enough weight

[TMHeimer]

We were overweighted on our check-out dives. Even on my first dive I knew that as I was up & down & working the BC like crazy. We never did weight checks- just used either an 8 pound or 12 pound belt in the pool and estimated weight at the shore (of course, it was November in Nova Scotia in wetsuits, so everyone doing weight checks would've been real frigid). Overweight is better than underweight, bad as it is. Maybe the philosophy here is many divers need at least a few dives to begin to figure out buoyancy, in addition to the weight check. I agree the instructor should point out & correct any other problems as long as the weight check has been done. If there are no other problems add more weight!

 

[ScubaBing]

I just got certified so no pro here BUT I"m a female that is naturally super buoyant - I can stand in any water without treading and not sink.

I used 24 to go down last week in fresh water, just 4lbs shy of a guy that was over 300 (I'm not anywhere near 300lbs <g>) so 10, if she's really buoyant is not a lot, depending on her weight, etc.

 

[MauiScubaSteve]

One way to get a decent answer on the internet is to give people the detailed information to work with. Filling out your profile is a first step.

Where do you live, what kind of pool was the confined water training done in (depth, length, width), was it the same pool that you checked her with no gear, if she had no gear, was she holding her breath, what kind of body of water are the open water training dives being done in (platform - quarry - freshwater), what is your girlfriend's height and weight, is she athletic, did she swim competitively, is she a comfortable snorkeler/freediver, what agency is the training, how many days long were each part of the training (academics, confined water, open water)???????

Never trust anything that bleeds for 5 days and doesn't die!!!!!

If you use your sig line in regular conversation and your gf knows you feel this way and knows you have it as your sig line on at least one internet forum for everyone to see, your instructor may be right that it is her fault.

 

[MauiScubaSteve]

Puzzling. The weight check was done? Yes, people can vary greatly in natural buoyancy. If the weight check was done, it's not a matter of an instructor being more or less flexible (it is what it is). After the weight check, 5 lbs. should be added as the tank gets lighter as air is used up (whether aluminum or steel-doesn't matter)--therefore you are 5 lbs. negative anyway at the start. Could there be any other reason he says no more than 10 lbs.?

With a typical AL 3000 psi 80 cft (77.4 cf), 2500 psi is 64.5 cf. One internet source lists a cf of air as being .08 lbs, so if you start with 3000 and end with 500 psi you used 5.16 lbs of air. The problem is that often for a girl that only needs 10 lbs the training may not be using AL 80 cft's.

If it were a Luxfer AL 50 cft (48.4 cf), there is only 3.23 lbs used at 500 psi, and a 63 cft would be 4.2 lbs, so unless you have more info about the training dives than I see in this thread you are assuming a few things to claim "After the weight check, 5 lbs. should be added..."

And how about your claim that "whether aluminum or steel-doesn't matter".....

A Faber low pressure (LP) steel 80 cft is stamped with 2400 as its working max pressure, but it can be filled to 2650 psi as long as it is still rated for +10%. At 2650 psi it is 78 cf, but many would still considered a 2400 psi fill to be full, which would only be 70.64 cf, and surfacing with 500 psi would then only use 55.9 cf (4.47 lbs).

An OMS LP 50 cft is 50 cf at +10% (2650), but again is marked 2400, so the gas used from 2400 psi to a 500 psi end is only 35.85 cf (2.87lbs).

Wasn't that fun!

Anyway, a better rule of thumb is to "add enough weight to make up for the weight of the air used."

 

[MauiScubaSteve]

I'm as green as she is, but what I've been hearing on the boards is that noobs like us need to be a bit careful about this philosophy. If her buoyancy check doesn't get her floating at eye level with an empty BCD and full lungs, she needs more weight and that's the end of it no matter what the instructor says. Even if it does turn out she still needs the extra 2kg/5# to account for an empty tank. If she's doing PADI it's right in the manual.

You may need to look at your PADI OW manual again. Are you sure it says full lungs and empty tank? I think it says "holding a normal breath" and "500 psi tank" (not sure what it says for bar).

Noobs like you do need to be careful with this philosophy!

 

[MauiScubaSteve]

Your instructor is a idiot! It's better to risk being a little overweighted than underweighted, as an uncontrolled ascent can be fatal

I think jumping to conclusions and hyping a possible fatality over the limited details here about not having quite enough weight are more significant evidence that the I word is a proper descriptor.

An uncontrolled ascent is much more likely when overweighted. There is more air in the BC of an overweighted diver so all that extra air expands and one accelerates to the surface. The real reason for this is usually the diver not understanding how to properly vent the BC.

When you are underweighted, you are likely spending much of the end of the dive getting all the air out of the BC and thus have pretty much no air in the BC to expand and accelerate you. The only acceleration is from wet/dry suit expansion and lung air expansion, and if your ascent speed never exceeds 60 fps is it really an uncontrolled ascent?

 

[Dave1981]

Your instructor is a idiot! It's better to risk being a little overweighted than underweighted, as an uncontrolled ascent can be fatal!

I'd suggest you need to rethink this, being overweighted compounds the problem of a runaway ascent. The more excess weight the bigger the problem as you have more gas in your bc to compensate for being overweighted, which in turn expands as you ascend.

Overweighting is a poor excuse to get people in and out of open water classes in 3 days IMO. If you can decend to start with then struggle to stay down then chances are you have breath control issues that need to be worked out. If the instructor is just not spending the time to sort that out that's another thing, but overweighting is not the solution to the problem.

 

[aquaregia]

she's having difficulty staying down once she's on the submersed platform. and i agree with the noob issue of not exhaling completely. but once she's down and not finning and bc empty she is still having a tendency to rise. seems she'sust naturally bouyant.
i do not want to see her waist her money on having to retake classes or take months to get certified.

If she's having an issue emptying her lungs because she's uncomfortable, it likely would be best for her to take months to get certified. I took an eight week course and I do feel that it helped me.

if she brings up the idea of more weight from what i'm told she gets corrected immediately. i don't what to do as i do not attend these with her. i know the instructor is a good teacher but maybe there needs to be some flexibility i don't know, i was taught to listen to the instructor.

This gets cultural. In California, where I live now, questioning authority and asking "why" is well respected. In other places, including where I grew up, "because I said so" is a frequently given answer, even among grown adults. If she's unhappy with "because I said so", and that's all the teacher can give her, then he might not be a good instructor for her. I've never done well listening to my instructors unless they can justify their teachings (although I do try).

 

[Erku]

You may need to look at your PADI OW manual again. Are you sure it says full lungs and empty tank? I think it says "holding a normal breath" and "500 psi tank" (not sure what it says for bar).

Noobs like you do need to be careful with this philosophy!

You're misunderstanding what I meant. I apologise for being unclear on the difference between "full" as in "holding a deep breath" and "full" as in "holding a normal breath", but the latter is what I meant. And the dive manual does in fact say exactly what I said: when the buoyancy test is done with a full tank you add a couple pounds to account, as I said, for the tank emptying. I wasn't writing under the assumption that I'd be being picked apart: I know I am a noob, but please don't assume I'm completely confused before reading what I said thoroughly.

In regards to philosophy of teaching, I may not know much diving, but I have been a professional teacher in the past. Making your new students uncomfortable with your subject matter is never a good plan. I would be wary, or even demand my course money back, around any teacher of a potentially dangerous sport who would rather obstinately hold to a rule than explain himself, no matter how much more knowledgeable - or even correct - he is. He's not there to tell you how it is, he's there to explain why it is that way.

 

[Togalive]

my girlfriend is trying to get certified but is having a problem with bouyancy. she lets all the air out of the bc but still has issues getting down and staying down. the instructor says 10# is enough and that she doesn't need any more weight and won't allow any more, that she is the problem.
question: aren't some people just naturaly more bouyant than others?
and shouldn't instructors be a little more flexible with this?
isn't it better to be slightly negative than to be positive at the start of a dive due to aluminum tanks being positve at the end of the dive?

Just my opinion, but an instructor who says 10# is enough and isnt willing to flex at all for a new diver sounds like a P.O.S instructor...If she has no air in her BC, and is emptying her lungs as much as she can, and still cant get down, there isnt much more she can do.