What do I need to do different??

[Dive-aholic]

Total ballast should not exceed the initial buoyancy of the suit, that leaves the wing to deal with the weight of the gas.

In any configuration the diver should select his gear so that his total ballast just offsets the buoyancy of his exposure suit with empty tanks. Total ballast is anything that does not float, i.e. harness, regs, lights, and negative tanks etc. If the total ballast exceeds the suit buoyancy *change* something. The answer to being overweighted is never a larger BC.

So Tobin has made these claims both here and on CDF several times. Here was my response:

The only suit more buoyant than my compressed neoprene dry suit would be a non-compressed dry suit and that's not happening. Smaller cylinders will not work for the dives I'm using my 108s for. And don't recommend a rebreather. I would still need the 108s for bailout at those depths so rebreather would only add more ballast to the configuration. My Faber LP95s are actually heavier than my Worthington LP108s when filled to 2640 (according to the charts). They equal out when cave filled, and I would lose 35cf of gas by going with 95s. I guess I could use LP85s since they're 2 lbs lighter each. But I'd have to add an AL80 to make up for the 65cf less gas. Oh wait, that puts the 4lbs right back on! Still the same amount of ballast and now I'm less streamlined because I'm carrying a 3rd cylinder.

So what's your solution?

I will add to this that my Worthington 108s are neutral when empty, but my Faber 95s are 1.2 lbs negative when empty. My Worthington 85s are 1 lb negative when empty. Now granted, Faber FX133s and FX149s do get 1.45 and 2.35 lbs positive, respectively, when empty, but my guess is they trim out horribly in sidemount so using those cylinders isn't an option.

FWIW, I can sink in my compressed neoprene dry suit without any ballast. Getting a thicker dry suit or heavier undergarments will only overheat me. I'm almost overheated in my current exposure protection.

So what's the solution? Tobin must not know because he won't answer my question. But he's pretty insistent that my configuration is wrong because I shouldn't need my wing to offset the weight of my ballast.

 

[TSandM]

Okay -- the Worthington 108s are neutral when empty. With 500 psi, and a regulator, they are what, two pounds negative? That's -4 for both. You have no backplate, and your light is about a pound negative, right? That's -5. I think you are diving Dive Rite fins, and those are probably neutral.

Your suit is what, maybe 15 pounds positive? Or maybe less? I know that with Worthington 95s (-1 when empty), bands, manifold, two regs (probably a total of -5 or -6) and an aluminum backplate, I needed a 7 lb tail weight to be properly weighted and balanced, with my dry suit and 200g undergarment. I would think you would need a bit more, being quite a bit taller.

So it appears to me that your exposure protection is more positive than your gear, so you need ballast. If that's the case, then all the wing you should need is the gas you intend to use, or the buoyancy you can lose from your suit. Doesn't that make sense?

 

[SuPrBuGmAn]

My advice is to ignore trolls on the internet or just screw around with em.




Granted, that line may do me no justice - LOL

 

[Dive-aholic]

While my suit may be 15 lbs positive, I can offset that without gear. I am a rock in the water and can sink without any ballast at all in my dry suit as long as I exhaust all air from it. So any gear I put on makes me negative. Add in 1st stages (2lbs each according to Tobin). With no stages I end up being about 14lbs negative with empty cylinders. Tobin states I need to drop ballast or use lighter cylinders to achieve neutral buoyancy with empty cylinders and that the wing is only there to offset the use of gas. My claim is that not all of us have positive buoyancy in the water and need some help from the wing to become neutral. Tobin says use lighter cylinders. Even if I went with the Faber FX149s, I would still be 8lbs negative with empty cylinders. Take the trim weights off (which would put me very vertical with 149s and I'm still 4lbs negative with empty cylinders. However, Tobin still insists that I should be able to be neutral with empty cylinders. He tells me to get a more buoyant dry suit. Well, I dive 69 degree water and sweat in my current dry suit and undergarments. Besides, at depth a non-compressed dry suit will compress and undergarments will compress, so that's not the answer. I'm just trying to figure out what his solution is to this since he's pretty insistent that it's always possible to achieve neutral buoyancy with empty cylinders.

 

[ucfdiver]

While my suit may be 15 lbs positive, I can offset that without gear. I am a rock in the water and can sink without any ballast at all in my dry suit as long as I exhaust all air from it. So any gear I put on makes me negative. Add in 1st stages (2lbs each according to Tobin). With no stages I end up being about 14lbs negative with empty cylinders. Tobin states I need to drop ballast or use lighter cylinders to achieve neutral buoyancy with empty cylinders and that the wing is only there to offset the use of gas. My claim is that not all of us have positive buoyancy in the water and need some help from the wing to become neutral. Tobin says use lighter cylinders. Even if I went with the Faber FX149s, I would still be 8lbs negative with empty cylinders. Take the trim weights off (which would put me very vertical with 149s and I'm still 4lbs negative with empty cylinders. However, Tobin still insists that I should be able to be neutral with empty cylinders. He tells me to get a more buoyant dry suit. Well, I dive 69 degree water and sweat in my current dry suit and undergarments. Besides, at depth a non-compressed dry suit will compress and undergarments will compress, so that's not the answer. I'm just trying to figure out what his solution is to this since he's pretty insistent that it's always possible to achieve neutral buoyancy with empty cylinders.

I don't see how you can sink a drysuit, unless you mean with tanks. Of course you can sink the suit with (full) tanks. I think what Tobin is getting at, is that when the suit is +15, you need at least 15-17 lbs (taking into account lung volume) of weight on you, however you accomplish that.

BTW undergarments in a suit do NOT compress because the suit is balanced with external pressure.

 

[cbrich]

Interesting.... You can sink in a compressed neoprene drysuit with undergarments, wow, I am impressed.

You have answered your own question. Ideally we want to be neutral without any air in the wing, but your specific body structures is outside of the norm. I can't think of anything you can do, unless you want to buy some Faber FX100LPDVB cylinders. These cylinders are about +2 lbs FULL, and about +8 lbs empty, but then again they are only rated for 80 cubic feet each.

Cylinder Specifications

 

[SuPrBuGmAn]

The answer is simple, surround yourself with way too many AL80s, drop the steels all together.

If its good enough for the Mexicans...

 

[ucfdiver]

Interesting.... You can sink in a compressed neoprene drysuit with undergarments, wow, I am impressed.

You have answered your own question. Ideally we want to be neutral without any air in the wing, but your specific body structures is outside of the norm. I can't think of anything you can do, unless you want to buy some Faber FX100LPDVB cylinders. These cylinders are about +2 lbs FULL, and about +8 lbs empty, but then again they are only rated for 80 cubic feet each.

Cylinder Specifications

You have your +/- mixed up.

 

[cbrich]

You have your +/- mixed up.

I guess you did not look at the link then!!! You are thinking of the FX100DVB, wich are -8.41lbs full, and -0.59 empty. The cylinders I posted are the FX100LPDVB.

Information straight from Blue Steel Website, if you don't believe me, Click the link.

FX100LPDVB:
Fill Pressure: 2,640 psig
Liters: 12.9
Cubic In.: 787
Cubic Ft.: 80
*Length In.: 24.80
Dia. In.: 7.24
**Weight lbs.: 24.9
Buoyancy Full: 1.65
Buoyancy Empty: 7.65

FX100DVB
Fill Pressure: 3,442 psig
Liters: 12.9
Cubic In.: 787
Cubic Ft.: 100
*Length In.: 25.39
Dia. In.: 7.24
**Weight lbs.: 34.3
Buoyancy Full: -8.41
Buoyancy Empty: -0.59

 

[ucfdiver]

I guess you did not look at the link then!!! You are thinking of the FX100DVB, wich are -8.41lbs full, and -0.59 empty. The cylinders I posted are the FX100LPDVB.

Information straight from Blue Steel Website, if you don't believe me, Click the link.

FX100LPDVB:
Fill Pressure: 2,640 psig
Liters: 12.9
Cubic In.: 787
Cubic Ft.: 80
*Length In.: 24.80
Dia. In.: 7.24
**Weight lbs.: 24.9
Buoyancy Full: 1.65
Buoyancy Empty: 7.65

FX100DVB
Fill Pressure: 3,442 psig
Liters: 12.9
Cubic In.: 787
Cubic Ft.: 100
*Length In.: 25.39
Dia. In.: 7.24
**Weight lbs.: 34.3
Buoyancy Full: -8.41
Buoyancy Empty: -0.59

Use some common sense... Do you really think that tank setup as doubles is almost as buoyant as a dry suit?