Best way to match wing lift to back plate weight?

[CycleCat]

I'm still a new diver and very new to BPW use. I had never heard of them until joining Scubaboard last year but after reading about them here and seeing one in use I picked one up from the classifieds here in SB for a good price. It's an aluminum plate with 32# wing. I took it into salt water for the first time for four dives in San Carlos on the Sea of Cortez a few weeks ago and realized I'm going to want a stainless plate eventually. I despise wearing a bunch of weight on a belt and will want to get more onto the rig. I know there are ways to add weights but I would like to keep it tidy by having the plate make up more of that weight that I'm wearing. With a 5 mil one piece and alu 80 I was wearing 24#. I may still be overweighted but am working on that and think I'm pretty close.

If I start piecing together another set I'm wondering how would be best to mix the pieces I end up with. If my next wing has more or less lift do I want to put the bigger lift on the heavier plate or just the opposite? I can see it working both ways.

Here's the scenarios:
-Warm water dive with 3 mil suit or less: Not a lot of buoyancy so lighter plate. Do I offset my lower buoyancy with the bigger wing or will the smaller one do?
-Cooler water with 5 mil or thicker suit (I will never dry suit dive): More buoyant so heavier plate. Since I already have suit-induced buoyancy will the lighter lifting wing suffice?
-Or do I have this all bass-ackwards and I should do the lighter lift with the lighter plate and heavier lift with the heavy plate?
-Quit worrying about it and just attach more weight to the rig I have?

I'd like to keep my weight belt down to 10-12# max.

 

[Centrals]

My personal suggestion :
1. Your wing is ok for both cold and water. No need to buy another one.
2. SS plate is normally about 1.5kg(~3lbs) heavier than Al.
3. You can add a single tank adapter to the plate. You also pack some extra weight on it.
4. Weight pocket at the cam band.
5. Trim your body weight should certainly help considerably.

 

[James79]

I'm still a new diver and very new to BPW use. I had never heard of them until joining Scubaboard last year but after reading about them here and seeing one in use I picked one up from the classifieds here in SB for a good price. It's an aluminum plate with 32# wing. I took it into salt water for the first time for four dives in San Carlos on the Sea of Cortez a few weeks ago and realized I'm going to want a stainless plate eventually. I despise wearing a bunch of weight on a belt and will want to get more onto the rig. I know there are ways to add weights but I would like to keep it tidy by having the plate make up more of that weight that I'm wearing. With a 5 mil one piece and alu 80 I was wearing 24#. I may still be overweighted but am working on that and think I'm pretty close.

If I start piecing together another set I'm wondering how would be best to mix the pieces I end up with. If my next wing has more or less lift do I want to put the bigger lift on the heavier plate or just the opposite? I can see it working both ways.

Here's the scenarios:
-Warm water dive with 3 mil suit or less: Not a lot of buoyancy so lighter plate. Do I offset my lower buoyancy with the bigger wing or will the smaller one do?
-Cooler water with 5 mil or thicker suit (I will never dry suit dive): More buoyant so heavier plate. Since I already have suit-induced buoyancy will the lighter lifting wing suffice?
-Or do I have this all bass-ackwards and I should do the lighter lift with the lighter plate and heavier lift with the heavy plate?
-Quit worrying about it and just attach more weight to the rig I have?

I'd like to keep my weight belt down to 10-12# max.

Wing lift is needed for 3 major reasons:

1) Offset weight of gas at start of dive (80 cf of air is about 6.5 lb, but you will have some still in the tank at end of dive, so figure a 5 lb buoyancy swing from start to end of dive)

2) Offset loss of buoyancy from suit compression at depth.

3) Be able to float the rig independent of you if needed (taking it off to get back on a boat, etc.)

So, rule of thumb on wetsuit buoyancy is approx 2 lb. per mm. So going to a 3mm from a 5 will only drop about 4 lb. Same plate should be fine for both. Aluminum 80 is roughly neutral full, so in terms of Reason 3, your 32 lb wing is fine even if all of the weight you had on a belt was moved to the rig (roughly 4 or 5 lb for the plate, and 24 lead, rig would still be 3 or 4 lb positive when fully inflated).

For reasons 1 and 2, 32 lb is plenty to offset gas weight and wetsuit compression.

So, as Centrals wrote while I was typing, you should be fine with what you have. Even if you swap to a steel plate and shift lead to cam bands or bolted to the plate.

Respectfully,

James

 

[James79]

Depending on how much you want to nerd out on it, this tool Optimal Buoyancy Computer is incredibly helpful with seeing how it all plays in.

 

[CycleCat]

3. You can add a single tank adapter to the plate. You also pack some extra weight on it.
4. Weight pocket at the cam band.
5. Trim your body weight should certainly help considerably.

My OMS wing has sewn in tank stabilizers so I don't need an STA but I didn't think about adding one anyway just for the weight. I have a V weight I was already planning to add. With those and a few cam band weights I should be close to where I need to be to only need 5# on each hip.

 

[CycleCat]

So, rule of thumb on wetsuit buoyancy is approx 2 lb. per mm. So going to a 3mm from a 5 will only drop about 4 lb. Same plate should be fine for both. Aluminum 80 is roughly neutral full, so in terms of Reason 3, your 32 lb wing is fine even if all of the weight you had on a belt was moved to the rig (roughly 4 or 5 lb for the plate, and 24 lead, rig would still be 3 or 4 lb positive when fully inflated).

[SNIP]...

So, as Centrals wrote while I was typing, you should be fine with what you have. Even if you swap to a steel plate and shift lead to cam bands or bolted to the plate.

You guys are killing my excuse to buy more gear! But the idea of an STA when it is not really needed on my setup never occurred to me. That and some cam band weights might be enough to get me where I need to be.

 

[James79]

You guys are killing my excuse to buy more gear! But the idea of an STA when it is not really needed on my setup never occurred to me. That and some cam band weights might be enough to get me where I need to be.

You say that... but I'm thinking of making a stainless plate just so I don't have to change lead between salt and freshwater. I do stuff on the cheap, so I'm only hating my spare time, not my wallet!

 

[Bob DBF]

I may still be overweighted but am working on that and think I'm pretty close.

The Optimal Buoyancy Computer is a good tool, but making a weight check at your safety stop each dive will help a lot.

With an empty wing, about 500# in your tank, at 15', you should be.neutral. On a shore dive, I just place the excess weight in a game bag on the bottom, on a boat dive I hand it off to a buddy. After a while you can estimate the change and do it on the next dive, I keep a cheat sheet for different configurations and tanks in my logbook. You don't have to be perfect, but it's nice to know. I usually dive a little over to distribute my weight evenly, or for conditions.

But the idea of an STA when it is not really needed on my setup never occurred to me.

I've tried a couple of stays, one put the tank too high off my back making it act awkward, the other wasn't noticable, so I don't use any. You might want to save your money for something else.

 

[CycleCat]

You say that... but I'm thinking of making a stainless plate just so I don't have to change lead between salt and freshwater.

That's kind of what I was thinking... a light setup for warm and fresh water, the heavier one for cool salt. Just grab the right one and go! But I need to figure this first one out first.

 

[James79]

The Optimal Buoyancy Computer is a good tool, but making a weight check at your safety stop each dive will help a lot.

With an empty wing, about 500# in your tank, at 15', you should be.neutral. On a shore dive, I just place the excess weight in a game bag on the bottom, on a boat dive I hand it off to a buddy. After a while you can estimate the change and do it on the next dive, I keep a cheat sheet for different configurations and tanks in my logbook. You don't have to be perfect, but it's nice to know. I usually dive a little over to distribute my weight evenly, or for conditions.

To add to this, the way I use the buoyancy spread sheet is to back-fill it to make it accurate, then use it to adjust for changes.
For example, I filled it out including best estimates for things like personal buoyancy and got my estimated weighting. I then proper buoyancy checks at 15 ft with a 500 psi tank and handing lead back and forth with my buddy. I then took this info and adjusted the Buoyancy spreadsheet (keeping the known facts accurate and adjusting assumptions like personal buoyancy) to match what actually worked. That is now my new baseline, and if I dive in totally new conditions (suit thickness, salt or fresh water, different tanks) I can just change that one thing in the spread sheet and get a pretty damn close estimate.

But my advice is always worth what you paid for it! lol