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> So now you have to remark the line? or bin the whole line? > as the markings are now out of calibration? How about just cutting it off to the next mark? It isn't like I'm likely to be diving for a little while so I have time to figure it out. Besides, retired wreck line is pretty good for crabbing and stringing ham radio antennas. > - I just see all this line marking as a convolution and a > source of confusion. That is because you really don't understand what I am up to. Identification of objects well off a wreck and identifying the positions with range and bearing from the wreck is the goal. The stuff about marking the line for zero-viz deco just wandered in. I don't even know if it is practical. Saturday I was over 150 feet off a wreck in about 10 feet of vis. Most of the stuff close to the wrecks around here has been picked over. > yes, the distance line would be used - but I would know how > long it took to get out there & hence back. I don't do radial searches. I do circular sweeps with a line. They let me cover a hell of a lot more ground. It trashes any attempt at dead reckoning on the bottom, so the line gets pretty important. If the current is getting to be an issue, I either call the dive or only work up current of the anchor. If the line breaks, I take a compass bearing on where the line was coming from and swim that way for a while. It hasn't been an issue since I don't let line get all that old. > If we couldn't get back to the wreck for what ever reason, > cut the line & ascend. In this case use the spool & DSMB > (Plus buddy has a DSMB to) See above. > Navigate by pilotage & compass - the turn pressure is just > that & do reciprocal bearing/direction That's useless on a desert bottom in low vis for any search pattern other than a very simple one. Dead reckoning is hard enough when you're only making a couple of turns. Do thirty turns with a little current and the picture turns to crap. Pilotage on a featureless stretch of sand while searching is so shaky as to be a waste of time. > | Now I _really_ don't like it. One of the things I want is > a "gofer", not > | someone on the same profile as I am. > > huh? I said most idiots have a hearing loss. (kidding) I *always* want someone on the same profile as I am + > next to me. I never said "no buddy." I want someone who can go up to the boat and report to the divemaster/captain/dive leader how I'm doing. That is in addition to a buddy. > We don't do 'same ocean Buddy' over here. The reports I'm reading indicate otherwise. _Every_ area has what we call cowboys. > | Didn't you _just_ lose three people wreck diving in the > Firth of Forth? > > Can't comment as I don't know the circumstances - what > happened? Mid May. 2 dead. 1 presumed dead. It's on the public safety list. > We don't anchor to the wrecks. We have (usually) a large > weight, which is precisely dropped on to the wreck, allowing > for the tide. Our Skippers pride themselves on getting the > part of the wreck the divers want to explore. You can see > the line on a good color sounder, going down onto the wreck. > The line has a large bouy & a trailing smaller bouy (the > size of a soccer ball) so that the direction & strength of > the tide can be determined. That would get blown into oblivion around here much of the time unless the weight was really heavy. I was on a very shallow dive the other weekend where I had to end the dive because the current was getting to be too much to handle. Getting the hook out of the wreck was quite a ride. > Even though the rough time of slack water is known, this is > still only a prediction. A skillful Skipper will 'shot' the > wreck & estimate the exact time of slack water - the smaller > bouy usually gets dragged under due to the tide. When it > resurfaces, it is safe to dive. We usually only get a tidal > 'slack' window of around 30 minutes in the English channel - > sometimes a bit more > on a neap tide & sometimes less or no slack on a spring. Ah, now I understand what you're up to. The length of the boat rides and steady currents around here force us to be much more open minded about the current we dive in. Some wrecks never cut us enough slack to allow that procedure. On some wrecks, losing contact with the wreck is a serious problem since you are going for a fast ride away from the boat and may surface beyond the horizon. I don't dive those when the current is ripping. You should at least be able to predict if the current is going to be increasing or decreasing during the dive. The exact time of slack water is nice to guess at, but the start of the dive can be altered to suit the conditions as found. Every once in a while I see a report of an anchored small boat planing completely underwater at the Chesapeake Bay Bridge-Tunnel. I've never seen it, but I can sure believe it. NetZero Platinum No Banner Ads and Unlimited Access Sign Up Today - Only $9.95 per month! http://www.netzero.net -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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