Dialing in wetsuit buoyancy at aquatic park (SF)?

[supersand]

I'm a newly certified diver (certified in warm water) and just bought a 7mm wetsuit and was thinking to take it down to aquatic park (close to my place) and dial in the baseline buoyancy in salt water without a tank and bc. I figured I'll just weigh down to eye level at half breath and then subtract out the negative buoyancy of my BC with plates afterwards using the online lift calculator in the bc section on this board. Im planning on doing a shore dive in Monterey very soon and would like to have my weight semi dialed in so I have too much air in my bc at depth. Anyone tested out their scuba gear at aquatic park before?

Erik

 

[astrofunk]

I swim at Aquatic Park, and as a diver, I've definitely been tempted to use it as a nice bit of confined salt water for messing around with gear. But I've always decided against it. For one thing, the visibility is generally about a foot; I usually can't see much past my elbow when swimming. For another, it's a marina, so I'd be worried about what kind of entanglement hazards are floating about, especially given the near-zero viz.

Would you survive your planned buoyancy test? Probably. But why not do the job right? It sounds like you're only looking to ballpark it for now, anyway. So why not get some time in a pool (try Wallins), do your check in full gear, and then do the quick math to estimate the fresh / salt water difference? Then when you get to Monterey you'll know you're already close. You'll still want to do a buoyancy check before (and at the end of) your first dive, but any adjustment should be small.

 

[rhlee]

I swim at Aquatic Park, and as a diver, I've definitely been tempted to use it as a nice bit of confined salt water for messing around with gear. But I've always decided against it. For one thing, the visibility is generally about a foot; I usually can't see much past my elbow when swimming. For another, it's a marina, so I'd be worried about what kind of entanglement hazards are floating about, especially given the near-zero viz.

Would you survive your planned buoyancy test? Probably. But why not do the job right? It sounds like you're only looking to ballpark it for now, anyway. So why not get some time in a pool (try Wallins), do your check in full gear, and then do the quick math to estimate the fresh / salt water difference? Then when you get to Monterey you'll know you're already close. You'll still want to do a buoyancy check before (and at the end of) your first dive, but any adjustment should be small.

I agree with astrofunk. If for no other reason, the math to convert fresh->salt is going to be much much more accurate than trying to lookup the buoyancy characteristics of your BC, etc... Also, the "floating at eye-level" metric is pretty rough; much more accurate to do the proper test in full gear.

 

[Gombessa]

Agree with all of the above. I'm sure you can find out how to determine the difference between fresh and salt water buoyancy, but the ballpark method (which turns out to be very accurate) is to multiply the total weight of you and all your gear by 0.025. So once you've determined your proper weighting in fresh water, put yourself on a scale (do it when your gear is dry).

If you + gear weigh 200lb, you'd need to add 5lb in salt water. If you're 240lb, you would need to add 6lb. If you're 280lb, you'd add 7lb. As you can see the swing is not great; a small 100lb girl may only need a couple of pounds less than a big 200lb guy.

 

[Chuck Tribolet]

It probably won't make a difference, but it's 0.0256, not 0.025.

 

[Gombessa]

I was taking into account the rain we've had over the weekend...yeah that's it

 

[mikemill]

It probably won't make a difference, but it's 0.0256, not 0.025.

Provided you have 3 significant digits

 

[supersand]

Hey everyone thanks for the suggestions perhaps I'll steer clear of the park. Maybe I'll just make a educated guesstimate when I go down to Monterey in a few weeks. I guess after the first dive I'll get a sense if I have way too much weight. I'm adverse to hauling all my online purchases down to wallins to use their pool (do they charge by the hr?) I guess thats a downside of buying online. And yes always round your sig figs to your least precise measurement

 

[Gombessa]

They don't seem to mind too much, just tell them you're not from the Peninsula and don't volunteer where you got your stuff. They do typically charge for pool use, it's something like $10-20/hr. Give them a call ahead of time to schedule, as you can only use the pool when it's not being occupied by a class.

 

[rstofer]

Unless you can stand up in the water, I certainly wouldn't put on a wetsuit with 25# of weight and then submerge to eyeball level.

One school of thought is to have a full tank, all your gear and then set your buoyancy to float eyeball high with an empty BC and moderate breath. The idea is that your wetsuit will lose enough buoyance at 15' to overcome the gain in buoyancy from a empty tank. To submerge, you kind of kick up and bounce down.

Richard