Sidemount HP120s?

I am a recreational sidemount diver.

I am also a big guy and can float 120s. I have an sms100 D with dual bladders and I often dive with a drysuit.
I bought lp85s for sidemount and they are very nice when over filled, but when normally filled they don't have enough air for me. I would like to have a bit more air.
For boat diving I only take the 2 tanks with me and dive both tanks both dives. Because I travel a lot I am having difficulty getting my tanks over filled. The shops don't know me and don't want to do it which is understandable. I think it would be best to just get tanks that I can get filled properly and not have to worry with. Even if 120s were underfilled I would be better off than properly filled 85s

I'm thinking about switching to 120s. They are the same diameter as my 85s so I that shouldn't be a problem. They are longer, but I am tall and have a long torso so I don't think that would be an issue.

I travel a lot and bring my tanks with me so I like to have one set. I could use these doubles or as single backmounts with my BP/W

Do any of you dive 120s? What should I look for? Which brands have better bouyancy characteristics? Does anyone want to trade? I am in NC now and travelling up the east coast towards NJ.

I use 120's backmounted, and have been wondering the same thing. I just picked up a SMS100 gently used, but haven't invested on the time to sort it out.

What I can tell you is that diving my twin LP80s (PSTs) I wear a 12# weightbelt (I'm in a Viking Protec suit). With the HP 120s, no lead is required. They are heavy mudders in and out of the water.

I'd prefer to wear the 120's since I can two decent dives out of them, with gas to spare.

For what it's worth, I was speaking to Steve Lewis about all of this stuff a while ago. I THINK he told me that he routinely dove 120s with AL80 stages on a SMS 75 while they were in development. You might tough base with him on here... Doppler is his handle.

I sidemount hp 120's. They aren't my favorite tanks but the best option for some profiles. I'm 6'3" so the length is fine, I use them with a drysuit because they are neg (and it's cold water). It takes a bit of getting used too but overall a good size and option for that capacity. If I'm not doing deco though I like the hp100s, a bit shorter, easier to manage and lots of gas.


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decompression:

I sidemount hp 120's. They aren't my favorite tanks but the best option for some profiles. I'm 6'3" so the length is fine, I use them with a drysuit because they are neg (and it's cold water). It takes a bit of getting used too but overall a good size and option for that capacity. If I'm not doing deco though I like the hp100s, a bit shorter, easier to manage and lots of gas.


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What takes getting used to? Do you mean they are easier to manage on land? I am going to be renting some soon hopefully if morehead city is still there next week after this hurricane passes.

I dive Faber HP120's and Worthington HP130's. I find the Faber 120's to act a little like AL80's at low pressures, i.e. they get butt light and way less negative. I need more weight with the 120's than the 130's. That said, I prefer to dive the 120's on most profiles. I'd really like a set of LP85's or even HP80's for recreational profiles.

the lp85s are nice. I don't even notice them and they ride pretty flat. I just wish I could get more air out of them

I have sidemounted my Worthington 120s back when I had a nomad, not so much for extra gas, but extra cylinders for a trip. Not too bad, i'm 5'11". I have not used 120s with my sms100 yet (bought from CA with mods) so a little less foot heavy than stock sms100. The SMS trims better for me with the 85s so I can imagine same for 120s.

Fabers will get positive, even around the last of the 1/3rds (if I'm not mistaken), Worthys stay negative empty. I guess "better buoyancy characteristics is subjective". Diving dry I would probably rather Worthys. Also nice if not doing 1/3rds and getting lower around 500psi. Also, add a couple of floaty aluminum stages and things start to get very positive. Go to XSscuba site and download the cylinder specs. Then do the same for Fabers. You can calculate the behavior of each tank then apply to your needs and style of diving. Do the calcs on the tanks at various pressures and you can get a feel for where the bouyancy will be for you.
HP120s are great singles for sure, especially at your height.

I have as much trouble getting good 3500 fill on my HPs as I do cave fills on my LPs in most places.


FYI: Worthington is not making steels anymore Total bummer. I just snagged four more new lp85s, 120s are hard to come by now. Nothing against the Fabers, I just prefer the worthys for buoyancy, but that is a personal thing.

Edit: The above referenced 7.25" tanks. 8" brings new pros/cons to the discussion...

00wabbit:

What takes getting used to? Do you mean they are easier to manage on land? I am going to be renting some soon hopefully if morehead city is still there next week after this hurricane passes.

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They move differently in the water. You could say they have kinetic energy behind them as you move your body positions under water they have more "pull" and tend to move you once you've finished moving. Also, changing them to different D rings and completely removing them takes a bit more effort/thought as they have much more heft than AL 80's or smaller steels. On land, they are a beast.


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I'm 6'7" and 280#. Last week I tried to optimize my trim sidemounting an HP120 as a single with a HOG sidemount bc. After considerable effort, I was able to get it close. That being said, I would not think twice about using double HP120's, but I cannot justify the expense for another one. I am an air hog compared to most of the people I dive with, but it would still be overkill. 100's would be sufficient and a bit easier to manage, I think. Just my two cents...

You might want to consider LP108's instead. Mine are Worthington and so might be hard to find, but I assume others make 108's. Most fills stations aren't going to be able to overfill your LP120's much. I dive lp108's and most often get them filled to 3600 or more. That's 147cuft, or slightly higher.

Fill capabilities are of concern here. How much pressure can your dive shop provide? Also, assuming a fill station can provide 3600psi you only end up with 130cuft in an HP120. If it was an LP108 you'd have 17 more cuft of gas! Furthermore, non tech shops seem to not even notice they are "LP" tanks. You generally at least get an overfill at least to the 3200 mark, even in tropical vacation diver locations.

If your fill station can only provide the more "average" 3200 psi. You're at 128cuft. In an lp108 you'd be at 130cuft. No big difference but more is better, right?

I bought the 108's when I was diving single tank and my sac was FAR higher than it is now. Still, it's a great feeling knowing I've got way more gas than I'll need.

The 8" diameter of LP108's kind of sucks. You get used to it, though. I've never been on a boat where the tank size was more than a minor annoyance.