Switching from BCD to BP/W

[kdagostin0]

I am going to be switching from a BCD and transition into a BP/W setup. I remember seeing a excel spreadsheet that helped figure out weight issue but cant seem to find it.
Basically I wear about 30lbs of weight on my current BCD and will using a 80 cubic steel. Adding weight from there I can fine tune it I'm just wondering if the steel tank will be TOO heavy.
Any suggestions?

 

[Colliam7]

I am going to be switching from a BCD and transition into a BP/W setup. . . . Basically I wear about 30lbs of weight on my current BCD and will using a 80 cubic steel. Adding weight from there I can fine tune it I'm just wondering if the steel tank will be TOO heavy. Any suggestions?

Yes, several.

First, it is VERY UNLIKELY that a steel cylinder will be too heavy, if you are currently wearing 30 lbs of weight (that is A LOT, even with a drysuit and a single cylinder).

Second, you will be changing from what is probably an inherently buoyant BCD - you don't specify what unit you are currently using, so the actual amount of buoyancy that you will lose (and the weight you can therefore lose) is unknown at this point. BUT, and this is very rough, you should be able to lose at least 2 lbs of weight just on the basis of the BCD's inherent positive buoyancy alone, probably more.

Third, you need to adjust for the metal that you backplate is made of (presuming you are not going with a 'soft' plate like a Transpac, or a Zeagle Express Tech plate, or an Apeks Travel plate). So, if you go with a steel plate, plan on losing about 6 lbs, if you go with an aluminum plate plan on losing about 2 lbs.

Fourth, you need to consider what cam bands you will use with the BP, and are they the same as your BCD cam bands. If you are currently using 30 lbs of weight you will definitely want to go with SS cam band buckles, not plastic buckles. If your current BCD has plastic and you change to SS, you can probably lose another 1 lb of weight.

Fifth, will you use a single tank adaptor (STA), and will it be a stainless steel STA? That may allow you to lose another 1 lb.

So, as one example, if you switch from a fairly buoyant, padded BCD, say a Zeagle Ranger, to a SS BP/W, and use a SS single tank adaptor, and SS cam bands, I would start with ~20 pounds, and try to work (down from there). As you note, a proper weight check is what will be required, but this might give you a start.

 

[Goat_Tower]

If you need 30# lead, the steel tank wont be too heavy. You can take some lead off if need be.

View attachment Boyuancy 02-14-2014.xlsx

I think that attached the spreadsheet. I downloaded an old version from the thread, and made some additions and changes. This one works well, but there may be nicer versions floating around.

 

[kdagostin0]

The BPW set i'm diving is a Hollis 2lb aluminum back plate, Hollis S25 wing with slots, Dive Rite basic Harness (2 inch nylon webbing, 2 bent shoulder d-rings, 2 waist d rings, 1 grommet and stainless steel belt buckle), Dive Rite tank straps (2)
and I am switching from a AquaLung Pro LT

Just to provide additional info

 

[scububa]

I agree with others that 30 lbs sounds high. What exposure protection are you wearing. Wet or dry, what kind of insulation or thickness if wet?

Primarily making any change like this means getting back into confined water and doing the empirical adjustments. Remember you don't just want to worry about getting down at the start of the dive, but also staying down for your safety stop, etc. at the end with a light tank. Heading to a BP/W means you might be heading to more serious diving where holding a deco stop is much more critical, so you want to start refining that safety stop now.

You'll not only have buoyancy adjustments to make, but trim. You might find a SS BP is the answer depending on your other parameters.

 

[fnfalman]

What exposure suit are you wearing? What is the brand of the steel 80 tank? Is it low or high pressure?

 

[CT Sean]

The BPW set i'm diving is a Hollis 2lb aluminum back plate, Hollis S25 wing with slots, Dive Rite basic Harness (2 inch nylon webbing, 2 bent shoulder d-rings, 2 waist d rings, 1 grommet and stainless steel belt buckle), Dive Rite tank straps (2)
and I am switching from a AquaLung Pro LT

Just to provide additional info

With an Al plate and no single tank adapter, you'll only be able to drop 2-4 lbs from your belt - depending on how "floaty" your current BC is.

 

[Colliam7]

The BPW set i'm diving is a Hollis 2lb aluminum back plate, Hollis S25 wing with slots, Dive Rite basic Harness (2 inch nylon webbing, 2 bent shoulder d-rings, 2 waist d rings, 1 grommet and stainless steel belt buckle), Dive Rite tank straps (2) and I am switching from a AquaLung Pro LT

With an Al plate and no single tank adapter, you'll only be able to drop 2-4 lbs from your belt - depending on how "floaty" your current BC is.

Possibly. I am betting he can lose a bit more, possibly closer to 5-6. While the PRO LT is not as floaty as a padded Ranger, for example, it is a fairly buoyant jacket BCD. I dive one similar to that in the pool (a Wave) and it is reasonably buoyant. But, all of this is quite speculative. Maybe, with a proper weight check, etc., he will be able to lose even more.

To the OP: please follow up after you make the switch and dial in your weight, and let us know that you ended up with.

 

[halocline]

The BPW set i'm diving is a Hollis 2lb aluminum back plate, Hollis S25 wing with slots, Dive Rite basic Harness (2 inch nylon webbing, 2 bent shoulder d-rings, 2 waist d rings, 1 grommet and stainless steel belt buckle), Dive Rite tank straps (2)
and I am switching from a AquaLung Pro LT

Just to provide additional info

You should get a steel plate, if you use 30lbs of lead I don't think you have to ever worry about being heavy in a steel tank. Why did you get a AL plate out of curiosity?

In fact, you're a good candidate for the DSS bolt on plates. That could get you 12 lbs or so of ballast and would at least cut down on the humongous load of lead you're carrying.

 

[Colliam7]

You should get a steel plate, if you use 30lbs of lead I don't think you have to ever worry about being heavy in a steel tank. Why did you get a AL plate out of curiosity?

Good question. To the OP (kdagostin0): I wasn't going to say this, since you mentioned you already had the plate. But, since halocline raised the issue - - I will definitely agree. If you are carrying 30 lbs of weight with your BCD, a switch to a steel plate, and continuing to dive a steel cylinder, would make a lot more sense than an AL plate. BUT, going back to your original question: As several of us have noted, you will probably be able to drop 5-6 lbs with the AL plate, but that still leaves a lot on your waist, which has a negative affect on trim for most divers. Are you able to maintain good horizontal trim with your Pro LT and the 30 lbs of weight, or do you notice any tendency to go a bit foot-down in the water? The bolt-on plates will definitely help offset that, irrespective of the plate material. It will allow you to move some more weight off your waist, to a point higher on your body. So, I will second that recommendation as well.