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How can you establish and maintain surface trim?
TRGscuba - 10/03/2019 7:27 PM
Category: Training
Replies: 5


Halfway through the first of two pool days I stopped because I was feeling sick and also very discouraged because I had a lot of problems trying to remain perfectly straight up when at the surface. Everybody else had no problem at all. Two weeks later, I tried again and I still had the same problem. I don’t want to give up scuba because of this since I have already invested a lot of time and money. There has got to be a way to fix this problem.

I tried lowering the height of the tank the 2nd time I went there and that didn’t seem to help, even though I believe I had it about as low as it can go.

I came across this article about surface trim which is what I was asking about.

1. I can’t make sense out of this. In the pictures to the right, does the blue rectangle represent the center of buoyancy or the center of gravity?

2. What are some ways you can shift your center of buoyance forward or backward as needed?

3. I had 2 lbs weights (2 of them) and 3 lbs weights (2 of them) for a total of 10 lbs. How should you distribute that weight? Should the lighter weights (2 of the 2 lbs weights) go in the front or in the back?

4. Also the first time I went, I had an XL wetsuit. The suit was so tight I felt like I was getting squeezed around my torso area so much that I felt like it was somewhat hard to breathe. The second time I went there I tried an XXL. That time I felt like my left thigh was being squeezed quite a bit. I know a wetsuit should be tight but do you have any suggestions on how to make things more comfortable?

5. My mask lets in water too. It seems like the water was leaking in through the nasolabial folds (the lines to the side of the nostrils)

Do you have any suggestions on how to prevent water from leaking in through my mask?

Any help would be greatly appreciated. This is so frustrating.
Eric_R - 10/03/2019 9:53 PM
You should bring Your buoyancy problems up with your instructor. This can all be sorted out in a pool where weights can be quickly added, removed and relocated. Every persons Buoyancy is different so eyes on observation is the best. There’s several ways to position weights on and around your rig.
As far as the wetsuit you may need a custom made one or see if your instructor has access to one of the newer hyper-stretch suits.
The mask leaking is a common problem. No two faces are the same so you may need to try several masks to get one that will seal. Your instructor or local dive shop should be able to point you in the right direction.
I think the blue rectangles represent the traditional location of your main weight system. The red is the various buoyancy bladder setups that BCD’s have.
LatitudeAdjustment - 10/04/2019 7:57 AM
You don’t mention what kind of BC or wing you are using. Some brands will float you face down if you add too much air.

Most students try to float to high on the surface and the more air they add the more the BC pushes them on their face :(

I use a Back Plate & Wing, my weight pouches are as far back as I can get them and if I use just a little air and arch my back I can float face up.

The wetsuit should not be tight, just snug enough to stop water from flowing thru and yes I’ve had some suits make me fell sick. The only time I ever came close to being seasick was from a 7 mil hood that was too snug around my throat. Now in cold water I wear a 2mil hooded vest with a 3 mil bennie. That keeps the head warm and blocks the water flow down the neck :)
MDW - 10/08/2019 5:48 PM
You should definitely NOT arrange your weights and BC for good vertical trim / buoyancy at the surface, as in the real world you will spend maybe 30 seconds at the surface at the beginning of the dive and a few minutes or so at the end of the dive. Meanwhile, you will spend from 30 to 60 minutes or more underwater, where you will want perfect HORIZONTAL trim and esy buoyancy control. To achieve this, weight yourself appropriately for the position you will spend the most time in (horizontal, underwater, with the least air needed in the BC to maintain depth and be able to do a safety stop. Once you achieve that, there may be some tweaks you can do to allow vertical trim at the surface, but make sure these will not mess up your underwater trim, which is far more important.

At the surface, as long as you can keep your head out of the water as needed, it is not really important for the rest of your body to be in a perfectly vertical position or any other particular position.
TRGscuba - 10/09/2019 7:29 PM
That makes sense. Regarding your last paragraph the problem is keeping my head out of the water. I keep going face first and the instructors couldn’t fix that. Nobody else had this problem so I don’t know what I was doing differently.
binobanana - 11/20/2019 7:12 PM
Found it!
The idea is that if you are correctly weighted, you should float at eye level with an empty BCD whilst holding that normal breath; Then, breathe out slowly and you should sink slowly, not like a brick to the bottom!