Doubts about tanks for wreck penetration

[rjack321]

RJack. That's more along the lines of what I'm thinking I could handle.
I presume you're talking DOUBLE 80s/100s. I'm thinking that I could dive 100s from a boat but not sure I could get up the ladder. How much of a PITA is it to break modular manifolded doubles down to two singles for shore diving? How much time does it take on average? A modular manifold like Dive Rite's would allow me two H valves for use with the singles. Can manifolds be prematurely worn out with constant reconfiguring or is it just a matter of going through O rings a bit faster?

Yes doubled lp85s/hp100s.

Breaking down doubles takes me about 30 minutes, assembly about an hour. Cross threading something and screwing up your manifiold would suck.

Its not something you want to do more than once or twice a year IMO. And of course you have to completely drain the cylinders to do it.

I have never used the plugs to turn my manifold valves into singles. Both dive-rite and thermo offer them. Popping those in would be easy.

 

[reubencahn]

Personally, I always dove hp100/E7-100 as singles and loved them. Taking RecTriox, and really thinking through gas management, I realized that they were fine for full dives to around 100ft or so, but at 130, they were inadequate if I had to fight current or do anything else that increased my SAC above .5. That's when I decided to move to doubles.

Double E7-100s are going to weigh about seventy pounds plus another fifteen for gas. (I can't find a weight for steel 72s but I think they are lighter.) An E8-130 and a slung 80 weighs about 74 pounds. But for those few moments you're getting on and off a pitching boat, the doubles have the weight evenly distributed on your back. With a slung bottle, you've got significant weight off to one side. I shattered several vertebrae, L1 though L3 in an accident when I was younger. I'm careful, though not paranoid, about my back. When carrying weight, I much prefer to have it evenly distributed, and the weight of the doubles is okay for me. On the other hand, I don't have any disc problems. I'm not sure how I'd feel about it if I did.

 

[DIR-Atlanta]

I'm sure this doesn't need to be said in the DIR forum, but since we have a few contributors to this thread who do not appear to be as well-versed in DIR procedures as the rest of us ...

Please make sure that if you are diving steel cylinders, that you have a balanced rig.

Steel tanks (and especially doubles) are kind of dodgy with a wetsuit, especially at the depths that you guys are talking about. Most DIR divers prefer double AL80s for ocean diving in a wetsuit, so you might want to re-think the use of steel tanks for this particular application. Of course, if you are diving dry, then the issue is "mute".

Either way, just make sure you have the weighting all sorted out before you jump in the water.

 

[rjack321]

I guess I wasn't clear...

I was refering to 2 alternate doubles scenarios
lp85s/hp100s with an AL80 stage
or
HP130 doubles

Same amount of gas (roughly) but I prefer to breakup the weight.

I would not advocate a single 130 with an AL80 stage. I haven't actually dived that combo, but it sounds very tippy (side-to-side) YMMV. In also sounds like a pain to coordinate rock bottom and turn pressures.

I suppose if anything more than a single is too heavy you could find someone to start you down a sidemount path. That might not be very easy in WA state though - since we really don't have any caves.

 

[reubencahn]

I guess I wasn't clear...

I was refering to 2 alternate doubles scenarios
lp85s/hp100s with an AL80 stage
or
HP130 doubles

No, you were clear. I was referring to an earlier post.

 

[jim T.]

Thank you so much guys. You've given me a lot of good info. and things I hadn't thought about in enough detail via lack of experience. I imagine it would be nice to have as simple as possible gas planning via the use of doubles RJack.

I hadn't been too concerned with the side pull of a slung 80 as I figured on having deck crew pass it down to me and I could hand it back up. Splitting up the weight was my first goal. Is it reasonable to expect that I can rely on boat crews to do that? If so, think it negates the problems mentioned above?

I think I could probably handle smaller doubles like 100s on a boat going in but that ladder bit. Too bad more boats don't use small lift booms or chainfalls, etc.

ReubanCahn, Thanks. That you can handle the doubles is definitely encouraging.
I had the two lowest vertabrae fused years ago. I have done squats/weightlifting and lifted up to 132lbs. In a perfect form exercise with care, I'm ok. It's the boat movement, whipping my back around and climbing with them in anything but perfect form concerns me. I throw my back out once or twice a year (muscle spasm stuff) and it's unpleasant to say the least!

It sounds like you're diving doubled 100s if I understand you correctly?

I do think what you're saying about even distribution of the weight being the main issue is right on. Guess I'm going to have to strap some doubles on and find out.

RJack, your suggested combinations give me a great base of sizes and combos to try. Thanks.

Others who use similar combinations, your experiences with them would be appreciated.

DIR Atlanta, It never hurts to remind people not to hurt themselves. I was a school teacher so I understand that prevention is worth a pound of cure! I will get good training with a doubles mentor or instructor if i buy them.

I probably would only use my doubles two to three times per year. Expense is very definitely a concern and I'd like to buy what will serve me best for the longest period of time. For several more years I don't anticipate diving deeper than 130-150 ft.

I'd like to dive the U Boat in N. Carolina (sorry I've forgotten it's number and I'll lose this post if I go back to look...) in 2008. Perhaps the most helpful thing would be to see what tanks combination would best serve me in:

a. An NDL dive.
b. A dive with minimal deco due only to any emergency/buddy assist, etc. that would make me a little over due.
c. short deco. If I remember correctly the wreck is 130fsw at the sand.

I'll be taking a gas planning class soon, but would like an idea of what's needed tank wise.

I want to ask all of these questons of a potential instructor, but if you guys would be willing to give me a scenario/cookbook recipe idea I want to buy my gear and approach instruction with what would be appropriate for me physically and meet with approval by most Deep Diving, Deco, Tech instructors down the road.

Hope that's not too unreasonable a request. Doubled 100s are looking like likely candidates. I think I'll have to do shore dives with singles after diving a moderately rough shore dive site.

I really can't thank you all enough for taking your time to educate me as to what I should start with anyway, tank(s) wise.

 

[diverrob]

I know this is a DIR post...but with your bad back have you considered a rebreather, either semi-closed like the Halcyon RB80 or closed circuit like a KISS? Most of the units weigh less than a single LP95, and will give you more time than a set of doubles. I definitly notice a difference in how my back feels after a day of diving between my twin LP95s and my CCR. The RB and training will cost a bit more than a set of doubles, but with a back injury it might be something to consider.

Rob

 

[Soggy]

Pony bottles -> Not DIR
CCRs -> Not DIR

If you want to know *why*, ask away, but don't try to figure out how to be DIR w/ a pony bottle.

edit: sarcasm removed....

 

[reubencahn]

ReubanCahn, Thanks. That you can handle the doubles is definitely encouraging.
I had the two lowest vertabrae fused years ago. I have done squats/weightlifting and lifted up to 132lbs. In a perfect form exercise with care, I'm ok. It's the boat movement, whipping my back around and climbing with them in anything but perfect form concerns me. I throw my back out once or twice a year (muscle spasm stuff) and it's unpleasant to say the least!

It sounds like you're diving doubled 100s if I understand you correctly?

For comparison sake, I'm squatting around 200 but using a Smith machine (the bar is attached to two vertical rails so path of motion is very controlled). I have no fused vertebrae. The fractures were not displaced though spacing between vertebrae was reduced significantly. Everything was allowed to heal without surgery. This may be a critical difference. I don't know.

I began with doubled AL80s because I was living in Fla and diving wet in the ocean. Now that I'm in (for me) the freezing waters of Ca., I've picked up a drysuit and a pair of LP80s. These are the same weight and buoyancy as the E7-100s but I was able to buy two cheaper than a single E7-100. (My single tanks are one hp100 and one E7-100 so I can' t just twin them.) They are also pretty close in weight, though not buoyancy, to the AL80s.

Since you're looking at further education, I'd recommend DIR-F or Andrew G's equivalent. You'll get plenty of gas planning info and much more. I'd also say to talk to an instructor now, before you make any equipment decisions. Most of the GUE instructors I've dealt with are incredibly giving of their time and are happy to answer all sorts of questions.

 

[rjack321]

I think you're probably thinking of the U352, which is 115' at the sand.

I would dive this on a single HP130 of 30/30 trimix with 20 minutes of no-deco bottom time. I'd prefer doubles, but would do it on a large single (119 or 130).

At my SAC rate of 0.5, I'd be using about 2.5cf/min on the bottom = 50cf. Rock bottom for this dive is about 40cf (1 min stops from 60ft). So you have a bit of extra gas to compensate for high consumption or 5 minutes over no deco limits.

This is not enough gas for any penetration whatsoever.