BP/W Selection & Weighting

[GoBlue!]

I agree, SeaJay. Our numbers were a bit different since I was trying to estimate what I'd need in salt water, but the concept was the same.

Of course, that would leave me w/o ditchable weight & 6# heavy at the start of the dive (in freshwater, that is; with the numbers you used, I'd have 6# ditchable in saltwater which would be very reasonable since it would essentially make me neutral if ditched). Will have to think about that...

Jim

 

[SeaJay]

I think you're "on."

Don't forget to calculate that most neoprene loses 80% of it's buoyancy at 100 feet.

...So in freshwater, if you were to jump in and immediately go to 100', and ALL of your 5lbs of you/wetsuit buoyancy was WETSUIT, then... 5(.80) = .4... So you'd be (-6) + (-2) + (-3) + (+.4)... (That's plate, STA, weight of tank full, plus wetsuit.) That'd be -11.6 pounds.

If you can swim that up, then it's not an issue. Remember, as you surface, you get the 4 lbs of your suit back... So as you surface, the -11.6 pounds goes to -7.6 pounds... And if your tank isn't full, then it's really -1.6 pounds.

That's the rig that I dive. I love it.

 

[GoBlue!]

OK. I've just bought 2 sets of ATX200/ATX40s (one for me, one for my wife), so now it's time to get back to thinking about the BP/W.

To resurrect this thread a bit, it seems that a SS BP/W is our best bet, although it won't leave us w/ much (if any) ditchable weight. Our diving is primarily warm water (salt & fresh), 3mm suits, single tank AL80 only....at this point.

As the posts above describe, me+suit needs about 5lb to counter my body+suit's buoyancy (at the surface). So, at end of a dive w/ an AL80 in freshwater, I'm looking at needing 8# of weight (3# for 500psig AL80 in freshwater + 5# for suit/me), which seems (as Seajay pointed out) a perfect amt for SS BP + light STA. Will obviously need a bit more weight in salt. An aluminum BP would need several more pounds on a weight belt (especially in saltwater), and that seems less ideal to me right now....

Now, a couple questions. I readily admit to not knowing much at all about dry suits, but anticipate taking that journey in a year or so. From all I've read, it seems that dry suit diving will substantially increase the amount of weight I'd need (keeping all else the same...i.e., AL80, single tank), so SS BP/W would be better than alum BP/W here as well (unless I move to steel tanks...or doubles...neither of which I've yet experienced to date). Is this correct?

Last, in the first setup mentioned, it seems that a 30# wing (I'm thinking Oxycheq) would be plenty of lift, as even if I lost ALL buoyancy from the suit at the beginning of the dive, I'd be looking at -11# (approx). As I'm not at all experienced w/ dry suit diving, I'm unsure if 30# lift would still be enough lift for this type of diving (still thinking a single tank setup).

I'm just trying to look ahead a bit & prevent regretting a wing size in a year or so when I'm looking to put together a dry suit setup with a single tank. *IF* I ever move to doubles, I'll obviously purchase a new wing at that time.

Help?

Jim

 

[SeaJay]

I certainly have found every word that you post to be true.

A 30 lb Oxy (or Halcyon Pio 27), a light STA, and a SS plate has worked out perfectly for me in a 3 mil, AL80, and fresh water. For salt, I dive the same rig, but add three pounds on either side of my rig. I can "swim up" all of the above.

Of course, your 3 mil is going to be a little different than mine... And of course, your body is likely to be different in terms of buoyancy, either more or less, depending on body density.

...But I think that most people agree that a light STA, SS "standard" plate, AL80, and a 3 mil is a good place to start your calculations. You'd have to be pretty radically different from what most people have experienced to not be totally thrilled with that rig... Especially as a starting point.

Most people who like the AL plates dive the same rig as above, but either without a wetsuit at all, or with heavier, steel HP tanks, not your regular AL80.

Those who tend to like the super-heavy, thicker plates typically are heavy cold/saltwater only divers who need serious ballast to sink, due to really thick exposure protection.

Of course, this may vary, for a variety of reasons... I'm simply making an observation - which seems to work for most, and which seems like it would work for you.

I love my Gary Hoadley backplates, but Scott Koplin and FredT also make excellent plates. The Halcyon plates seem to be fairly good, but slightly pricer, and with some lack of hand-crafted attention to detail... Especially in the smoothness of the slots. I personally favor the Koplin "light" STA, but they may be difficult to obtain, and Oxycheq makes a great one, too. Like most, I prefer to use a STA, even when using a wing that doesn't require one (the Halcyon Pioneers).

Lastly, if you do find that these plates don't "nail" it for you and that instead you need a little more or a little less weight in a plate, new plates are very inexpensive, and/or all of the above I'm sure would be willing to exchange so that you've got the right plate.

PS: Nice regs.

 

[GoBlue!]

SeaJay once bubbled...
I certainly have found every word that you post to be true.

A 30 lb Oxy (or Halcyon Pio 27), a light STA, and a SS plate has worked out perfectly for me in a 3 mil, AL80, and fresh water. For salt, I dive the same rig, but add three pounds on either side of my rig. I can "swim up" all of the above.

Do you ever dive dry? I'm wondering if a 30lb Oxy could be used with a single tank setup w/ dry suit & SS plate/STA. Or, should I get the 45# as I understand that the profile is not really any different (although one could point to the "dynamic instability" idea, described on the baue.org website & elsewhere).

Perhaps there's no way I can really predict my dry suit needs, since I've never done it. Fair enough response. I'm just trying to avoid a purchase now and another single tank wing purchase in a year for dry suit diving, as I anticipate needing a doubles wing a couple years down the road when I get to that!

Jim

 

[GoBlue!]

Don Burke once bubbled...
In your case, I think you're going to end up with an aluminum backplate. While you might be neutral with the steel plate, 400psig, and no weight, not having enough ditchable weight to keep yourself on the surface with a full tank and failed wing doesn't give me a warm fuzzy feeling about your safety.

I'd be 11# heavy max, I think, at the beginning of a freshwater dive if my suit TOTALLY compressed w/ a SS BP/STA & full AL80, assuming my body is neutral (which it's not...my wetsuit isn't totally responsible for needing that 5#). That is, 8# for BP/STA + 3# full AL80. In salt, however, let's estimate I'd need another 5# (may be a bit of an overestimate, but it's close); now I'd have 8# BP/STA + 2# full AL80 + 6# ditchable, or 16# heavy max at beginning of dive....which could be reduced to 10# heavy if the 6# was ditched.

True, it wouldn't be fun to tread w/ 10-11# at the surface for awhile. Hmmmm.....

Wish I had someone with a setup nearby I could mess with for awhile!

Jim

 

[SeaJay]

I was talking wetsuit.

I can't speak with any authority on diving dry... I don't own a drysuit yet, so my experience is limited.

I have noticed, however, a propensity for people recommending the 36 pound Halcyon wing for drysuit diving... Or the 40 in Oxycheq.

Sorry I can't be of more assistance there. To really answer that need, you'll have to ask someone who dives dry regularly.

My hunch is that the 36 or 40 would suit you better in that case... But that's just a hunch, based on the recommendations that I've seen here.

 

[GoBlue!]

Finally had a chance to dive this rig.

With an AL80, SS BP (Oxycheq) & light STA, was perfectly neutral at 500psig on the surface in freshwater without a weight belt.

Added 5# to a belt for saltwater, and while I never breathed the tank down to 500psig, I believe I was just a tad overweighted if anything....

Thanks to all who provided advice before I bought the setup. Absolutely love it.

Jim