Trim: How To Distribute Weight

[Coldwater_Canuck]

This is one of those questions that I know "you'll have to try it yourself" to get perfect, but I'd just like a starting point.

I have weight in three spots: belt, front BCD pockets, and BCD "trim" pockets at the back hugging the bottom of the tank. Any opinions about the best way to distribute the weight between these three from a trim standpoint? Another concern is how comfortable the rig is (putting all the weight in the BCD or all in the belt is not an option I want), but from a trim perspective are there any general ratios people use? Thanks.

 

[jtpwils]

I think you pretty much answered your own questions. Some folks like it separated for "ditching purposes" - meaning you can ditch weight to get more positively buoyant but not all of it so that you don't "launch" after a release. Others will argue that "ditchable weight" isn't required at all. Others like to separate it so that some is carried on your shoulders and back (BC weight) and some is carried by your legs (weight belt).

I know that I didn't help a lot but I felt sorry for you seeing so many views and no answers so I gave it a shot. LOL

 

[Bubbletrubble]

With regard to a "starting point," why not just start with most of the weight in BCD front pockets and/or weight belt? You'll probably end up feet heavy. Then, move small amounts of weight to the trim weight pockets. Check your trim. Keep shifting around the weight until you're horizontal. At some point, you might find out that you need trim weight pockets on the top tank camband. XS Scuba has some relatively inexpensive weight pockets that slide right onto tank cambands.

It's best to do all of this with a knowledgeable buddy, since lots of subtle factors can affect trim (posture, position of legs, where the air bubble is in your drysuit, etc.).

AFAIK, there's no magic formula for distributing your weight optimally. Just trial and error. Be patient. You'll get there.

 

[stargost]

I have found out that with a steel tank, i have a higher tendency to tilt if I put too much weight in the trim back pocket of the BCD. So i put more on the ditchable front pocket.
With a AL tank, i have no choice as I need to fill both at max ! :blinking:

Weight belt is a pain, and i feel better without it.

Now based on the number of dives I have, it may just be pure coincidence, and I'll come with a new story next week !

I have a 1 pound ankle weight on arround teh valve tank. One way to adjust the weight in odd number, and for some reasons (maybe still coincidence), it allowed me to lower the overall position of the tank which makes stability better. But, maybe just lucky when tried

 

[plumcrazy]

Greetings, here is what is working for me so far. I put about 1/3 of my total weight in the rear trim pockets with the remaining 2/3 in the front BCD pockets. I do not wear a weight belt. I found that if I put any more weight in the rear trim pockets I tended to rotate face up. I was speaking with another fella who owns the same BCD and he was putting equal amounts front and rear. The biggest diffence between the two of us is probably 200 lbs !! I am a scrawny little dude while he is uh well............. not so scrawny. This is still awork in progress for me. Hope this helps

 

[Ytsejam]

I am diving a single steel 15L tank with a 3.2mm wetsuit. I put 6 pounds on my belt and 6 pounds on the front pockets of my BCD.

I only have a few dives under my belt, but so far it seems that this configuration works best for me.

 

[Davidstealey3]

your right it is going to be a trial and error process. you do want the weight to be distributed in a way that you are horizonal in the water, but this is while you are not swimming. you will be able to be horizonal while swimming, but when you stop do your feet start to drop?

you might not have to put a trim pocket on the top band of your bc ( provided you have two straps compared to one ) you might be able to put the tank valve a inch or two higher then usual when you attach the bc to the tank. this will put the weight of the valve up some and might correct the problem without additional weight. or do this and remove a pound or two from the belt or bc, if it will not affect your ability to ascend and decend. as you are still a new diver, you might not be letting all the air out of your lungs when you decend.

try some different configurations to see what works. you might even find after doing more diving some of these issues might resolve themselves as you get more comfortable in the water

good luck

 

[Buoyant1]

It's all experimentation, find your "fulcrum" point and add or subtract until you get it right. Sometimes it's as simple as moving your cylinder up an inch or two. I can't believe how many divers I've seen that have their tanks halfway down their back, then when you see them in the water they are "vertical roto-finners" ($1.00 to my friend Jeff for that term!)

What's worked for me in the past is getting my weighting correct, then analyzing my trim during the course of a few dives. I've mostly kept 10lbs in trim pockets, and any other weight in my dump-able side pockets, then worked on tank placement. If I max it out then I take other steps. You can usually compensate by changing the placement of your hands on the dive...further out front, or closer to you, until you get a common spot.

I just went through this again with learning to dive in a dry suit.

 

[TSandM]

There are three issues with distributing weight.

First off, there is fore and aft balance. Because we float, we are subject to the inherent physics of the distribution of lift and weight. If the lift is all in the bladder of the BC (which runs from the shoulders to the waist) and the majority of the weight is in the vicinity of the waist (integrated weight pouches and weight belt, with a relatively light tank) then it is almost certain that the diver will be forced into a feet-down position, or will have to fight constantly to avoid going there. This is the situation many or most divers find themselves in after class, and it's exacerbated by the typical posture fault of bending at the hips and dropping the knees, which further tends to rotate the diver to a vertical position.

Solving the problem requires fixing the posture, and redistributing weight. Trim pockets are good for this, if they are high on the BC, but I believe the OP describes them as being on the back but at waist level, which means they are not useful in this way. (This is something I've seen on a number of BCs, and I simply don't understand.) Moving the tank up on one's back can help, and weights can be affixed to the camband/s, either by threading or by using weight pockets. Tank or ankle weights can be wrapped around the tank neck, although this is a kludgy solution.

The percentage of weight that has to be moved up is impossible to predict, but you can get some idea by seeing how rapidly you rotate into the vertical position, if you start horizontal and stop finning. (Make sure the posture is good before doing this test!)

The second issue is creating a "keel". With the tank, which is a large mass, sitting on top of your back, it's very easy to be unstable in rotation along the longitudinal axis of the diver ("turtling"). Moving ballast to the diver's front as much as possible will help with this. Integrated weight pouches are generally on the side and toward the front, so they're good for this. Putting weights on the belt as close to the diver's front midline as they can practically go will help, as well. Trim weights, being on the back of the BC, are a negative in this regard.

The third issue is balancing the weight from side to side, so that the diver isn't constantly compensating for being off balance. This is more of an issue for new divers, I think -- it bothered me a lot in the beginning, but nowadays, I can swim around with two extra tanks attached to one side of me without heeling over, so I've learned something that allows me to compensate pretty automatically.

You might enjoy reading the articles on levers on THIS site - they're quite good.

 

[Johan Broere]

It depends what I am up to. If I go clamming I go extra heavy in the front pockets, so I can dig face down laying on my belly. When I go play with sea lions I put all my weight in the back pockets. I only need 6 pounds this time of year. That way I can spin and twirl around just like them. Also do a proper weight check. If you don't need the weight, you don't need to distribute it.