The Big Doubles

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The LP-104s (middle) beside the Double 80’s (left) and LP85’s (Right)

Shortly after Tina got her tech upgrade,  I scheduled a weekend with Mer and also got mine.  It’s still very much a challenge for me  to have the  type of precision in the water needed for the upgrade,  but we have been practicing a lot and I was ready as ever.  The day I went for mine was following a work/training trip to Detroit.  I flew home on Friday evening late and immediately got up to drive to Troy springs on Saturday.  I was pretty whooped and didn’t really have the best day diving honestly.  I passed,  but was somewhat surprised.  I must have squeaked by enough on the skills but to me I felt sloppy.  Mer had us do valve drills, ascent and SMB. I also did some kicks because I had to upgrade those skills from funds. Overall it was a good feeling to finally have it in the books.

Following the tech upgrade,  Mer wanted us to start diving in cave doubles, (the big doubles)  to get used to them. Our plan is to take Cave 1 very soon and we needed to get plenty of open water practice in the big tanks so that we weren’t trying to get balanced and trimmed out during a cave class.  Up until now we have been diving double worthington lp-85s.  Typically in North Florida, cave divers use LP-104, LP-108, HP-130, and HP-133. These tanks are 8″ in diameter and hold a lot of gas.  The gas comparison of a single 104 filled to a pressure of say 3800 psi holds nearly as much gas as two aluminum 80’s filled to the standard 3200psi.  So a set of double LP-104’s cave filled, for example would be like wearing two sets of double 80’s.  Obviously more gas is better in an overhead environment.  That being said, the typical  North Florida cave doubles are not the largest tanks made.  To my knowledge the LP-120 is the biggest tank, but you won’t see too many people diving it because it is so big, it’s completely unmanageable for a typical person.   The tanks mentioned above provide the best balance of gas volume and stability in the water.

During the  following weeks after the tech upgrade, I searched around the inter web and found a few sets of used PST-104 tanks. I ended up buying 3 complete sets to make two matching sets. I got a pretty good deal on them since they were used.  The PST-104 is no longer in production so they can be hard to come by.  In fact PST went out of business a few years ago.    The ones we got were almost as old as me, but in good shape. Why not just buy new tanks you ask? Well first the cost. I could get two sets of used tanks for 1 set of new. And secondly the PST tank is somewhat coveted because it’s slightly heavier than the newer HP-130 when nearly empty and some claim that it’s better to trim out.

The interesting thing about PST tanks is that over the years the die that they have use to make the tanks has changed and many tanks are not exactly the same. The dimensions vary enough that even ones made a month apart won’t be exactly the same. This can be tricky when putting a set of doubles together.  Ideally the tanks you make into doubles will be pretty darn close in size otherwise you may end up putting unnecessary stress on the manifold once the bands are on the tanks.  PST tank are known around High Springs as “snowflakes” no two are alike. But people love them, they tend to hold up for years, and i you look at Extreme Exposure’s rental fleet it’s almost all PST LP-104’s.

Double LP-104

Double LP-104 and Thermo Manifolds

Since the doubles we found were used,  they came with a mix of skinny bands and various valves. Two sets  came with thermo manifolds, the other set came with Sherwood. I ended up buying new bands because all the bands that I got were somewhat trashed and I really like the look of the larger bands. So I ordered two sets from Dive Gear Express.  The thermos were fine and I only had to replace the knobs.  After the new bands, and knobs showed up I  got visuals and put everything together.    Since this wasn’t my first set of used tanks I learned a good lesson the hard way:  Even if the tanks are filled when you go to buy them from someone, do your self a favor and make the seller drain the tanks to look in them. One set I got had “fresh visual inspection and hydro” but when I opened them up I saw they had not been fully dry before someone filled them and they had some surface rust on the inside.  The other two sets were beautiful inside.  The set with rust will need tumbled and this will be an extra cost. I may sell them.The Big Heavy Doubles

We decided to test drive the new tanks at Blue Grotto, and our first dive was not really that bad. i was expecting them to be noticeably different but they weren’t.  I didn’t add any tail weight and we both used our 40# wings which worked just fine. However, Just like our first few dives in the 85’s we were off-balance and we expect it will take some time to dial them in perfectly.   In the LP-85, I need a little bit of tail weight. Depending on my undergarment I use about 4 pounds. This helps trim out the tanks for me. Tina uses slightly less I think maybe 3.

The biggest difference is the weight on land. A set of cave filled LP-104s is 115lbf compared to something like 90 for the 85s and even less for the AL-80s. Fully geared up with all the other stuff it’s like having a small person on your back.  You definitely need to take your time in while walking. The stairs at the Grotto were a killer, but not as bad as when we went to troy for our next dive.  Walking back up the damn switch backs after being weightless during the dive made us feel like we were 500 pounds.


Tina at Blue Grotto in Florida

So far we  have had a total of  4 dives in the double 104s and I have to say I really like them. I’ve adjusted my harness a bit to lower the tanks as they sit on my back and I tightened up my crotch strap some.  I may even like them better than the lp-85 for stability.  I also love the thermo manifolds. They are so easy to do valve drills with because the knobs are easier to turn compared to the $100 DGE manifolds. I guess you get what you pay for.

The next few months will be more training dives, more valve drills and dialing in the gear.  We also got some other new gear to play with, which I’ll do a separate blog on..