A weighty question

[TexasMike]

A few questions about weights for the benefit of myself and other not-so-newbie divers.


1) Determining my weight requirement: I am still working out the weight requirements for my gear setup in freshwater diving (3/2 full 1-piece wetsuit, booties, Zeagle Ranger BC, Zeagle 50D/Flathead Regulator). Currently I strongly suspect that I am setting myself up with too much weight (15 lbs, 6 in each pocket, 3 on lower tank strap). Reason for suspicion is that I tend to yo-yo to the surface too easily when at depths less than 12 feet (remember, I often dive at Athens Scuba Park which has a max depth of 28 feet). This occurs when I add a bit of air via the inflator to acheive neutral but it seems to take a more than a "squirt" to keep off of the bottom (aka slowing my descent), and if I cross a the "magic depth", I'm all of a sudden too positive and up to the surface I come. Then I am dumping and the process might repeat itself. And it really happens when I start task loading like starting to swim on a compass bearing.

This most often happens during a free descent (no reference), but if I descent along a buoy line (say to one of the student platforms set at 20 feet), I get below this "magic depth" and the yo-yo doesn't happen. I should also add that once at depth, my boyancy control while swimming is fine, and none of my buddies have observed any swimming positions that state too much weight.

Any suggestions on how I determine the proper amount of lead to have for my gear setup? Procedural suggestions would be helpful. Where do I start and what checks should I perform at depth to check if weight is right on or needs to be changed again?



2) Weight Placement: Once the proper amount of weight is determined, any suggestions on distribution? So far I've detected no problems with floating feet, so I don't think I need ankle weights. And the 3-pounds on my tank band have helped me float upright in my Ranger. But do I need any weight there? Should it be all in my weight pockets?

I have had some difficulties with the trim pouch on the tank band. During my dives, I head to the training platforms at Athens and am trying to work out hovering while being both horizontal and in the Budda position. But something is not placed right as I tend to slowly roll to one side. During one dive, my buddy (who is also a Tech Diving instructor) tried to move the pouch around to "center" it, but we couldn't find the right spot. I would still roll to one side.

My desire is to be able to hover without rolling. So any placement suggestions that can achieve this would be helpful.



3) Adding weight for Salt Water: Is there any rule of thumb as to how much additional weight is required to transition from fresh to salt water (i.e. a percentage)?



4) Is there a "magic" depth where you become negative? As I mentioned in #1, I've found there is a a particular depth where when I am above it, my boyancy is harder to tune with air in my BC, resulting in either excessive adding (I'm decending too fast) or dumping (I added to much to counter the descent and am on the express "up" elevator). But when I am about 6-10 feet deeper, this problem disappears. Has anyone else noticed this?



Any other hints or tips about weights and boyancy are very much appreciated. Especially if you dive with similar equipment to mine (the Ranger or other back inflation BC's).

And if I get a chance to read them before heading to Athens this weekend, I will be sure to report on their success Sunday night.

 

[Warhammer]

1) Alot of divers, including myself, weight themselves to be neutral @ 15 without any air in the BC and 300 to 500PSI in their tank. This does make you slightly positive when you ascend above 15ft. Others want to be weighted so that they are neutral on the surface with an empty BC and 300 to 500PSI in their tank. This is the general rule taught by most agencies. So you'd just check for the one you wish to achieve. An easy way of checking would be to carry some of your weight in your Ranger's non-ditchable pockets on each side, say a couple of pounds on each side. Then while your making your safety stop (or at the surface for neutral bouyancy there), empty your BC and hand 1 of the weights to your buddy. Check it and repeat if necessary.

2) I also dive a Ranger and I don't use a tank weight to offset it's tendency to push your face foward. I usually surface swim on my back, so it doesn't present a problem in that respect. However, for an unconsious diver it would be a problem if his buddy wasn't able to assist.

I'd think that if the tank weight was your problem, you'd turn turtle instead of just listing to one side. But you may be correcting it before it gets that far, so hard to say. Try it without the weight and see how it goes. You can also try placing a weight on each side of the tank, Zeagle makes pouches for this, or maybe a weight in the tank boot. You may also have something with enough weight on one side that you don't on the other, a light for instance.

3) Get on a scale in full gear and get your weight. If you don't have a tank, then weigh everything else and then get your normal tanks weight from a chart and add it to the result. Then multiply that number by 1.6 and divide by 62.4. The result will be approximately how much weight you'll need to add for salt water. But the only way to determine it exactly is on a dive.

4) Your seeing the effects of your wetsuit's bouyancy and compression. Remeber the greatest pressure change occurrs from 0 to 33 feet, so the greatest compression of your suit also occurrs here. Add small amounts of air and then give it time to react, then add more if needed. It's best to start adding early on your descent. If you don't, then you'll pick up momentum and it will be harder and take longer for the air you add to conteract your bouyancy. This takes practice, lots of practice. Same goes for an ascent, start deflating early. If you're deep, then the suits bouyancy changes won't affect you as much as when you are shallower. It's hardest to obtain and maintain neutral bouyancy in shallow water, again because that's where the most change occurrs. Keep at it and before long it will be second nature.

 

[Frog]

Here is a buoancy calcultor to determine the weight of your tank. http://www.subaqua.co.uk/cgi-bin/cylinder-buoyancy.cgi I thought i would add something too. Why have the tank weight on the bottome tank band. It should be at the top to promote head down/ horizontal trim. I can see how you might think that this will make your "roll" worse but it shouldnt. Hope this helps you. Cheers

 

[TexasMike]

Frog: The weight on the bottom band was ostensibly to assist in upright surface floatation. But after reading what Warhammer contributed, I may try not using it and see if that corrects the roll

Warhammer: Thanks for your comments. Your explanations make sense and should help alot. And I agree with the practice practice practice bit.

I two of the trim pouches, but I may try one dive without them as you suggested to see what happens there.

For the neutral @ 15, what "attitude" do you usually hover at? Head up/feet down, horizontal, or what ever happens?

Again, thanks for the comments.

 

[scubakat]

Hi guys, I dive a ranger too and find that it's harder for me to maintain propper attitude than it is for me to stay face up at the surface So I clip 2lbs to each shoulder strap. That seems to trim me out. I don't use weight on my tank bands, but I may try putting some on the tank neck one of these days. I also find that using a steel tank makes life a lot easier. And yay! I get my drysuit out of the shop today!!!

-kate

 

[TexasMike]

Oh yeah....clip weights....:bonk:

I think the on-premesis dive shop at Athens sells these and it would make it simpler to "diagnose" both my rolling and amount of weight problems.

Thanks for reminding me of these, Kate!

 

[Frog]

Texas Mike Hi. Yeh thats why people use BC keel weights on there tanks to gain the correct posture on the surface with back inflation BC's/Wings. This is also often called BMAP ( Ballest Mediated Airway Protection). Mounting weights on the top of the tank rather than the bottom doeasnt make any difference to surface positioning in my experience. Placing them at the top of the tank should also stop/reduce the "roll" effect. Take a look here http://www.halcyon.net/mc/06b_mc.shtml

 

[scubakat]

Hey TexasMike... I don't know what your shop will charge you for them, but you can easily make a pair. Go to your local sporting goods store and pick up a pair of stainless steel snap clips (I bought the el-cheapo ones - yes I know they will corrode), then head over to the fishing section and grab a pair of weights that you think will work. I have them in 32oz and 20oz cannonball weights, but I've seen folks with different shapes. Now attach them together with your favorite zip tie. Make sure that you trim or file off the sharp edge of the zip tie. Snagging that with a cold hand would not feel too hot!

-kate

 

[Warhammer]

I'm interested in hearing about your results from not using the tank band weights. I've been pondering the thought of buying some the Zeagle pouches myself. But more for somewhere else to put a little weight when I'm carrying alot than anything else. I don't worry too much about the face down deal because I've gotten use to it, I guess. And I never dive solo, so it isn't a real issue yet. To tell you the truth, I don't even notice the face down deal anymore. I'm sure it's still there, but I just don't notice it.

I usually hover on the safety stop depends on several things. If I'm making a free ascent, I usually hover horizontal and just off the line but within range of it, if one is present. If the there is much current at all, I'll hold the line, why fight it? But I'll still be horizontal until I start to ascend, this allows more room on the line for other divers. If I'm doing a free ascent with my wife, I usually hover vertical so I'm in a better position to assist her if need be. But I always get vertical before I start up from the safety stop so I can turn and look in all directions easily.

 

[TexasMike]

Kate, Thanks for the tip about the fishing section. I'll check out the local Oshman's tonight

W.H., Will do about letting you know results. And I am thinking of getting/making a 6 to 8 foot lanyard with a snap clip on it for hanging off of the ascent line at safety stops. This way I can clip on, have something of a visual reference and also be out of the way of the other divers.

And I thought about you hanging horizontally, and then going upright to surface. Be neat if you could just flip over on your back and just slowly rise up like a submarine.


All in all, I think my plans for determining proper weight is to dive with my usual 15 pounds, but exchange about 3 to 5 pounds of my bean-bag weights for the clip weights and no tank weight, swim around until I burn down to 500 psi, ascend along a reference to 15 feet, and then hand off the clip weights to my buddy until I can hover neutral.

Then once that is determined, I will play with placement.