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On Wed, 9 Jun 1999, Bruce R'. Miller wrote: > > The other point of discussion involved whether you intended the > LastStopDepth variable to affect the rest of the stops. I don't imagine > that you did. > Hi Bruce, how you been? I figured you wouldn't mind if I posted this, as I saw your question in a thread someone forwarded to me. The answer is no, I didn't intend to do that - it's either a bug or a feature, depending on how you look at it. :) The original idea was to have the last stop depth not affect the other stop depths, because many (most?) people these days do the 10ft stop at 15 or 20ft. More comments below. > From: Mike Beresford [mailto:mberesford@am*.co*.za*] > > As I understand it, the factor is used to extend the time spent, for deco > calculation purposes only, at each entered waypoint. Thus if you use a 50% > factor, and have a waypoint of 10 minutes durtaion, the program calculates > deco as though it were a 15 minute waypoint. Correct? That's pretty much it. Conservatism is not applied to deco stops, of course. > That's all fine, except when the layout of a cave forces long waypoints > during ascent. My usual cave site here in South Africa is actually a flooded > mine, and to get to the 110 m deep vertical shaft we have to swim for about > 8 minutes at 20m in a haulage. So on the way in, the program (at 50% factor) > assumes I'm ingassing at 20m for 12 minutes instead of the 8 minutes I'm > actually there. Fine, that's conservative. But on the way out, won't it > assume I'm outgassing for 12 minutes at that depth, instead of the 8 minutes > I am actually there? In other words, won't the "conservatism factor" lead > the program to believe that I have outgassed more than I really have, and > underestimate the remaining deco time? > Yup, that's an issue, but there's a workaround. Keep in mind that conservatism is pretty inexact anyway, (like all decompression issues), so I wouldn't lose any sleep over it. If you're worried about it, the thing to do is lie to ZPlan and tell it your 8 minute swim is something shorter - 5 minutes or whatever. Of course, if you're using runtime tables, you'll have to make the adjustments to your runtimes manually. Personally, I cut all my tables with zero conservatism. The thought is that it's good to know the minimum amount of time you need to deco if you had to get out of the water quickly. Also, of course, don't forget that Buhlmann stuck some conservatism into the algorithm itself - it only looks liberal because people are so used to padding it, or looking at their dive computers, which universally add some conservatism. Regards, -Will -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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