Adjusting my trim

[battles2a5]

Spectrum's post is spot on. Nereas' post is rubbish, as usual. I have a couple of points to add to Spectrum's:

- Tie a lead weight to a balloon and drop it in the water. What happens? The weight goes down, the balloon goes up. The same thing happens w/ you in the water. The weight on your weight belt wants to go down and the air in your BC wants to go up, so this will rotate you around your center of gravity into a head's up trim position. A BP/W puts the weight right under the wing, so the natural position is level trim (in general). This is not something that cannot be overcome. As Spectrum stated, move that weight up on the BC, play with the fins, add weight to the cam bands. All of these will help. It also helps to make sure you only take the lead that is needed; this will minimize the cantilever effect mentioned above. Sounds like you are using minimal weight now, so that may not be an issue.
- As for the vid above, it is all a matter of trim, bouyancy, propulsion, and posture. The trim takes a little work, as we have discussed. The bouyancy is something you will get a feel for. You need to use enough air to get "truly nuetral", where you don't kick to hover and you can control whether you ascend or descend with your breathing. Propulsion takes practice; start with frog kicks, then build from there into helicopters, back kicks, etc (whole different thread). And posture is something you can do now. Arch your back, keep you head up, extend your arms in front of you and your knees/fins up. In this position, you essentially extend the lever and you have more leverage at each end, effectively increasing your control over trim.
- In summary, experimentation and practice will get you where you need to be Enjoy the journey!

 

[battles2a5]

A couple of more things I forgot to add:
- When experimenting, just tie a bolt snap or clip to a weight and put it in different positions around your rig to see WHERE you need the weight. This is easy in a pool where you can make multiple changes in one session. Once you establish this, you can go out and buy what you need to get there. Nothing worse than buying something you don't need.
- What kind of tanks are you using? If you are planning on buying tanks, this will give you a lot of flexibility in trimming out. For instance, a new-gen HP80 is much shorter than a AL80 and will spread more weight over your upper body. So you could likely drop 5 lbs of lead and have the rest where you need it. Conversely, a HP120 probably would make your current situation since it is so long. Just another variable that you can look at while you work this out.

 

[Deefstes]

Wow! Thanks for al the great advice. I've got a lot to play around with now and I'll tweak my setup until I get it right.

I do have low cut lightwheight booties so there's certainly one thing I can consider changing, never thought of that. I have Mares Plana avantiX-3 fins which are positively buoyant. Also, I have a 5mm full body wetsuit.

The one big variable in the whole equation is the cyllinder that I use. I don't have my own and have to rely on rental cyllinders wherever I go. The problem is that you never know what you're going to get. But for the most part I end up diving with a 12 liter 230 bar steel (sorry, I don't know the imperial units for these cyllinders).

At any rate, I will definitely see if I can move some of my weights to the shoulder straps or cyllinder neck and see how that works. As you said, there's not much to play with as I'm not really using much weight but I'm sure I'll figure something out. I think I will always have at least 1kg in each integrated pocket. They're easy to ditch and I can swim to the top with no BC inflation and 2kg (on my shoulders or kidneys or whereever) without a problem.

Thanks again.

 

[TSandM]

I think Spectrum's post really pretty much nails it, but I just want to emphasize a couple of things. One is that trim pockets located over your kidneys are really not very much different from weight in the integrated pockets, so it's pretty likely that you will have to move weight higher on your body than that. The XS Scuba weight pockets, which have already been suggested, are a good way to do that. If the cambands will come off your BC, try threading one pocket onto each side of the camband, and then tucking the pockets close to your back. Putting weights out on the outside of the tank will increase any tendency you have to roll.

Second, a significant part of trim is posture. If you look at the diver in the video, his body is quite flat -- there is no bend at his hip joints. Most people tend to bend there, so their knees are lower than their chest. You can actually learn to compensate quite a bit for unbalanced gear by being disciplined in your posture. A very flat body, bent knees, and arms out in front of you give you quite a few variables to play with. You can test different degrees of flexion of the knees -- If your fins are positive, bringing them closer to your body will bring your head up, and putting them farther away will bring it down. Your arms are probably negative, so extending them out in front of you will help bring your head down, too.

Precise buoyancy control really only comes with time and practice. Proper weighting is the beginning of it, to minimize the air you have to deal with in your BC. But the most important things are to control your breathing, and learn to anticipate the need to add or vent air BEFORE you are moving in a direction you don't want to go. If you get anxious or worried about your buoyancy, you'll tend to breathe quickly and with your lungs quite full, which makes you more positive and adds to the problem. And if you miss the subtle cues that you are positive (gear feeling lighter on your back, a need to keep your lungs mostly empty, or any information you get from your ears) you can quickly end up with big oscillations before you can control them, and obviously, in three feet of water, you can't afford that!

One of the things I found most helpful as a new diver was to pause in my kicking from time to time and just glide. If I found myself sinking, I knew I was negative and compensating with my fins. If I found myself rising, the reverse was true. A frog kick is a good kick for this, because it has a built-in glide phase, but you can do the same thing just by pausing your flutter kick for a few seconds.

Have fun with this -- Developing good trim and buoyancy control is the key to placing yourself precisely where you want to be in the water, which helps everything about diving, from critter-watching to buddy skills to photography.

 

[Deefstes]

One is that trim pockets located over your kidneys are really not very much different from weight in the integrated pockets

That's what I thought. Seeing as the kidney pockets are at more or less the same height as the integrated weight pockets, if you're in horizontal posture, they should have more or less the same leverage effect. Thanks for clearing that up, it makes me wonder what the purpose of those pockets are.

 

[Kern]

But for the most part I end up diving with a 12 liter 230 bar steel (sorry, I don't know the imperial units for these cyllinders).

Thanks again.

12 lts x 230 bar = 2760 lts or ~ 100cf

 

[JeffG]

The one good use of ankle weights.

You can wrap it around the tank neck or around your belt. It allows you to adjust the "trim" weights easily and helps in "debugging" what is required.

 

[don Francisco]

I agree 100% with the posters who write of shifting weight upward, without the need to repalce any equipment. It isn't what equipment you use but where the center of gravity ends up.

But that's only half the story.

The center of bouyancy is the other half. Going back to the balance beam approach, just as shifting weight upward lowers your head, so will shifting bouyancy down.

You didn't mention it, but if you are by any chance wearing a shorty wetsuit, get rid of it. Shorties add bouyancy to the torso but not the legs, making trim difficult for atheltic divers who have lean, muscular legs (cyclists, runners, ice skaters, etc.) Even if you manage to shift weights to acheive trim, you'll be using your back muscles to hold your legs up. To find out what this will be like, lie face down on your bed with your hips at the edge & try to bring your legs level with your body. In the water the effort will be greatly reduced due to bouyancy, but why have any effort.

If you're already wearing a full suit & have exhausted your options for shifting weight, you might add bouyancy to your legs by placing improvised floats in your wetsuit. Experiment with scrap styrofoam, or empty pill bottles (soda bottles aren't rigid enough). If this solves your problem, you can make something more elegant later.

As to minimum ditchable weight, here's my approach. I figure the only changing bouyancy during a dive is from the wetsuit compression. I assume that it will lose about half it's bouyancy when compressed. I know it's bouyancy by the difference in weight I use with or without the suit, so I need to be able to ditch weight equal to slightly more than half the difference. In my case that means that with my 3mm suit I can carry 4 of the seven total #s of my weights in the kidney pockets. In reality I could put it all up there since 3#s isn't much to work against if my BC fails.

Good luck, keep experimenting until you dial it in; keeping notes on what worked best, since it will be different when you change wetsuits.

 

[nereas]

You can load up your BCD with all sorts of tim pockets, front and back, top and bottom, sure. It will feel uncomfortable, and it will look really dork-ish. Go for it, fine.

A BPW is immensely more practical however, as far as trim is concerned. The BCDs are designed for beginners and intermediates, who are best served with a "vertical" trim.

 

[nereas]

Spectrum's post is spot on. Nereas' post is rubbish, as usual. ...

So, how do you like your own trim pockets? How many do you have, NC ??