View Full Version : Pre-dive Surface Buoyancy Check (BP/W)

06-23-2009, 10:31
When I went through my OW class, we did our pre-dive (water surface at eye level) buoyancy checks in just our wetsuits, boots, and mask. For the class we wore positively buoyant, non-weight integrated jacket style BC's. I have now done 2 dives in my BP/W and I am having some trouble with getting my weight dialed in. I felt I was probably over-weighted as my buoyancy was all over the place. It didn't help that I was in a shallow quarry, where my depth maxed at 22' and averaged around 15'.

Now that I am in a negatively buoyant BP/W set-up, should I do the pre-dive buoyancy check wearing the backplate since it will account for some of the weight that would normally go on my belt or should I continue to check it the same way we did in class?

Sorry for my ignorance, but I am not diving with anyone else wearing a BP/W.

John Yaskowich
06-23-2009, 10:53
When I went through my OW class, we did our pre-dive (water surface at eye level) buoyancy checks in just our wetsuits, boots, and mask.

I don't see how a bouyancy check without all your gear is going to tell you anything. You need to balance out all the weighty and floaty things you are taking underwater with you. The configuration of your gear can drasticly change the amount of lead you carry.

06-23-2009, 11:07
Checking your buoyancy with the eye level test is in my opinion worthless. You need to configure your BP/W to have good trim as well as the correct amount of weight. You can't do this vertical at the surface. Spend an hour or so in the quarry adjusting your setup correctly.

I felt I was probably over-weighted as my buoyancy was all over the place.

I don't think being all over the place would be weighting (unless you were just a little underweighted) but buoyancy control. Get your weighting and trim down, and buoyancy control will come with more dives with your new setup.

06-23-2009, 11:47
I don’t get the weight check you guys did without your full kit on either??? Any type of check you do for buoyancy and trim needs to always be wearing your full set of diving gear. Anytime you change anything to your setup such as a new suit or fins or whatever you need to be ready to readjust your weight or distribution of weight.
As far as being overweighed in general. I think that can cause some trim and buoyancy issues at depth because all that air you have to add to your wing has a tendency to move all over the place inside the bladder as you move around. Plus as you come up and down in depth all the extra air expands and compresses making you have to constantly make little adjustments. You were so shallow though that I don't really see that being your issue.

06-23-2009, 12:05
I took my OW class through school, so we had upwards of 30 students, rather than the normal 3-5, so I don't know if that would have been why they had us do the checks that way or not. My NAUI book talks about doing it that way also, so I just figured that was the way to do it.

I will definitely take more time to get everything dialed in and dedicate a dive to doing so. I think it was partly that with it being my first trip to the quarry that I was overly excited about site seeing...stupid. I think I took for granted that I had no issues what-so-ever with buoyancy on my last dive, but of course I wasn't wearing a new 7mm wetsuit and a new BC system.

I'll work on it more next time and do it in full gear. Thanks!

06-23-2009, 14:50
Changing anything of consequnce in your rig pretty much requires a weight check. New BC and Wetsuit are definite recheck indicators. Just remember that if you are doing a weight check with a full tank-no matter the size or metal-find out the bouyancy characteristics of it empty and add that your full tank weight check. Luxfer AL80's are 4.4 pound light when empty so add 4 pounds. i.e. if you find that with a full breath you are perectly bouyant with 17 pounds, make it 21 or 22pounds to start the dive.

Steel tanks are very manufacturer varied, but almost all are either neutral when empty or still negative. The onle steel tank I found that was light when empty was a Faber HP149 and it was 2.4 pound bouyant and has a dry weight of 50 pounds.

Tassie Diver
06-23-2009, 18:14
The float at eye-level test with wetsuit and weight belt was so that open water students would not be over-weighted after their rig was removed. This prevents them sinking like a stone if they remove their rig on the surface.

I consider correct weighting, to be neutrally buoyant at 3 metres with no air in my wing and minimal air in my drysuit with only 30 bar gas in all my tanks, ie at the end of the dive.