How much lift is really needed or is too much?BCD?

[firedogut]

Ok about to buy a BCD and want to know who much lift i should have and what is over kill. To start off with i will be diving a single tank set-up mostly just rec diving. In the next few years I plan to do some more advance stuff and start using 2 tanks. One of the BCD's i'm looking at is 75lbs in lift (for the size i need).
to much for single tank?

I don't want just answers like..."it's too much." please go into depth. it is too much because.....

Also what LB of lift would you tell someone to buy?

 

[mempilot]

I dive a 30lb wing with this single tank config (it is plenty of lift for me):

Single steel 80 tank
6lb Stainless Steel Backplate
My gear (lights, reels, etc...)
Scuba Pro Jet Fins (neg buoyant)
Wetsuit with 6lbs of weight or Drysuit with 8lbs of weight
Deep (135 or shallower)

I weigh 170lbs.

With doubles, I go to a 55lb lift wing.

Not knowing your size or other equip, it's hard to give you any advice.


The deeper and heavier you go, the more lift you'll need. When I go deeper than 135 for deco dives, I use doubles and a bigger wing (BC). I also dive deep with a drysuit which gives redundancy in the lift. I also carry a lift bag, which gives redundancy. But for recreational, 30lbs is more than enough for me and I could get away with much less. My last jacket style BC was 24lbs of lift.

Hope that helps a little.

 

[firedogut]

The reason i was also asking about that BCD is beacuse i can get it from a LDS for $199.99 (he making room for the Rig Pro). Its the RIG II. :11: I've read 100's of post on the RIG II and about 1/2 love it and 1/2 hate it. most of those who hated it could only say (what will you do with 15 rings?....) If i want i can always cut some off. takes 20 sec to cut through the steel.



Now if i only inflate the BCD 1/2 then i should be only using 35 lbs right?


if you can know of a good BCD that is weight intergrated and won't cost me a arm and a leg let me know. and please no one tell me to go to LP. I want a waranty with my BCD not a piece of toliet paper saying its a waranty.

 

[Snowbear]

You need enough lift to keep you and all your gear and weight floating on the surface. That's it. The problem with more lift capacity - it comes with more drag, even though you don't fully inflate it at depth. Depending on design (I know nothing about the RIG II), a large wing can also fold around a single tank and become tricky to vent. 75# is more than most people need even with steel doubles, BP, canister light, etc.

 

[jplacson]

firedogut, I used to think "wow! more lift! that's better...just in case!" ... in case of what? you might need to lift a treasure chest of the sea bed? hehehehe...

seriously, I originally wanted to get the Zeagle Ranger (about 45#) and then wanted the 100# OMS rig... both are decent rigs used by a lot of tech divers.

But since being introduced to DIR (raises shield to deflect incoming flames) I've learned that 30# is more than enough for most divers diving a single tank.

I currently use a Halcyon Pioneer 27# wing (feels more like 25#) and was even drawn to the older 18# 'batwing'.

The point is to dive with the minimum amount of drag. And the larger the wing, the more lift, and also, the more drag. Having a lot of lift is great and all, but not really important. Just learn how much weight you really need (the minimum) and you'll find that 30# is way more than you'll ever really need on a single tank.

*Remember, it's a buoyancy COMPENSATOR... not a life jacket. Buy a SMB or redundant floatation for surface swims.

 

[DA Aquamaster]

Not to disagree with the DIR divers out there (also raises shield to deflect incoming flames) but only half the BC's job is done underwater. I dive with a 75 lb wing on my recon and actually like it. With twin steel tanks and the weight required to compensate for a 7mm wet suit or adequately insulated dry suit for cold water dives, the "extra" lift is nice to have on the surface. It gets you a little higher out of the water which is nice in choppy conditions.

When I eventually retire the current setup, I will most likely go with a 55-60 lb wing but I regard this as about the minimum for cold water diving with doubles.

For single tank cold water diving 45 lbs is a decent figure and for single tank warm water diving a 28 lb wing may be perfectly adequate.

The comonly reported risks with a bigger wing are that (1) it will fold around the tank, and trap air, or alternatively (2) will provide additional room for expansion and consequently more lift in the event of a runaway inflation or ascent situation.

The first problem is a design issue rather than strictly a lift problem and my recon's wing works very well with a single tank and also works very well with mu doubles. Wings in the 50-75 lb range are capable of working well with both singles and doubles if properly designed. So some large wings will have problems and others won't, size is just not the whole issue.

The second problem is 99+ % preventable with good techniques and proper weighting. And in the unlikely event that it does occur is, contrary to popular urban dive legend, not all that big of deal. Drag increases as the square of the velocity so it takes four times the thrust (or lift in this case) to double the speed (or ascent rate.) And in a proper flared out of control ascent position the extra 35 lbs of lift in a 75 pound wing over a more common 40 lb wing will produce only a very small increase in ascent rate as the drag is already very high in the first place and the original ascent rate rather low.

A dry suit produces a much greater risk in this regard as the average pilsbury dough boy'ed extra-large size drysuit has a huge amount of potential lift compared to even a 100 lb wing. Yet no one is advocating that drysuits be left home as unsafe.

So in short I will gladly choose the added convenience and safety of a well designed 60-75 lb wing at the surface over a 30-45 lb wing and accept the minimally higher and largely theoretical risks involved.

 

[jplacson]

I was thinking along similar lines, but ended up going for minimal lift... but carry redundant floatation... whatever BC I used, if I was dead tired, I'd be safer hanging on to a CC SMB or something... maybe even clip it to my front D-rings to keep me floating head-up.

 

[rcrs007]

Hmm199$ is a good price, but if your really going to go into technical diving in the next little while you'll prob end up wanting a bp/harness/wings setup when you get there.

I had a Zeagle Ranger with 45lbs lift that I used for single tank diving and I hated it. My wings were always like a bun for a hotdog (tank). Compared to a back inflation bc I used at work with doubles the Zeagle sucked buoyancy and drag wise.

What I did was sell my zeagle (well not yet sold, but maybe one day it will sell) and buy a bp/harness/27#wing for myself. I did that because: I can always put a larger wing on when necessary, I can gradually buy technical gear and add it to my harness (meaning I can buy a HID light and have a place for it to go while I save up for tanks) and when it comes to buying my own doubles it will be simpler to do the "weight up/get used to bp/wings setup", transitioning for bouyancy comp to bp/wings/doubles immediatly would be more difficult.

If a 27lbs wing can do for alum single tank diving in a trilam drysuit then 75pounds would be way overkill. I almost got caught up in the "bigger-wing-is-better" attitude, luckily Scubaboard and TDS was there to point out that when it comes to lift, it's not always bigger is better.

Ryan

 

[ScubaRon]

See the calculation of exactly how much lift you minimally need in the following thread.

Some (say 10-15 lbs) of extra lift capacity does no harm and may help you on the surface in rough water, but too much can cause several problems:
- large wings tend to wrap around your tank ("taco-ing") and trap air so it is difficult to dump it.
- large wings act like a sail when diving in strong current
- drag

FYI I dive in salt water with 30 lbs. lift in a 7 mm full wetsuit and a AL 80 tank and 36 lbs weight.
ScubaRon

 

[IndigoBlue]

Ok about to buy a BCD and want to know who much lift i should have and what is over kill. To start off with i will be diving a single tank set-up mostly just rec diving. In the next few years I plan to do some more advance stuff and start using 2 tanks. One of the BCD's i'm looking at is 75lbs in lift (for the size i need).
to much for single tank?

I don't want just answers like..."it's too much." please go into depth. it is too much because.....

Also what LB of lift would you tell someone to buy?

Your B/C (buoyancy compensator) at a minimum needs to be able to float all of your gear at the surface. "All of your gear" means your tank(s) when full, your reg(s), your light(s), your weights, etc.

There are several ways you could calculate the required amount. Archimedes comes to mind, in one instance. Or you can "borrow" or rent various B/Cs with various lift capacities, and attach all your gear to each of them, and conduct the experiment.

That is the minimum.

Many divers love to dive with this minimum sized B/C capacity. They have various reasons for doing so.

If you are an instructor or divemaster, then a larger lift capacity than "the minimum" is very nice, if not critical, for assisting students, hauling around extra weights between students and the dive float, etc.

DA Aquamaster also gave you some other reasons for when additional lift capacity is nice. Its your call. You are the certified diver. No one else can tell you what is "too much."

By the way, for reference, some divers use the term BCD (buoyancy control device). The two terms of course are synonymous. FYI.