I find myself a bit heavy with my double steel 100's and aluminum plate unless I am wearing a heavy undersuit with my 2.5mm neoprene drysuit. I have seen plenty of divers with WAY more gear than I use and wonder how they can remain neutral and still carry all the gear? I'm not using any additional weight. How do you tech divers get around being overweighted with gear? I can't imagine what it would be like in a tri-lam suit!
Since I'm a "new to doubles" diver how do you define "neutral" when wearing them? Do you still get the tanks to 500psi and let all the air out of the wing? I now have in my stable a pair of Genesis HP100's which I have one dive on (my 5th dive in double 100's). I weighed the rig yesterday (glutton for punishment I know) and it was 107 pounds with 2100psi in the tanks. The tanks/bands/manifold were 94 pounds alone which is 66 pounds more than my weightbelt in my single tank set-up. I guess I'm wondering why the answer to the OP's question isn't "put a little air in the wing". My set-up feels fine to me but since I'm not very experienced with doubles my "feels fine" might not actually "be fine" but how would I know?
Ber,
You're correct...when over-weighted putting gas in the wing would be a correct response. (And Kompressor offered a very nice post regarding variances among divers.)
But the weight issue can be significant. One goal is to be diving with the least amount of gas in the wing necessary, to reduce drag among other things.
I use a set of PST E8-130s on a 6 lb SS plate (Thermo manifold and 3" bands). I use no other weight at all. On land IIRC the rig weighs out between 105 and 110 lbs.
Additionally, I'm weighting with one Luxfer 80 (EAN50), one Luxfer 40 (O2), and one Luxfer 2015psi 14 cu ft argon bottle.
With backgas, deco tanks, and argon tank very nearly empty, and zero gas in both drysuit and wing, I hold stops anywhere between 10' and the surface. I hold stops at something like 3' or 4' in confined fresh water specifically to ensure that there is no vertical drift going on. The same outcome occurs both with the deco tanks slung as well as with them jettisoned.
The objective is obviously to ensure that under a worst-case scenario, as light as I'm likely to get, given a deco obligation I can still hold my stops and control my ascent all the way to the surface.
Clearly, though, if I have gas in any of my tanks I will have
some degree of negative bouyancy remaining. (I'd like to hope I never find myself in a situation where the world has gone to crap and I have near zero gas in the tanks with a deco obligation! But if it ever happens, at least I won't be humiliated by dying with poor bouyancy and trim!
) I'll never be quite that light if all goes according to plan, but I weight myself so as to be neutral with my tanks nearly empty.
The other side of the coin is that the swing weights on those five tanks are significant. If you fill all five of them and overfill your backgas a bit you're looking at a combined weight increase (negative bouyancy) of some 28-30 lbs in compressed gas alone. Consequently at the beginning of a dive you're going to be heavy (although its also true that you'll be putting some gas into your suit as you descend), and you're going to be adding gas to your wing to achieve equilibrium.
Given the fact that you've already got swing weight of the compressed gas itself to compensate for, you don't want to have extra weight to deal with resulting from being overweighted to begin with (from a poor selection of steels, plate, or whatever).
FWIW - I also have a heavy plate (12 lb) and V-weights (10 lb and 8 lb) to use as either conditions (e.g. Weezle in very cold water) or circumstances change. I use the V-weights, for example, if diving a set of aluminum 80s in the drysuit. Weight yourself under different conditions, and write it down somewhere to refer to it as you find yourself in different circumstances. It's going to vary.
This is why a diver should make an effort to select a set of steels, a plate, and a drysuit and undergarment that allow the diver to be neutral - not negative - at the surface at the end of the dive. (I don't dive heavy steels in a wetsuit for precisely this reason, but if other guys want to - have at it.) From this perspective, jduncan is saying that he's too heavy in his steels unless he's wearing a neoprene drysuit, and I'm agreeing with him.
Hope this example made some sense.
Doc
