Getting to the perfect buoyancy

[Uncle Pug]

Originally posted by Zept
I am a she and I wear a 3/2 wetsuit (and I still get cold). I use an AL tank, but I'm not sure of the size, because it isn't mine.

So far my best solution to the 'sinking feet' problem is to waggle them gently when I need to stay in one place -- not elegant
Zept

Roaky, Zept, Bob & Zept

Roak:
The reason I say last resort on the ankle weight is that the other options should be tired first... not that the ankle weight on the tank neck is a no-no, it just isn't the *elegant* solution.

Zept:
Please try moving the tank up just a little in the BC even though you feel you will hit your head. BTW...what regulator are you using and is iy your own?

Bob:
You are right about steel tanks being easier to trim, but they are a no-no with thin wetsuit...low weight requirements that we are working with here....that and the fact the Zept is just borrowing the Aluminum tells me that steels might be out of reach at this point anyway.

Finally Zept again:
Since the suit is not keeping you warm enought perhaps when you can afford it a thicker suit would be in order...that will allow you to add more weight to distribute for trim. And if you need to make minor fin movement to keep yourself in trim....no problem - but do try to avoid hand movement.

 

[roakey]

Originally posted by CaptAl
The question is ... how much additional weight should be added to achieve the same buoyancy in salt water? Is there some standard or do I need go through all these suiting-up options again?

CaptAl:

Nope, no need to go through them again.

See post http://www.scubaboard.com/t4213/s.html

In there I have the exact formula for translating your FW weight requirements to SW.

Roak

 

[roakey]

But it's just a matter of degree.

Zept, I'd throw a 1kg-ankle weight around your valve and see how that works. If you start standing on your head, then back off and try more subtle ballast shifts forward like what Uncle Pug is suggesting or putting a 1kg weight on your tank's cam band.

If your pitch is still legs down you now know that the most radical fix, moving 1kg forward to the valve, still isn't enough and you don't have to mess with the more subtle shifts that have been suggested. Look on the bright side, your trim wil be better; it may not be perfect, but your rig is very well balanced.

An AL80 actually swings from about -3 to +3 (buoyant) from full to empty. Air weighs 1 pound for about every 13 cubic feet, so 80 cubic feet of air weighs 80/13 = ~6 lb.

You're one of the few cases where I can say: Don’t go to a steel cylinder. Not only is it too negative, giving you little if any ditchable weight, but the forward ballast shift I still don't think would be enough.

Getting a heavier wetsuit will give you a little more ballast to play with. I dive a 7/5 in water that's in the mid to upper 70s (Fahrenheit). What's the water temp where you dive?

Roak

 

[Bob]

Zept,
Are you diving with a 3/2 Farmer John or a 3.2 mil one piece? 8 lbs with a Al tank and the Farmer John isn't alot of weight. As a point of reference, one of my lady dive buddies weighs 118 lbs and dives in SW with only 8 pounds. This with only a dive skin plus the Al 80 This is why I asked you to consider a LP steel. The 3/2 Farmer John would actually be 5 mil on your upper body. That, plus the natural bouyancy of the lungs and the Al tank would automatically drag you into a heads up, feet down position when you stop moving. A LP 65 or 80 would take care of that problem. Dive Safely. :tree:Bob

Pug: I suggested that Zept should try a steel tank, as in rent or borrow. No one buys dive gear unless they've tried it out first, do they?

Roark: I do like the idea of the ankle weight around the tank valve.

 

[Uncle Pug]

Originally posted by Bob
Pug: No one buys dive gear unless they've tried it out first , do they?

I buy dive gear it to try it out all the time....
Then I take it to ebay and make a little money....

 

[Zept]

Steel tanks: I think Roak and Uncle Pug are right, a steel tank would make me unredeemably negative, at least at the beginning of the dive. I'd rather be badly trimmed but able to surface than horizontal and stuck on the bottom!

Ankle weight around the neck of the tank: makes good sense for a physics point of view, but would it not tend to move around and bang against the first stage? Also, I'd have to buy a set, and that'd be a bit weird ('Why are you buying ankle weights?' 'To stop my feet from sinking').

Thicker wetsuit: might end up being necessary, but I'm hoping to avoid buying another one, at least for the moment.

Wetsuit boots: might be the answer. I can't justify new fins at the moment, but a pair of 5mm booties might add enough buoyancy to bring my feet into line. Or maybe I just like that solution because I fancy better fins

I don't think my trim is catastrophically awful at the moment, so I'll probably just carry on in less-than-textbook fashion -- but thanks for all your ideas!


Zept

 

[The Chairman]

There is ususally more than one way to do it right! SCUBA is about fun, fun, fun, for the majority of us. Somehow, it seems that part of our clan has focused on the technique side and they get a bit head strong about what is right or wrong. While that is OK for them, it might not be the way for you (or me!!!). As Walter pointed out, your body can make a ton of changes, without any conscious thought, to keep your attitude in the water correct. Don't go taking a course on diving physics or physiology just because some want you to spend your entire time diving in a perfectly horizontal position. Spend enough time so that you can SCUBA safely at any one particular depth, and then go play with the fishies! Time will cure the rest! The only other area I would spend a lot of time on trim is my Christmas tree!

BTW, I stand by my first post as the best way to get started!

 

[roakey]

Zept,

I'm going to address something different for a moment, brought up by something you wrote.

You don't have booties, no problem. But do you have a hood, even a Polartec one?

If not, I would spend my time and money on this first, it'll make you more thermally comfortable in the water. A Polartec hood won't add to your forward buoyancy, so I'd opt for that over a neoprene one.

Your comfort is of a higher priority than fixing your trim.

Because despite what some people may insinuate, ALL of us think SCUBA should be all about fun, fun, fun and the equipment and techniques that some may suggest is all about improving that fun.

Roak

 

[The Chairman]

Methinks me touched a nerve... ah well, such is life! BTW, I am just now heading out the door to go to Alexander Springs to work on my daughter's buoyancy control. No lie, she has been out of the water way too long, and wants to do New Years Day in the open ocean. Not without a refresher dive on skills she doesn't!!! Have fun, I'll be thinking of you @ 25 ft!!! BTW, we will bring Cheese wiz for the brim and bass!!! One of the highlights of diving Alexander is feeding the way too tame fish. Did I tell you I LOVE Florida???