Determining weight needed

[Aanderson81]

Since you are doing this in a pool why not actually place weight on the wetsuit until it sinks.
I would not be surprised if it took 6-7 lbs to sink a new 3mil. Older suit sure 4-5 probably.

Full face mask probably captures nearly a liter of air so 1kg or 2.2lbs seems reasonable. Do you
worry about CO2 build up in full mask? I have never dove with one (thus the question).

No, the mask has an internal silicone bit that acts as a baffle that forces the air out the bottom vent which prevent CO2 build up. Not something I am all that concerned about.

 

[TMHeimer]

You did a weight check. Seems like a lot of weight for those suits in fresh water, but who knows. I started a thread a while ago wondering why I needed so much with my 7 mil wetsuit in salt water. Despite those saying you can drop weight as your diving improves, I can't see why--unless you're figuring your inflating/deflating BCD skills improve.---But that can't affect the proper weight check. A couple of instructors at our shop agreed with me. I dropped 6 pounds as my wetsuit aged, and put it back on for the new suit--weight check said to do so.

 

[RainPilot]

New divers tend to breathe in the top half of their lungs, ie they are subconsciously not exhaling fully as per normal breathing. That leads to a pound or 3 extra. Also, since they are told not to "breathe shallow" they overcompensate by breathing full in and full out, known as "high tidal volume" divers. Since they tend to bob up and down with this, being overweighted reduces the tendency so once they breath normally again there's a pound or 2 to be lost.

 

[mattia_v]

I think it's a few things - you have your breathing under better control as you improve your diving, and you feel more comfortable being a little more 'on the edge'. There's a false sense of security being able to descend easily when overweighted, and it's how a lot of us learned (sitting on the bottom of the pool/on the sand). The way I'm weighted now, I can barely stay put on the bottom if there's a little current, because my weighting is dialled in.

I've also found body composition makes a huge difference. Dropping about 12 lbs of weight (more lost in fat, some gained in muscle mass) let me drop the amount of additional weight from 10 lbs to 4 lbs (Alum BP/W, AL80, 3.5mm wetsuit). The gear was the same, the level of experience was pretty much the same too. Only difference was the adapter for the reg, which weighs about a pound I'd guess, so a little less extreme than that. I could probably drop another 2 lbs (tried it out at a shallow safety stop with empty tank), but this works for me right now.

 

[oly5050user]

Did a refresher in the pool for a 245 lb customer last Friday...he insisted he needed 22lbs in a 3mm wetsuit..got him to 8lb ..he can descend easily and remain at depth easily in our 10' deep pool.
Besides breathing short breaths rapidly he moved his feet ands culled with his hands while trying to descend. Once he stopped moving so much his breathing finally slowed down and now able to descend.

 

[TMHeimer]

New divers tend to breathe in the top half of their lungs, ie they are subconsciously not exhaling fully as per normal breathing. That leads to a pound or 3 extra. Also, since they are told not to "breathe shallow" they overcompensate by breathing full in and full out, known as "high tidal volume" divers. Since they tend to bob up and down with this, being overweighted reduces the tendency so once they breath normally again there's a pound or 2 to be lost.

I can see that. To be honest, I'm not sure about breathing normally is vs. breathing with the top half of lungs. Assume normal breathing is not with just the top half. If so, why would a new diver do this? Anxiety perhaps, or not being used to breathing through the mouth only? I can say that I THINK my breathing is exactly the same as when I started diving, and had no anxiety back then. As mentioned, I dropped 6 pounds as the old wetsuit aged and put it back on with the new one--so back to square one. I use a lot of weight--maybe I've not been breathing right for 12 years?

Re RainPilot's point about overcompensation and becoming "high volume divers"-- I have not done this--just breathed normally same as on land. Never thought about it since everything seemed to go fine. Maybe because I believe on land I'm both a nose and mouth breather?

I recall learning in the Deep course that it's good to take deep slow breaths to minimize friction in dead air spaces. Again, never thought about it and all was good.

 

[RainPilot]

Most snorkel divers and such are used to holding their breath so often when they start scuba they subconsciously try to keep a "fuller" lung. Not everyone by any means but I see it a lot.

The fact that your weighting stayed consistent indicates that you were probably pretty relaxed and comfortable from the get go.

 

[TMHeimer]

Most snorkel divers and such are used to holding their breath so often when they start scuba they subconsciously try to keep a "fuller" lung. Not everyone by any means but I see it a lot.

The fact that your weighting stayed consistent indicates that you were probably pretty relaxed and comfortable from the get go.

I see what you're saying. I snorkeled for 40 years prior to OW course and of course took a deep breath to head down (after maybe 3 breaths of hyperventilation--something I wouldn't recommend --I've recently had the "blackout even in shallow water" discussion on another thread). When starting OW I didn't take a deep breath since I knew I had access to air anytime.

 

[boulderjohn]

A while back I did the OW checkout dives in our local reservoir for some divers I had not had in the pool. One of them had used a 7mm suit in the pool so that he could get his weighting nailed down for the OW dies ahead of time. He told me he absolutely needed 22 pounds. His pool instructor had done a good job of making sure he had that right. By the time we did the 4th dive, I had him down to 10 pounds, and he was amazed at how much easier it was to dive and especially maintain trim without all that unnecessary weight.

When I have worked with students in 3 mm suits in the pool, my neediest students usually start with about 10 pounds. The biggest problem I have with most students is that I am supposed to show them the value of trim weights, which means I have to out weight in 4 different places, and they don'[t need enough eight for me to distribute it like that. Some students don't need any weight at all. When I am in the pool with a 3mm shorty, I don't need any weight.

 

[TMHeimer]

Everyone's body makeup is different of course. We used 8 lb. and 12 lb. soft belts for the pool sessions. I used a 12, which was a bit heavy, but 8 was not enough. That's with the shorty.

John-- I assume a big part of how much weight each student used has to do with student's size. When you started your most needy ones with 10, how much of that did they shed during the course?
There's a big difference between 10 and 0. Also, was the student with the 7 mil using a farmer john and in salt water (I assume fresh?)-- man, 10 pounds for that? Or maybe it was a one piece 7 mil?