How much lift?

[Beefcake]

In researching options for a new BCD, I have noticed that the larger sizes offer more lift, but not all are the same. Is there a formula to figure out how much lift I need? I am a big guy (6'2" 250#), and with the cold water up here I have to wear a thick suit (I'm diving a 7mil farmer john and 7mil top, with 7mil boots, gloves, and hood). Obviously, this much neoprene is very bouyant, and I only have aluminum tanks right now, so I dive with a crap-load of weight (up to 50+ pounds at times; I'm getting more comfortable and can sometimes drop that down a little). Anyway, I am considering a new BCD for a couple of reasons; first, my butt is smaller than my gut, so my weight belt doesn't stay up very well while making shore entries - I need integrated weights (or I could add shoulder straps to my weight belt, but I don't want to hinder my ability to get positive in a hurry if the need ever arises). The second reason for a new BCD is that I sometimes have trouble getting positive enough for the surface swim back. How much lift do I need?

I know that some of the issue is weighting, and I am going to put some effort into getting a handle on this problem this spring. I am often scared that I am way over-weighted, but I also know that I can't get down to a 30# belt like most of my buddies. The least that I have gotten down to is about 42# in optimal conditions. However, the repeating scenario has been that I gear up, make the hike, then the surface swim, and by the time I'm ready to submerge I'm breathing hard and can't get negative, so I have to add weight. At the end of my dive, even though my tanks are lighter, I'm usually so relaxed that I am way over weighted.

Oops, I guess maybe this should have been two threads (one to explain lift to me, and one for everyone to laugh at my rookie breathing causing weighting problems!).

[Heavy D]

This should help. It is written for a BP/W but just make the appropriate adjustments for your BC.

The Deco Stop

[DMWiz]

Here's this link to a very handy buoyancy calculator spread sheet.

And this thread will most likely answer any questions you may have about using the spread sheet.

Hope this helps you.

[Beefcake]

HeavyD- Thank you. Unfortunately, I can't open the link (looks like I have to join the website first; I'll check it out).

DMWiz- Cool spreadsheet. Now I just need to experiment to see how bouyant my suit / hood / boots / gloves are. This gives me a starting point. With some approximate numbers that I threw in, it shows that I need 30# of weight and 34.95# of lift. I need to figure out how much more lift for my actual weight, but I'm thinking a 55# wing or BC is about right.

[Straegen]

I have a question on this as well since I am not getting the concept fully.

Assuming I have a 8lb SS plate, 2lb reg, 10lb full tank, 30lb wing and just enough weight in a belt to make me in a swimsuit neutral at the surface. If my wetsuit is 22lb positive at the surface, I will need to add 3lb to sink and another 8lb to compensate for an emptying tank. Is this correct? If it is don't I add 20lb (for the rig) + 8lb + 3lb for 31lb meaning I need a wing at least that large since an exposure suit could in the worst case scenario contribute zero buoyancy?

[navyhmc]

Go ahead and join Beefcake, a lot of good info there, even if you're not going tech. (I just did if only to see Heavy-d's link.)

[Beefcake]

I'll probably check it out. I've spent the last couple of hours playing with that spreadsheet and researching BCDs. Now I understand why so many guys up here are sporting the SeaQuest Pro QD+ (54# of lift and weight pockets for 42#). It also explains why I feel over-weighted in my current BCD. Not sure why I'm in such a rush; I can barely afford top ramen until the economy rebounds....

[navyhmc]

If keeping a weight belt on is an issue, try one of the harnesses. I use a DUI weight harness and will never go back to either a weight integrated or weight belt. It's actually comfortable. I have found that sometimes I forget to take it off during surface intervals.

I changed from a BCD to a Backplate/Wing set up with a DR transplate harness, I like the quick relase buckles. Not DIR, but it works for me. BP/W isn't for everyone, but it definitely works for me. That and with a 6 lb stainless BP, that's less lead to fight with. but be warned, if you go this route, you'll find yourself gravitating towards doubles-I did.

Good luck and good diving

[Beefcake]

Yeah, I can see the advantages to the BPW setup, but I really don't mind a jacket style. I haven't checked out weight harnesses to see how they release; that could be an option. And I'd love to switch to doubles someday, but my budget is pretty tight right now. With my size, I suck some air at depth, but I think a steel 120 tank will put me about where I want to be for a while (my girlfriend is using an al80, and my other dive buddy has a steel 100cf tank, so I just need to get to where our bottom times are similar). It looks like there have been some XL Pro QD+ vests on the classifieds here in the $200-250 range in the last year; I think that might be my target to start saving for.

[navyhmc]

Originally Posted by Beefcake

Yeah, I can see the advantages to the BPW setup, but I really don't mind a jacket style. I haven't checked out weight harnesses to see how they release; that could be an option. And I'd love to switch to doubles someday, but my budget is pretty tight right now. With my size, I suck some air at depth, but I think a steel 120 tank will put me about where I want to be for a while (my girlfriend is using an al80, and my other dive buddy has a steel 100cf tank, so I just need to get to where our bottom times are similar). It looks like there have been some XL Pro QD+ vests on the classifieds here in the $200-250 range in the last year; I think that might be my target to start saving for.

Just stay away from the LP 121, that thing is a monster.

see my picts in this thread: lp 131