Are there solid buoyancy add ons for doubles?

[Peter_V]

I've got a set of Hi Pressure steel doubles and these things are seriously negatively buoyant. Not only don't I need weights, I have to partially inflate my wing to get neutral at the beginning of my dives.

My problem is that I'm getting into tech diving and all the extra equipment is only going to make things worse. I'm trying to avoid having to get a larger wing.

Does anyone make a positively buoyant, non-compressible (i.e. solid) add-on for doubles? Perhaps something that would fit between the tanks on the back?

I could MacGyver something out of PVC pipes, but I'd prefer something a bit more professional looking.

Thanks

 

[zaberman1]

I would say having something like that, depending on the type of technical diving you are getting into, may be doing more harm than good and offer a VERY big failure point. Get a dry suit, use an al bp, and get a dual bladder...

 

[M_Bipartitus]

Remember that you need to be enough negative at the start of the dive so that you can still stay down at the end (with say 500psi.) In a set of HP doubles you could have as much as a 20lb swing due to air use. I suppose it would be less with proper gas management, but none-the-less you should be able to keep the rig down if low on air.

 

[Gombessa]

I've got a set of Hi Pressure steel doubles and these things are seriously negatively buoyant. Not only don't I need weights, I have to partially inflate my wing to get neutral at the beginning of my dives.

The question is how much. You SHOULD need to partially inflate your wing to get neutral at the beginning of your dive, by roughly the weight of your gas (12-20lb typically).

What kind of steel tanks are you running? There are negative tanks (~-2 when empty) and there are NEGATIVE tanks (~-7 when empty). The latter aren't great choices for doubles.

 

[Scott]

I have to partially inflate my wing to get neutral at the beginning of my dives.

That's typical with HP steel doubles. What is your buoyancy like at the end of the dive?

My problem is that I'm getting into tech diving and all the extra equipment is only going to make things worse. I'm trying to avoid having to get a larger wing.

You're going to have to fork out the $$ for a proper wing if you're going to go into tech. I seriously doubt any tech instructor would let you in the water, let alone a pool without the proper equipment. I know my tech instructor wouldn't.
If they did I doubt you would find a buddy to dive with. McGyvering a a rig will put you and the team at risk.

 

[StreetDoctor]

You should be negative by the weight of your gas at the beginning of your dive. You should be able to figure that out based on your tanks. For me I dive double worthington HP130's and I'm almost 20lbs negative at the beginning of the dive. With my drysuit and undergarments I need about 2.5lbs in a tail weight to make me neutral with empty tanks. Double bladder is a bad idea, you have a drysuit and a lift bag/smb capable of *some* lift in case of extreme emergency. I wouldn't think about diving them in a wetsuit. If you don't have a drysuit look into some double AL80s

 

[fdog]

I've got a set of Hi Pressure steel doubles and these things are seriously negatively buoyant. Not only don't I need weights, I have to partially inflate my wing to get neutral at the beginning of my dives.

My problem is that I'm getting into tech diving and all the extra equipment is only going to make things worse. I'm trying to avoid having to get a larger wing.

Does anyone make a positively buoyant, non-compressible (i.e. solid) add-on for doubles? Perhaps something that would fit between the tanks on the back?

I could MacGyver something out of PVC pipes, but I'd prefer something a bit more professional looking.

Thanks

This is normal. Welcome to non-ditchable weighting.

As mentioned above, a dry suit is a good place to start, to get your weighting under control.

There are many good reasons for so much of the "tech" setup in all its' nuances. In the interests of saving you money (by not having to buy everything twice), may I humbly suggest that you either find a very experienced mentor, or, take an Essentials/Fundies/Intro to Tech class?


All the best, James

 

[scubafanatic]

I've got a set of Hi Pressure steel doubles and these things are seriously negatively buoyant. Not only don't I need weights, I have to partially inflate my wing to get neutral at the beginning of my dives.

My problem is that I'm getting into tech diving and all the extra equipment is only going to make things worse. I'm trying to avoid having to get a larger wing.

Does anyone make a positively buoyant, non-compressible (i.e. solid) add-on for doubles? Perhaps something that would fit between the tanks on the back?

I could MacGyver something out of PVC pipes, but I'd prefer something a bit more professional looking.

Thanks

...not sure how to put this gently.....but your 'clever' solution is wrong on sooo many levels! When you say you're are getting into tech diving...do you mean you're teaching yourself and getting an internet-based certification of some sort ??? ...I challenge you to find a tech instructor that would have anything whatsoever to do with your proposed solution...you will not be permitted to do any such thing...no way...no how!

...whatever you do, don't pose this question on a tech oriented scuba board (thedecostop.com) as you would be the laughtingstock of the universe over there!

...just being honest with ya!

 

[Scared Silly]

When you say HP cylinders which ones? Faber made some MP that are 3498psi (3180 psi + 10%) that are seriously negative. These cylinders are not a good choice for doubles. The exempt HP cylinders are fine for doubles. If you are using the later then as other people have said look at your over all buoyancy and what you are experiencing is normal. That said, I dive with a bladder that provides 45-50lbs of buoyancy which is plenty for most doubles.

 

[Peter_V]

Ok I guess I deserved that.
So, some more details. I haven't used the doubles in a couple years. Originally they were double Worthingtons and were pretty negative even when empty, IIRC something like 8 lbs negative just for the tanks. I used a 45lb wing and had to fill it about 1/2 way at the beginning of the dive and still had to use with empty tanks to get neutral at the end.
I've since switched tanks and the new ones are about 8 lbs lighter (out of the water, haven't had them wet yet) so might not be so bad.

When I said I was getting into tech, I meant that I was taking a couple classes next month, TDI Advanced Nitrox and Decompression Procdures, possibly Extended Range.

I just got an email from the instructor and he says my 45lb wing is unacceptable, 55 lbs is the minimum he'll allow and he'd prefer larger.

So my question is now moot.

FWIW I don't forsee owning a drysuit anytime soon. It would be nice to have, but I just blew a whole years diving budget on the tech classes.
Besides, for over 80% of my dives so far, I haven't needed anything more than shorts and a teeshirt and I've only had one trip where I needed anything more than a 3mil.

Thanks everyone for your replies.