Help with Decision

[kensuf]

lp85s are a great choice for drysuit diving up to the 200ft range, and hold up well past there to about 250 (maybe 270 depending on your plan) with just the addition of a stage. Really great tanks. Pair with a 40lb doubles wing and a simple backplate and you've got a top notch platform. Wing and plate can be had used for cheap on ebay if you're patient, tanks are probably about 500.

For cave stuff you really need the extra volume of a set of 104s and a 50-60lb wing. I suggest crossing that bridge when you get there.

wreck penetration and/or technical diving with decompression is really no place for a single tank, H lave or not.

^^ This.

 

[mick allein III]

Okay, I'm convinced. H and Y valve not the way to go. Help me between back doubles and sidemount. I was surprised that people said SM was bad on a boat. I think handing your cylinders up before climbing the ladder would be easier in sidemount. Reactions.


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[rx7diver]

I think handing your cylinders up before climbing the ladder would be easier in sidemount.

Which is why a single + bailout can appeal to some people: Hand up bailout bottle, hand up weight belt, climb ladder with only a single, reasonably lightweight tank (PST HP 100 or PST HP 120) on your back and your fins in your hand. Your just-turned-sixty-year-old back, hips, and knees will thank you.

Safe Diving,

rx7diver

 

[dumpsterDiver]

I dive about that deep with one of those 149 cu-ft steel tanks. It is not so bad, it feels no different that the 125 faber tanks I have that are rated at 2640 psi which I have been using for 20 years or so. I would hate doubles for my type of diving. However, if you really want to do penetration dives in 150 feet, you probably don't want to be using a y-valve.

I have done some pretty aggressive dives with a big single, a back mounted pony bottle and a slung deco bottle,, yet I still have a rig I can swim around with. Oh yeah, and I get out of the water wearing the rig with NO ladder.. we have to kinda hop up on my one buddy's platform.. It sucks, but is still doable.. for now.

I used to do solo dives to 180 using a big tank and y-valves.. Did it for a few years, but I took them off and now use a pony bottle I think it is safer. FYI I got 3 y-valves in the members section forever.

 

[rx7diver]

... yet I still have a rig I can swim around with.

Yes.

A couple of years ago I rediscovered the joys of diving old-school steel 72's (71.2 cu ft @ 2,450 psig). (Soon after my twin daughters arrived—2 years after my OD, original daughter, arrived—I began diving recreational, open water exposures only, so a 72 suits me just fine for a lot of the dives I do these days.) I was/am so surprised to be able to feel the extra drag of a 7.25" diameter tank (Luxfur 80, PST HP 80, or PST HP 120) as compared to a 6.9" diameter tank (the steel 72)—whether diving wet or diving dry! The extra drag from the extra cross-sectional area (41.3 sq in vs. 37.4 sq in) is surprisingly noticeable!

You'll almost certainly feel the extra drag of a single 8" diameter tank (50.3 sq in), and, especially, of doubles, whether 6.9" diameter (LP 85's) doubles, or 7.25" diameter doubles, or, especially, 8" diameter doubles.

Safe Diving,

rx7diver

 

[rongoodman]

Okay, I'm convinced. H and Y valve not the way to go. Help me between back doubles and sidemount. I was surprised that people said SM was bad on a boat. I think handing your cylinders up before climbing the ladder would be easier in sidemount. Reactions.

You've already received a number of recommendations for back mount as opposed to sidemount for diving off a boat. It's one thing taking your time getting your sidemount tanks organized in a quiet pool outside of a cave entrance, another thing entirely having to get geared up on a crowded bench and then making your way to the back of the boat. Gearing up in the water might be OK, or in the case of rough conditions or a required hot drop, maybe not. Look at it this way--on the boats you dive from on the Great Lakes, how many sidemount rigs are you seeing, as opposed to back mounted doubles?

 

[mick allein III]

I was interested in both Dumpster Divers post and rx7divers earlier post. Dumpster Diver seems to do deco on a big steel 149. Do you all think that a y valve on steel 149 with reg for breathing and bc and a reg for the Drysuit inflator with a 40 or 80 cf pony and. Deco bottle would be safe for nonpenetration dives into 140-150 range?


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[rx7diver]

I was interested in both Dumpster Divers post and rx7divers earlier post. Dumpster Diver seems to do deco on a big steel 149. Do you all think that a y valve on steel 149 with reg for breathing and bc and a reg for the Drysuit inflator with a 40 or 80 cf pony and. Deco bottle would be safe for nonpenetration dives into 140-150 range?

mick allein III,

When I did my IANTD Deep Air course (ca. 1994), several of my fellow students certified wearing a single HP 100 and slinging an OMS 46 deco (either EAN36 or Oxygen—I don't recall now which). However, I certified wearing manifolded double HP 100's and an OMS 46 deco. I have always been more comfortable with the idea of doing decompression diving wearing back-mounted doubles (whether independent doubles or manifolded doubles).

When I did my IANTD Advanced Deep Air course (two deco gases) shortly thereafter, all of us students wore manifolded doubles (HP 65's, HP 80's, HP 100's, or OMS 125's).

I wore manifolded double HP 100's during my first attempt at IANTD Technical Nitrox (three nitro mixes), and manifolded double HP 120's during my successful, second attempt.

All of this diving was Great Lakes diving. I was living in Ann Arbor MI at the time.

My posts earlier in this thread addressing single back-tank diving pertained to non-deco, non-penetration diving to perhaps deeper recreational depths (130 ffw plus or minus), but not deep recreational depths.

Safe Diving,

rx7diver

 

[mick allein III]

Thanks for the clarification.


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[DaleC]

There are two things to consider with a Y/H valve. One is that a tank O ring failure depletes all your gas. Two is how hard it is to reach and manipulate the valves, which is necessary for isolation. If you went that way it would be something to test for. I have dived single HP130's and find them a little wobbly, especially if you have a Nighthawk which does not have a BP I believe (at least they didn't when I dove them).

As a long term solution for the type of diving you are describing I also think you need to move to either SM or BM doubles. The majority of the training and planning with partners for those dives will revolve around those platforms so, unless you plan to solo a lot, you will always be the odd man out otherwise.

But, if you just want more gas using your current system, as an intermediary step, you could sling an Al 80. This was the first step I took when I wanted more gas than my St 72 and an Al 40 would allow. Cheap and easy and the skill of slinging bottles will transfer down the road. All one needs is a tank, some rope, two boltsnaps and a reg set.

I only suggest that as an option for discussion sake and do not advocate anyone just load up on gas and get themselves into trouble. All the issues of deco and overhead diving still apply.