Quick question about weighting

[Dive n00b]

Hey All,

I know that there are a bunch of variables to consider such as the type of tank we will be diving etc... and I know from reading here that there really is no substitute for a proper weighting test... but...

At a high level, how much additional weight should I start out with knowing the following things.

My most recent set of dives in Punta Cana (my OW cert dives) we dove 3mil shortys and those ghetto fins that you put your foot into without boots.

Assuming the rest of the gear (tank etc..)is the same (which it likely won't be... although I know Stuarts Cove uses scubapro gear), how much extra weight do you think I'll need to take to compensate for diving in a full 5mm suit, and my own Mares AvantiQuattro fins with 5mil mares boots?

FWIW the instructor for our OW dives strapped us with 15lbs of lead.

From reading the archives, I think that may have even been a bit much, but I'm not certain and am looking for some guidance on how much weight to start with at SC's on Monday. Reading a few of those stories about poorly weighted divers popping up to the surface while trying to do their safety stops has got me thinking.

Thanks all...

Cheers!

 

[snhrph]

You should do a surface buoyancy check before descending. You really do not want to carry extra lead - you WILL use more air as you will need to compensate by inflating your BCD to become neutral at your depth, and that will in turn add to the drag, which leads to increased air consumption.

As for your worries about poorly weighted divers popping up to the surface while doing the safety stop... How did they descend in the first place if they were so "light"??? While I agree that "artificial intelligence is no match for natural born stupidity", I believe that there are other reasons for early surfacing - not being able to control buoyancy, inflating BC instead of deflating it, equipment malfunction (human factor is a more likely culprit), etc...

I also dive with Mares 5mm boots and Avanti Quattro Excel fins. The fins are negatively buoyant, and that will help you offset the buoyancy of your boots. So now you only have to worry about the 5mm wetsuit.

I observed that some DMs like to keep their newly certified and "certifiable" divers on the "heavy" side as it is easier to compensate by inflating BC than to swim after a run-away diver heading for the surface. Therefore it is quite possible that you were dived over weighted when you were completing your OW.

Stuart's Cove will probably have you do a "check-out" (shallow) dive first, before taking you on more advanced dives. that first dive would be a perfect opportunity to fine tune your weight requirement. Don't be shy to ask your DM for his or her input and help.

Good luck and enjoy your trip.

 

[miketrance84]

I would say your WAY overweighted. 15lbs in a shorty thats a ton of weight. I wear 8lbs in a full 3mm wetsuit and an Al80 tank. Like was previously said most instructors will overweight their students.
Overweighting is done for a few reasons,easier to submerge as a new diver, easier to control and its easier to perform skills on the bottom of a pool. Most new divers, I did this too, dont fully exhale on decent which makes it extremely hard to break the surface. As you improve your skillset you will use less weight until you actually get to the correct amount.

Everytime you dive practice bouyancy. It will get better with every dive if you actually practice. Once this skill is learned well lots of things will improve SAC, less weight and a more enjoyable dive.

 

[Bubbletrubble]

I think snhrph and miketrance84 gave good advice. Let the dive op know about your level of experience. Ask the DM to help guesstimate how much lead to wear. If you're diving AL80 tanks, I wouldn't be surprised if he gave you as much as 18 lbs. since you're wearing a 5mm wetsuit. If the wetsuit is new, he may suggest even more to begin with.
Regardless of how much weight you start with, do a weight check on that first dive with the help of your buddy. It'll be time well spent. Oh, and don't forget to write down that number in your logbook (along with the kind of tank you used, thickness of wetsuit, etc.).
Relax and have fun diving.
P.S. You referred to closed heel fins as "ghetto fins." I know of some quality fins that are of the closed heel variety. FYI, some gear reviews have demonstrated that closed heel fins outperform open heel fins in the water. It's possible that having a bare foot in the fin pocket allows more force to be transferred with every kick. Something to think about.

 

[kadleck]

I would say your WAY overweighted.

Whilst that is a possibility (instructors do tend to over-weight beginners so they can kneel on the bottom easily), but with a 3mm wetsuit and AL80, I dive with 16lbs and I am not over weighted. I basically float too well is all (fat floats, though I am not clinically obese!! ). I cannot free dive without 6lb weights strapped to me. It impossible for me to leave the surface, and I am not unusual in this. In fact, I think it's a good thing - If I shed my weights (as I did many times during rescue training), I could float all day even without a BCD. Trouble is, someone else had to dive down to retrieve my belt - there is no way I could do it!

Re: the initial question - do a proper weight check. It is not difficult, and if you dive with the correct weight you will find neutral buoyancy far easier to achieve, and you'll be more relaxed as a result.

 

[Dive n00b]

thanks for all your feedback people... one last question... what is the best technique for a quick and effective surface weight check...

I'm not quite sure I recall correctly... something along the lines of when you are vertical on the surface of the water with an empty bcd, you should be at about eye level with the water, and you should start to sink when you exhale the air in your lungs.

Is that correct?

 

[baz500]

This should be done with 50bar in your cylinder and this is why we do most weight checks after the novices very first dive.

 

[snhrph]

thanks for all your feedback people... one last question... what is the best technique for a quick and effective surface weight check...

I'm not quite sure I recall correctly... something along the lines of when you are vertical on the surface of the water with an empty bcd, you should be at about eye level with the water, and you should start to sink when you exhale the air in your lungs.

Is that correct?

That's correct. Make sure you keep the regulator in your mouth when you do that

Another important aspect to remember is that aluminum tanks are negatively buoyant when full and slightly positively buoyant when empty or almost empty. So ideally, you would do the surface weight check at the END of the dive when there are 500 psi in the tank left.

If you do the check at the beginning of the dive, then add 5 lbs to offset the buoyancy you will gain towards the end of the dive as you empty the tank. This is less of an issue with steel tanks, but I think that most of dive shops in Caribbean use aluminum tanks. The only place I got to dive steel cylinders was in Tahiti.

Again, your DM should help you with this. Make sure you review the process with him/her, and have one of the boat crew hand you the extra weights or take the excess from you.

Good luck.

 

[herman]

...............................................................If you do the check at the beginning of the dive, then add 5 lbs to offset the buoyancy you will gain towards the end of the dive as you empty the tank. This is less of an issue with steel tanks, but I think that most of dive shops in Caribbean use aluminum tanks. The only place I got to dive steel cylinders was in Tahiti.


Good luck.

Tank material does not matter at all, tank size does. What you are compensating for is the reduction in the total weight of the tank and air. 80cf of air weights a little less than 5 lbs and this is the weight loss you are compensating for, it does not matter if the tank is steel, aluminum or plastic (if there was such a thing). So for a full 80 cf tank you add 5#, for smaller tanks you add less and for larger tanks you add more, based on tank volume not material.

As for the original question, you really do need to do a good weight check. It's likely that you will be overweighted at 15 lbs. If you have to guess, go on the heavy side. While not the best for air comsumption it's a lot easier for a new diver to deal with a little excess weight than to be too light.
When you are doing your weight check, cross your legs at the ankles. All of us tend to naturally slowly kick at the surface. This slow kicking will increase the appearent amount of weight you will need by a good bit.

 

[spectrum]

If you do the check at the beginning of the dive, then add 5 lbs to offset the buoyancy you will gain towards the end of the dive as you empty the tank. This is less of an issue with steel tanks, but I think that most of dive shops in Caribbean use aluminum tanks. The only place I got to dive steel cylinders was in Tahiti..

Cylinder material has nothing to do with it. That all gets washed out in doing the actual weight check exercise. The dynamic thing is the depletion of tank contents. With air weighting about .08 LB per cubic foot an 80 CF cylinder has about 6.4 pounds of "material" in it. Allowing for reserve you should be weighted to about 5 pounds less that what you start with hence the 5 pound removal.

My suggestion:

Remember to set your weight so that you bob vertically at eye level at the end of your dive with an empty BC, an average breath, your feet still (crossed) and about 500 PSI in your cylinder. A deep breath should get your mask out of the water and a deep exhale should sink your mask. Do all of this while breathing from your regulator. The end of the dive is the defining moment for your weight requirement and you want just enough to let you stay down in the shallows with a light cylinder.

You can make the same test pre-dive with a full cylinder and add 5 pounds to compensate for the buoyancy gain you will experience as you breathe the tank down. Be sure to repeat at the end since you are apt to have some stowaway buoyancy (trapped air) in your gear early in the dive. You are safer being two pounds heavy than 2 pounds light.

Pete