Most Common Doubles

[jgarysmith]

What is the most common double set up being used out there for wreck diving? Depths of about 100 to 125 ft with no- deco, just trying to get as much bottom time with Nitrox. Is PST E 8 119's too much to handle, I own one, and considering getting another to double in the future. How about PST E 7 100's

 

[fdog]

I have switched to PST E7-100s with a Sea Elite manifold. While diving wet, these have had no issues.

All the best, James

 

[jgarysmith]

Thanks for the response, because I too dive wet. At least right now I do. In colder water I use a Mares semi-dry. I think doubled 100's would be a great set up. Not too hard to handle. Did you use bigger set up before and switch to the 100's?

 

[Ontario Diver]

What is the most common double set up being used out there for wreck diving? Depths of about 100 to 125 ft with no- deco, just trying to get as much bottom time with Nitrox. Is PST E 8 119's too much to handle, I own one, and considering getting another to double in the future. How about PST E 7 100's

Like everything else on this board... the answer is "It depends"

What is your gas consumption like? At 120 feet, using EAN30 you still only have a 10 min dive time before a deco obligation kicks in.

These are rough calculations not meant for gas planning...DO NOT TRUST MY MATH - PLEASE GO AND FIGURE IT OUT FOR YOURSELF. (Blatent attempt to ditch any liability )

10 min bottom time at 5 ata = 50 min Surface equivilent.

120ft to surface ascending at 30 ft per min is 4 min at an adverage of 60 ft (3 ata) is 12 min Surface Equivilent.

5 min Safety stop at 1.5 ATA is 8 min Surface Equivilent

So you need a minimum of 50 + 12 + 8 = 70 min of Gas.

If you are an air hog (like me) with a 1 cu ft per min air consumption rate. You could "IN THEORY" (that is Latin for "like an idiot") do this dive with a single AL 80. Of course you have no safety margin.

If you like your 119, adding a 30 cu ft pony for a redundant air source would probably work out well for you unless you are doing penetrations etc. In which case, you'll cover all of the gas management in you advanced nitrox/deco procedures course.

A pair of 119s are quite heavy to haul around unless you are planing on going technical.

Double 80 are another option.

I would suggest going larger only if you are going technical.

 

[jgarysmith]

I am a gas hog. I do have a 19cf pony bottle that I also use. I agree, I think 2 of these 119 would be a load. I have dove some 120ft dives and had to head up before my time because of running out of gas first which was why I thought the 119 would be a good choice. All the more experienced divers on here will say to work on your breathing, which I am and do agree with, but it is nice to have the security of the extra air. I am not too worried about the extra weight, I just lose it from my belt to compensate. Thanks for the response.

 

[fdog]

Generally I dive with a 7mm Henderson semi-dry. The doubles before the 100's were old 2250 psi steel 72's. No real big issues between the two, besides the 100's weigh a bit more.

All the best, James

 

[pescador775]

Good advice,
JGSmith, you received a number of good, well informed responses here. Nice to see. Unless you are making long dives on the Ocean Venture, etc and using trimix, the double 100's will provide all the air you need and, in addition, lugging and donning these tanks is not unreasonably burdensome to the average, fit male. The Mares semi dry sounds like the way to go when diving the thermocline which, as you may know, offshore VA Beach runs 45-55 F.

 

[rescuediver009]

Don't know what your weighting is like, but I found that when I used the double 100's (not E7's, an older version HP tank) that they were not suite as negatively buoyant. I find that when wearing double OMS/faber steel 98's you get the same gas volume and alot less weight on your belt. Combined with an SS plate you will do fine.
Personally my favourites are the OMS 112's for added gas, but judging by your weight restrictions, I would not recommend them. Over 2 hours of bottom time, avg. depth = 70-80 ft.

 

[LUBOLD8431]

Well, I use Faber 112's (doubles) for deeper technical diving, and PST E7-100's (singles or doubles) for shallower dives. The buoyancy characteristics for these cylinders is almost identical, so it doesnt require alot of changing of my system. I need alot of weight to get down, otherwise I would think about AL 80's for a set of doubles as well. From my experience, the 100's are great little doubles and will work well for intermediate depths no-deco diving. They will give you a large safety margin though, and these dives could be accomplished safely on smaller doubles (80's or 72's). I am a firm believer in using the right cylinders for the dive, and not going overboard (while still keeping a nice safety margin). However, not everyone can afford to own four or five sets of doubles (using different cylinders for different dive plans). So, pick a cylinder that will work for the dives that you are doing now, or planning to do in the immediate future. My recommendation would be the 100's or AL 80's.

 

[Curt Bowen]

What is the most common double set up being used out there for wreck diving? Depths of about 100 to 125 ft with no- deco, just trying to get as much bottom time with Nitrox. Is PST E 8 119's too much to handle, I own one, and considering getting another to double in the future. How about PST E 7 100's

If I was to dive at 100 to 125 I would use something much lighter such as double 80's or steel 85s. Double 120's are way over kill and way to heavy.

Maybe even just a single 120 filled to 3500 would work.