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The Atpac was a BC with a wing and the backpack had a chamber where you could put lead shott. The bottom of the backpack was hinged so you could open it and all of the weight would in theory dump out. Basically one of the first weight integrated BCs.
So was it any good? I read something about in its day be labeled as 'dangerous' - and many shops didn't want to sell it because Watergill had recommended new buyers to receive training in its use - kinda of like what Dacor did with the Nautilus.
Sure wish I had one of those Nautiluses these days. They seem pretty cool.
Did you read the info about the Watergill FailSafe Regulator?
"It is two balanced piston regulators in series to form one big regulator. Either piston can fail and the regulator will still work. The Failsafe System regulator would also sense if the diver stopped breathing. Pressure would then build in the first stage, and slowly inflate the BC automatically, bringing the unconsious diver to the surface."
Thats neat! Home come all these cool innovations never carried into the 1990's? Seems the Dacor Nautilus and Watergill AirPac are pretty cool pieces of gear.
While scuba gear has come a long way since those days in some ways I think a lot of the older gear was very innovative and based on some sound idea's. Sad that many of these things are no longer around...
For instance, the new Aqua Lung Mistral double hoser. Its built on a Titan that has a 'cheesy-looking' silver finish on it - its not even chrome finished. $900 US Dollars for a regulator and it doesn't even have a chrome finish and has a bunch of plastic on it. How disappointing. At least the DA's had metal boxes and parts!
I used an AT Pac early in my career (mid 80's) and was actually quite happy with it even though it was considered obsolete then. I was even happier when the obsolete BP/wings and back inflate BC concept came back into vogue. The At Pac was very much an ABS BP wing in form and function with the exception of the chamber in the plate for the shot. (see pictures)
The At Pac used a 8 inch long 2 pronged pin to hold both sides of a stainless steel door in place at the bottom of the shot chamber. (see picture)
The "dangerous" reputation came from two problems.
First was a tendency for the shot to hang up in the opening of the door as over time the relatively large shot (about 1/4" in diameter) would settle and tend to form an arch so that most of it would stay in the pack in an emergency. It's really hard to bounce up and down and shake it loose in midwater. The shot chamber was large enough to accomodate a LOT of shot, so most people only needed to fill it about half way. This caused problems with the shot shifting so Watergill resolved this by using plain old glass marbles to fill the unused space. The larger size of the marbles however would agravate the problem of arch formation, so they had to go in first with the shot underneath which made changing weight a true PITA. But once the weight was adjusted, it was an innovative and very effective system, assuming you never had to dump all the shot in an emergency.
The second problem was more serious as the over pressure relief valve was built into a fitting that accomodated the corrogated and LP inflator hoses. (see picture) It was a little small and if you got into a rapid ascent with the 45 lb wing, it was theoretcially possible to blow the seams on the wing as the air would expand fastert than the OPV could vent it. The resulting negative bouyancy from a ruptured wing then made the problem of the lead shot not wanting to leave the pack, even after you pulled the pins on the door, a very personal and alarming problem. Consequently, I did not know many At Pac divers who put all of their weight in the pac itself. We put about half our weight in there and considered it permanent.
Along the same lines, after retiring our At Pacs we also filled the plastic hardpacks on the conventional BC's of the era with shot as well and carried about 10 lbs of shot as non ditchable "integrated" weight long before the term became popular.
A third safety concern with the At Pac is that the seams on the bladder in fact had a tendency to separate once the bladder got old. One of mine died this way.
Another potential problem is that some At Pacs (I'm not sure if they were early or late production) used a plastic inflator/OPV fitting that had a tendency to crack and leak where the quick disconnect attached. This led to the early retirement of many At Pacs. My other one died this way and the remaining functional At Pac I own is a combination of the bladder off one and inflator parts off another.
The streamlined fairing that went over tank and wing is pretty cool and is very similar to what is now seen on some rebreathers.
DA Aqua Master,
Very cool! Thanks for the nifty explaination. Sounds like it was a innovative idea but had a few shortcomings.
I'm quite interested in the Dacor Nautilus rig. ew1usnr had mailed me a copy of a diving magazine's review of the Nautilus when it was introduced and it sure sounded nice. Last summer there was a nice one on eBay for sale and I missed placing my final bid on it and hence lost it. I'd love to have one still and keep looking every chance I get.
I'd love to show up on a dive charter or do a shore entry dive and have divers look in amazement while I donn the Nautilus! <ha!>
The "dangerous" reputation came from two problems.
The second problem ....
A third safety concern...
Another potential problem ...
Hey, come on, Aquamaster! Sweet ol' Grandma may have some gas, but there's no need to tell everyone about it.
I dived my AtPac from '71 to '78, and when I got back into diving went quickly to the "new" BP/Wing because (I said) it made sense, and because it felt so much like diving my AtPac.