BCD Bladder size for double tanks.

[KDiver]

Hi. I'm looking to get a double tank configuration and I currently have a dry suit and a 45lb bladder on my BCD, with almost 30lbs of weight. When I calculate the difference in buoyancy of the Single AL vs double Steel tanks, I still come out with enough buoyancy in my bladder to serve my purpose.

I was just wondering what anyone with more experience in the matter might think. Is it safe to have doubles with just a 45lb bladder? I haven't bought anything for the double tanks, but I figure it's worth doing my homework before I invest.....

Oh, btw, I'm looking at 100s or 120s (ft^3)...
Thanks!

[owlbill]

First of all, welcome to the forum.

Now, back to business LOL. What other gear are you using? 45lb of lift might be borderline, but possible. Most people with doubles (maybe not 100s) are using closer to 50-55lbs.

What type of bladder is it? If it is shaped properly for doubles, I would say try it on a nice simple dive and see. Full tanks, all you gear, all your weight etc (fully loaded) and see how it performs. That is if you can get double tanks to try out.

Perhaps some others who have tried more variety in wings will add some info.

[KDiver]

Hi owlbill,
Thanks for the welcome.

I'm not sure what you mean by other gear. But I have a drysuit (I planned on using that as my redundant BCD, tho I hear there's controversy on that front:). I also have been using mainly the drysuit as the BC lately(tho I still wear the bcd vest), but I think that's a whole other thread). Other than that, I've been interested in the worthington double cylinder set. Although to update my previous post, I'm more interested in the 119 tanks now since they seem to be the best deal in terms of price and real volume.

I've got the Aluminum backplate (I figured once I go doubles I wouldn't want the extra weight of steel) so I'm hoping that can help me to reduce my weight; even with the 30 lbs of extra weight with my present drysuit/AL backplate/single AL tank configuration. So when I calculated the diference in buoyancy on paper from single AL to double Steel, it seems to workout ok. I just want to make sure that my theoretical calculations parrallel people's real life experience before I end up hurting myself;).

[owlbill]

Sounds like you have put some thought into this. Drysuit for backup buoyancy is fine by most, a lift bag or similar might be better, but not absolutely needed at first. With the equipment you mentioned, a 45lb bladder might be ok, but just ok. A 50-55lb might seem a bit more comfortable at the surface. If you already have a 45lb, you could just try it when you get the rest of your stuff and if it is not enough, get a bigger bladder at that time.

sorry if I sound a bit confusing, but i am very tired LOL.

[MikeP]

Stay away from 119s as doubles, they are great for singles only
As doubles, they have a tendency to make you head heavy.
Don't buy the hype that bigger is better, 80s or 100s are perfect, add or subtract stages as needed for extra range

As for the wing, 50-60 is the norm, but your 45 will do.
I've seen 130s and deco bottle held up by a 40# wing before, all be it in flat water.

Mike