Please evaluate my weight calculation, Buoyancy

[rnln]

Previously, I went with back inflate BCD, and the jacket BCD before. Now, I am ready with my BP/W. This will be the first dive with BP/W for me. Can experienced help evaluate my plan on weight below?

I am 5'9", 200lbs on average day.

I used back inflate BCD, 7mm farmer John wetsuit, AL80 tank, 30lbs weight. I could get down ok.

With jacket BCD, 7mm farmer John wetsuit, AL80 tank, 32lbs weight. I really had hard time to get down. The dive master had to help pulling me down a bit to initiate the descenting. Still, I had hard time staying down there.

Now, I have BP/W. Base on the back inflate with 30lbs of weights:
OMS stainless steal back plate, DSS single wing: - 7lbs
5mm wetsuit, non-farmer John: - 4lbs

30 - 7 - 4 = 19lbs. Should I try 19lbs? Or should I start with 20lbs to make sure can get down, rather a little heavier than lighter?

Thank in advance.

 

[saxman242]

rather a little heavier than lighter?

Always better to be too heavy than too light. I'd start at 22 lbs and see where you're at.

 

[scubadada]

Nothing beats the weight check at your SS and the slow, controlled ascent to the surface. I dive a back inflate, with an AL80, I use 14 pounds with a full 5 mm +/- a 5/3 mm hooded vest. You did not give your size, I'm about 5'10". 185 pounds. 20 pounds sounds like it may be a place to start. Really, 7 pounds from a back inflate to a BP&W? I dive a SP Knighthawk. Better to be a little heavy than too light

 

[Erik Forsberg]

If you can't get down with a full tank, you won't be able to hold a safety stop.

Add 5lbs at least first or to your buoyancy check with a bear empty tank.

 

[rnln]

Nothing beats the weight check at your SS and the slow, controlled ascent to the surface. I dive a back inflate, with an AL80, I use 14 pounds with a full 5 mm +/- a 5/3 mm hooded vest. You did not give your size, I'm about 5'10". 185 pounds. 20 pounds sounds like it may be a place to start. Really, 7 pounds from a back inflate to a BP&W? I dive a SP Knighthawk. Better to be a little heavy than too light

Sorry, I missed my size. I just added it.
I took 7lbs off for the DSS SS back plate, and 4lbs to go from 7mm farmer john to 5mm 2 pieces.

 

[scubadada]

Sorry, I may have missed it, is your BP&W with a steel or AL backplate? That may have been my problem.

 

[rnln]

Sorry, I may have missed it, is your BP&W with a steel or AL backplate? That may have been my problem.

I never wear a BP/W. This will be my first time, it will be SS, DSS. I have worn jacket and back inflate BCD.

 

[scubadada]

I never wear a BP/W. This will be my first time, it will be SS, DSS. I have worn jacket and back inflate BCD.

The SS backplate certainly explains some of the weight change, thanks

 

[martincohn]

Its too important to "think" you have it right. Test it!

1. Get a tank with 500 PSI and test your buoyancy. Can you hold a safety stop?
2. Yes, great you passed your buoyancy test.
3. No, adjust and repeat until you do.

Its too simple of a task to risk not getting it right. And the potential complications of an uncontrolled assent definitely aren't worth it.

 

[rnln]

Thanks everyone,