Trim weights

[flyboy08]

so I'm going to be doing a dozen or so dives this December in CZM. My goal is always to pick something to work on during these trips. This time, I want to shed weight. I use 16 lbs broken down into 4 4lbs weights two each in my quick release pouches.

My goal is to get down to 12 with no other changes to my diving profile. New BC with about 5 dives on it......

Question. I've not used my rear trim pouches.....I've always felt in an emergency, I'd rather not have to reach back trying to remove the one or two pounds of weight. Am I being to conservative here?

Should I go with 5 pounds X two in the QR and 1 to 2 pounds in the rears? I realize I have to try various configurations and these dives will afford me this option.

This will be a buoyancy and trim trip

 

[EricTheDood]

Trim changes depending on the tanks you're using and where they're positioned on your BCD.

5+5 in the ditchable pouches and 1+1 in the rear trims should be fine. Or you can do 4+4 and 2+2. It's not going to make that much of a difference. Instead, use the same configuration each time and adjust your tank position.

In an emergency, you don't need to remove your trims. Remember the "C" in CESA stands for "controlled". The point isn't to shed every ounce of weight and rocket to the surface.

 

[mi000ke]

I just went through the same thing - in fact exactly - went from 16 lb to 12 lb. But we did it in two steps. I had 12 lb in my QR hip pouch and 4 lb up on my shoulders (I like to keep the trim weight accessible as well). We pulled the trim weights out just to calibrate the best overall weight. Then once that was done, worked on trim based on body rotation. I ended up with the weight divided 4 trim/8 QR. But I think the weight distribution is something you will need to calibrate empirically.

 

[rongoodman]

Why do you think you need to shed weight? Do you have some reason to believe you've been carrying too much?

 

[Jim Lapenta]

People need what they need as far as weights go. The issue is when they have not been trained to determine what they need with accuracy. Trim weights are great if you can get them in the right place. Most BC's don't allow you to do that. Trim pockets are placed way too low on the back. Your kidneys are not air spaces.
The other issue you run into is this mistaken belief that you have to be able to immediately dump all your weights instantly. At most, for a properly weighted diver, you should not have to dump more than 10-15% of your weight to start to get positive and stay positive.
If you are carrying 16 lbs, and that's what you need, dropping 2 -3 lbs is more than enough to give you time to leisurely drop more at the surface. Worst case scenario with an integrated BC and an exposure suit is you dump the whole rig.
My general rule is if I am using more than 10 lbs and I'm not using my BPW with steel plate, I put the needed lead in two or more systems.
In my 5 mil with an al 80 I need 14lbs. 2 lbs go in each waist weight pocket on my HOG comfort harness with soft pack. 2 in each cam band pocket and the other 6 in my mako rubber belt with pockets.
If I completely lost the wing I could swim this up. To make it a little easier I might drop 2 lbs.
That would let me control my ascent. On surface, if need be, I'd then drop the belt in an emergency.

 

[decompression]

I'd say, that a nice expensive holiday might not be the best place to be experimenting on your gear. Better to enjoy the dive. If you can, hit the pool for an hour and that will help immensely.

But, to streamline things a bit, first see how much weight you actually need.....get every bit of air out of your BCD, place it in a mesh bag with whatever you are wearing that's positive, place in water (pool, bath tub etc) and place weights in the bag until it sinks.

Now if you are not at either extreme of personal weight (super skinny or morbidly obese) you are just about there.....remember to add 4 lbs to offset the Al80 if that's what you are using.

So, once you've determined your actual weight requirements, then you can start with "weight placement " for optimal trim. This varies a lot due to BCD design, body position and composition (long legs etc).

Also, if you are weighted correctly, ditchable weight becomes much less of a factor, this frees you to place your weights where it makes most sense. Only a couple lbs ditched should make you positive.

 

[DevonDiver]

I've not used my rear trim pouches.....I've always felt in an emergency, I'd rather not have to reach back trying to remove the one or two pounds of weight...

Bear in mind that you ONLY need to dump sufficient weight to gain positive buoyancy. That needn't be ALL your weight.

There are some safety benefits to intelligently splitting weight into ditchable ballast and permanent ballast. If you did need to ditch weight at depth, having only slight positive buoyancy prevents uncontrolled hyper-fast ascents.

You need to ensure sure two certainties...

1. You would float to the surface, having dropped weight, if you became unconscious underwater.

This is only an issue in OOA scenarios, as otherwise you can inflate your BCD. Even then, you would probably be neutral (should be... if diving properly...) when an OOA issue occurs.

Simply beginning an ascent will cause you to gain positive buoyancy as you rise - air expansion in your favor. The danger is primarily only if you OVER-VENT your BCD on a CESA.

You would think make that mistake if you practice CESA and get fluent with it.

2. You can gain positive buoyancy at the surface, for safe and stable flotation.

For long float/drifting diver scenarios, you have ample time to remove and ditch trim weights.

For 'panicked diver' scenarios... the best preventative is to repeatedly practice oral inflation at the surface. If that's instinctive and ingrained, then being a couple of lbs negative should be manageable.

..... As you can see.... I offer skills solutions, rather than focusing only on weight ditching to get you out of the sh!t.

Its convenient.... sometimes fun... to obsess over dive kit and configuration. We see lots of divers doing that. We see FAR LESS divers assiduously practicing emergency skills like CESA and BCD oral inflation.

Skills are WAY BETTER than kit, when the excrement contacts the oscillating blades..

If perfectly weighted, you should be exactly neutral on your final stop, with no air in your BCD. You can see that for much of the dive, losing only a couple of lbs will make you positive.

You are heaviest at the start of the dive, just upon reaching bottom depth. You are carrying the max weight of gas, plus have lost the most buoyancy from your wetsuit. Understand how much you need to ditch at that point, to *just* gain the slightest positive buoyancy.

For most divers, there is no harm in putting 2-4 lbs into trim pockets.

But.... do this based on a calculated balance of weighting.... and test it... before relying on it.

 

[DevonDiver]

.... remember to add 4 lbs to offset the Al80 if that's what you are using.

Most manufacturers quote AL80 positive buoyancy, when empty (i.e. max) at 2.1 to 2.4lbs.

Specification tables are available online for most cylinder manufacturers.

 

[flyboy08]

All great replies....I don't wear a wet suit, I only wear a rash shirt and with my new BC, I'd like to streamline my profile....maybe 16 is accurate, but I want to try and shed to see if by chance, I'm carrying a few extra pounds needlessly.

I like the pool trick and will give that and my gear a splash and see....as you can see, I took the AOW recently and enjoyed the buoyancy class....I have a large chest volume and hence take in a good amount of air. I would like to work with this air more closely.....and less weights.

It's something to play with on this trip.....this won't interfere with the enjoyment of the dive or me having to be watchful of my buddy (wife) and six other divers

 

[flyboy08]

Why do you think you need to shed weight? Do you have some reason to believe you've been carrying too much?

It's my nature! Being a pilot for the past 30 years and having to go through recurrent simulator training every six month my brain is programmed to always work on something to become better at it.....I can shut down an engine in three seconds blindfolded, but every six months I have to go by the checklist ( which is the proper way) and follow the procedures for shutdown....we all become complacent no matter what we do and regardless of how long we have been doing it...

If I shed one pound, then I have accomplished what I set out to do.