Spherical Chicken

Trimming out divers in warm water and single tanks is relatively easy. Where things become difficult is with cold salt water, with a lot of buoyant insulation and big steel tanks. Some divers with skinny bodies and big ape arms and legs will find this easier, but for the rest of us, getting into a decent trim position in cold water can be a huge struggle. There are some tips, however, that can straighten just about anyone out.

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.