BCD and tanks

[Underwatermike]

Hi all! I'm brand new here and looking for a little knowledge! I've been diving for over a year now and am buying a tank. I do a lot of colder water diving using a 7mm wetsuit. With a AL80 tank I need a ton of weight to get under. I did some research and have come up with a LP 108 steel tank for it's bouancy characteristics and air capacity. I'm 6'4 250lbs so I should not have much trouble with the tank size. Just wondering if my Mares Hybrid Pro Tec BCD is up to the task for that size tank. Thanks!

 

[dumpsterDiver]

Using this heavier tank is going to cause you to remove some lead from your belt, maybe 6 lbs or so. The net affect on your BC is nothing. Technically.. since the larger tank holds an extra 1 lb of air or so, the weight swing will be an extra lb during the dive, but this is splitting hairs.

 

[decompression]

Hey Mike,

Yes, the LP108 is going to get some lead off your waist. I'll go one step further and suggest getting a backplate and wing. Here's a little hypothetical breakdown....

Let's say you need 30 lbs of lead;
-6 backplate
-4 tank
-8 weighted STA
So now your left with only 12 lbs on the waist, or less if you place some in trim pockets.
Also, I'd bet the Mares BCD is about 4-6 lbs positive.....and less 4 lbs positive from The AL 80 as well.

I'm 6'3" and 280 lbs, in a drysuit in fresh water I use 32 lbs. 10 is on my waist.

 

[Underwatermike]

Thanks guys!! Good info!

 

[cool_hardware52]

Hey Mike,

Yes, the LP108 is going to get some lead off your waist. I'll go one step further and suggest getting a backplate and wing. Here's a little hypothetical breakdown....

Let's say you need 30 lbs of lead;
-6 backplate
-4 tank
-8 weighted STA
So now your left with only 12 lbs on the waist, or less if you place some in trim pockets.
Also, I'd bet the Mares BCD is about 4-6 lbs positive.....and less 4 lbs positive from The AL 80 as well.

I'm 6'3" and 280 lbs, in a drysuit in fresh water I use 32 lbs. 10 is on my waist.

I agree with the concept, but I'd use slightly different numbers for the "rig"

Long pattern Back plate and Harness -8 lbs
Bolt on weight weight plates for the LP plate -10
HP 100 instead of the 108 -2 (vs maybe -1 for the 108 empty) E8 130 or 3443 120 if more capacity is desired, both are ~-2 empty.
Regulator -2

Ballast provided by rig with an empty cylinder -22 lbs
Rig max negative with a full tank -30

Wing required something greater than 30, probably 35 ish.

Unlikely that a 7mm suit even on a bigger guy will be more than + 30.

Assuming his suit is + 30 at the surface it will be less at 15 ft (SS depth) If we assume it will be 26 lbs at 15 ft he will need ~4 lbs on a belt.

**All numbers are estimates and I strongly recommend verifying the actual buoyancy of the divers suit**

Tobin

 

[decompression]

When in doubt....always go with Tobin.

 

[The Chairman]

Get the tank(s) and have fun. Your Mares BC will handle it just fine. I believe it's a back inflate, so a BP&Wing doesn't have any real benefit over it. I'm not a big fan of the vest style, but at least it has neutral buoyancy padding. Dive it until you get tired of it.

 

[Colliam7]

Just wondering if my Mares Hybrid Pro Tec BCD is up to the task for that size tank.

I am not altogether sure what you are thinking of with regard to 'that size'. The LP 108 is a bit heavier than an AL80, it is similar in length, it is 8" diameter cylinder compared to a 7.25" AL80. But, as several have said, however, there should be no issue at all with the Mares Hybrid Pro Tec and a LP108. You will find that moving to a LP108 from an AL80 will allow you to drop at least a couple of pounds of that weight you are having to carry (I presume you are planning to buy new, which probably means a Faber LP108 - if you can find a used, galvanized 108, the weight drop might be a bit better).

As an aside, I doubt you came to this forum looking for a new BCD. But, it does appear that your selection of a cylinder foir purchase reflects a desire to minimize the added weight you are having to carry. So, to support another poster's comment: More than a few of us, who needed to add A LOT of lead to our belt, our rig, etc., because we dive cold water with buoyant exposure suits (7mm neoprene wetsuits, drysuits, etc), have found that there is considerable benefit associated with moving from a padded, positively buoyant BCD (like the Hybrid Pro Tec) that required us to add even more weight, to a negatively buoyant steel BP, which puts weight where it is most advantageous (aligned with the physiologic center of lift), and reduces the total amount of weight carried.

If you ever have a chance to try a SS BP, take advantage of the opportunity, and see what you think. There is nothing wrong with the Hybrid Pro Tec. But, if you diving is cold water / thick exposure suits, it may needlessly add to your weight burden. Just a thought.

 

[tbone1004]

I wouldn't go LP108 unless you can get cave fills regularly. On a cost/weight advantage they don't work over the AL80. HP100's make more sense, or HP120's since you're tall. I don't like 8" diameter tanks if you are tall enough for the 120's. They are typically 4-5lbs heavier and don't carry a significantly larger amount of air. A 120 vs a 108 however is a couple of pounds lighter and holds more air, so you're in a win win.

Yes the long backplate from Tobin would be the best solution for you. However there is no need to spend the money to replace your existing BC as it is sufficient for what you are doing. Ideal? No, but it will work no different with a steel tank than it would with an 80

 

[diversteve]

What some people don't realize here is that with the side/back panels being removable on your BC - it basically is a soft backplate/wing.