Doubles, Weight and Dry

[Meng_Tze]

.....
Essentially you have no ditchable weight, and therefore you have no way to establish neutral buoyancy during your dive.

????????????

 

[Colliam7]

Does this sound right? … Am I way off or am I close?

As I understand what you have laid out, you are generally correct in your approach. A couple of questions about specific parameter values, and a couple of comments on the math.

Steel 130’s weigh -10.5 lbs full and -1.0 empty each
The Manifold and Regs probably another 3.0 lbs (need to get this spec)
SS Backplate - 6.0 lbs
Total full system -29.0 lbs Full and -11.0 Empty

The reference data I have suggests that at least some of the 130s are somewhat more negative (-14.6) when full, but I mention it only to encourage you to make sure you have the right specs for your tanks (and for the regs and manifold, as you note you will do). My math comment is about the total. If each tank is -10.5 full, that is -21 for doubles, plus -3 for the regs, plus -6 for the BP, or a total of -30, rather than -29. Procedurally, I understand your approach and agree with it.

AL80 -2.0 full and +4.0 empty

Again, I use slightly different numbers for AL80s (-1.4 and +4.4) PER TANK. Not a problem with the concept, just differences in the parameter values.

Diving Dry this weekend I used 16 lbs lead (6 lb Backplate and 10 in pockets) and was probably 2 lbs heavy at the end where my al80 was close to +2.0 buoyancy. That means I would need 12 lbs to get down with no tank, right?

I am presuming you are saying +2 because you had around 1000 psi left, correct? Other than that question, your approach appears logical. You used 16lbs and were two pounds heavy, so you needed 14. You had +2 of buoyancy, so without that you would have needed 12 lbs. That is, of course, without the tank BUT WITH the reg. Don’t overlook that 1 lb or so.

Next question, if it takes 12 lbs to sink me and my suit and the double steel 130's weigh -29.0 I am good with no weight? That's sort of a duh.

Yes (and yes), and the 1 lb difference in the total for the double 130s doesn’t change that.

Then next if every 362 lbs in the tank is equal to -1.0 lbs bouyancy then hypathetically speaking, if I came up with 362 lbs in the tank (Maybe I got tangled) I have -9.0 for the regs, manifild and backplate

-2.0 for the tanks empty
-2.0 for the 27 CF of Air … -13.0 buoyancy at the surface.

The approach is correct. Obviously (and I am sure that more than a few will point this out) it is a theoretical calculation which should be empirically verified, etc., etc. But, conceptually, I don’t see a flaw in the logic.

 

[ucfdiver]

This is what I would call unsafe diving.

Essentially you have no ditchable weight, and therefore you have no way to establish neutral buoyancy during your dive.

Say what?

 

[nereas]

Say what?

Eubonics, n'est pas?

 

[LavaSurfer]

As I understand what you have laid out, you are generally correct in your approach. A couple of questions about specific parameter values, and a couple of comments on the math. The reference data I have suggests that at least some of the 130s are somewhat more negative (-14.6) when full, but I mention it only to encourage you to make sure you have the right specs for your tanks (and for the regs and manifold, as you note you will do). My math comment is about the total. If each tank is -10.5 full, that is -21 for doubles, plus -3 for the regs, plus -6 for the BP, or a total of -30, rather than -29. Procedurally, I understand your approach and agree with it. Again, I use slightly different numbers for AL80s (-1.4 and +4.4) PERTANK. Not a problem with the concept, just differences in the parameter values.

Thanks, The numbers were from OMS's Website.
CE130-K @ 237 BAR -10.5, -1.0 Empty.
The same for the AL80. Actual numbers are -1.9 and +4.0
My error on the math. Thanks

I am presuming you are saying +2 because you had around 1000 psi left, correct?

YES.

Other than that question, your approach appears logical. You used 16lbs and were two pounds heavy, so you needed 14. You had +2 of buoyancy, so without that you would have needed 12 lbs. That is, of course, without the tank BUT WITH the reg. Don’t overlook that 1 lb or so. Yes (and yes), and the 1 lb difference in the total for the double 130s doesn’t change that.The approach is correct.

Yes, Reg weight, Thanks. Left that one out.

Obviously (and I am sure that more than a few will point this out) it is a theoretical calculation which should be empirically verified, etc., etc. But, conceptually, I don’t see a flaw in the logic.

Here is my thought, Use the AL Backplate instead of the SS, dive with the belt and play with the weight. After I drain the tanks, I can mess around with weight and even try different undergarments. Once I get the weight dialed in in the Quarry I can make some educated guesses in salt. I just didn't want to do a Dirt Dart but that doesn't sound like it would be the case.

This works!
Thanks

 

[ucfdiver]

Eubonics, n'est pas?

Care to explain your view on how this is "unsafe"?

 

[nereas]

Care to explain your view on how this is "unsafe"?

Is this what "say what" means in Eubonics? What a marvelous language it is.

Anyone who needs such an explaination should not be diving.

 

[ucfdiver]

Is this what "say what" means in Eubonics? What a marvelous language it is.

Anyone who needs such an explaination should not be diving.

I guess I shouldn't be diving then. I dive with 2 LP108's and a backplate only in my drysuit.

 

[PfcAJ]

Is this what "say what" means in Eubonics? What a marvelous language it is.

Anyone who needs such an explaination should not be diving.

Eubonics? Anyone who spells 'ebonics' wrong shouldn't be posting on internet forums correcting someone else. They probably shouldn't be diving, either.

 

[nereas]

Eubonics? Anyone who spells 'ebonics' wrong shouldn't be posting on internet forums correcting someone else...

But you DO know how to spell it, don't you!