Determining weight needed

[Aanderson81]

Today I did a pool session and decided to work on my weight amounts for both with and without my wetsuit (3mil) and had a few questions on my approach.

First I used the Divebuddy online calculator. It said the following:

Skin: 7lbs +/- 1lb
3mil: 15lbs +/- 2lbs

So with this in mind I got into the pool with all of my gear but no tank. Then I added and removed weights until at mid breath the waterline was somewhere near my eyes and forehead, exhaling would cause me to sink inhale would cause me to rise. After this these are the numbers I got

Skin: 14lbs
3mil: 16lbs

I am a bit confused here. I really expected the skin to be a lower number. Again this was without tank and literally being at the edge of the pool adding and removing weight then stepping back and relaxing and see if i sink. It wasnt a dive or anything like that where I was being subjective with my buoyancy.

Any thoughts on these numbers. I am a larger guy and I was using a full face mask which leads to a little more (~2lbs extra on my back trim pockets) weight than I had before from my experience.

 

[tursiops]

How were you breathing while the water was at eye level? Snorkel? You can easily hold 4-6 lbs buoyancy in your lungs, more if you are a "larger guy."
Best to use a tank that has about 500 psi in it; gives you a way to breath comfortably, and is realistic as to what you need to know.
How much do you weigh, and what is your height?

 

[flyboy08]

It's your internal volume...keep in mind weighting will be totally different in salt water.

 

[Aanderson81]

I was using an Ocean Reef Full Face mask with surface air valve. I had the SAV open. I would hold onto the edge and breath a few times to relax then breathe in fully then left it out a normal breath, didnt force it out, but didnt feel like I was at a full breath.

I am 5'11" and around 270.

I suppose that I may have had some air trapped in my BCD as I did the 3mil first and the skin second, but i thought i did a decent job at emptying it but dont think I really confirmed the second time.

 

[Aanderson81]

It's your internal volume...keep in mind weighting will be totally different in salt water.

Yeah, I have some decent numbers in salt water just from past dives (skin and 7mil, no 3 mil which is what I will probably be using more and why I was getting these numbers). I was just surprised that the 3mil didnt make that much of a difference.

 

[RainPilot]

I add 4lbs in salt for my 3mm full from 2lbs for rash vest and shorts.

I would be very surprised to see a wet 3mm take 7lbs plus to sink it.

 

[DogDiver]

I would start my students in Michigan with 7mm two piece wet suits with this formula.
10% of your body weight +4 pounds.
Worked well as a starting point. Then adjust up or down as needed.

 

[Aanderson81]

I would start my students in Michigan with 7mm two piece wet suits with this formula.
10% of your body weight +4 pounds.
Worked well as a starting point. Then adjust up or down as needed.

I find my 7mm to be around 34-36 lbs in salt so that doesnt sound too far off

 

[RainPilot]

I would start my students in Michigan with 7mm two piece wet suits with this formula.
10% of your body weight +4 pounds.
Worked well as a starting point. Then adjust up or down as needed.

I used the same formula when I started diving. That gave me 22lbs with steel tanks. Once I learned about neutral buoyancy and started doing proper weighting I went down 10lbs for a 7mm with al tanks.

 

[gfaith]

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).