Tag: BCD

Well Balanced (physical, not mental)

Next time you are on a dive boat or with a group of divers take a close look at what they are Next time you are on a dive boat or with a group of divers take a close look at what they are wearing, especially if you are in the tropics. Are they all dressed the same? Do they all look the same? From my experience, the range runs from just a bathing suit to a full 1/4-inch farmer John, with bodies that are thin, heavy or all muscle.

Why do divers wear weights in the same place?

If divers all have different equipment, dive suits and body builds, how can they all wear weights in the same place? Think about this for one minute. One diver is wearing a dive skin, another has a short-sleeved shorty with high cut legs. Another diver is wearing just the farmer john part of their suit and not a jacket. Another diver has on a long sleeve 1/4-inch jacket only. Some BCD’s are negative while others have a tendency to float. No two divers are alike, yet all wear their weights pretty much in the same place.

Look at a fish. How does it swim? Horizontal in the water. Yes, trumpet fish stand on their heads, but they are not swimming! Fish are balanced, divers are not. The heavier part of a diver’s body is usually the legs. The lighter part is the chest area where the lungs are. So where do we put weight? At the heavier part. Where do we put air? At the lighter part. None of that makes sense. Basically, all of the dive equipment is saying “Stand up in the water.” Not only that but the tank located on the back tends to make a diver roll over on their back. There is no balance here at all.

Some divers are foot light, but a vast majority of divers are foot heavy to varying degrees. This means that when a diver stops kicking the feet tend to drop. In some cases, a diver’s normal swimming angle can be up to and in extreme cases more than a 45-degree angle to horizontal. This is not only uncomfortable but very inefficient. Inefficiency means more work. More work means breathing more and more breathing means more work to stay down. This turns into a loop which most people solve by adding weight. This increases the foot heavy problem, and the cycle continues.

Divers who are foot light have a solution, ankle weights. But what do foot heavy divers do? No one has really marketed anything to solve this problem. There is a buoyancy video that very clearly shows that swimming horizontally is correct and foot heavy or foot light is bad. If you are foot light it says use ankle weights and stops there. It says absolutely nothing about foot heavy. What do foot heavy divers do?

The solution is to add weights towards the top of the diver. I wear 12 pounds of lead with a 1/4 jumpsuit, and I am very foot heavy. Or as some would like to say, an air head. Regardless, my weight configuration is 6 pounds at my waist and 6 pounds toward the top of my tank. With this set up, I am horizontal in the water. To go down I simply swim down and to go up, swim up. Almost all the kicking power is used efficiently. Foot heavy divers tend to kick themselves toward the surface. Their answer? More lead?

Foot heavy divers also have great problems swimming in any kind of current, from mild to Foot heavy divers also have great problems swimming in any kind of current, from mild too strong. Think of an airplane which is flying along happily. Now bend that wing up and what happens? The plane goes up. The pilot can counter this with trim tabs, but the efficiency drops. Pilots also load planes for best balance. Divers just put weight around their waist with no thought to balance.

Balance is different from weight

A diver who is correctly weighted and balanced with 6 pounds on the waist and 6 pounds at the top would also be correctly balanced with 10 at the waist and 10 on top but not correctly weighted. Make sure you make a clear distinction between these two.

One can get into numerous formulas of weight distribution over the cross vector of air control flow factors divided by depths of compression volume with force equal to the division of the equation of nonsense, but fish don’t do that so why should we? Next time you are in the water try a simple experiment. Go down to about 20 feet and simply try to lie horizontally in the water. Absolutely no air can be in your BCD. Absolutely none, zero, zilch, zip. Why? Because how much is in it? The same as yesterday? The same as tomorrow? This experiment must have a constant and that can only be with an empty BCD. Don’t kick or try to do anything. Just see what your body does. This may take a few seconds, so wait. If you are foot light, then ankle weights might help. If you are foot heavy, then weights must be added somewhere else.

A short weight belt with one lead weight on each side placed between the tank and backpack, above the tank band, works very well (and it is cheap!). Some packs with twin bands have problems as do soft packs. Some ingenuity is required to see what your particular BCD will allow to work. Ideally it would be great to have either a BCD or a wetsuit top with many small pockets all over the top (front and back) where weights could be placed to accommodate each individual’s equipment and body build. As this isn’t the case a short weight belt is a start. One diver, as an experiment wore a weight belt up under the armpits. Just an experiment, but it helped! Weights in the top back of the BCD do not help the roll over problem but for whatever reason this has not affected my diving. Others have said they can feel this weight trying to roll them over. Again, this is a start. Until someone makes extra weight pockets all over the place there aren’t too many options.

Dropping weights in an emergency

Now the big argument. How does one drop the weights in an emergency? First, and most important, weights have only one function for most recreational diving. That is to make a diver as close to neutral as possible. Weight should not plunk you to the bottom and then put air in the BCD to lift you up. It’s right back to the first problem of weight on the bottom and air on the top.

There are counterarguments. It is unusual for someone to have all their lead on the top. If weights have to be dropped then those around the waist can be dropped. No, you don’t go head heavy. There are divers who wear no lead at all. How does someone who wears no lead drop a weight belt? If two divers are very well weighted and balanced, one with lead and one without, both can swim to the surface with virtually the same effort or lack of effort. Divers who are overweighted have to work to get up or drop belts.

Wetsuit compression

Other complaints are about wetsuit compression. Wetsuits do compress but not to such a tremendous degree that 30 pounds are needed at the surface and half a BCD full of air is required at 60 feet. That is a bit of an exaggeration, but the point is there. Obviously full 1/4 farmer John will be quite different from a 1/8th inch shorty. Still compression is not so severe. I find with a 1/4-inch jumpsuit that through kicking a bit differently, breathing a bit differently, I can control this to most acceptable depths. Some have argued than changing your breathing is bad. Don’t we change our breathing all day long? Walk up the stairs and see what happens. Have someone scare you. I’m not talking about hyperventilating underwater or holding breath, just relaxing more.

Most divers complain about an area from the surface to about 15 feet of water. This “problem zone”, as I call it, is where divers have trouble getting down at the beginning of a dive and staying there at the end. For most divers’ extra lead is the answer. Unfortunately, this creates balance problems for the vast majority of the dive. Why be correctly weighted for a few minutes and out of balance for an hour or so? To get through the problem zone at the beginning of a dive it is critical that no air is in the BCD. A good strong surface dive can put divers deep enough underwater that a few kicks will propel them past the problem zone.

Old versus new BCD’s

Something else should be looked at now. Many older BCD’s have hollow hard packs. These packs hold air. Most have two tiny holes in the bottom to drain water. Heaven forbid anyone would want to get a dive boat wet. The only way to get air out is to stand on your head. The holes are too small so you may be standing there for quite some time. Drill these two bottom holes to at least a 1/2-inch diameter. Also drill two large holes at the top in the handle. Some packs have solid handles so look at yours. If so, find the highest point possible and drill one hole on each side. One manufacturer was clever enough to put a small hole almost at the top but on the inside, so it is restricted by the divers back. Many BCD backpacks are now made with holes top and bottom, but these should be much larger. The air should get out instantly. Many who have drilled out their packs have taken off two pounds of lead. Think about that. They were wearing two pounds of lead for the first few seconds of the dive. After the pack emptied, they carried two pounds of unnecessary lead. Many of the newer BCD’s now have a plate for a backpack and no air gets trapped at all.

Carrying unnecessary lead is like going shopping with $100 in pennies in your pocket. It makes you tired carrying it around. When you get tired you have to work harder to get things done. Work means breathing more which means floating more. The more you float the harder you have to work and once again a vicious cycle begins.

Are you floating upwards?

The next part of the problem occurs when divers get back near the problem zone at the end of the dive. Here the main complaint is tanks getting lighter. Tanks do get lighter but only one breath at a time lighter. It is always interesting to hear someone say, “When my tank hits 1000 psi I shoot to the surface.” Are they saying that at 1001 psi they can stay down? Something is wrong here. My suspicions are twofold. First anyone who is naturally foot heavy tends to kick to the surface as already discussed. Compound this with a slightly lighter tank and shallower water, many divers simply kick to the surface. Second, many still have air in the BCD adding to the problem.

Try another experiment. When in shallow water just stop. Do your feet sink? For many this sends a signal to their brain that they must be floating towards the surface. If their feet are sinking, then their head is shallower than their feet. They aren’t getting shallower, but they think they are. The immediate reaction is to try to kick back down. Try kicking to get down when your head is pointing up. Also not wanting to “float” to the surface can put a bit of adrenaline in the system which makes one breathe more and here we go again.

Relation between fins and buoyancy

Use of fins, as trivial as it may sound, is related to buoyancy more than one may think. The more efficient a kick the less work, the less work, the less breathing and so on. Watch other divers underwater. See how they kick. Is it efficient? Are they moving along effortlessly or kicking like crazy and hardly moving? Almost everything one does underwater is related to buoyancy. The less efficient a diver is the more they breathe. Here we go again. The more they breathe the more they float…!!!

This is just a small sampling of what can be done and a few options to try. Some things work great for some divers and other things for other divers. Without experimenting though, one would never progress.

Bruce Bowker

The BCD Wars

At some point, I can’t quite remember when, someone, somewhere decided to have a BCD war. Mine is bigger than yours so mine is better. The next day his was bigger than mine and so on until we all arrived at BCD’s with some amazing and ridiculous amount of lift. This war spilled over to the general diving community and people were told the more lift the better the BCD. Manufacturers made bigger BCD’s and then, through marketing, told everyone they needed them.

Are Heavier BCD’s Necessary?

Being a diver who has spent time in both cold (under ice) and tropical waters, my observations are far from limited to one area of diving. I had a discussion once with a diver who did most of his diving on North Atlantic wrecks. He was in one of my buoyancy classes and made it very clear that my ideas probably worked well in warm water but for his type of diving a BCD with 65 pounds or more of lift (that’s what he said!) was necessary. Asking why, he explained because of the heavier equipment worn and heavier wetsuits. He also explained that his kind of diving used twin steel 90’s or 120’s and with all that weight, plus 2 heavy knives, lights that sink plus a few other odds and ends and X pounds of lead, 65 plus pounds of lift was necessary.

Let’s examine this a bit closer. Are these divers with all this heavy equipment, which is apparently already dragging them down, wearing additional lead on a belt? If so, why? If I put weight on my back (e.g. heavy tanks) then some amount would come off the weight belt. If I leave my knives and lights home, perhaps use an aluminum tank, then I would add some lead. But to add both weighty equipment and then lead to the belt is counterproductive.

One of the primary objectives of good diving is to get as neutral as possible. Pure neutrality is quite impossible though, because of numerous factors such as breathing, wetsuit compression/expansion and the tank gets lighter with each breath taken. But getting close is what a good diver strives towards. With that in mind, why would someone make themselves so negative that they would need 65 pounds of lift? Or even 50 or 30 for that matter. The only explanation would be, for example, a diver who actually needs 28 pounds of lead but wears 58, so a BCD with at least 30 pounds lift would be needed just to get neutral.

Wetsuit compression

Wetsuit compression always enters into any discussion about cold water BCD’s versus tropical. This is pointed out quickly in any argument for those who wear oodles of lead with inflatable boats strapped to their backs. Wetsuits do compress but not to the degree that the kind of lift some claim is necessary. Again, I wear a heavy wetsuit (I have even worn a full hooded farmer john in tropical water) as do some of my staff, and none of us, no matter what depth (even very deep) have any trouble with buoyancy. Nor do we put air in our BCD’s to compensate. I can see the reason some people do need to overcompensate with a BCD. They are so overweighted that they would be walking on the bottom. Instead, they inflate the BCD and more or less walk through the water because of all the air lifting them at the top. So where is the argument about wetsuits?

A friend of mine completed his second diving expedition to Antarctica. He wore a total of 50 pounds of lead. No BCD’s were worn at all. The 50 pounds made him “neutral.” No need for 65-pound lift BCD’s. And that has got to be some of the most extreme diving there is.

There was an article in a well-known dive magazine which was about selecting a BCD. It said something to the effect that one should choose a BCD with 10 or so pounds more lift than the total weight worn. As an example, it said a diver who wears 30 pounds of weight should have BCD with at least 40 pounds of lift. I read this twice to make sure I understood and wondered why a diver would wear 30 pounds if it made him 30 pounds negative? 30 pounds should make him close to neutral negating the lead. So, a BCD with just a little lift would be fine.

Why I never put air in my BCD underwater

I never put air in my BCD underwater. I use my BCD for 3 reasons only. One, it is great way to keep a tank on my back. Two, it meets a requirement of not diving without one and three, the most important, it makes a great surface flotation device. And that is what it should be, an SFD. A true buoyancy compensation device would be designed completely differently.

Generally speaking, the less buoyant part of our body is from the waist down. Where do we put weight? On the waist. The more buoyant part of our body is from the waist up, the lungs. Where do we put air for buoyancy compensation? At the top. Because of the design of a BCD this air is always at the highest point. Our equipment is making us stand up in the water. It is all backwards.

This makes many divers foot heavy. In being foot heavy the diver’s angle to the water is always in a “head pointing up” manner. This can also be referred to as “air head” but foot heavy sounds nicer. This angle can be slight, or I have seen in many cases quite severe. Every time a diver kicks, part of that force is propelling the diver up and part forward. Part up, part forward. A very inefficient kick. To keep from going up with each kick, a diver must add weight. Where does that weight go? Around the waist making the diver even more foot heavy, compounding the problem. Inefficiency usually means breathing more. More air in and out of the lungs makes a diver float more, compounding the problem. If you float you add more lead and on and on, we go…

Not one BCD on the market is correct

Not one BCD on the market is correct. I don’t need 20, 30 or 40 pounds of buoyancy control. A diver should not need more than a few pounds of control. Because manufacturers always like to make things enough for everyone, I would say 8 pounds of control is an awful lot but let’s use that for the sake of discussion. Any more than 8 pounds of lift and I highly suggest taking that much lead off and emptying the BCD. Why would I want 8 pounds of air in my BCD and add 8 pounds of lead to equal the air when I can get rid of the air and the lead?

Where should this 8 pounds of buoyancy control be? Definitely not at the neck. This lifts a person up at the head creating a very bad swimming angle. This is what every single BCD on the market does. Not at the feet which is impractical and lifts the feet up. The only place is in the middle which balances the diver. This cannot be in front (on the stomach) as it would flip the diver over. Years ago, one manufacturer had a horse collar BCD with both bottom and top flotation. The idea was there but done all wrong. The place for an 8-pound bladder would be at the bottom of the BCD and at the back.

There are some arguments against this. Yes, it would need a separate inflator – one that is very restricted so it would inflate very slowly. The actual partitioning of an existing BCD should not be too hard as all that has to be done is ultrasonically seal it. A simple manual dump valve could be installed since it is an easy place to reach. Another argument was that it would require another inflator, more hoses etc. This can be worked out as either a separate hose or incorporating the current one to do two jobs. Many got upset when the auto inflator first arrived. “All of them there extra hoses!!” Hoses became accepted but it took how many years to finally get rid of CO 2 cartridges and thank you for getting rid of them.

BCD’s have come a long way since horse collars, which still have a use in certain places. But BCD’s have been mostly marketed and not designed to a diver’s needs. The current rash of BCD’s designed especially for women also leave a bit to be desired. Only a few are really designed for women. The rest, well, just marketed as such.

Too many divers are sold a BCD that is much too large

I am sure I would be sold a large and if I told the store salesperson, I was wearing a 6mm wetsuit, I would be forced to try even an extra-large. A salesman was in my store recently with a sample of a “woman’s” BCD. It fit me well and it was supposed to be a woman’s small! I am sure if I had been in someone else’s shop, I would not be allowed to buy something that small even though it was a great fit. “You need bigger especially if you are wearing a wetsuit.” When I think of how much “bigger” a wetsuit makes me, it just isn’t much. I certainly don’t look like the Michelin man when I wear it so why do I need a BCD 2 sizes larger than what fits me? I guess I just need all that lift! Ah, the BCD wars.

Bruce Bowker