Considering small doubles (~50's)

[undrwater]

About me:

• Frequent solo beach diver
• Freedom Plate with Oxy Sig 30# (has the stand-off on the bottom)
• 19 cu' catalina pony
• Worthington HP 100
• Fusion (sport skin) DS
• No tech ambitions

What I'd like to do is perhaps simplify a bit. I am thinking that if I doubled some smallish tanks (~50's as mentioned above, or?) with an isolation manifold, I can eliminate the pony. I have also heard that doubling in this manner can increase stability, which would be great as I have started video (taping?) my dives. I have plenty of opportunities (I think) to get some mentor-ship on utilizing doubles in a rec OW environment.

The questions:

• Is this crazy? (I'll make up my own mind, but I'm happy to hear your opinions)
• Has anyone modified the Freedom Plate for doubles? (If you are a local machinist and feel confident you can do this, please PM me)
• Anyone with a similar experience...I am interested in hearing your experience

I'm hoping I've provided enough information. Thanks for looking, I look forward to any responses!

 

[rjack321]

lp50 doubles (with a single outlet manifold) were pretty popular ~35yrs ago. It was the most common way to get 100cf of gas since most everyone was diving lp72s and compressors often didn't go to 3000+ psi. With the advent of 3500 psi tanks these small doubles became extinct. In your case you will find them expensive to maintain and fill compared to a single, but only slightly more than the single + pony. The real issue is that in some failures you won't know what is leaking. So you'll be blindly shutting off valves behind your head, you might get the correct valve shut down, but depending on the situation you can end up completely baffled since you can't see the problem back there. I'd stick with the slung pony or if you really want to spend money and time futzing, sidemount.

 

[Searcaigh]

All the points above by rjack are valid, however I have recently doubled two of my 50s, and will use them for specific dives on various wrecks that I am currently photographing along with my other HP twinset.

With my HP6.9L twinset I have been using it with both tanks isolated recently to determine the effect on my buoyancy, and so far I cannot detect any change, the LP50s might be different, I have not used them yet.

BTW undr the weight of LP50s is 30Kg including the wing and no regulators attached (66.13lb).

 

[waterpirate]

As Rjack said to simplify. Your idea is sound, but not without instruction and practice diving them and doing valve drills to stay sharp. No biggie, reallly, just another skill. I love my lp 2win 72/s for the shallow stuff where a single would be enough gas.
Eric

 

[knfmn]

Your idea is very reasonable. You can get a set of double 50's at DIve right in scuba. http://www.diverightinscuba.com/catalog/tanksaccystanks-faber-lowpressure50dubspackage-p-3623.html.
I find that doubles have a great impact upon trim. They tend to force you into horizontal trim right away. I would second the suggestions to get used to doing valve drills, however. It's something you're going to have to be able to do.

Kristopher

 

[Rhone Man]

The plan appears sound to me. The main downside seems to be cost - don't underestimate the price of the double manifold, bands and your new doubles wings. You may also find that your LDS charges you double for fills and more than double for VIPs.

Not sure that I entirely buy the shutting down leaks argument - not for pure recreational diving. You are not appreciably worse off than if you had a mounted pony.

 

[bamafan]

I have a set of faber lp 50's that I use for sidemount diving small stuff or short dives. I love them they are almost like not having anything on. If you can get a cave fill you will have about the same cf of gas as an aluminum 80 in a lot smaller tank with better buoyancy charicteristics

 

[CT-Rich]

I haven't dove doubles, but it seems to me that this configuration will not give you as much gas as the your single 100. If you dive the twins and set 500 psi as your flat minimum (forgetting about reserve for the moment) you are going to leaving a lot more gas in the bottles. Also, my steel 100 weighs something like 45 lbs. ( I have the exact number some where) and if you are going to put twin AL 50 on, you are going to be adding additional ballast. Nothing prevents you from doing this, but it seems like the benefits are small when you think about doing a shore entry with 66 lbs of tanks on your back. For the weight, I would think a 100 or 120 would be a better investment. The cost of maintaining a single larger tank will be much lees than a pair of twins. If you are interested in more more gas from a safety perspective, maybe an upgrade on the pony might be good, or as was suggested, going side mount. Seems like they might be more practical for shore diving solo. Side mount will lower your center of gravity in surf and would give you better trim and more access to the manifolds.

 

[KD8NPB]

72s will be cheaper, as the market is already saturated with them.

Fill them with EAN32 or EAN36 and you have a brilliant mid-range setup.

 

[dumpsterDiver]

How deep do you dive? Double 50's sounds like a ridiculous solution to me... If you want to reduce gear, use the 100 steel and drop the pony down to even a 6 cu-ft tank.. That should get you from 100 to zero feet, with very little trouble and negligible weight and drag (and cheap too).