Buoyancy and trim issues.

[atlas750]

I am using a backplate/wing single tank set up. I am still having difficulty getting trimmed out to a horizontal position while stopped in the water. While moving forward my trim is good but when I stop my feet sink and I tend to go vertical. I am wearing a weight belt with 6 Lbs and use jet fins. I was wearing a 3mm wet suit. Thanks for the help.

 

[Jim Lapenta]

Al or steel plate? Jet fins are negative. One thing that does help is to use a modified frog kick with your feet up. Where are your hands positioned? This makes a difference as well. Another thing is your height and weight. What tank are you using? I dive only steel and with a 3 mil need no weight. In saltwater with a 3 I use 4 lbs with an al 80 but my fins(Hollis F1's) are neutral in saltwater. I'm 5'7" 160. are you arching your back at all? A bit more info on wing, plate, personal stats would help. It sounds at first that you may be relaxing your position when stopped and perhaps have a couple pounds too much on the belt. But with out the additional info it's hard to say.

 

[Splitlip]

If you are using a steel plate or steel tanks, I suspect you are over weighted.

If you are using an aluminum plate, you might move the weight higher up.

 

[elan]

move your weight up, move your weight off the belt to trim pockets. Use shorter tank and move it up. If you use an SS place use AL instead and the rest of the weight move up. Play with this options and find what works the best for you.

You can also adjust you trim by bending the knees more and lowering your head.



Most likely moving the tank a bit up and weight off the belt to the trim pockets on the top belt. You will be surprised how much difference can 6 lb make.

 

[fnfalman]

Also, do you curl your legs up or do you stick your legs straight out? I don't know of anybody that trims horizontally while hovering absolutely still (no fin movement for station keeping) with the legs sticking straight out.

 

[rongoodman]

You might try a pair of OMS Slipstreams--similar shape to the Jets, but much lighter.

 

[chrisculina]

Also, having a friend film or take photos while hovering and swimming can be a real eye opener. It often feels different than it looks, and hard evidence will help you to make your adjustments correctly.

 

[Peter Guy]

Everything everyone else said -- BUT, sometimes, it just doesn't work with the gear you have. I'm a cold water diver (primarily) but when I go tropical, I often have difficulty trimming out with a single AL80. Rather than fight it, I've just decided to accept it.

Yes, I could spend time and energy moving the BP up/down, tank up/down, weights here and there and/or buying new fins -- but towards what end? I'm down there to have fun and look at the pretty fishies. As long as I know where my fins are, I can pretty much stay out of stuff and not disturb the environment -- especially on a wall!

Enjoy the dive.

 

[TSandM]

To distill all the good advice you've already gotten:

First, do a formal weight check to make sure you are carrying the correct AMOUNT of weight.

Second, have a buddy take a look at your posture underwater. If you dive with your legs flexed at the hip (we call that "dropping the knees") you will tend to rotate feet down when you stop. If your posture is good -- body flat, knees bent to whatever degree is appropriate for your gear and your conditions, then you move to the next step.

Third, look at the distribution of things which sink and things which float. In a 3 mil wetsuit, you don't have much flotation on your legs, so your major upward force comes from the air bladder in your BC. Downward force comes from full tanks (but, if you are diving Al80s, not from empty ones!), your weight belt, and your fins. Your fins are a bigger component than you might think, because they are out at the end of a long lever arm. Bending your knees shortens that lever, but it may not be possible to shorten it enough.

I use 12 pounds with a 5 mil suit and 2 mil hooded vest and an Al80 and my Jets, and to balance properly, I have to put a lot of that weight on my cambands.

 

[D_B]

I'll add one more thing about hand/arm placement (mentioned in Jim's post)
With the gear configuration I have, to keep in trim in my wetsuit I dived with my arms at my sides (or at least not in the hands clasped "superman" pose) with my drysuit I can have my arms out in front