Steel tanks & wetsuit - some real experience to go with the claims....

[Genesis]

I've put together a set of HP100s that I intend to soak real good this weekend if the weather permits.

But in the meantime, before soaking them REAL GOOD (in 100'+ of water!) I had to check my weighting, because I KNEW it would be off compared to a single tank rig.

So I took the rig out the back door and into the water behind the house, and dove it with 500 psi in the tanks (which I put there intentionally for the purpose of this test.)

Config was a SS BP, double HP100s, 500 psi of gas, 3 mil wetsuit, booties, and the usual mask, fins, etc. Wing is an Oxycheq 70.

Now the general rubric is that you don't dive steelie doubles in a wetsuit. The argument goes something like this - a complete BC failure will kill you.

Hmmmm.. will it?

Let's see where I ended up.

With no gas in the wing, and the tanks at 500 psi, I was just slightly negative at the surface. So, I can stay down when low on gas at any depth from max to zero.

I needed no belt.

Ok, now let's look at the potential issues.

With the tanks chock-full, they hold about 15lbs of gas. The suit will lose about 75% of its 10lbs of buoyancy at 100'. So I could be, conceiveably, -22 at the bottom with full tanks.

I probably can't swim up -22. I'm going to try, but I doubt I can do it. My primary anchor on Gig is an FX-37, which is -22, and I can JUST BARELY swim that up (without using any lift), and not for very long. So this could be a problem - a big problem! On the other hand, adreneline is a big motivator..... so I might be able to swim it up. I can guarantee you that I wouldn't enjoy it though.

Ok, but there are other things that can kill you down there too, right? And we manage them with redundancy of some kind. So let's look at the options and let's not add higher risk things to the kit to get rid of lower-risk dangers!

1. Go to AL tanks. This would mean that you have less gas (160cf .vs. 200cf), but it would also mean that you must carry weight, because empty those twin AL80s are going to be +8! So the TOTAL SHIFT from HP100s to AL80s is about 11lbs - meaning I will need 10-11 lbs of lead. And if I ditch that accidentally on the bottom, I am inexorably positive (the amount of weight EXCEEDS the shift of my suit from the surface to the bottom) which means there is a good chance I get an uncontrolled, unstoppable and immediate ascent. It is more likely that I will accidentally ditch a belt than have a complete buoyancy system failure. I've seen several inadvertant ditches in the last year, but no total BC failures. So the proposed "DIR" solution trades a very unlikely failure for a more-likely failure, and the latter one can kill you just as dead (especially if you have a deco obligation when it happens!)

2. Only fill the tanks partially full. Heh! What a concept! If I only fill to 3000 psi, I have effectively two AL80s worth of gas (160 cf) and they are 3lbs less negative. That 3lbs probably DOES make the difference in terms of being able to swim up the kit, but still doesn't make it fun. But if I only need 160cf of gas for the dive, that offers no penalties over double AL80s - and is easy to implement.

3. Dive this configuration with a drysuit. Since a membrane drysuit does not shift buoyancy during a dive with depth (if dove correctly), I am now at most -15. I CAN swim that up. I now have to carry weight, and have the risk of an inadvertant ditch, but I have that risk in any drysuit configuration. A good choice if I need the drysuit for exposure protection, a bad choice if I don't, as I'm ADDING more-likely failure points (see #1 above.)

4. Use an AL BP. This is a possible solution. It leaves me with a few lbs of lead on the belt (about 3), but is otherwise system neutral. If I ditch the 3lbs, I can swim that up (it has the same effective impact as (2).) The 3lbs is LESS than the shift of my exposure suit with depth, which means I can AVOID an inadvertant Polaris if I accidentally ditch it. In both cases I have to be willing to ditch the KIT at the surface if there is a complete buoyancy system failure, however. The gain here is real - but not all that material. (Note that the AL BP + taking only 160cf of gas, however, is a pretty significant change.)

5. Dive this kit only where there is a hard floor at or above the MOD. Why? Because I always have the choice of intentionally dumping half the gas. With half the gas gone, I can easily swim up the kit. The problem is the time that it takes to do that; thus, I don't dare rely on this without a hard bottom. But with a hard bottom if I dump half the gas (7lbs) I am now -15, which I can swim up, and likely only -5 or so at the surface (my suit gets most of its buoyancy back, and I breathe some of the remaining gas.) With an isolation manifold ditching half the gas is reasonably safe; I can shut down a reg that freezes during the dump and allow it to thaw.

6. Carry a smallish (~25lb) bag. Why a small one? Because I don't want to overfill it accidentally and end up with a rocket ascent! A small bag has less risk of this than a large one. Plus, its easier to carry. If you suffer a complete loss of buoyancy you use the bag as a lift source, partially fill it, and swim up the kit.

So which combination of these make sense?

From where I sit #1 (AL tanks) does NOT make sense. It actually INCREASES risk rather than decreasing it, as it requires me to wear more weight than my exposure suit changes buoyancy, thereby guaranteeing trouble if the weight is inadvertantly ditched.

Thoughts?

BTW, my comments on my soak test will be posted when I'm back from it, along with my attempt to swim up the rig from the bottom (I'm gonna try, and will also take a bag with me and try THAT as a means of managing a BC failure....)

[DeepScuba]

I await your "soaking" results, as I have pondered the same question (But less pondering than you I might add).

[Genesis]

in fresh water there's no way I'd want to dive this kit. I'd be horribly negative, and even an AL BP wouldn't help much, as that only changes the total picture by about 4lbs.

In fresh water, I'd want the drysuit.... but then again, in fresh water I bet I'd be cold enough that I'd NEED the drysuit! :)

[paulwlee]

If you are so worried about losing the weightbelt, you can put your belt under your crotchstrap so it will hang in case of an accidental release. You can also use two buckles, if you are really worried. IMO, this will make sure that the chances of accidentally losing the weightbelt will be as unlikely as losing the wing.

You still have the ability to ditch and be able to surface. Better than sinking to the bottom.

[Scuba_Vixen]

Paul mentioned the double buckles, a popular safety trick...and putting it under the strap..If you do both and still loose a belt, I don't want to guess what you were doing down there....

That said, there's always redundant bladder wings..as you said, bc failures are rare, and the chance of both failing simultaneously must be about nil...(unless you shoot thru them or something .... still pretty hard to do)

I personally would have to go with the Al bp, all the weight that high would dump me face down, I need weight at the hips for proper trim...you may be different....If I shifted the tanks wayyy down, then I couldn't reach the valves..negating the safety of diving doubles....not a good option....

Just take your regular bag and reel...worst case, you shoot it from the bottom and wind yourself up.

Can you really maintain trim with HP100's and a sst bp and lo lead? That would have me standing on my silly blonde head.

Darlene

[Genesis]

wear the belt under the strap.

But that makes the weight very difficult to ditch. Oh sure, I can, but its not easy. I changed to doing this after nearly losing my belt on a dive last winter at 100' in my drysuit.

The pucker factor on that dive was considerable - fortunately I caught the belt before it slipped completely off!

Sink to the bottom? If the bottom is above the MOD of what I'm breathing, do I care? Not so long as I can get off it and back to the top in a CONTROLLED fashion!

The problem with ditching is that it is VERY likely to lead to an uncontrollable ascent. Trying to figure out if I can ditch and not Polaris is not always obvious, as it requires that I do a fair bit of math and also account for whatever gas I will breathe on the way up. If I'm wrong I've got real trouble.

I agree that as a "last possible way to avoid death", I'd ditch. But to my way of thinking, such a scenario should simply never arise. If it does, it happened because you did not plan your dive properly. The solution is "don't do that!" :)

All I NEED to be able to do is regain the surface in such a situation, right? And once I get there, I have to be able to ditch enough negative weight to STAY there, right?

Remember - we're talking about a one-in-a-million failure here.

We have to cover it somehow, because the goal is that no SINGLE failure kills you. But it is EXTREMELY unlikely to have a complete, 100% buoyancy failure. So in protecting against this killing us, let's not add risks that are MORE likely to kill or injure us!

So if the floor is above the MOD for my mix, and I sink to the bottom with a wing that loses its corrugated hose on entry, what are my options? I'm not dead or injured, and in fact I have 200cf of gas with me! I can breathe down there - and work on a solution - for a looooong time. In fact, at 4 atm I probably have at least 45 minutes to figure something out before I'm screwed (accounting for the rest of the gas as being needed for deco if I stay that long, assuming I'm decoing out on backgas.) If I know where the anchor is, and dove off the back of the boat and sunk, I easily have enough time to take off my fins and WALK to the line on the bottom!

If the failure happens after I've turned the dive, at thirds for a pentration dive or at "deco if any plus reserve" requirements for an OW dive, I've almost certainly breathed enough gas to be able to swim the kit up - so the issue doesn't arise EXCEPT on the initial decent.

Ok, back to options....

I can vent off half the gas. If I do that now I am no longer all that negative, and I can swim up the kit. I KNOW I can swim up -15 for at least a while. I won't like it, but I can do it. The good news is that it gets better as I burn gas (and I will be!) and as my suit's buoyancy comes back. Since I have a manifold, even if I vent off the gas and freeze the reg I'm venting from in doing so its not a big deal - I just shut it down and let it thaw. Then I swim up. Elapsed time - 5 minutes or so. No big deal, even if the floor is at 130'. I'm still within the "no deco" limits!

Or I can pull a bag, sling my left arm through the straps, put JUST ENOUGH air in it to make it possible for me to swim up, and do so. The idea here is NOT to treat the bag as a BC - but rather as just enough lift so I can swim up (you can't get precise enough with a bag's dump to avoid trouble, in all probability - so I wouldn't try.) Elapsed time, ~2 minutes, and that's being REAL careful about it.

If I'm at or near the anchor or ascent line, I can climb it. A pain in the butt, but doable. No risk of dying there; again, I have a lot of gas to breathe (that's the entire problem, natch!)

So exactly HOW do I get killed doing this?

Now I agree that if I'm doing a wall dive, where there is effectively no floor, the risk is much higher. In such a situation I'd argue that you MUST ALWAYS be able to swim up your kit without deploying "extras", not because you can't deploy them but because in the time it takes to do so you might easily exceed the MOD and tox. But in that case what you're REALLY arguing is that when diving double tanks, irrespective of their construction, your exposure protection can not have any buoyancy shift at depth - that is, the only truly acceptable exposure protection is a membrane drysuit.

[roturner]

Genesis once bubbled...
I've put together a set of HP100s that I intend to soak real good this weekend if the weather permits.

But in the meantime, before soaking them REAL GOOD (in 100'+ of water!) I had to check my weighting, because I KNEW it would be off compared to a single tank rig.

<snip>

It sounds obvious to me that you'd want redundancy in your buoyancy. You mentioned two alternatives (drysuit and liftbag). Either one of these would be acceptable but a drysuit gives you a much faster and more controlled reaction when you don't have a hard bottom. I don't know if you've ever used a drysuit but it could take a few dives and a lesson in the obvious to get it down.

The other obvious option that I would adopt from the get-go is the AL backplate.

An option that you didn't mention is to dive a dual bladder wing with a wetsuit

R..

[Genesis]

Darlene, I was fine in the bay yesterday with this setup in terms of trim, but I had light gas (~500 psi) as the objective was verifying weighting. Perfect horizontal trim was a snap.

I'll know what happens to trim in OW tomorrow if the weather holds..... but I don't expect trouble. I've dove these tanks as singles dozens of times, and they don't shift their center of mass and buoyancy much at all from empty to full.

I dive dry in the winter here. In the summer its not all that good of an idea - you will get SMOKING hot on the surface once you zip up in very short order, even if you skimp on the underwear.

Its bad enough with a 3mil - I sometimes have to jump in to get some water in there so I can have some evaporative cooling to avoid overheating.

[Uncle Pug]

Genesis once bubbled...
I sometimes have to jump in to get some water in there so I can have some evaporative cooling to avoid overheating.

[SeaJay]

You wrote a lot, dude, and so forgive me if I'm simply reiterating things that you've already said.

Here's what I understand:

1. Salt water
2. Your question pertains to diving wet, but a possible solution is to dive dry... Although that doesn't seem to be optimal.
3. The idea is the "correct" doubles rig, and you're considering the DIR method and how it pertains to you - and it appears that you're finding out that there may be a way to do this that disproves this tenant of DIR.

Okay, firstly, in the defense of DIR, I will tell you that in my DIR-F course AndrewG never said, "Always dive AL tanks when wet, 'cause otherwise you're gonna die." Instead, he simply gave examples like the one you're mentioning above and had us crunch the numbers. We found in class the same situations that you have above.

Let me know what's wrong with these suggestions:

Twin AL80's on a STEEL backplate. This gives you about 3-9 pounds ditchable (depends on you), which would be nice if for some reason you had to swim up FULL tanks. You and I both know that if you're diving in 1000 feet of water, the idea of a catastrophic bladder failure (which admittedly isn't exactly a common occurrence) is pretty nerve-racking. I don't know that you'd want to rely on the idea of dumping enough gas to get positive or managing even a small lift bag in that situation. Conversely, I agree that dumping all of your weight doesn't make for a very safe ascent. Why not dive with this rig? If you're just looking for more gas, sling a stage. You're probably going to want a different mix anyway, since that much gas is really only going to be useful in a staged deco dive. This would also allow for a whopping ~240+ cuft of gas, if you do a 10% overfill.

Optionally, you could do twin steels with an AL plate, it appears... But you're awfully close, as you mentioned, to your limits (if not over). You've worked on the numbers with empty tanks, it appears, but what if you're not empty? If you can't swim up 22 lbs when empty, what do you think the chances are that you're going to be able to swim up ~35 lbs? I believe that's why DIR recommends diving dry in that situation... Because there's a redundant source of buoyancy. Of course, as you mentioned, it certainly does introduce new failure points and things that have to be managed. This option also would mandate that you get the high pressure fill in your steel tanks. While that's not a problem for you (since you have your own fill station), when you travel you might find that sometimes you can't get a hp fill at some locations. Of course, this suddenly makes your hp 100's a pair of steel 70's. :(

The last I looked, AndrewG (training director of GUE) advised highly that if you dive wet, you use AL tanks - pretty much for the reasons you mentioned above. However, he did not lay down a blanket statement - he simply said to crunch the numbers and find out if the tanks you want to use can be dived safely.

...And based on your example above, it appears to me that diving a double hp 100 (steel) would not allow you to dive safely while wet... Especially if there's no bottom, like you and I dive.

Oh, by the way... I understand that you tested the hp100's for trim (while wet) and found that your trim and buoyancy were good with an AL plate... But I personally found that combination to be prone to "turtling," as it brought my CofG too far behind my CofB. I found the AL80's and a steel plate much better for trim while wet.

...But that's an individual thing too...

[Genesis]

unless I leave the zip undone! :)

That's a less-than-suitable alternative.....

One of the reasons I dive dry in the winter, in fact, is that I can leave the suit ON while moving the boat between dive sites, and it provides me with exposure protection out of the water as well - maknig it MUCH more comfortable to do so.

[Genesis]

If you can't swim up 22 lbs when empty, what do you think the chances are that you're going to be able to swim up ~35 lbs?

No, these are full numbers.

Let me do 'em again....

From my "single tank" HP dives, I KNOW what I need. I need 2lbs on a weight belt with a SS BP + STA, single HP 100 or 120, and a 3 mil wetsuit and booties. Without the 2lbs, I cannot stay down at the surface with a nearly empty tank - even on a full exhale. With it, I am neutral at the surface with 300 psi in the tank, and can control my position in the water with nothing other than breathing mechanics.

Now I KNOW that the tank is -1.5 empty, as I dove with 6lbs with an AL80 on the same rig, and the AL80 is +4 empty. That's what's published, and its about right. Both of those numbers are with valves (which are about a pound each.)

Nitrox weighs about 1lb for every 13cf.

The plate weighs 6lbs, and the STA weighs 2 (measured). The harness is effectively nil, as it is very close to completely neutral.

I am (personally) about +1 or so. I am very close to neutral in fresh water; I can sink with a full exhale in the pool.

The exposure protection (3 mil full suit with booties) thus must be roughly +10 at the surface. (-1.5 - 6 - 2 - 2 + 1) = -10.5, which means the suit must be +10, give or take 1.

Ok.

The twinset in question is twin HP100s, and so is -3 for the tanks. The two valves .vs. the manifold is probably a push. The bands and the STA are pretty much a push. This bears out, in that when I did the weight check with the twinset and my exposure protection, with the tanks intentionally filled to only 500 psi, with no gas in the wing I was just barely negative (maybe -0.5) at the surface. So, within my measurement tolerance, removing the 2lb weight belt was an almost perfect adjustment.

Now, with 200cf of Nitrox in the tanks, I have 15lbs (roughly) of gas in there. If we assume my exposure protection loses 75% of its buoyancy at 4 atm, and very little thereafter (probably accurate or close enough for this purpose) then my maximum negative buoyancy is -22.

My boat's anchor is -22 (FX-37). I CAN swim it up, but its not much fun. I've done it to move it off a wreck when I didn't have a bag with me (yeah, I know, silly me), and was successful without using the wing as a lift bag (which I don't do as I KNOW that's grossly unsafe.) But it was WORK. And actually, it is somwhat worse than -22, since it has chain attached to it, and I have no idea how much THAT weighs; all of it wasn't in free water (some on the wreck), but some was, and it definitely counts!

Chain is HEAVY!

So, assuming the tanks are CHOCK FULL, I can swim up the twinset from the bottom with a TOTAL buoyancy failure. I do not know exactly how much margin I have on that; it depends on how much the chain contributes to my experience with the anchor. I will, however, find out this weekend by simply trying to swim the kit up with a dumped wing from the bottom and see if I can make headway, and if I believe I could make it from 100' down, assuming no shortage of gas (if the tanks are more empty, its much easier of course.)

If the tanks are EMPTY, I should be negative ONLY the loss of buoyancy from my exposure protection. I can EASILY swim that up; that's no different than a single steel or even a single aluminum - you're gonna be negative your exposure protection's loss in any event.

Barely isn't good enough, so I need alternatives. But ditchable weight isn't necessary a good alternative. The problem isn't the tanks, its the weight of the gas and the buoyancy shift of the exposure protection, neither of which I can avoid except by carrying less of either, or getting rid of the shift in exposure protection buoyancy (diving dry.)

Ditching weight at the bottom is only reasonable IF you know you will the weight of gas to offset it when you get up in the water column - otherwise its very dangerous.

That means you must be able to make a prospective calculation on your gas consumption rate before you dump the belt, but your consumption is going to be radically higher at that point due to the brown-water syndrome. Get it wrong and you do the missile imitation. I think the odds of being right on this one suck.

As for why dive a twinset at all for these exposures, the answer is convenience as much as anything else. I've been doing some "two dives on a single HP120" stuff recently, and really like it. No screwing with the tank between dives, etc. There is also another advantage - I get much, much better overall runtimes.

Here's why that works:

Let's say you took a single HP100 with a 19cf pony. You go down to 130. You are limited not necessarily by your gas consumption, but by your safety factor. IF your primary tank/reg fails, you must be able to make the ascent AND ANY REQUIRED DECO on the pony. I can make the ascent on the 19, but deco? Only if its a small amount! Anything else is grossly unsafe, as if I end up having a problem with the primary reg down (e.g. freeflow, first stage problem, etc) I'm hosed. I have to be on my way to the surface immediately on that pony. Second, if I fill that pony with 50/50 as a deco gas to use starting at 70', and the problem happens at 130, I'm skerewed with no way out of the hole I dug for myself. If I pull the deco bottle down there I am at severe risk of a tox hit, and besides, even if I don't tox I've just blown my dive plan in terms of gas consumption, and may not have enough mix to complete the deco. So, for planned deco this doesn't work, as my deco gas isn't breathable at the bottom and I have no redundant bottom gas.

Second, safety demands that I not push the reserves on that tank. If I am buddy diving, I must leave gas for my buddy as I am his redundancy. Thus, I cannot invade the last 500psi or so of the tank, because its HIS. If he breathes faster than I do (and most of my diving partners breathe at anywhere from half again to twice as much gas as I consume) then the ratios get even worse; a couple of guys I dive with would be unsafe to buddy with if I didn't allow for 1000 psi on an airshare ascent. If I'm solo then my pony is my redundancy, but its ALL I have, so I have to be conservative there too, because I COULD have a failure on the backgas.

If I come back on the boat with that 500 psi, its unusable. If I have three tanks, and do three dives, I have the equivalent of almost half a full fill that I cannot utilize. If I'm buddy diving, I may come back on the boat (depending on my buddy's consumption) with 750 psi or more, simply because I have to allow for a potential ascent sharing air with him, and in that case its even worse.

Now consider the twinset.

Same three dives.

I require only TWO tanks instead of three. On the first two I have lots of extra backgas. If something breaks, I have redundancy; I can turn off the offending post or in the extreme case isolate. I lose my second (and possibly third) dive, but I don't lose my safety.

I can also go all the way to the wall on all EXCEPT the last dive on that twinset without risk, as in THIS case the redundancy is my "next dive"'s gas supply!

Let's say my "rock bottom" reserve is 30% - that is, I want to leave 30cf in the tank for brown water (non-overhead environments here.) This is 90cf between three 100cf tanks! But on a twinset, I leave only 30cf - on the last dive - on the first two, I have godawful amounts of redundant gas. So I have 170cf to breathe.

In most cases, I can do three dives on one twinset, yet I am carrying less gas in total than between three AL80s, and far less than three HP100s. My safety factor is much higher on the first two dives, and identical on the last.

If I decide to do planned deco, and sling a deco bottle, I have redundant backgas and no longer need to fear a failure at depth with a gas supply I can't breathe down there. In fact, I can now do a first dive of the day as a decompression dive, and do another, on the same backgas, as a no-deco dive, provided that I have enough to breathe. While I won't get THREE dives out of a set of doubles doing this, I will likely get two, with the second being a "NDL" dive.

Double HP120s get too heavy for this to work, as the negative buoyancy gets out of control and they are long besides. But the funny thing is that the HP100s, because they are so much shorter than the AL80s, are actually MORE comfortable in the water (at least they were in the bay yesterday!) than either AL80s or a single HP120. The double HP100s are above my butt with the valves right at head level, I can get to everything easily, the isolator is right at my head, I don't bang my head on the tank or valve, and in general its a very comfortable setup.

Yeah, its heavier out of the water. So for the 2 minutes I spend climbing in and out, its heavier. I humped the entire kit from my dock back to my pool yesterday afternoon, about 300' or so, and from where I stood up to the dock (about 200' out) and it wasn't bad. The 20' I have to carry it on the boat deck is a non-issue.

I don't see the downside to diving the twins, but I do see plenty of upside. Besides, if I take 'Mix training, twins are a necessity - may as well get used to them now.

[SeaJay]

It boils down to this...

If you can swim up your twinset with an empty bladder and full tanks... And if the weight distribution feels good... Then I wouldn't worry about it.

If you can't... Well... Then either you need a redundant source of buoyancy or enough ditchable weight to ensure your return to the surface. If you don't, then you're using the wrong gear.

There are other options, too... A thicker wetsuit (which, of course, has all sorts of drawbacks, including the fact that it might not be the right exposure protection), bleeding your gas down to get more positive (slow and permanent - not to mention that you're draining your life support) and a lift bag (doable in a pinch, but difficult to manage when doing the 50 other things in an emergency).

Bottom line: If you can swim up the rig, I wouldn't worry about it. If you can't, then I'd consider sticking with different tanks.

Sorry I'm not as verbose today. :D

[Don Burke]

Genesis once bubbled... Now the general rubric is that you don't dive steelie doubles in a wetsuit. The argument goes something like this - a complete BC failure will kill you.Actually, the guidance from a rather outspoken DIR authority is that you need to be able to survive a BC failure, swimming if you can, dropping something if you have to.

I've seen a message from him saying that there are some steel tank setups that work with a wetsuit, normally with an aluminum plate.

It's either on techdiver or quest.

Granted, most of the time you need to go to aluminum tanks to come up with enough ditchable weight. That isn't a hard and fast rule.

[Genesis]

Ditching only works if the negative buoyancy you have is a constant.

It is not in a wetsuit. It is not even in a drysuit, but it REALLY isn't in a wetsuit.

If you ditch in a wetsuit, and cannot stay down as a consequence, the too-rapid ascent is extremely dangerous - and task-loaded, its doubly bad.

More when I've tried swimming it up :)

[Doc Intrepid]

Have you ever heard of 'analysis to paralysis'?

You're gonna burn out a circuit worrying about this.

Get an aluminum plate. Get an OMS wing with double bladders.

Go dive the steels in a wetsuit and enjoy it.

No worries.

Doc

[MikeFerrara]

HP 100's work ok with two piece 7 mil suit. Even your water isn't warm enough for me to dive in a three mil.

[Hallmac]

Genesis in your senerio of ripping a hose on entry why wouldn't you just flip the tanks up side down and inflate the wing with your second stage. You could then gain the lift needed control it with the dump valve and swim it to the shore or boat after inflating at the surface?

Hallmac

[Genesis]

Its 80-83F on the bottom at 100-130 right now! How warm do you need it to be?!!!

I'd ROAST in a 2-piece 7 mil right now... plus the Michelin Man thing doesn't work for me... I hate it. A 3 mil hooded vest under my 3 mil full is good for me down to the mid 70s, at which point I give up on the wetsuit and go dry.

Last weekend it was 80F at the surface, 82-83 below about 30'. The reverse thermocline is back and will be with us until about the first week of December, at which point I give up on the wetsuit and go dry until May. :)

[paulwlee]

Looks to me like you just don't like the idea of ditching weights at all. In that case, the tank choice really doesn't matter. (As long as you can be properly weighted -> not overweighted, and let's ignore trim for this discussion.)

If you are set on diving with your wetsuit, there are only two choices left. Dive with some other lift source such as a lift bag and reel/spool, or dive with smaller tanks.

[Genesis]

.. I believe that ditching at depth (.vs. on the surface) is a poor choice in nearly all cases....

And also not necessary, as there are other choices.

I hate "solutions" that bring more risk than the original problem being guarded against. That is, if I have a risk of one in 100,000 of something bad, and the "fix" for that can hose me 1 in 10,000 uses, I'm actually 10x WORSE off to try to mitigate the original risk!

Lots of stuff in diving seems to be that way - people and agencies have issued some "rule of thumb" without thinking it through.....

[mgri]

Did Genesis just surpass SeaJay for longest post ever?

I'm just poking guys. I like reading both of your posts because you guys like to "think out loud".

Quick question on the weight of a typical DIR/HOG rig. Has anyone every checked to see if all the D-rings and stainless or brass clips adds up to negative weight or do you thinks it's a wash due to the buoyancy of straps and cams? Sometimes I feel like I've got an extra 3lbs of steel and brass.

Mark

[Scuba_Vixen]

and swim your butt up..once the suit uncompresses, you can use the reel drag to control the ascent..once at the surface at the boat, reel the weight home...

Not bad thinkin' for a blonde, eh?


Me, I'd still go the Al bp and redundant bladder bc...as previously suggested..



Darlene

[SeaJay]

mgri once bubbled...
Did Genesis just surpass SeaJay for longest post ever?

Mark

Not even close. :D There's been times when I've written small novels... And done that many times in a single thread. :D

Gen, I don't really see the problem here... The bottom line is, "Can you swim the double hp100's up (AL plate, salt) with a 3 mil wetsuit on?"

If not, then opt instead for a pair of double AL80's on a steel plate and put the extra few pounds on a belt or in some other ditchable form. I doubt you'll ever use that, though, since you'll probably be able to swim this rig up anyway.

And dude, if you don't need it to be ditchable, then put your weight somewhere else... Like thread onto your webbing somewhere. Or, you could use a little of each so that your ditchable is only a few pounds...

[Boogie711]

... do you mean as in similar to the e7-100's from PST, or are they a different setup? Just curious.

[Genesis]

Twin E7-100s, the new ones with the standard 3/4" neck threads.

[SeaJay]

I can't wait to see if you can swim those up, Gen... 'Cause if you can, I might look into that setup myself...

Those new E7's have some serious promise.

[divermasterB]

Nice discussion here.

Every time I have been in my doubles setup, I have been in my drysuit.

LP95's w/Steel BP

I dove them once in a pool with no exposure protection and they were very negative. I am going to have to look into an AL BP before I try to take this setup to a warmer climate. Even dropping the AL BP seems like I will need to come up with some more buoyancy. I generally wear a 3 mil shorty in anything over about 72 degrees.

[ERP]

Aren't the new E7-100's the same size as the old LP80's?

I have a set of 80's doubled up on a SS backplate and I'm a good 8lbs heavy in fresh water with an empty tank wearing a drysuit and 300wt fleece undies.

I haven't gotten them to the ocean yet, but I figure I'll need only a couple of pounds at most.

I'd think it would be a pretty extreme effort to swim them up full if I were diving wet.

[sasdasdaf]

In anything less than a drysuit, your double LP95s are going to be extremely negative. The most positive rig I have dove with was comprised of a drysuit, DUI 400G undergarment (which is very positive) and AL backplate. With double LP95s, I was probably just right in salt water.

So if you are diving with an SS plate, you could switch to AL and improve your weighting. And if you are in fresh water, you should definitely switch.

In a wetsuit LP doubles are a bad idea.

[Genesis]

are -1.5 each, with the stock valve. Doubled they're about -3 + the bands, or -5 or so total, when empty.

I had 500 psi in them when I started my weight test, and was about a pound or two heavy with the wing empty. I had ~2.3lbs of air in the tanks. That means the rig was almost EXACTLY neutral with no gas at the surface in a 3 mil wetsuit - for me.

We got blown out this morning, but we're going tomorrow AM - I'll post my results in the evening when I get in..... If I don't post tomorrow night then you'll know that I sunk like a stone :)

[newton]

Ditching isn't *ALWAYS* bad!


Genesis once bubbled...
.. I believe that ditching at depth (.vs. on the surface) is a poor choice in nearly all cases....


First of all, I highly commend you on doing your own analysis of what's going on, regardless of what anyone else says. Ultimately, you are responsible for your own life, regardless of what anyone else recommends.

Having said that, I disagree that ditching at depth is *never* the right solution. I've read most of your posts regarding ditching on DB the last few months, and I agree with most everything you've said.

Ditching a *LOT* of weight at depth and turning yourself into a Polaris missle is not a great solution if there is a better solution to be had. (And, we're having this discussion to see if there is a better solution.)

One of the solutions you've thrown out is using an AL plate, which gives you 3# of ditchable weight. I'd like to see more like 4-6# of weight with doubles, but I think ditching that much weight (at depth) is not the end of the world.

Heck, if you can swim UP 22# of weight, then you should be able to easily swim DOWN the extra 6# of buoyancy (worst case) you're going to have as you approach the surface.

Ditching a few pounds of weight isn't going to cause you to become a missle, and unless you're completely out of air and have no air left in your tanks, the loss of a few pounds will still allow you to control your ascent.

At the two extremes we have way too much weight at the beginning of a dive. Losing your wing at this point is *VERY* bad, and is probably the most likely time for it to occur. (Forgot to turn on the tanks, forgot to hook the inflator hose, the wing snagged and ripped off entering the water, it didn't work and you didn't realize it until after you're in the water, etc..). Dropping 6# of weight at this point would still require you to swim up your rig, regardless of where in the water column you're at since you'd be negative. Ditching is a good thing here.

At the other extreme, we're going to assume somehow you've lost your wing at the end of the dive. Again, this is *much* less likely simply because generally speaking, usually things break when they're first used. However, Murphy would tell us otherwise, so we'll plan for it. Somehow we screwed up, and we've got just enough air to get to the surface (assuming we have to work our tail off). At this point, we're no longer 22# negative. There are two solutions at this point.

1) Don't ditch the weight, and swim up the rig. Heck, assuming we've done a dive, we're no worse off than we were at the beginning of the dive when we chose to ditch the weight last time this happened.
2) Ditch the weight. (Note, if we can handle dropping weight at this point, then we should be able to handle dropping weights at *any* other time during the dive, since at this point it will make it the hardest to deal with)

So, instead of -22# at depth, we've lost 15# of gas, so we're at -7#. If we ditch the weight (let's say 6#), we're still at -1#, which is easily managable. Unfortunately, the -1 is going to end up at +9 at the surface (due to wetsuit compression adding 10# of buoyancy).

I guess I'm of the opinion that if I can swim *UP* 22#, I can pretty easily swim *down*, or more realistically, slown down my ascent even with +9# of buoyancy.

Again, doing a risk analysis, I believe the most likely chance of failure is at the beginning of the dive. Ditching a small amount of weight at this point I would not only say is acceptable, but optimal. (Again, the amount of buoyancy change would be far less than the shift due to air consumption). This is *ESPECIALLY* important of you've got no bottom, or the bottom is deep enough to be unsafe for your mix/training.

At the end of the dive, even those there is the risk of becoming 'overly buoyant', you can offset that risk by either not dumping your weightbelt, or by understanding that the loss of weight will cause buoyancy issues, but these issues can easily be overcome by swimming down to slow your ascents to a managable.

(I'd argue that one should feel comfortable with ditching the weightbelt in *ALL* situations, since if you're in a bad situation, task loading will be hard enough that you don't want to have to determine if you've got enough 'air' in the tanks to offset the loss of the ditched weight.)

Feel free to flame away where I've missed out on some important detail!


Nate

[Genesis]

is that when it becomes a problem you're low on gas.

That is precisely when fighting to stay down is bad, because your supply is limited.

Otherwise, I agree. But if I can swim up the rig, or find an alternative (such as a bag) to a completely dead BC, then I think I prefer that.

I'll post more after tomorrow when I dive 'em....

[SeaJay]

Looking forward to it, Gen... Let us know how it goes.

[Genesis]

Did two dives on my new doubles set today.... twin Hp100s.

I've got some work to do with the position of the bands and where the wing is. I was butt-light on the first dive (full), and butt-heavy on the second (half full at start), which was pretty bizarre. . You get the opposite shift with ALs and to some extent with single HPs, but not with the doubles. I think the bands need to be moved up on the tank (I'm about an inch or a bit more below the break; I think I need to come up about a half-inch or so. I had the wing on the bottom set of holes (up as far as it could be set) so the only way to get more "offset" is to move the tanks down. That shouldn't cause valve access trouble.

(Does that make sense in terms of which way to move the bands and wing? I think I've got the mechanics right on this....)

I also discovered that the "fit" of the plate harness is WAY more important. I had just replaced the webbing, and it was too loose on the first dive. Adjusted that, and it was much better on the second.....

As for swimming up the twins from 130', not with the Quattros. But I also attempted to salvage a lost anchor, which was about the same weight as my anchor, and there's no way I could swim IT up with the Quattros either. With the Twinjets I'd have been able to do it - so its lift bag time for me (which I had with me) if I dive these wet with the Quattros - but not by much. With the Twinjets, even though I know they're "devil fins" according to many, I'm sure I could swim them up. Then again blades have always been a bit "strange" as fins for me...

Reboarding was nowhere near as tough as I expected, nor was gearing up.

The "big deal" was trim, and I suspect that with adjustment to the band and wing position that is readily solveable.

With the two dives, even with my gas consumption a bit higher than my usual (about 0.5 for SAC) across both, I still did both dives and had a third of my original gas remaining. I could have conceivably done a third today, but we ran out of daylight.

It is like learning to dive all over again though from a trim perspective...

More bubble time to follow...

[SeaJay]

If you can't swim that rig up, then it sounds like you're using the wrong gear.

It sounds to me like you'd be better off with a set of double AL80's on a steel plate.

Or, dive dry.

I'm not a fan of leaving it up to a proper lift bag deployment to save my life. What if you drop it during deployment?

Even if it's done correctly, it'll still take all sorts of precious time to get deployed... And you'll still have the problem of being submerged in like 5' of water when your bag hits the surface. Of course, by then you'll have more buoyancy in your suit, but you get the drift...

You know, Gen, right about now I could point out that all of this thought and conversation and experimentation could have been avoided if you'd just believed what DIR was teaching... That as a general rule, AL80's should be used when diving wet...

Would you like a glass of Kool-Aid? :D

Of course, I'm just teasin' ya, bud. :D

[Uncle Pug]

You might want to put the bands right up to where the tanks start to round over. I only have one set of holes in my Explorer wing so that part is easy for me. :D

[100days-a-year]

THanx for takin' the time to try all these different configurations and report back.I'd be interested to see how much actual bouyancy is lost in a wetsuit at depth.It would take say increments of #1 at mebbe the surface and at 100'or a stainless fishscale tied to an empty suit a the same depths.I often see divers overcompensate for wetsuit bouyancy.Never good to be heavier than you can lift with your BC and tanks full but I see it.

[ERP]

I had the bands about a half inch from where they start to round over on my LP80's and ended up moving them the extra half inch down.

[Genesis]

I may as well just use the Twinjets :) I know I can swim that rig up with them on my feet, and will test it once again shortly (as soon as the weather stops blowing - its supposed to be ugly this coming week)

The bag is easy - I DID try that. Slip the strap over the left arm, then inflate. With very little gas in there I can easily swim it up. That's not coming off during deployment. And this IS only to cover the one-in-a-million shot of the BC being totally hosed at the start of the dive, with a maximum mass of the gas.

This was the first time I really made a "maximum power run" with the Quattros, and I was shocked at how much weaker they are than the Twinjets when you really have to put the coal to them. I had run into issues with currents before, but this was the first time I could quantify it - and trying to lift that anchor was enough for me to be able to quantify it. The thrust difference has to be at least 30% - and perhaps more. Since I HATE Jetfins, and the Quattros I can deal with but they just don't do it in terms of power, I guess I either have to learn to live with the Quattros or just dive the Twinjets :)

Will move the bands this week since I have to dump to refill anyway (my O2 bottle isn't full enough to mix on top of what I've already got)

Twin AL80s are going to make me MAJOR butt-light when they get drained. I suspect I'd be REAL unhappy with the trim in those... probably beyond what I can fix with band and wing positioning.

More as I know more.... this is an interesting exercise, and I really like not banging my head on the tank or valve diving the doubles.

BTW, the dreaded "turtle stuff" wasn't a big deal. Yeah, I could get "overcenter" too far and roll on my back, but it was easily recoverable. No problem there of substance.

[Dryglove]

Dont worry about twinjets. Just get a set of these and you will easily swim your doubles up

http://www.jetboots.com/rndimg/diverad3.jpg

:D

[Genesis]

Uh, yeah, that would work.

Seriously, the Quattros may just be a matter of technique. I've dove the Twinjets for a long time, and have gotten used to them. I can both flutter and frog in them, and my reason for getting a pair of Quattros is that I can't back up worth a damn in the Twinjets, and figured that some day I'd find that important - also, there is a conceivable snag risk from the slot on split fins.

Anyway, I find that I can get a lot of power with a frog, but its not consistent (that is, its "bursts" of thrust, as a frog is, rather than smooth thrust with a flutter), and that the flutter is nowhere near as powerful with the Quattros as with the Twinjets.

I had run into current with the Quattros the other day (before the doubles) and really had to WORK to beat it - a current that I didn't think would have even bothered me in the Twinspeeds.....but today was the first time I really QUANTIFIED the difference with an attempted dead-thrust test.

There was an anchor down there that I wanted to salvage. I was going to bag it, but had to move it a bit first, and figured I'd swim it up as it was either as heavy or a bit lighter than the one I have on my boat. No dice with the Quattros. I later ended up giving up on the salvage, as I was unable to separate the anchor from the mess it was entangled in, but it gave me a really good opportunity to get a "benchmark" on the fins.... which up until now I had not managed.

Always interesting testing new stuff..... :)

[Uncle Pug]

I don't think you will be swimming them up with your splits either.

[Scuba_Vixen]

You called the fins twinjets several times, but from the description of what they could do, they sounded like twinspeed (longer and without the holes in front of the foot pocket)...then at the end, you called them twinspeeds, would you clarify please...

Keep us posted

Darlene

[Genesis]

They do have the "holes" :) The pockets are open at the front.

I have a pair of the black ones (negative) that I've put spring straps on and like a lot. My reason for working with the Quattros is really more of a preparation thing (as is the doubles) as "hard" overhead environments and splits don't seem to get along well among the people who I've talked to.

Nonetheless, the Twinjets simply have WAY more thrust, although if this is a matter of technique I suspect that more dives on the Quattros will correct that as well. They're relatively new to me (perhaps a half-dozen dives overall)

[Boogie711]

I hate split fins - I like the big paddle fins. I find it gives better control over buoyancy, and you can haul ass if you need to. They're great for frog kicks.

Anyway, I had Quattro's. Good fins, no complaints. But I just went to a set of IDI Power Fins, and love them - they're supposed to be the clone of Jets, just shaped a little different, and with a larger footpocket.

If I was going to do it all over again, I'd get Turtles or Jets. I can't back up worth a damn in my Quattro's, but I can do it just fine in my IDI's.

[roturner]

Boogie711 once bubbled...


<snip>

I like the big paddle fins. I find it gives better control over buoyancy, and

<snip>

This is an interesting comment. Would you care to elaborate on that?

R..

[Boogie711]

I don't want to hijack the thread.

I just feel that with stiff fins, you can make little, careful, controlled movements. If you're in a hover and feel yourself drifting or moving slightly out of trim, you can make a slight twist with a toe or ankle and gently correct the movement right away. With a 'floppier' fin, you can't do that.

[Genesis]

Hm... may have to try those.

The problem I had with Jets was that the foot pocket sucked canal water; the fin never felt secure on my feet, and I never had the kind of control I should have.

The power fins appear to have a longer foot pocket.... which might make them acceptable to me. I'd love to find a decent paddle fin - so far I'm just not "getting there" with the ones I've tried in terms of being able to actually get results when in a current or otherwise NEEDING power.

Ok, enough thread hijacking - back to the doubles! :)

Looks like we're going to be blown out here for the entire week - perhaps the weekend will be ok to get out... Check this forecast for today...

A SMALL CRAFT ADVISORY IS IN EFFECT

TODAY
NORTH WINDS 20 TO 25 KNOTS...WITH GUSTS TO AROUND 30 KNOTS
EARLY...BECOMING NORTHEAST AROUND 20 KNOTS BY AFTERNOON. SEAS 4 FEET
NEAR SHORE AND 8 FEET WELL OFFSHORE THIS MORNING...4 TO 6 FEET THIS
AFTERNOON. BAYS AND COASTAL WATERWAYS ROUGH.

Eeek. I think I'll clean the house :)

[Genesis]

I have found that I can go to an AL plate with the double HP100s, and still remain neutral very close to the surface with low gas.

Dove them today set up on the AL plate, along with moving the bands up higher. They're dialed. Not much different now than diving a single, except that I have a lot more gas.

My trim is back and I can easily swim them up, stuffed full, from 120'. No problem at all (with a pair of IDI "Jet clones", which actually FIT my feet, unlike the SP jets.)

I like 'em a lot.....

So much for not being able to swim up double steelies in a wetsuit. I can indeed do so, and I need no belt at all.

[ElectricZombie]

Genesis once bubbled...
It is more likely that I will accidentally ditch a belt than have a complete buoyancy system failure. I've seen several inadvertant ditches in the last year, but no total BC failures. So the proposed "DIR" solution trades a very unlikely failure for a more-likely failure, and the latter one can kill you just as dead (especially if you have a deco obligation when it happens!)


If you are worried about a weight belt coming off, you might want to try a channel weight. It is a piece of lead that fits in the recessed channel of the BP.

I rarely ever wear any additional weight with my BP/Wings setup, but when I do, I use a weight belt that has 2 metal buckles. I would balance the rig so that only a small amount of weight needed to be on the belt.

[jonnythan]

ElectricZombie once bubbled...


If you are worried about a weight belt coming off, you might want to try a channel weight. It is a piece of lead that fits in the recessed channel of the BP.

I rarely ever wear any additional weight with my BP/Wings setup, but when I do, I use a weight belt that has 2 metal buckles. I would balance the rig so that only a small amount of weight needed to be on the belt.

But then he couldn't ditch that weight and it would be no different from just wearing heavier tanks.

I find this whole thread very interesting. I think the answer is to go with the Al 80's and a few pounds on the weight belt... wear a belt with the 8 or 10 pounds necessary to compensate with a SS buckle under the crotch strap and I don't think there would be any issues.

[ElectricZombie]

jonnythan once bubbled...

But then he couldn't ditch that weight and it would be no different from just wearing heavier tanks.


The key is to have a balanced rig. If the rig is balanced properly, there is no need for ditchable weight. If a rig is balanced, you can swim it up from the bottom at all times, even with a failure.

I dive AL doubles with a steel BP when wet and no additional weight. The SS BP adds just the right amount of weight to properly balance the rig. I can swim it up at all times so, ditchable weight is not needed.

[jonnythan]

ElectricZombie once bubbled...


The key is to have a balanced rig. If the rig is balanced properly, there is no need for ditchable weight. If a rig is balanced, you can swim it up from the bottom at all times, even with a failure.

So how would you balance his rig? With full Al 80s on his back and a channel weight, how negative will he be at 90 feet in his wetsuit?

[ElectricZombie]

With double 80's, he can probably just use a SS BP with no additional weight and be pretty well balanced. You should not need a channel weight when wet using 80's. Depends on his exposure protection though. If he dives a drysuit, then he might have to add the channel weight.

[jonnythan]

ElectricZombie once bubbled...
With double 80's, he can probably just use a SS BP with no additional weight and be pretty well balanced. You should not need a channel weight when wet using 80's. Depends on his exposure protection though. If he dives a drysuit, then he might have to add the channel weight.

You didn't even read the original post did you?

The question is how negative will he be at 90 feet with double Al 80s? Once you figure out the answer to that, decide if he's going to need to have some weight ditchable.

[Genesis]

swim up double HP100s, full of Nitrox, in a 3 mil full wetsuit on an AL plate from 120'.

No problem at all.

I dive that configuration with no ditchable weight.

[Padipro]

Genesis once bubbled...
Config was a SS BP, double HP100s, 500 psi of gas, 3 mil wetsuit, booties, and the usual mask, fins, etc. Wing is an Oxycheq 70.

Now the general rubric is that you don't dive steelie doubles in a wetsuit. The argument goes something like this - a complete BC failure will kill you.

Hmmmm.. will it?

Let's see where I ended up.

With no gas in the wing, and the tanks at 500 psi, I was just slightly negative at the surface. So, I can stay down when low on gas at any depth from max to zero.

I needed no belt.

I find it hard to believe that you can be so positively buoyant with this rig even with only 500 PSI in the tanks. I'm using double 3300 PSI AL 90's with an AL BP and a new 5 mil semi-dry suit in the ocean with no added weight and I sink like a freakin rock even with the tanks near empty.

Scott

[100days-a-year]

I believe the 90s to be about -7 each full.Hard to find any lit on them as they were a small run for a short time.BTW,I have swum up full lp95s with a SS B/P and no rubber during the summer.It wasn't fun but I'd forgotten my stringer and I wanted to see how difficult it was.The HPs are less negative so I doubt it would be that hard.

[Genesis]

are neutral to slightly negative empty.

So are HP100s.

Now LOW PRESSURE tanks are major negative empty, and with those I'd have a problem.

I do NOT like being overweighted - beyond the obvious dangers, it makes trim nearly impossible to get right.

[100days-a-year]

My lp95s with SS B/P with about 700psi in them were less than 10# negative on a scale UW.I figure the bands,manifold and BP were -7lbs and the webbing,empty bladder and accessories were +2 leaving the 2 tanks @-2.5 each roughly.With neoprene it would be nasty as the weight required to sink the rubber to compression depth would add to the load at depth making them real heavy full .