Weighting? Freshwater+back-inflate BC -> Saltwater+SS BP/W

[stuartv]

I just had my Buoyancy Control this past weekend. It was in a pool (fresh water). In my 3/2 suit, with an XS Scuba back-inflate BC, and an AL80, I felt very dialed in with 10# of weight. That was enough to get down and to stay down with a 500 psi tank.

I am eagerly awaiting today's arrival of a new-to-me DSS steel BP/W setup.

And I am going to Riviera Maya next week where I am hoping to dive this BP/W.

My Buoyancy Control instructor suggested that when I go from fresh water to salt water, I should add 4# of weight. And, for my first dive, I should add an additional 2# to compensate for nerves/excitement, etc.. Does that sound right?

I've read what I could find on here about how much my weighting would change going from a BC to this BP/W. What I've been able to gather is that it sounds like people generally drop around 6 # when going from a BC (of some type) to a DSS SS BP/W.

Does that also sound about right?

So, when I go to RM next week, diving my same 3/2 suit, etc., but using this new BP/W, I should probably start out with 10 # of weight? And expect to maybe drop a couple of pounds for my second or third dive, as I get more comfortable?


And if all that sounds right, I saw that DSS has 8 # weight plates that can be mounted on the back plate. That might get me to just the right weighting without having to carry any weight in weight pockets or on a belt. That sounds great... except, would it really be wise to dive that way, where I would have no ditchable weight at all? Or would those bolt-on weights really be for when I dive with my 7mm suit, where I took 20# in the pool?

TIA for the advice!

 

[Lorenzoid]

My BC--a DSS Medium steel plate and wing plus associated hardware--weighs about 6 lbs. When I dive an Al 80 with this rig in a well-worn 3/2 fullsuit, I put a 1 lb. weight in each pocket of a pair of pockets on the upper camband for a total of 2 lbs. of lead. If the dive op doesn't have 1 lb. weights, I might use a single 2 lb. weight in one of the pockets or even ratchet it up to two 2 lb. weights in the pockets for a total of 4 lbs. If your rig is similar to mine, you shouldn't need more than 4-6 lbs. of lead to dive a steel BP with an Al 80 in a new 3/2 fullsuit, even as a new diver. If you were to dive in board shorts and no wetsuit, you could almost certainly get away with no lead at all--just the 6 lbs. contributed by your rig.

But no need to be overly concerned with calculating your correct weighting in advance. You can start with something like 4 lbs. of lead and if on the first dive you feel you want to add or subtract weight for subsequent dives, you can do it. The first dive of a dive trip is usually done with a goal of helping the divers get their weighting correct and otherwise shake out the rust, especially if you let them know you're a new diver.

The bolt-on DSS plates are indeed for divers with thick wetsuits or drysuits. Not applicable to Riviera Maya diving. Besides, you're not going to carry lead weights with you in your checked or carry-on baggage. The dive op provides weights.

 

[decompression]

Let's see,

3mil suit- +4
Al 80- +4
Plate, -6

So you would be +2 before adding weight, add 2x 4lbs weight and that should get you in the ballpark for salt water. Probably loose a couple lbs after a buoyancy check. Place a couple pockets on your belt before you go. Sad that your instructor didn't mention a "balanced rig" calculation.

The plates are definitely for thicker exposure suits. Not necessary and cumbersome for warm water travel diving. Enjoy!


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[stuartv]

Thanks.

The bolt-on DSS plates are indeed for divers with thick wetsuits or drysuits. Not applicable to Riviera Maya diving. Besides, you're not going to carry lead weights with you in your checked or carry-on baggage. The dive op provides weights.

That's what I thought. I just wanted to confirm. My instructor did say that dive ops normally don't have 1# weights, so my instructor always takes 4 x 1# weights with him, to use if he wants/needs to.

Oh, and Lorenzoid, you didn't say, but, regarding your own weighting, I assume you were talking about all in salt water?

 

[C Dub]

Lorenzo and Decomp are spot on.

Just to give you another data point for future reference, when diving my steel BP and STA, full 7mm semi-dry, hood booties gloves, with an HP100 or LP 95, I only add 6 or 8 pounds to my belt, depending on how many lights, ponies, etc I'm carrying for that dive.

I've gone as low as 4 pounds. The safety stop with 1k PSI was a bit dicey.

 

[stuartv]

And back to a question from my OP: It sounds like you (at least Lorenzoid) are putting what weight you do carry into trim pockets on the cam band. So, is it really wise to dive this way, with no ditchable weight?

 

[Dhboner]

Ditchable weight can also mean "accidentally dropped weight" which would result in a potential uncontrolled ascent. A balanced rig (meaning you can swim your rig to the surface in the event of a wing failure) is the best approach for an experienced diver but it is not always practical for a beginning diver (who may need to add/subtract weight). For instance, a dropped weight belt on a deep dive with a decompression obligation could be catastrophic. For your purposes keep your weight on a belt or in pouches.

 

[decompression]

I'll answer this one, many divers don't have ditchable weights. As I mentioned above they dive a balanced rig which may or may not incorporate ditchable weight.

The reason being, an uncontrolled ascent can be very dangerous, to negate this some ensure the weight they need is secure and retains the ability to swim controlled to the surface.

If you only require 4-8 lbs they can easy be kept in ditchable or non-ditchable pockets on your webbing.

When trained properly, the situations that would require you to do a buoyant ascent are few.


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[stuartv]

So, for my edification (and education), is a rig "balanced" at the start (full tank) or end (500 psi) of a dive?

And is "balanced" meaning neutral buoyancy with an empty BC at the surface? At 15 feet? Or where?

 

[C Dub]

I was taught 500 PSI, at the surface, empty BC, water at eye level = proper weight.