Why do I sink?

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I don't have much experience diving in a 3mm, but 12-14 lbs. doesn't sound like a lot to me. Am I missing something?

Anyway, if you sink when you're head-down but not when you're head-up, I guess you could be over-weighted, and just be unconsciously finning to compensate, which works in every other orientation. Have you ever tried going head-down (or head-up) high enough in the water column to have some margin for error, and seeing if you come back up when you inhale? I haven't tested this out, but it makes sense that if horizontal trim creates more drag moving up and down, then vertical trim would make you float higher and sink farther with each breath.
 
Horizontal trim might not be "necessary" but if you want to go forward(or backwards) when you kick, as opposed to up or down, it makes a lot of sense.
Obviously. Horizontal trim is good for horizontal movement. Especially in swim-throughs. Horizontal trim is a good tool. But it is a means, and not an end.
 
First the thing about you go head down.. do you go head down and stay at depth or sink. the head down says youhave too much weight on the head end lower you tank etc. if you overall sink then you are overall heavy. Yes placement of the lift and weight of your rig is important. first get neutral. do the 500 psi at 20 ft thing and get neutral with no air in the BC. add and remove weight as needed...... then relocate the remaining weight to get the teeter totter to ballance. Keep your weight low. not on the tank center on the back but on the belt or chest. that makes you belly heavy and will tend to make your natural position belly down and laying flat. if you put it on the tank center above you then you tend to roll to easy.
 
First the thing about you go head down.. do you go head down and stay at depth or sink. the head down says youhave too much weight on the head end lower you tank etc. if you overall sink then you are overall heavy. Yes placement of the lift and weight of your rig is important. first get neutral. do the 500 psi at 20 ft thing and get neutral with no air in the BC. add and remove weight as needed...... then relocate the remaining weight to get the teeter totter to ballance. Keep your weight low. not on the tank center on the back but on the belt or chest. that makes you belly heavy and will tend to make your natural position belly down and laying flat. if you put it on the tank center above you then you tend to roll to easy.

OK. That's the help I was looking for. Reduce and reposition my weights to closer to my core. I guess its really a no brainer but then, so am I.

Thank you.
 
This is the trim police, get your hands [knees] up!

Classic!
 
Anyway, if you sink when you're head-down but not when you're head-up, I guess you could be over-weighted, and just be unconsciously finning to compensate, which works in every other orientation.

First the thing about you go head down.. do you go head down and stay at depth or sink. the head down says youhave too much weight on the head end lower you tank etc. if you overall sink then you are overall heavy.

Whether a diver sinks depends on their buoyancy not their weighting, unless they have more weight than their BC can compensate for, in which case they will be swimming up.

It's an easy guess that a diver is overweighted because the finer points of weighting are usually not covered in an OW class, but whether a diver moves up or down in the water column is dependant on buoyancy control. Overweighting may make it more difficult to maintain buoyancy when shallow, but not impossible.

If it the idea that there is a direct relationship between weight and buoyancy is one reason divers are overweighted to start with. The "if you float you must need more weight" syndrome along with "if you hold are able to maintain depth you are properly weighted". Well I've held a safety stop holding a 15# anchor, not recomending this to anyone, so other than demonstrating risky behavior, does this mean I'm weighted 15# light normally?

In inverting, the OP could be lowering his BC in the water column and making it slightly less buoyant, either by how he inverts and/or by the trim lowering his head and that end of the BC. Tricks like this are not easy and any small factor can cause failure. I agree that the OP should be properly weighted, which may help if he is not already properly weighted.


As far as trim goes, ones weight should be adjusted so one can maintain any position, or just to maintain the position you perfer. Proper trim is more a personal preference rather than a law.

Bob
 
I'm totally fine hovering with my belly down in the horizontal position. I'm like the Forest Gump of hovering. It is only when I roll over with my tank down and belly up like so many of my goldfish as a child that I start to descend in the water column no matter how big of a breath I take. After much discourse on this thread and, I would hope, good-natured ribbing, it would seem that since my weight is almost entirely on my back, it is the relative position of that weight compared to my buoyancy device (my lungs) that causes me to descend as I don't when I am horizontal belly down.

Yes, I know I need to work on how much weight I am using. That is my next goal along with my breathing rate. That is one of the things I love about diving and why I dive (yes, gratuitous plug for my other thread...Why we dive). I can learn and improve on a regular basis.

Now if I can only apply that same logic to being a husband and father.
 
I realize I may have misread the OP. Are you saying your body sinks when you go in a head-down position, or that your head sinks when you're neutrally buoyant in the water, causing a head-down position you weren't trying for?

And @Bob DBF you're right; it's not about being over-weighted. If it's the first of those two scenarios above, though, he could be negatively buoyant, which can be fixed with more air in the BC rather than removing weight. But if someone feels like they're neutrally buoyant except when they go head-down, do you think the unconscious finning hypothesis is reasonable?
 
when I am trying to swim belly-up on my back, so to speak, I slowly tilt head down until I do a very slo-mo summersault backwards. I think the whole situation is caused because now I have shifted all the weight to underneath me where normally it is above.

I am actually very good at going head down as I like looking in nooks and crannies and have practiced it a lot.
 

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