder, Mr. Balder states in part: " ANOTHER WARNING: Do not depend exclusively on your reserve system to call your attention to your low air supply. Be the kind of safe diver who can predict by his own deductions just when his air will be nearly exhausted. " I havn't seen it discussed on this site but there is a big difference between the "feel" for low on air that you get with a DW Mistral or Voit 50 Fantom than with the more sophisticated, balanced regulators like the Royal Mistral and Royal Aquamaster. The difference with the balanced regulators is much more subtle, if you don't pay attention you can breathe through your J-valve reserve.
Frank
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Post by seakrakken on Nov 7, 2005 22:49:46 GMT -8
Frank, In the days of "OLD" divers did some math prior to hitting the water. Math which was intended to give the diver an excellent estimate of their air consumption and just how long their supply was expected to last given their proposed diving plan profile. This math has been discussed on this forum in other threads and is readily available for download out of the Navy Diving Manuals. I don't know your experiance or training level so, please forgive me if come across offensively I really don't mean to... It seems alot of this math has been dropped from the modern courses and it really needs to be brought back. Knowing your own breath/lung capacity and aspiration rates/minute is the start of the biometrics needed to play the game. Next start calculating your air consumption rate at any given depth. Then make a dive plan/profile which enables you to "By the Numbers" safely descend to planned depth with a predetermined dwell time and then be able to ascend and have a safety deco stop with a comfortable reserve left over after it's all done. This was how it was all done when there were no SPGs or J-valves. I deleted the next three paragraphs of my post to spare everyone from boredom ;D
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Post by duckbill on Nov 8, 2005 1:41:23 GMT -8
The difference with the balanced regulators is much more subtle, if you don't pay attention you can breathe through your J-valve reserve. Frank I would suspect a problem with the J-valve seat if I didn't notice the restriction, balanced reg or not..
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Post by Captain on Nov 8, 2005 6:29:16 GMT -8
In several old J valves I worked I found the nylon seat deterioated and had to replace it. Some of the very early ones have a metal ball shaped seat and they do not go bad.
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Post by SeaRat on Nov 8, 2005 18:59:21 GMT -8
I have a number of J-valves, and all restrict very well. On my double tank units, the J-valves are good enough that I can leave the reserve up, drain the units of all other air, and disassemble the valve. When I get it put together again, I can trip the reserve and get the 250 psi in each cylinder. My UDS-1 is similar, but shares the reserve cylinder with two other cylinders, rather than one. One tech diver I dove with using my UDS-1 was startled when I showed him my SPG, and it read barely 200 psi at the end of a 90 foot dive. Then I tripped the J-reserve, and I was at about 650 psi. That made him feel better.
A very good, balanced two stage regulator will allow you to breath the tanks down to the reserve, or if it is tripped (or if you use a K-valve), to nearly zero pressure. Therefore, you need a well-maintained J-valve if you have no SPG, even in shallow water, with a well-maintained balanced two stage, double hose regulator.
My UDS-1 is the worst on this count; I can breath it down to about ten breaths without registering any breathing resistance. But it has a great J-valve, and accomodates a SPG too.
The UDS Mistral can be breathed way down, and is at its easiest breathing at about 500 psi. Those who never get a tank below 500 psi miss all the benifits of the single-stage, upstream design. When you think you are in regulator breathing heaven with a Mistral, you're just about out of air!
The AMF Voit 50 Fathom regulator is a single stage, downstream regulator. It gets slightly harder to breath at low tank pressures (or a lot harder, if you use it as the factory set it up--the large orifice needs to be pointed down the intake hose.
The Healthways SCUBA regulators, at least a lot of them, had a restrictor orifice built into them, which made them difficult to breath at about 300 psi unless you ascended.
John
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