Best guess, will I be too heavy with this tank?

[PfcAJ]

Backplate is the standard SS DiveRite, it's 5.5 lbs on land. You are right, the tank is -1.4 lbs empty, but ~-7 lbs full (both in salt water). I won't be using a drysuit, but will eventually get a good dsmb as you mention.

What is their (DIR's) concern with steel? I don't want to hijack my own thread here, but curious.

Steel DOUBLES paired with a wetsuit almost always creates a situation where you can't swim against the weight of the tanks+gas if your wing fails.

Steel singles, on the other hand, are generally light enough where you can swim against it. Exceptions might include big lp120s, HP130s, and the like.

You need to be able to do these things:

Swim against the weight of a full tank with no air in your wing from depth. *reason - If your wing fails, you aren't a lawn dart headed to Davy Jones Locker. Wetsuits loose buoyancy at depth* If you can't, you need a lighter tank OR a drysuit.

Maintain a 15' stop with no air in your wing and minimal gas in your tank (like 500psi or less). *reason - Tanks become more buoyant when empty. If you can't hold a stop when your tanks are empty, you'd cork to the surface. If you have to put air into your wing, you're carrying unneeded weight.* If you can't, you need to add or subtract weight.

Your wing needs to be able to float your full tank and all your bits and bobs without you in it. *reason - if your wing can't float your kit, you're unable to doff your equipment in the water* If it cant, you need a bigger wing.

 

[CT Sean]

Unless you're diving overweighted, 25 lbs of lift is plenty for a single tank and 3mm wetsuit. Remember that it is a buoyancy compensator, and what it exists to compensate for is wetsuit compression and tank weight drop from breathing the air. I don't know your personal weighting requirements in your current gear but I know I'd be overweighted in a 3mm suit with a -7lb tank and -5.5lb backplate - even in salt water. This doesn't mean my 25lb wing is too small, it means my SS backplate is too heavy.

 

[certainmisuse]

Yes, you'll probably be too heavy...with a steel backplate, that steel tank, and no wetsuit. The full tank plus reg plus backplate is about 14-16 lbs negative; what is going to offset that? An almost full wing?

To keep this thread updated, I believe at this point if I decide to even attempt this rig, I will be in a 3 mm wetsuit.

 

[certainmisuse]

I do have one comment, and just to add a bit of humor. If I have a wing failure at depth (again, <30 ft mostly), I'll breath down my cylinder while standing on the bottom, then when ready, start kicking. Since I plan to do exclusively shallow diving, compression of the wetsuit should not be too bad thus offsetting a good bit of said negative buoyancy. Sorry, had to.

 

[CT Sean]

Even entirely seriously - a 3mm full suit adds very little buoyancy - mine seems like it adds almost none. Couple lbs from the suit plus 6 from the tank and a 25 lb wing still has lots of spare capacity

 

[tursiops]

a 25 lb wing still has lots of spare capacity

...if it is functioning. Got to plan for the worst.....

 

[certainmisuse]

Even entirely seriously - a 3mm full suit adds very little buoyancy - mine seems like it adds almost none. Couple lbs from the suit plus 6 from the tank and a 25 lb wing still has lots of spare capacity

I am very curious to hear if folks have accurate readings of wetsuit buoyancy. Just anecdotally, I know my 6 mm I use to dive had a crap ton. One of the reasons I'm not interested in cold diving anymore.

 

[tursiops]

I am very curious to hear if folks have accurate readings of wetsuit buoyancy. Just anecdotally, I know my 6 mm I use to dive had a crap ton. One of the reasons I'm not interested in cold diving anymore.

My 3mm provides about 4 lbs buoyancy at the surface; my 5mm adds another 4 lbs; my 7mm adds yet another 4 lbs. My 3-5mm hooded vest adds another 2 lbs. That is for MY size and brand wetsuit...MS or LS. YOUR size and brand will be different.

 

[CT Sean]

...if it is functioning. Got to plan for the worst.....

If it's not functioning - does it matter what the capacity is?

 

[tursiops]

If it's not functioning - does it matter what the capacity is?

That's the point, isn't it?