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At 11:36 AM 1/8/00 +0000, Mark Dixon wrote: >Firstly I would just like to thank you guys for decoplan - got my copy this >week and I'm really pleased with it. The key factors for me are simplicity, >ease of change of variables and simple range planning. Keep up the good >work! >> Hi Mark, Thanks for your comments. I am actually very excited about the future of this effort. We have some great plans to use this as a tool to promote a solid educational base. I hope to have the help files heavily expanded for the developing upgrade (free of course). >Best of all I can now dive with an understanding of how I have set the >safety factor - which leads to my first question. The first decision is >what gradient to commence using these tables on. >> I have seen several mails on quest addressing this and a very good response by John so you may have the answer you were seeking. I will add a couple points. I recommend something in the order of 30 low and 80 high to start with. I personally prefer a higher surface gradient but this is more likely to generate bubbling at the surface. Actually in our longer dives I surface with greater than 100% which is something that we discussed inserting into Decoplan. Actually I think I discussed it and most people looked at me like I was daft<g> However, we are still discussing some of this for educational purposes. Realistically 100% is really NOT recommended for most people. There is a lot of power in this kind of flexibility but a great deal of responsibility as well. Personally, I will generally run 30/100. I have also played with higher deep gradients ie 40-60 and inserted the deep stops myself. Of course the more you start playing this kind of game the more you open yourself up to risk. I have always inserted my own deep stops but now I have a logical starting place. It is odd how close we were to a logical range despite the apparent "guessing". I will use this max stop depth to give me a starting point and then start a slow ascent from this range. With low gradients and shorter bottom time such as 10-30 gradient and 30 ish BT I will usually abbreviate these stops a bit. For example, I will often start the 1 minute stop and then when it is done restart the next minute and begin my slow ascent. By the time I reach this stop I will have less than 1 minute. I usually follow this until I am within a couple stops of the "real"stop and then back down a bit. Keep in mind that what you are doing is trying to keep a good gradient while reducing the risk of bubbling. As we insert some of the bubble theory etc we can have even more fun with these ideas. The shallow area is the section that is least "justifiable" under conventional thought. I should point out here that on short dives we are usually pretty close to a reasonable decompression. You probably noticed that G's deco was pretty close to that calculated on DecoPlan. Keep in mind that blowing off 10 minutes of a 30 min deco is skipping 1/3 of your deco. To do that on a 15 hour deco we have to lose 5 hours. The risk to long decos is primarily one of exposure (O2, water, waves, weather etc) but in the area we are talking about you are looking at a couple minutes. As for the last part of the deco- In the cave environment on long dives I will do a very slow ascent like the one discussed by George. However, in the ocean on short dives I usually do about 1/4 of my 20' time on the ascent/at ten feet. Practically speaking this is easier and force the slow ascent. Did you read the longer discussion about deco stages that I posted to Quest? This grabs each section of the deco profile for discussion. If not please let me know. I had made the initial (blind) decision to run with something like 80 - 85% >while I get comfortable with the tables - can you elaborate on the studies >you refer to? >>> That is why the default is set in this range. It is a good start. On the Britannic we ran conservative profiles in this range due to the location and my disinterest in Greek chambers<g> Buhlman spent some good time cataloging M-values and consistently found an increased risk in the upper 80% range. I personally have seen a great increase in bubbling near and beyond the 100% range. Best, JJ -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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