Pool vs OW...difference of buoyancy?

[mudguppy]

Okay...
Say, in the pool, I need no weight diving in a skin with an AL 80 FULL and 2 lbs of weight with same skin and tank at 500 lbs. I am also VERY relaxed in the pool.

When I go to open water will the same weighting still work or will I need to take into account different factors?

I know if I go to a warm ocean I need to account for the salt water. If I dive the hot spring I need to account for the warm water and hot spring bubbles. If I am diving even a very familiar place but have a buddy I am very nervous about I will not be as relaxed. I know if I have a different suit I need to adjust for that, or for a steel tank.

So...my question:
Where do you draw the line at being too picky about your weighting?

Is there a set formula that anyone does that takes into account many different factors without ending up too overweighted? Or is it just okay to dive overweighted?

Is it just a science that you learn to account for all applicable factors for each dive?

Now I am writing this it seems somewhat silly and obvious, but I think I would still like some opinions on just how picky people get...if they take into account the relaxation factors and some of the more not so obvious things. I figure I could maybe learn something from the inquiry.

If anyone can make sense of this, opinions are greatly appreciated.

Thanks ahead...MG

 

[WillAbbott]

Well, I'm a new diver so I don't really know, but... From what I've seen, heard, experienced... you eventually just get a feeling for it... my instructor just threw weight belts together for all of us based on our weight, and knowing what gear we would have... he was very close +/- 2lbs on average....

From what i know, obviously you need more weight for a wet suit (thickness makes ALL the difference) I would assume from what I know/understand that if you dive in OW the same as you did in the pool only a few extra lbs maybe needed if any... now if it's salt water you will need a few more (my guess would be 5-10lbs more, but I don't know for sure)

Someone with a LOT more knowledge than I will hopefully respond and let us both know... but since I saw it and no one had replied yet, I thought I'd throw out what little knowledge, guessing, and understanding I had

BTW for reference, I used 4lbs in the pool with a shorty 3mill wet suit (and the same without the suit, though I may have not needed it) and in OW, Fresh water, I used 25lbs with Full 2peice 7mill wet suit, hood and gloves (just a tad over 15% of my body weight of 160lbs)... all other items remained unchanged....

 

[Big-t-2538]

Of course, this applies to OHio divers with quarter inch, or 6/7 mil johns, shortys, and hoods. We suggest the students bring 12% of their body weight along for their check out dives. We work on getting them weighted properly from there. Since there is a big bouyancy difference between them in the pool and ow with a full wetsuit, this can take some time. Generally we are quarry diving, so getting the students in the water with full suit, hood, BC, weight belt isn't a problem. We work on weighting before we get them in full gear, we tell them to exhale completely, and they should feel like they are just starting to sink. Sometimes, 12% is more than enough, more often than not, 12% is within 2 lbs one way or the other though.

On a personal note, I've been able to notice a difference in my weight as I become more relaxed in the water in the last year. For instance, when I finished my advanced class, I was wearing 28lbs on my belt, and I weighed in the neighborhood of 255lbs. Currently I am wearing 23 lbs, due to 2 reasons, 1...I lost 35 lbs, and 2...I am much more comfortable in the water now. I'm not saying that I wasn't comfortable before, but I am much more relaxed now than I ever have been in the water. Much of that is due to confidence adn experience below the surface.

 

[Rick Murchison]

Salt water is right at 102.5% as dense as fresh water. Therefore, you will need to weigh 102.5% what you weigh when you are neutrally buoyant in fresh water to be neutrally buoyant in salt water - because you will displace the same volume of water and that volume will weigh more.
So, get on the scale and weigh yourself and all your gear, then add 2.5 pounds of lead for every 100 pounds of weight. That is, if you weigh 200 pounds with all your gear, add 5 pounds of lead for salt water to achieve the same buoyancy with the same rig.
Rick

 

[Dectek]

Thanks Rick.
That is the third formula I have seen on this board for fresh to salt weighting. Yours is the quickest and requires no calculator or fingers.

 

[DiverBuoy]

mudguppy ...Since you said "open water" and didn't clarify that you meant salt-water not fresh "open water", I'm going to assume since this is a buoyancy discussion that salt-water is what you meant.

If you think about it by the time the students go from the pool to the ocean they are already more relaxed and are likely to start migrating toward weight reduction (at least in the sizes we are talking about here - 2 lbs for example).

We know this - you must add weight in salt water due to the greater positive buoyancy characterists of the object that now displaces a volume of heavier water. Student comfort will in-turn likely shed these 2 lbs difference. So ... the key is instead of shedding the weight - leave it on, given the student's comfort it will now be sufficient to compensate for the salinity in the sea. Of course always bring extra weight to plan for contengencies.

-My $.02 worth