AT-PAC

[JohnA]

First some back ground, I started diving a WaterGill At-Pac in 1978 (prior to that I used a ScubaPro BCP), with a retractable bladder. I used that unit until about 1995 when I swapped it out for a back-plate/wing (not that big of difference).

First, from the first time I saw an At-Pac with a ferring in 1978 until today I still believe they are one of the coolest looking units ever available! In or around 1987 I contacted WaterGill (at that time SeaPro) to purchase a ferring, I was told they had one left but it had a crack on the top (more on that), I bought it anyway but lo and behold never used it. Well yesterday with some time on my hands I pulled out the old At-Pac, laced up the ferring and wing, attached my WaterGill FSDS-100 to it and gave it a preliminary test in the pool. Here are my observations.

After attaching the pack to my trusty steel 72 (with the marks still on the tank for the stainless steel bands from the At-Pac from years ago), lacing in the ferring, I attached the regulator and then attempt to latch on the other half of the ferring. For some reason I can’t seem to get it to properly latch, as if something is blocking it, guess what, it’s the regulator yoke knob! I readjust the bands moving the rig higher up on the tank and it still touches but can be closed. Now I know why the ferring was cracked from the factory, these ferrings were molded before WaterGill produced this regulator and the fit is off. It would work fine with a smaller yoke knob, like a ScubaPro MkVII.

Okay, now that I have it together, off to the pool, with the 72 steel and in fresh water w/o a wet suit I needed no weight in the pack. FYI, this is not a unit that you want to forget to turn on your air, once the ferring is in place you have absolutely no access to the valve. It is a bit cumbersome to walk with unless it is on your back, hand holds are not great. Once in the water your head will continually hit the back of the ferring in any position, annoying to say the least. I swam back and forth in the pool and could feel a slight drag, when pushing off the wall to simulate a current you can really feel the size of ferring on your back. On the surface I fully inflated the pack and was lifted up to my waist! (a bit higher than my 30lb Halcyon wing!). Without weight in the pack and fully inflated you have to fight the unit not to turn you on your face, but once you reduce the air in the wing it becomes just like any other small wing

It was a good test, it pointed out some short comings of the unit before I attempt a beach dive with it later this summer.





Other observations, my standard regulator for years was the Watergill FSDS 10 (mk 5 clone first stage) but in this test I was using the FSDS-100 which was Watergill's “fail safe” regulator with 2 partially independent piston 1st stages in one block that was designed to automatically inflate your At-Pac if you stopped breathing or if your tank psi fell below 500. Well, I have never been able to get it to actually work; the factory set up is for the primary side to have an IP of 160 and the reserve side to have an IP of 210, when you stop breathing the high side leaks into the low side and over pressures your down-stream power inflator. I put the regulator on the bench and find that the low side is only showing about 120 and the high side is 145 psi. So I disassemble the unit and wipe it all down, re-lubricate all the o-rings and reassemble. By just doing that I was able to get the low side up to 140 but the high side went to 230! Yikes, considering lp hoses are only rated at 250. No wonder you don’t see many of these regulators around. Base on the high side reading I don’t believe I will ever actually used this other than in the pool.



John

[luis]

Thanks for sharing.

I always thought it was an intersting device. Never liked the idea of the automatic inflating regulator.

[JohnA]

I still believe the FSDS 2nd stage is smoothest breathing regulator ever produced, it may not have been the highest performer, but it breaths like silk, it was rated “C” by the US Navy. Some of the performance problems may be attributed to the poor performing 1st stage, which has a pretty significant ip drop when you breathe from it, about 40 psi (same with the FSDS-10). I hooked up the 2nd stage to my Apeks DS4 1st stage in the evening (the Apeks drop is only 5 psi) and cranked the ip up to 160 per WaterGill spec, and I will take it beach diving again set up on that first stage and see how it works. My guess is that the 2nd stage is starving for air due to the poor first. BTW, don’t tell my wife I have all these extra regulators!

John

[SeaRat]

Interesting...I would think that they would have designed it so that it would not hit the back of the diver's head. I have the Dacor Nautilus and the USD UDS-1, and neither of those will hit the back of the diver's head. You might want to let a bit more webbing out for the shoulder straps, and cinch it down at the waist to hold it. But that may also allow it to float in an odd shape, so try it in the pool and not open water.

John

[JohnA]

Remember that this was the first unit built that used a fairing (spelled Ferring in the WaterGill price list?) to cover the tank. The UDS-1 avoided the problem with short tanks, Dacor (and ScubaPro) kept the fairing below the tank valve, reducing the size by close to 10".

Last weekend I took it out for a beach dive and wrote myself a report:

I entered the water and let the pack settle down; I must dumped some air from the wing so as not bob in the water. I am only using a rash guard, so the weight box in the pack is empty, with a steel 72 I require no weight. I put on my jets and start surface swimming on my back to the reef. First thing I notice is really a lack of drag, which was common when on your back swimming with the WaterGill wing w/o the retractable bladder, but I does roll a bit from side to side. I was half way to the reef but the water was so clear that I decided to drop down and swim underwater the rest of the way. I deflated the wing and dropped to the sand. Adjusted the pack on my shoulders since the unit has a tendency to ride up on the surface due mostly to the excessive buoyancy of the 60+ pounds of lift.
As soon as I start to swim I immediately noticed (again) that swimming horizontally you are forever banging your head on the top of the fairing, to avoid this it would be necessary to put some weight in the pack, so as to swim in more of a 45 degree angle, something I noticed in the pictures of divers diving these fairings in the old NASDS text books. So I adjust a bit to a more "heads up" position and start to swim around the reef, problem solved. Also, as you exhale, again swimming horizontal, you can hear the expelled air going into the opening of the fairing and exiting out the bottom, this also has a tendency to give you a see/saw effect as the air exits, it is also noisy. What I don’t notice is any drag, whether my imagination or not, but it feels as if I am moving cleaner through the water, but I was diving in virtually no current.
Not to rub it in for those of you that live north, but that day on the ocean was perfect, water temp was at least 85, flat calm, clear, and I only ventured out to the beginning of the 1st reef, less than 100 yards off shore.

John

[SeaRat]

John,

I am envious. It is 98 degrees out here in Beaverton, Oregon right now, and was 102 yesterday (very uncommonly hot here). I was in 80 degree water today too, but it was an outdoor pool. Visibility in the pool (after they added chemicals) was about 15 feet). But I enjoyed some snorkeling anyway.

Keep trying the Watergill ferring (did I spell it right?). The literature on the Dacor Nautilus states that it takes about seven dives to get really comfortable with it, and I suspect that the same is true here. You may have a bit lower profile than the Nautilus too, as it has an air space of almost two inches between the tank and the other side of the unit, due to the fact that it has to provide a continuous air field for the unit to operate correctly. Yours has the bladder, which makes it work much differently. But with time, you may grow to love that unit. It certainly is an eye catcher.

John

[JohnA]

Yes. The one she has now is for me! Let me know if she wants pictures of the others. She has my email

John

[JohnA]

William,

I sent her everything I had yesterday. Let me know if she got them.

John

[nikeajax]

Okay, I stumbled and tripped when I found this thread! Kinda stunned still I know DD needed to see this thing: yeah I know, now yer totally PO'ed at me cuz this thing is way boss an' you need one... MUHAHAHAHAHAAA!

JB

[diverdon]

Jan 9, 2017 17:44:53 GMT -8 nikeajax said:

Okay, I stumbled and tripped when I found this thread! Kinda stunned still I know DD needed to see this thing: yeah I know, now yer totally PO'ed at me cuz this thing is way boss an' you need one... MUHAHAHAHAHAAA!

JB

You have NO idea    what I would give for that...

Thanks, JB! I agree, it is cool!

DD

[SeaRat]

I did not ever use an AT-PAC, but do have a bit of information on them. They used a lead shot system for weights, and I have heard that if this system is not taken care of and the lead shot removed periodically (like after every dive), the shot can become stuck together and will not release.

Overall, it is a pretty good system, and have a friend who used it for several years. But, and this is a big "BUT," I also know of one fatality that occurred in the 1970s in Clear Lake, Oregon apparently attributed to both lack of training and the use of an AT-PAC. The diver went into the water thinking the AT-PAK was hooked up, when the inflation system apparently was not hooked up. He was also overweighted, and sank to the bottom in about 90 feet of water. He could not get back up, and may not have had his regulator in his mouth when he entered the water, but the divers found his body on the bottom. The weights had not been released. All this is "hear-say" information, coming through the dive community in the 1970s, so I don't know how much weight to put on it.

So even if this is bogus information from way back, be careful with any AT-PAC to ensure that weights can be released, and that the inflation system is hooked up. (This goes for any diving system, even our vintage diving, where some still wear their weight belt under their vintage harness, just because it was done on Sea Hunt.)

The Dacor Nautilus, which both Don and I have and use, has a solid weight system which will not hang up when released unless there is a tank boot on the tank. By the way, I think of these as the beginning of modern diving, and not a vintage diving technique, as they had integrated, push-button inflation systems for buoyancy control.

John

[nikeajax]

John, if and when I get a Nautilus, could I use iron weights instead? I realize I'd have to custom make them, but I realllllly don't like the idea of using lead. I guess my question is, does it have a large enough compartment needed to use iron because I'll need more space?

JB

[SeaRat]

Jan 11, 2017 15:32:17 GMT -8 nikeajax said:

John, if and when I get a Nautilus, could I use iron weights instead? I realize I'd have to custom make them, but I realllllly don't like the idea of using lead. I guess my question is, does it have a large enough compartment needed to use iron because I'll need more space?

JB

Jaybird,

Unlike rhe At-PAC, the Dacor Nautilus uses a chute system, with solid weights instead of lead shot. Here's what it looks like underwater:



Note the weights are not rectangular, but rather have one flat face and one curved face, allowing the to slide easily inside the chest.


Here the Dacor Nautilus is free in the water, floating far enough out of the water to keep my Trieste II from free flowing.

The weight mold is made for lead, and fits the cause of the Nautilus well. I've found that the weight system is very sensitive, and so need to be very careful. See this funny YouTube Video to see what can happen.


Concerning the use of lead, in its solid form it is not much of a toxicity hazard. If lead is heated well above its melting point, it can vaporize, which then condenses into a very fine fume, which can be breathed. This is why I use a respirator with a HEPA filter (PM-100 filter), which filters any particulate greater than 100 microns, when I mold lead.

Iron weights could be used if they fit into the weight chute in a manner which allows their easy release. But while the weight chute holds 16 pounds of molded lead Nautilus weights, if lead weight belt weights were side (which I did for several years), I could only use 3 pound weights (for 12 pounds total). If iron weights were used, you could probably only use about ten pounds in the chute due to both the lower density of iron and the shape differences.

The At-PAC, with its weight pouch, is different, and therefore needs special attention with the lead shot.

John

PS, I have substituted Flckr images and a YouTube video for the lost PhotoBucket images.

[scoobypro]

Just joined and stumbled upon this. I have been an At-pac Diver since 1988.
I was working for a Marine science company in Orange County California, and back inflation Bcs were mandatory.
The At-pac was the #1 choice amongst the scientists and techs.
I was hired as a diver, and that first At-Pac was very heavily used, and completely hooked me into back inflation.
I still know a number of divers that use At-pac's and I am just about to start a rebuild on two of them.
One of them will be going to a friend of mine who will be using it for work. He's a marine biologist, so it's back to work for one of them!
The other one will be for my use.
Although I am still using my trusty OMS system, I honestly still prefer the At-Pac!
I will post a few pics here soon.

[crabbyjim]

In the 1970’s there were a couple of divers in our group who used At-Pacs.  They wre pretty slick and streamlined with custom graphics of the fairing.  They wore the rig into the water then removed it, turned it straps side up and used it like a dive float to fin out to their destinations.  With the fairing and self contained weight they were bulky and heavy but the users didn’t mind.  I don’t know why they weren’t more popular.


Returning to Searat’s comment about weight belts under tank straps, we always put out weight belts on first because it was easier that tank first then weightbelt.  If you don’t use a crotch strap the weight belt shouldn’t hang up.  In the days when we practiced doff and don in the ocean, the weight belt came off first and was draped across the thighs, tank then removed, weight belt placed over tank, one last breath then turn off the air and head to th surface.  Then we dove maillott (sp) dive boards it was bc first, then weight belt then tank. Never had a weight belt foul the other gear.