• Concurrency: 1.9.x uses O/S threads but only allows one to run at a time.
• RAM consumption: On top of memory hungry frameworks, you throw a naive garbage collector and then paste around the concurrency problems by using unicorn and going back to an Apache 1.3-era preforking model, which chews up RAM which is the primary scalability limit of todays apps in a virtual server highly service-oriented world.
• File Descriptors: ruby uses select() instead of poll() and only supports 1024 fds (really?!!?!?)
• Garbage Collector needs to be generational, parallelizable, and have concurrent tenured collection: It is a stop-the-world, non-generational collector
• Pooled, Threaded Backend Connectors: mysql gem only supports one connection, need mysql-plus fork, who knows about postgres — what about pooled HTTP connectors that use HTTP/1.1 keepalives?
• Thread-safe, Reentrant libraries: Based on the mainstream VM being essentially unthreaded, lots of research needs to be done to make sure the libraries and frameworks being used are safe.
• Ruby Apologists: These are not awesome features, these are design bugs. They need fixing, they don’t need a community of people defending them as good.

The problem with non-threadsafe libraries makes just throwing Jruby at the problem more than worrisome. I’m going to wind up needing to do research on which libraries and frameworks are Jruby compatible and potentially bringing along a large debugging problem. The lack of It-Just-Works-Out-Of-The-Box is not the awesomesauce I was looking for in Ruby. There’s undoubtably a way to make it all work, but the effort level looks to be high, and it looks like not only is not everything going to work, but apparently a lot can be expected to break. If Ruby is going to continue to be a leading web framework it needs to work out-of-the-box and if someone runs through one of the popular Rails books out there they should get a nicely scalable web application that comes out of it — they shouldn’t need to spend months turning themselves into a ruby ninja with esoteric knowledge of which bits of ruby can be glued together to produce scalability. It should just work.

The La Nina conditions in the Pacific will transition to ENSO neutral in the summertime and then into a wintertime El Nino, but those warm temperatures will not show up as record breaking temperatures until 2013. Global temperatures will be warm, but I don’t expect more than 0.50-0.55C above baseline on NASA GISS. This is still on par with 1998 even during a La Nina phase, but I don’t expect to see surface temperatures exceed the 0.58 value for 1998. I do expect to see an extremely warm year in 2013.

It is possible that arctic sea ice melt may exceed 2007 this year, but I think that 2013 or 2014 will be the safer bet for a new low in arctic sea ice. The ‘typical’ year for sea ice has been getting so close to 2007 lately that all it will take is winds that are favorable for melting and even in a year following a La Nina we may see a new record in melt, but I’m going to guess that this doesn’t happen. Ice melt should be very close to 2007 this year.

I also expect a simple reversion to the mean for massive weather disasters this year. I don’t think that the trend will hold up and that the record of 2011 will stand for some amount of time (5-10 years at least). With the back-to-back La Ninas we might get back-to-back increasing weirdness of the weather, but 2011 is such an outlier that I think that we’ll see reversion to the mean — although we’ll still see an increasing average mean in weather disasters.

I think there’s a good chance that Europe and Russia may have continuing hot summers and weird weather. That seems to be their new normal. Siberia will, of course be hot. Weird regional weather elsewhere in the world may occur and I think that’s very unpredictable, but it becomes more and more likely over time as the climate warms. I expect that regional extreme climate will surprise us again in some largely unpredictable way in 2012 — I expect that globally the theme will simply be a warming trend, and will be more of what we’ve seen in the past.

I also predict a reversion to the mean in rainfall again as well, which will mean that the sea level drops of the past 2 years will revert and sea levels will rise modestly and start back to trend (trending higher) again, but don’t expect to see any records set here either. Deniers, I do predict, will continue to whine about the seas have stopped rising so that climate change is a hoax.

As far as climate denialism goes I suspect there’ll be an outbreak of category 5 bullshit again this year. With it being 2012 and as I expect a relatively calmer year than 2011, the look-its-not-the-end-of-the-world meme will probably gain a lot of force in the denialism community.

Of course I continue to expect the trend of actual climate science to continue to produce results more in line with the worst-case IPCC predictions and which will continue to paint a bleaker picture.

And since this is an Election year and since I expect it to be calmer, I can’t imagine that there will be much useful and significant progress on the policy front.

For 2013 I expect to see a strong El Nino, of >= 2.0C to develop as the ENSO system has had time to recharge over the past 2 years and this typically precedes a strong El Nino. As a result I expect to see surface temperatures in 2013 to crush records, along with a lot of climate disasters, plus a collapse in the arctic ice in either 2013 or 2014. But that is the year after next.

Since the question came up over if a 40# wing would be capable of floating gear when boat diving and ditching gear on the surface I went out and did some tests with my gear, with full tanks, throwing the gear into the water and adding lead until it sank. The tests in freshwater were in some cases done with gear configs that I wouldn’t necessarily dive in freshwater because they were too inherently overweighted (although they do highlight what might happen if divers forgot to adjust gear for freshwater compared to salt).

Test Config

• freshwater
• steel backplate
• Al14 argon bottle (full)
• Salvo 10Ah Can + Halcyon EOS head
• No v-weight
• Halcyon 40# Evolve Wing

Lessons

The first lesson is to use an Al backplate for freshwater and Worthington tanks. Otherwise the diver is likely going to be horribly overweighted. With 2.5% density change between freshwater and saltwater the roughly 300-350# of diver plus gear (for roughly ~200# males anyway) is going to need to subtract 7.5# or so of weight going to freshwater.

Double-130s are for helium mixes, not for nitrox 32%. Beginning divers should be buying 40# wings and double-100s not 60# wings and double-130s. This is a mistake that seems to get repeated with every generation of newbie technical divers (including myself), but double-130s filled with nitrox 32% are silly. Even for Tech-1 level diving, double-100s/double-85s make a nice single dive. The advantage of double-130s with Tech1 dives is in being able to do two technical dives off of a single fill, or when needing substantial amounts of reserve gas due to overhead penetration.

40# wings will float a properly balanced rig for recreational diving in double-100s, or Tech 1 diving in double-130s. There’s no real need for 60# wings outside of Tech 2 level diving (even with double-130s), or in the edge case of support diving for Tech 2 divers when the diver may have lots of 32% in backgas and may be very overweighted in order to deal with light stage bottles the bottom team may be handing off.

When it comes to undergarments as well, it is possible that undergarments that have a poor trade off between buoyancy and thermal characteristics could lead to divers needing substantially more lead than the config that I use in order to sink. The problem there is a poor choice of undergarment. The solution is going to be better thermal solutions (undergarment or possibly heating vest) which have better thermal properties in trade off for how much loft they have and lead they need to sink.

Another problem leading to large size wings can be that the diver is inherently overwieghted. This may be due to the diver not understanding how to get all the gas out of their wing and drysuit. And while I weight myself for a flat wing with no gas, I do shoot for comfort with low tanks, and I do consider that the dive may end with an empty, buoyant Al80 in the case of Tech 1 level diving. Having a nearly empty stage, 1000# of backgas and needing to breathe out of the bottom of your lungs is not a fun way to end a technical dive, and probably not safe, so my configurations weight me properly for that. The 3.5# of estimated “overweight” on my double-130 config that i actually use in the lake is there for comfort.

The question of rescuing a diver in double-130s and 40# wings is also a question that depends mostly on if there is nitrox in the tanks or not. With two divers in double-130s and 40# wings filled with 21# each of 32% simple math shows that it will be difficult to raise a diver off the bottom using a single wing. However, with helium in backgas, 16# are dropped off that equation and the 40# wing should be sufficient. Again, the bigger question here is why the divers are diving with that much nitrox, and at that point we’re typically talking about recreational diving, where the double-130s are overkill.

Summary

This gear config question I think highlights one of the original Hogarthian principles of not bringing gear you don’t really need. Recreational dives on 32% with double-130s is clearly overkill, as are adding 60# wings to that config. LP-85s and HP-100s are much better suited tanks if redundancy is required or for new technical divers. The leap straight from single tanks into double-130s and 60# wings is a common mistake which seems to be repeated in every generation of new technical divers. Even now I’m less and less comfortable with even doing Tech1 level diving in double-130s, when most Tech1 diving simply doesn’t require that much reserve gas.

The question also shows how poor initial gear config choices and poor skills may lead to a cascading effect of more poor choices. Divers need to understand how to dump gas effectively and how to weight themselves correctly to begin with. They need to both not be overweighted and not underweighted. The selection of tanks and backplates and other weight need to allow for changing gear configuration between freshwater and saltwater. The selection of drysuit undergarment and thermals equipment needs to reduce maximize the amount of warmth for the amount of lead needed to sink the diver. A diver that is carrying a lot of excess lead needs to question and solve why that lead is there in the first place, and not simply continue to compensate by using oversized wings.

The problem with 40# wings and double-130s is also seen to largely revolve around misusing those tanks on training dives filled with 32%, and not using them on technical dives with helium.

OOPS: pressed ‘publish’ too soon — come back in a few days for tests in saltwater…

STOP: Bad Trim

Get your trim sorted out. With a 20-30 degree head up trim it will be much more difficult to accomplish a valve drill. The tanks will pull away from you, it will be more difficult to get your head up higher, your posture will be all wrong and you will start to visibly struggle. That typically leads to divers kicking around the dive site and to bad buoyancy control during the valve drill.

I’ve written up a whole article: Steel Doubles, Cold Water and Trim, on fixing trim in doubles. All of these problems should be addressed first before the diver starts to think about valve drills. It is entirely possible that the diver has gotten ahead of themselves and need to go back to single tanks to learn what trim and stillness really mean before attempting them in doubles. Trying to do valve drills before learning trim is definitely putting the cart before the horse, and will just lead to struggling.

This is a case where it is desirable to be able to hit zero to 10 degrees of trim while at rest and still before attempting a valve drill. And this isn’t just about looking good or being a Trim Nazi, this is about starting off comfortable in the water and being able to demonstrate a comfortable valve drill without struggling. If you watch a GUE instructor demonstrate a valve drill they will begin from a position of having very good trim and will execute a drill with very little motion or struggling. Those two things go together, and the ability to be trim and comfortable and not struggle is not just for super-human GUE instructors.

STOP: Loosening up Waist Belts

You don’t need to do this, and this is counter productive to trim, and its a symptom of bad trim and tanks sliding down your back due to fighting 30 degree or worse trim. You need to be able to lean forwards and get to zero trim — comfortably — and then your issues that make you think you need to loosen up your waist belt will go away.

STOP: Hiking up Tanks

Same thing. If you are reaching back and grabbing your tank valves and hiking them up 9 times a drill before every time you manipulate a valve you need to rewind and fix your trim issues and other positional issues first. This is a symptom of other problems that hiking your tanks up isn’t addressing.

STOP: Tight Undergarments

If you stretch your hand above your head and across to your other side in your undergarment and the seam down the side of your body constricts that motion then your undergarment is likely too tight. Get a bigger one or get a custom cut, or lose some [more?] weight.

STOP: Tight Cave Cut Suits

Get a standard custom cut DUI and not a Cave Cut and your valve drills will thank you. Drysuits do not have to be perfectly tight, the point of them is not to try to be so tight to avoid getting gas in them — its the users job to manage getting the gas out of the suit, not to have the suit attempt to do that for them. The snugness may feel good and help avoid some dumping of gas, but the mobility restriction is not going to be worth it.

STOP: Running Too Much Gas in Your Suit

If you have a large bubble of gas in your suit and you go into a trim up position so its up near your shoulders and you reach back with your left arm in order to manipulate a valve you will dump an enormous amount of gas out of your suit. Any excess gas (which we often have in doubles when doing valve drills since we’re 20# overweighted by having double-130s jacked up with 32%) should go into the wing, not the suit.

DO: Get Trim and Still

Trim is more than just being flat, it is all the rest of the body position that comes along with it. Read my article on trim again and go out and practice being comfortably trim before you attempt valve drills. Keep in mind that trim position is about the entire body position — knees are not bent, fin tips are out, etc — it is more than just about being flat.

When you find trim you also need to be still, and you need to be conscious of how much fin motion you have. When under stress (and ideally a valve drill should not be stressful, but it often stresses out students) your fin tips should still be roughly flat and should not be agitated and moving. Any GUE Instructor should be able to demonstrate a valve drill with minimal fin motion throughout the drill and will make it look easy and that is what we are looking for.

Start with trim and still. If you can’t do a valve drill without kicking up a ton of silty bottom then you both have bad trim and are not still. Your fins are down in the muck, kicking around and stirring it up, and the valve drill probably isn’t teaching you much other than possibly the correct procedural sequence (although you are probably stressing yourself out substantially and you’d learn more if you were more comfortable).

DO: Head Up, Shoulders Back, Elbows In

This is important enough that I wrote a whole different article on Valve Drill Positioning, which you should read. The net result is that you should be able to put your head back (helping you with trim position) and bump your head against your isolator (even with significantly dropped tanks). From there it should be relatively easy to put your hand on the back of your head and naturally reach your isolator.

If you have difficulty, when standing up without gear, in putting your head back and reaching the back of your head then you probably have mobility issues and need to work on some stretching and PT. That is going to be the fastest way to help reach your valves, not trying to hike them forwards.

DO: SLOW DOWN

“Slow down to speed up”

“Slow is smooth and smooth is fast”

Don’t try to rip through the drill, you’ll forget the steps and struggle and ultimately wind up going slower and it’ll take more time to learn how to do a naturally correct valve drill. Keep it slow and smooth and don’t struggle. Don’t get so fixated on reaching your valves and signalling rapidly with your light, and fixated on your reg about to breathe hard that you allow your body to tense up, your trim to break upwards (and the tanks to slide back) and your fins to start going. You should be able to reach backwards with a mostly smooth motion to reach your valves without moving the rest of your body — your arm and hand should mostly move in isolation to the rest of your body.

It is true that valve drill should be done efficiently and at a higher level (generally Tech2/Cave2) speed and efficiency become more of an issue. For the diver just learning skills, however, speed is counterproductive and pointless if the drill is not done correctly or it causes near epileptic seizures. It is better to slow down movements to the point of exaggeration in order to isolate them and get the drill done correctly.

DO: Stretch

Stretch out and work on getting your head up and work on mobility in your upper vertebrae. Stretch out and work on shoulder mobility and being able to reach behind you.

If you find yourself not able to do a valve drill when trim and want to start hiking your tanks up and doing other kinds of cheats, you probably need to fall back on simple stretching exercises.

Everyone is Head Heavy

Seriously. Double tanks, cold saltwater, heavy drysuit, and everyone is head heavy. The divers who are diving around with 30 degree head up trim are not doing that because they are head light — they are compensating by migrating the gas bubbles up to their shoulders and dropping their knees to stabilize themselves against tipping over forwards. Head Heavy is always the problem to fix in these conditions.

Single Tanks Are Easier

Single tanks are way easier to trim out. New divers without doubles experience may not notice this, but single tanks are way more head-light, and proper body positioning alone should get divers into correct trim. Some adjustment may be needed with weighting, but a single steel, with a weighted STA and a few pounds on a weight belt is usually a configuration that can be trimmed out by anyone with practice.

An exception to this might be very short divers where a weight belt around their waist comes ‘high’ up on their gear, where some form of plate weight / tank weight placed lower than the waist will have enough of a lever arm to trim out the equipment. What we’re looking for is 6-8# or so placed near the bottom of the tanks, with the rest of the weight roughly ‘centered’ (SS backplate, steel tanks, weighted STA).

Divers should ideally achieve stillness and good body position and trim in singles before moving on to doubles, which only make everything much more difficult.

Also conceivably, single tank divers may be head light. Particularly with Aluminum tanks and a large 20# weight belt divers will tend to be head light. That is why Steel tanks and a weighted STA can help to distribute appx 10# of weight *forwards* on a single tank diver. A single tank diver may also need to bend their knees more, bringing their fins in to their body and shortening their legs in order to prevent their feet from dropping. It is only the *double* tank divers who are always head heavy. This is why single tanks are generally easier to find trim position somewhere simply by adjusting body position.

Tank Selection

Most commonly used tanks can be trimmed out well. Double Aluminum 80s in cold water, however, are a bit vile (Apologies to Bob Sherwood, but I hate ‘em). The only advantage they have is that you usually can’t find a large enough v-weight for them, so the diver is forced to wear 8# or so on a weightbelt in order to get enough lead on them to sink. On a roughly 6-foot tall person this is ideal because the weightbelt will come low enough to produce a lever arm to counteract the butt-light nature of aluminum tanks. Given that you have to add so much lead to Al80s to sink them, it is actually a lighter configuration to use double-HP100s where you get more gas, have to carry less lead, and overall your geared up weight is going to be less. The only real advantage of the Al80s might be slightly lower weight of the tanks, but adding huge v-weights will eliminate this advantage entirely, so this only applies in the case of having a very large weight belt. The lighter weight of the tanks also doesn’t produce any additional safety for the diver when climbing up ladders in rough seas compared to steel HP100s.

Also to be avoided are double-LP72s. They are thin walled steel tanks with little metal on the butt end of the tanks and are much harder to trim out than other steel tanks. They are also lighter and more buoyant and require more lead to sink, similar to double-Al80s.

The old PST HP100s with smaller necks are more difficult to trim out, but they’re on the edge and it is possible to trim them out and dive them just fine, but shorter divers will find them easier to trim out. They would probably need to be avoided by taller/bigger divers with short arms/legs who have more difficulty with smaller tanks.

What works? I can attest that PST E8-130s and LP104s, Worthington/XS-Scuba X7-100s, X8-119s, and X8-130s all make fine doubles along with Faber LP85s. Its likely that most of the rest of the tanks of similar construction will also work, although shorter tanks will tend to be more difficult (e.g. I prefer 130s over 119s).

Stillness

You have be able to get still in order to determine if you are trimmed out correctly. The hands and feet need to be able to be quiet with no errant fin kicks, or you will not be able to determine what your trim really is. It is entirely possible to trim out poorly configured equipment by finning nearly constantly and doing a ton of work. The diver’s trim will look good on video, but they will be constantly moving, doing lots of work and they will be nearly exhausted by the effort.

Trim and balance should be evaluated from a position of stillness in the water. If a diver is still and they wind up “lawndarting” head-first in an uncontrollable forwards roll, then this is an indication of the need to fix either body position or weight distribution. By being still the diver can get this information about what their weight distribution is really like — otherwise the diver may be able to achieve trim but only at the cost of constantly kicking forwards to counteract head-heaviness.

Zero Trim

In order to evaluate trim the diver really needs to be able to get both still and get to zero trim. Most divers have a poor concept of what trim position feels like and it typically feels very head-down to them. This is likely the result of getting into doubles too early, with bad trim and swimming around head up with roughly 30 degree of trim all the time. Actual flat trim feels wrong and this feeling needs to get broken. Its likely that the diver attempting to find flat trim will be head-heavy and really flat trim will cause them to ‘lawn dart’ and they will fight this feeling.

Being Flat: No Dropped Knees

Divers will typically attempt to stabilize themselves against being head-heavy by going head-up and dropping their knees. The diver need to both get to zero degree trim and lift their knees up and get flat. This very often feels completely unnatural and out of balance and the diver will fight this position, but this is the position that we are shooting for.

Fixing Body Position: Head Up

This is huge. If divers drop their heads they are both less aware and they are going to find their bodies following and they will tip forwards. This will result in more feelings of head heaviness and the divers will break trim and go 30 degrees trim up at which point they’re looking roughly forwards again. What they need to be doing is looking forwards from a zero degree trim position with the back of their heads likely resting on their isolator valve. The head should be up until it either hits the isolator valve or the diver reaches a physical limit.

Fixing Body Position: Arms Out

Putting the Arms out stretched in front of the diver (often with the hands clasped) can help to counter balance the head-heavy feeling of steel doubles. The insulation in the arms and hands will act as little pontoons to help the diver out a little bit.

Fixing Body Position: Feet Back

The heavy jetfins that divers wear are negative, however, and getting feet out in back will also counteract butt lightness that the diver has. Again diver typically dive with a lot of bend at their knees and extending their knees feels like they are going to be dragging/dropping their fins. The diver should be able to stretch out and feel like they are ‘lying flat’ while their knees will actually bend sufficient to pull their feet away from the bottom enough to kick perfectly well.

Fixing Body Position: Butt Tight, Back Arched

This position should not be exaggerated too much but it helps to lengthen the diver, gets the knees into the correct position so they aren’t dropped and adds a little bit of leverage to the couteracting of the butt down positioning. It should be a relaxed, position, however, and the diver should not be sore after getting out of the water (although if the diver holds this position and gets sore, they’re getting the right idea, they just need to relax a bit to find the happy medium).

Fixing Body Position: Fins Back or Slightly Up

What is trying to be avoided here is two things. One is the common case of divers with dropped knees and fins dropped who create silt devils behind them as they frog kick. The other common case is divers with too much of a bend in their knees with their calves and fins pointed straight up, sculling to stay down. The fins should be ideally back, so that if the diver executed a frog kick the impulse of the water would be straight back, or else with fin tips *slightly* up.

There is one exception which is when dropping down, negatively buoyant around a line, it will be advantageous to get the fin tips all the way up, otherwise the water will catch the fin tips and tip the diver forwards onto their head.

Fixing Procedures: Using the Wing for Lift, not the Drysuit

Using the drysuit for lift and carrying a large bubble causes a large host of issues, one of the biggest is simply gas in the legs and gas distributed in a poor fashion along the torso leading to bad trim issues. It is likely that large gas bubbles in the suit also leads to chronic 30-degree up trim issues as the diver is constantly fighting the tendency of the tanks to go head-down and for their feet to fill up with gas, so they want the large bubble of gas in their suit up near their shoulders. Another problem with over-using the drysuit is that divers will tend to auto-dump gas out of their drysuit as they are doing skills like valve drills and will constantly find themselves sinking and adding gas to their drysuit. The drysuit needs to be lofted properly and not run ‘shrinkwrapped’, but a large bubble will not help with trim or buoyancy.

When a diver is getting ready to evaluate their trim and get still, they should really dump about as much gas as they can get out of their drysuit — breaking trim in order to fully migrate gas out of the legs and get gas out of their torso and shoulders (an exaggerated breaking of trim may be useful to really assert that any excess gas in the drysuit is gone). Ideally they should try to dump gas out of the drysuit 2 or 3 times until it becomes difficult to find any more gas to dump. This may produce a drysuit which is slightly more shrinkwrapped than is ideal, but migrating gas from the drysuit to the wing will assist in being trim and eventually in controlling buoyancy. It will be easier to find trim position from a slightly shrinkwrapped position and later find a happy medium than to attempt to find trim position with a large drysuit gas bubble. Eventually simply driving a drysuit all the time with the correct amount of gas becomes easy to do almost unconsciously, but to start with the diver needs to consciously work on managing the distribution of gas between the drysuit and the wing.

Putting It Together And Still Being Head Heavy

So the diver puts everything together: Arms out, Head up, Feet Back, Back Arched, Butt Tight, Knees up, Fins Back (Thanks here to Bob Sherwood for this entire recipe) and they rotate into a zero degree trim position and if they remain still they tip on their head, so they have to fin. After awhile they get tired and the trim breaks up to 20 degrees and the knees drop. If the diver has really made a good effort to fix body position issues then the problem is actually in the gear and the weight distribution.

Fixing Gear: Dropping Tanks

Tanks can be dropped all the way until the top of the valves are even with the top of the divers shoulders by loosening the shoulder strap. The isolator valve should be out of the divers way and the diver should be able to get their head up and look forwards without being obstructed by the isolator. This will push the center of gravity of the heavy tanks lower and will balance out the diver better. Most divers starting out with fully cinched up shoulder straps that are tight will need to loosen their shoulder straps by at least around 4 inches. That is right, I said 4 inches. Or more.

At this point forget about the fact that the valves are moving further away from the divers head and the effect on valve drills. Divers who are not trim in doubles should not worry about reaching their valves, that is putting the cart before the horse. Divers will also find that as they achieve trim position their tanks don’t fall back as far and they can actually get their head up while doing the valve drill such that the effect of dropping the tanks is largely neutral in how much the diver needs to reach in order to be able to hit their valves. It sounds like magic, but it is the benefits of fixing problems in the right order and the right way. Tightening up shoulder straps to reach valves results in bad trim, tank falling away, divers dropping their head and not fixing their poor form in reaching for their valves.

If you already have cinched up shoulder strap and you cut your webbing in a “DIR” fashion in order to not have excess (“don’t take what you don’t need”) the bad news here is that in order to drop your tanks enough you’ll need to buy new webbing and rethread your harness. Sorry. If it makes you feel any better: Been There, Done That. Wait for a good long time before cutting excess harness material, you might find that you really want to drop your tanks another 1-2 inches more and have to rethread again.

Setting your shoulder straps like this isn’t necessary in warm, fresh water and may seem extreme to divers in those conditions reading this. Well, this write-up sort of isn’t for you. This is for 50F salt water conditions or colder. At the same time, its perfectly reasonable to dive configured this way in warm, fresh water, and tanks should still be dropped enough to get the isolator out of the way of the diver’s head. If you are diving in warm fresh water and don’t have trim issues, but have a difficult time looking forwards without hitting the isolator, then you can still adjust your harness looser and all of this still applies the same.

Fixing Gear: Tighten Crotch Strap

Obviously now that the shoulder straps are looser the backplate falls further down the body and now the crotch strap needs tightening. It doesn’t need to be too tight, the crotch strap is not what holds the tanks to your body. The crotch strap is there for towing and to not let the tanks ride up too far.

Fixing Gear: Tighten the Waist Strap

Okay, if you noticed that all this loosening of the harness is going to make the tanks floppy on your back, this is how to fix that problem. Tighten up the waist strap good and tight. But, do not do this when you are floating on the surface with your wing floating your tanks up high. Either do this while walking, when gravity is pulling your tanks down, or do this after dropping down in the water and being in trim position. Or ideally, do both, since on land its difficult to fully get the waist belt tight when your dry suit is all lofty and floppy on land.

Once your waist strap is tight, the shoulder straps will be tighter and even if you flip over turtle, the doubles should not fall away from you or be floppy when rotating side-to-side. This should also pull your tanks down and tight and make holding trim position even easier. This is my secret weapon in being able to float in zero trim with good posture without kicking at all and being relaxed and being able to operate from a stable platform well.

And this is really the secret to stability. I’ve had GUE instructors in warmer climates unaccustomed to adjusting backplates in this fashion look at me floating in the water and tell me that I’d need to be tightening up my shoulder straps — who have then forgotten all about that being a “problem” after the dive and never mentioned it again. Loose shoulder straps don’t necessarily mean a problem in the water, you just need to tighten up the waist belt. So while you don’t necessarily need to adjust straps like this in warmer climates, you can go from cold water with your backplate adjusted this way to diving a wetsuit in warmer water without needing to fiddle. Just tighten up the waist belt.

Fixing Gear: Short Divers and Short Plates

If you are 5’4″ or so and drop your backplate down so that the waist strap is coming across the midpoint of your hips and your crotch strap is almost nonexistent, while you are still hitting your head on your isolator and can’t look forwards, and you have a ton of back pain because you can’t arch your back in a full-sized plate, then you need a smaller back plate. This will greatly help you in dropping your tanks, being able to get your head up, and arching your back without pain. While somewhat shorter divers may be able to drill holes higher up on the plate to drop the tanks down relative to the plate a bit, at some point the geometry really needs to be changed so that the waist strap is moved up and this gets the plate off of the diver’s lower vertebrae.

Fixing Gear: Tail Weights

This is coming way last in this article due to what priority it should be given. After fixing body posture and tank straps you should be able to trim out most steel doubles with a standard v-weight running the length of the tank. Most divers, however, reach for a tail weight first. This is not to say not to do this, and I’ve got a small roughly 4# tail weight that I commonly use for tanks that don’t need it. But you should find with experience that you don’t need a tail weight as much as you thought you did if you fix all the other problems.

Fixing Gear: Weight Belts

If you have a long enough torso that a weight belt around your waist is lower than a tail weight (most guys 5’10″ or taller) then putting weight there will be even better than a v-weight. Of course this makes the weight ditchable, which is often what we don’t really want in technical diving since ditching weight would mean getting very bent. If you want to see what moving weight around will do for you, however, throw on a weight belt instead of a v-weight and see how much easier trim position becomes. It should be much easier to get still and hold position without tipping forwards. Even if you don’t wind up wearing a weight belt it might be useful for ‘training wheels’ to learn proper position as you are adjusting your gear (or it might be temporarily useful for — *cough* — looking really pretty in courses when you’re task loaded with a ton of other stuff).

Again, though, divers with shorter stature may find weight belts actually counter productive depending on where their waist is relative to the rest of their gear.

Misc: Fresh Water

Oddly, it appears easier to trim out tanks in fresh water than cold water. I believe this may be due to the effect of saltwater buoyancy on all the divers body and drysuit/insulation and the center of that combined torque being below (along the divers body) the center of gravity of the diver and gear resulting in a net effect to produce head heaviness in salt water compared to fresh. Even though you may need to take a tail weight off when going to fresh water, you should find that trim is easier.

Misc: CF200s vs TLS350s/FLX

CF200s are warm and snuggly, but also harder to trim out. An FLX or TLS will be colder, but easier to trim out. The CF200 is actually more negative of a suit (don’t be confused by thinking neoprene should float, the CF material doesn’t) and I don’t understand this effect on trim since it seems opposite what I just wrote about fresh/salt water, but the effect on trim seems to be real. I have no idea how other drysuits fare this way.

High Standards

We need to have high standards for having trim position. This is in order to achieve numerous goals of moving through the water: non silting kicks, efficient kicks, lower gas consumption, lower CO2 build up, better buoyancy control, and above all else a more stable platform in the water.

Divers should be attempting to hit a zero degree trim angle when relaxed and stationary or kicking in a plane. It is not being a trim nazi to have this as a desired reference point. And the simple fact is that by shooting for zero trim, a diver will typically be able to find a comfortable 0-10 degree trim position, which will only deviate up to 20 degrees under a lot of stress. By accepting that “20 degree trim is good enough” at neutral and relaxed, that will lead to 30-40 degrees of trim when stressed which is simply going to negatively impact performance.

By having bad trim it will make valve drills harder, it makes knees drop, which affects anti silting kicks, any errant kicks will propel the diver up in the water column leading to the diver maintaining slightly negative buoyancy which will produce yo-yo’ing under task loading.

The National Socialist Party of Trim

Where the focus on trim gets silly is to take this desired zero degree trim and to place it above everything else missing the bigger picture. When divers dump gas they need to roll and break trim. When going up or down in a cave or wreck divers will need to break trim. When using fin kicks for buoyancy control divers will need to adopt a head-up or head-down attitude in order to kick to go up or down.

Where the focus on trim gets silly is this idea that divers must always be board flat at all times. Combined with the idea that breath control should be used as the primary mechanism of buoyancy control. This is a common mistake that newer divers make when learning breath/buoyancy control, which produces too little buoyancy adjustments in the wing and drysuit, and complete neglect of using fins to kick up or down.

The overfocus on trim can lead to new divers floating to the surface in perfect trim form, while not breaking trim to dump gas. In tech divers, you sacrifice one of the best ways to initiate changes in depth, or to quickly control a buoyancy problem by using your fins. Watching divers float away or sink in trim while fighting to deal with buoyancy and not simply breaking trim and kicking would be comical if it wasn’t actually dangerous on a real tech dive.

Trim and Comfort

It hopefully goes without saying that a diver that has to fight to stay in trim constantly and is not comfortable has a problem where trim is impacting their ability to dive negatively. Trim position should not be difficult, it should be natural. And that is where skill needs to come in fixing the divers body position, their weighting, adjusting their tank straps (typically lowering their tanks), tightening up the crotch strap, and tightening up the waist belt. Addressing more fully how to correctly address these problems requires another article, but the end result should be a diver who is comfortable with 0-10 degree trim.

Comfortable divers in trim will have more situational awareness, more enjoyable diving, and will lead to substantially more success in more advanced courses. Divers who struggle with trim constantly in an effort to look good without fixing fundamental issues in their balance and stability in the water are not going to be doing themselves a favor.

Summary

Trim is measured when the diver is not changing buoyancy control or deliberately breaking trim to accomplish an action. And there is a bigger picture to why trim is desirable other than simply looking good. You should above all else be able to feel that you move through the water more efficiently when you are in trim position, and it should make your diving more enjoyable. When maintaining trim is not helping your diving, it should be broken (usually temporarily).

And it still is desirable to refine how much we break trim. Newer divers will need to break trim and roll more in order to dump gas. Some drysuits have poor dump valve placement and will require a more exaggerated position in order to dump gas. The concern placed on this is often vastly out of proportion with its significance, however. A diver should first be concerned with having stable trim position at rest, and then with many other skills such as team positioning and situational awareness, before needing to focus on the refinement and finesse of breaking trim to dump gas.

Incorrect Position: Head Down, Shoulders Forward, Elbows to the Side

If you stand up and try to reach back to something behind your head like you are trying to reach for your isolator, chances are that this is the position that you will find yourself in naturally. This is also the position which makes it the most difficult to reach your isolator. Dropping your head and your shoulders makes it easier to reach something attached to the back of your head, but your manifold is attached to your back, not your head. This position pulls your head away from the vertical line of your back and that makes it harder for your arm to reach backwards and feel where the isolator would be.

Correct Position: Head Up, Shoulders Back, Elbows in Front

By getting your head up and shoulders back, you should be able to nearly hit your head on your isolator valve. If you can’t, then I’d suggest practicing shoulder and head positioning until you can touch your isolator valve with your head, or nearly so.

Once you have this head position, you should be able to easily reach back to the back of your head and your isolator valve will be right there. This is make easier by pulling the elbow in front of you and having your arm closer to your ear. This arm positioning makes it easier to rotate your shoulder back to reach valves.

For folks with mobility issues this may be more difficult, but fixing these issues will make everyone have an easier time at doing valve drills. It may also be possible to isolate and focus on the individual mobility issues that divers have with valve drills.

Body Position

Body position also needs to be correct. The diver should be in trim position and nearly flat, back arched somewhat and butt tight. Knees need to not be dropped, and fins should be flat or slightly pointed up (not pointing straight up, and not dropped into the muck). All of this will help balance the diver and produce a stable platform for the valve drill. More on this later.

Stable Platform

This is the key skill to practice going in to it. The ascent drills in fundies are sort of about this, and if you’re practicing ascent drills that is the generally correct idea. But the real focus should be on moving up in the water column and acquiring a stable platform at every level. To begin with, if you are behind in the timing, its actually better to extend the stops and gain that stable platform rather than cruising through stops trying to hit the time. It is, of course, important to be conscious of time and to add back in the ability to nail stops based on time. It might be better to practice ascent drills with 2 minute timed stops to begin with.

The whole team should come into the stops and be able to adjust buoyancy and find the stable point around the correct stop depth (e.g. ideally 20 foot, not 19 or 21 foot). The team should communicate that platform and then be able to maneuver into position. Then, signal the team to move up.

At the stable platforms you should obviously be able to do work there (gas switches, deal with failures, etc), so it may be a good idea to throw in OOG drills as task loading while you are at a platform. Then solve that issue properly (and slowly) and then move up. The focus should be on accuracy to begin with and not on the rush-rush-rush to complete deco.

Once a team has a stable platform, then efficiency components can be added to that. Shooting a bag could be done while moving up in the water column from stop to stop, for example. However, we have that task to work on coming *out* of Tech 1, however, so this is not a skill that needs to be done *before* Tech 1. Before Tech 1 the focus should be on gaining that stable platform, using 2 minute stops, adding OOG drills when you are comfortable and building up comfort with the platform. Shooting a bag and spool it up can be added as additional task loading, moving smoothly between stops, finding the platform, clipping off the spool, then moving up again.

Again, SLOW it down and find the stable platform. If you are rushing to the surface trying to hit a schedule and never finding the stable platform, that will not be serving you well going into Tech 1 and your gas switches will look like a bit of a mess. Definitely maintain awareness of time, and you can try to time stops exactly, but use long enough stops that you have time to find a stable platform.

Team Positioning

Team positioning around the upline makes all the skills easier and you do better if you’re closer around the upline either in a triangle formation or in the 3 abreast line formation for current. It makes things substantially easier to be close and to maintain closeness and to not drift and then have to reform.

Just adding accuracy to team formation can add considerable task loading to an ascent. If you can’t reach out and touch the line or a buddy you are probably too far away and need to focus on repositioning.

Role of the Captian

A deco team needs a captain, and they’re the ones calling the stops and signalling the platform (their depth gauge is the authoritative depth gauge — in the event of a discrepancy maintain stop depth with the captain). If you are natural not a leadership type and tend to be more passive and in control of your own situation and not inclined to jump in, this will be an essential skill to learn since everyone takes a rotating turn at being captain.

The Line is the Repair Shop

Divers without problems should stay away from the line, and avoid dragging the line and forming a bowstring. Do not carry the line over to divers who are out of position, get them to come back into position.

But when divers have issues they should swim into the line and use it as a reference. The simple presence of a diver on the upline should alert the other team members that the diver has an issue. To help fix the issue another diver can swim into the line from the other vertex of the triangle. This has the important feature of keeping the line in the upline in the middle and not losing it. If either diver swims past the line to get to the problem or to get to the solution then the upline has gone behind someone and the team is now out of position.

When throwing an OOG at a stop, try to keep the upline in the middle, have the distressed diver signal and swim into the line and the diver delivering gas react by swimming into the line.

Practice Your Back Kick

Being able to maneuver midwater at a platform and maintain team position requires a good back kick. You can bump around for position, but ultimately the back kick is going to have to be solid. That should be practiced as part of practicing the stable platform. In order to have a stable platform and good back-kick trim and buoyancy also need to be there along with the rest of the fundamental skills of course.

Skills Not To Practice

The wrong focus would be on bottle juggling, since there is basically zero bottle juggling in Tech 1. Also, there’s no mask off ascents in GUE Tech 1, so there’s no need to practice that much. Bottle switching also should not be practiced since you don’t want to wind up practicing “cowboy switches”.

Most of the skills on the bottom are going to be fairly straight forwards for anyone with a Fundies Tech pass and the failures will be introduced on land, and will be somewhat telegraphed about what is going to happen during the dive, so there shoudln’t be a ton of surprises at the Tech 1 level. I would get off of that bottom and simply work on the midwater platform.

Final Lesson: Do Not Argue With Laura About Deco.

At least not on dry land. Wait until she gets cold in the water and starts thinking about how a hot cup of coco will taste… =)

Instances of this family provide a small amount of consistent CPU resources and allow you to burst CPU capacity when additional cycles are available.

Well, one of my micro instances has looked like this with 98-100% steal cycles for hours:

08:59:32          CPU     %user     %nice   %system   %iowait    %steal     %idle
09:00:01          all      5.51      0.00      0.00      0.00     94.49      0.00
09:01:09          all      1.04      0.00      0.01      0.00     98.85      0.09
09:02:02          all      3.41      0.00      0.00      0.00     96.59      0.00
09:03:01          all      1.09      0.00      0.02      0.00     98.84      0.05
09:04:02          all      1.74      0.00      0.00      0.00     98.24      0.02
09:05:02          all     10.15      0.00      1.46      1.74     69.08     17.56
09:06:03          all      4.66      0.00      0.03      0.31     94.75      0.25
09:07:05          all      1.46      0.00      0.00      0.00     98.54      0.00
09:08:02          all      2.98      0.00      0.00      0.00     97.00      0.02
09:09:04          all      3.40      0.00      0.02      0.00     96.28      0.30
09:10:04          all      1.59      0.00      0.00      0.02     98.40      0.00
09:11:15          all     10.16      0.00      0.79      0.83     80.32      7.91
09:12:02          all      2.06      0.00      0.02      0.00     97.88      0.04
09:13:03          all      4.32      0.00      0.00      0.00     95.61      0.07
09:14:01          all      0.00      0.00      0.00      0.00    100.00      0.00
09:15:01          all      3.99      0.00      0.00      0.00     95.99      0.02
09:16:01          all      2.35      0.00      0.00      0.48     94.37      2.80
09:17:01          all     16.01      0.00      0.81      0.61     76.10      6.46
09:18:01          all      0.00      0.00      0.00      0.00    100.00      0.00
09:19:02          all      0.79      0.00      0.00      0.00     99.19      0.02
09:20:02          all      4.56      0.00      0.02      0.00     95.43      0.00
09:21:03          all      0.00      0.00      0.00      0.00    100.00      0.00
09:22:15          all     10.84      0.00      0.76      0.61     83.74      4.04
09:23:01          all      3.70      0.00      0.00      0.00     96.27      0.02
09:24:05          all      5.87      0.00      0.00      0.00     94.08      0.05
09:25:02          all      0.00      0.00      0.00      0.00    100.00      0.00
09:26:01          all      2.02      0.00      0.00      0.03     97.95      0.00
09:27:01          all      0.00      0.00      0.00      0.00    100.00      0.00
09:28:02          all     11.65      0.00      1.09      1.06     77.05      9.16
09:29:09          all      3.24      0.00      0.00      0.00     94.92      1.84
09:30:13          all      2.13      0.00      0.00      0.00     97.87      0.00
09:31:01          all      1.99      0.00      0.00      0.00     97.98      0.02
09:32:02          all      3.43      0.00      0.02      0.00     96.56      0.00
09:33:01          all      0.22      0.00      0.05      0.25     96.12      3.36
09:34:02          all     14.96      0.00      1.16      1.29     70.74     11.84
09:35:01          all      0.95      0.00      0.00      0.00     99.05      0.00
09:36:17          all      5.62      0.00      0.03      0.00     94.36      0.00
09:37:02          all      0.00      0.00      0.00      0.00    100.00      0.00
09:38:02          all      1.84      0.00      0.00      0.00     98.13      0.03
09:39:01          all      1.92      0.00      0.27      0.71     87.51      9.59
09:40:14          all      8.11      0.00      0.43      0.35     87.92      3.19
09:41:01          all      2.46      0.00      0.02      0.00     97.50      0.02
09:42:02          all      2.22      0.00      0.00      0.00     97.78      0.00
09:43:02          all      2.00      0.00      0.00      0.00     98.00      0.00

Note that sar is taking up to 14 seconds at times (e.g. 09:40:14) in order to gather statistics, and it is quite light weight and doesn’t do much other than read a bit out of /proc.

This is so bad that the instance is having 600+ms ping times:

64 bytes from 50.18.x.y: icmp_seq=0 ttl=53 time=609.608 ms
64 bytes from 50.18.x.y: icmp_seq=1 ttl=53 time=1107.454 ms
64 bytes from 50.18.x.y: icmp_seq=2 ttl=53 time=107.230 ms
64 bytes from 50.18.x.y: icmp_seq=3 ttl=53 time=605.416 ms
64 bytes from 50.18.x.y: icmp_seq=4 ttl=53 time=1104.728 ms
64 bytes from 50.18.x.y: icmp_seq=5 ttl=53 time=104.510 ms
64 bytes from 50.18.x.y: icmp_seq=6 ttl=53 time=633.574 ms
64 bytes from 50.18.x.y: icmp_seq=7 ttl=53 time=1133.371 ms
64 bytes from 50.18.x.y: icmp_seq=8 ttl=53 time=133.149 ms
64 bytes from 50.18.x.y: icmp_seq=9 ttl=53 time=631.604 ms

That means that interrupt context and enough horsepower to respond to an ICMP ping is not able to run at all for 600+ ms.

And the problem is definitely on the EC2 side, I’m getting clean pings to the internet:

 1  a.b.c.d  102.019 ms  15.208 ms  13.735 ms
 2  69.17.83.233  11.109 ms  10.859 ms  10.363 ms
 3  209.247.91.169  10.861 ms  12.741 ms  12.855 ms
 4  4.68.105.30  11.484 ms  16.482 ms  17.860 ms
 5  4.69.132.49  27.975 ms  28.601 ms  30.103 ms
 6  4.69.153.18  30.226 ms  28.726 ms  28.478 ms
 7  4.69.152.16  28.352 ms  61.582 ms  31.225 ms
 8  4.53.208.22  31.100 ms  30.775 ms  30.788 ms
 9  72.21.222.208  32.222 ms  32.219 ms  30.851 ms
10  72.21.222.255  33.224 ms  31.350 ms  31.226 ms
11  * * *
12  * * *
13  * * *
14  50.18.x.y  393.064 ms  1500.394 ms  989.786 ms

This isn’t “small amounts of consistent CPU”, this is useless. They’re clearly prioritizing micro instances down to the point where if the server is otherwise being utilized 100% the micro instances get completely queue starved.

The other one-way valve is on the inside of the P-valve inside of the delrin screw on the P-valve. Inside of that screw is a tiny little plastic piece called the ‘duckbill’ which is a another one-way valve. In a balanced valve while we want gas from the suit to be let into the P-valve, we don’t want urine in the P-valve to be let into the suit. The duckbill is the one-way valve that accomplishes this.

There is a trick with a leaking duckbill. When you look at the screw and the leak, the obvious solution that comes to mind is to tighten that thing down like any good gorilla would do until it stops leaking. That is incorrect in this case. What that will do instead is push the duckbill in further and cause it to deform more and leak more and potentially deform the duckbill permanently so that it needs replacement.

In order to check the duckbill unscrew the delrin screw and remove the plastic duckbill with tweezers (very careful so you don’t tear it). You will then probably want to sterilize it since the next step is to test that the duckbill works by putting a little positive and negative vacuum on it. When you blow into the other side of the duckbill it should blow out of the duckbill. If you then suck on that side (somewhat gently) it should hold a little bit of a vacuum — do not whale on it or else you’ll eventually manage to deform it, which is bad.

If the duckbill is in good shape then you need to put it back in the p-valve and screw in the delrin screw. You probably want to have about 1.5 to 2 threads still visible in the delrin screw and not screw it in all the way. You should then be able to screw closed the outside valve on the P-valve and should be able to put positive pressure into the end of the P-valve and it should not leak. If it leaks, you should try UN-screwing the delrin screw — you’ve probably screwed it in too far and need to back off.

Okay, there was a little too much screwing in that description…