interesting weighting question

Darin · Oct 3, 2005

Hi all,

I got an interesting, issue. I hesitate to call it a problem because I've just learned to deal with it and it doesn't seem to be a big bother.

See, here it is. I've got lead legs. If I remain motionless in the water at depth, my legs will soon sink, making me vertical. I have rather muscular legs and that I know is the reason.

As long as I maintain even the *slightest* amount of movement, it doesn't bother me, and my legs stay where they need to be. Like I said, not really a problem for me. Maybe this is just normal?

Are your legs negative too? Does it bother you?

I have some weight pockets on the back of my BC (Zeagle Ranger LTD) and I noticed that they can be switched to the top strap, moving my center of gravity higher, I think this might help, when I actually put weight in them that is.

What do you think? Other ideas? Don't worry about it?

Thanks!

Darin

EDIT: I should add that I have had good luck diving in my drysuit W/O ankle weights...legs seem to behave better....

Dragon2115 · Oct 3, 2005

Darin:
I have some weight pockets on the back of my BC (Zeagle Ranger LTD) and I noticed that they can be switched to the top strap, moving my center of gravity higher, I think this might help, when I actually put weight in them that is.

EDIT: I should add that I have had good luck diving in my drysuit W/O ankle weights...legs seem to behave better....

Darin,

Yes it makes a difference in what exposure suit you're wearing. My wife for example is perfectly in trim when in a 3/2 mm shorty with just a weight belt. In cold water with a full 7mm suit and 7mm boots she needs ankle weights. You will need to learn how much weight, and where to locate it to get yourself in trim for the different diving conditions. If you want to really get this down to a fine art take the Peak Performance Buoyancy class.

Diver0001 · Oct 3, 2005

Darin:
Are your legs negative too? Does it bother you?

In my drysuit if I stop moving it's like I'm hung on a thread.

In a wetsuit my feet will sink unless I transfer weight from the weight belt up higer on my kit. Some BCD's have trim pockets at shoulder level and the (upper) cam band can take a kg or two.

Also, the type of fin you have makes a big difference. Plastic fins are less negative than rubber ones etc etc, but I'm sure you know that already.

R..

spectrum · Oct 3, 2005

I started out foot heavy. A mentor said your weight looks OK but you need move some weight higher on your body. Moved 6LB to the trim pockets and never looked back. Think not that your feet are heavy but that your chest is light. there's a fulcrum in there somewhere.

Pete

donacheson · Oct 3, 2005

spectrum:
I started out foot heavy. A mentor said your weight looks OK but you need move some weight higher on your body. Moved 6LB to the trim pockets and never looked back. Think not that your feet are heavy but that your chest is light. there's a fulcrum in there somewhere.

Pete

You're right about there being a "fulcrum". Your weight can be considered to be concentrated at your center of gravity (CG) and the offsetting (and comparably large) buoyant force at the center of buoyancy (CB). If the two are coincident, your trim is perfect. If the your CG is higher on your body than your CB, then your feet will tend to float; vice versa if your CG is below your CB.

However, it's not easy to predict exactly where your CG and CB will be located. If you extend one arm, both change a little bit. As you consume air, your CG, but not your CB will change a bit (unless your CG is, by coincidence, located at the CG of the air in the tank.) Just getting them close to one another seems to be sufficient since small motions of the fins can easily keep one trimmed.

Whatgoesdown · Oct 3, 2005

Darin:
Hi all,

I got an interesting, issue. I hesitate to call it a problem because I've just learned to deal with it and it doesn't seem to be a big bother.

See, here it is. I've got lead legs. If I remain motionless in the water at depth, my legs will soon sink, making me vertical. I have rather muscular legs and that I know is the reason.

As long as I maintain even the *slightest* amount of movement, it doesn't bother me, and my legs stay where they need to be. Like I said, not really a problem for me. Maybe this is just normal?

Are your legs negative too? Does it bother you?

I have some weight pockets on the back of my BC (Zeagle Ranger LTD) and I noticed that they can be switched to the top strap, moving my center of gravity higher, I think this might help, when I actually put weight in them that is.

What do you think? Other ideas? Don't worry about it?

Thanks!

Darin

EDIT: I should add that I have had good luck diving in my drysuit W/O ankle weights...legs seem to behave better....

I have the same issue! Generally, I don't wear more than 2lbs of weight and I'll put them in the trim pockets and carry a spare couple of pounds in ditchable pouches if I'm working. If I stop I scull slightly with my fins to keep them up but for safety stops I extend my arms forward so that I can watch my computer and balance out completely horizontal. Move a little weight up at a time and make sure that you are able to ditch enough to make you slightly positively buoyant if the need should arise.

Incidentally, starting with the most basic courses, I tell students to put their weightbelt a little higher up than a regular belt (around the belly button seems best) this has virtually eliminated the problem of correctly weighted students kicking up to the surface because their legs hang below them.

Hope this helps!

Charlie99 · Oct 3, 2005

donacheson:
CG and CB....... Just getting them close to one another seems to be sufficient since small motions of the fins can easily keep one trimmed.

One reason they just have to be close, is that if you have an air bubble in your BCD bladder or wing, that bubble will shift as you change orientation. Usually, the shift is in such a direction as to keep you in your new orientation.

cobaltblue · Oct 3, 2005

Try adjusting how high you tank is on your back. That's what works for me. I have to adjust it up or down depending if I dive wet or dry. I use steel tanks but I would imagine it would still work with aluminum.

Doc Intrepid · Oct 3, 2005

Bingo. Where your tank rides relative to everything else plays a huge role. Move your tank higher. No more lead legs...

Darin · Oct 3, 2005

You guys rock!

Thanks for the great info, I'm going to try all of the ideas, one at a time.

Never thought about moving the tank a bit higher, I'm gonna try that, as long as it doesn't bang me in the back of the head....I've always put it down pretty low, well, my 5'7" body doesn't allow me to put it up real high anyway.

I think I will put the weight pockets in the back on the top strap with a couple of pounds in them to start.

I took the PPV class but haven't done the specialty yet, we'll see how it goes.

Thanks again guys...

Darin

interesting weighting question

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