Size of wing in relation to carried weight?

[Ob1Stogie]

Just so I understand what size wing I need, I should get a bag that will offset the negative boyancy weight of my tank and the carried weight of my lead?

If so, my Faber 104 is roughly 10lbs negative at the start of a dive, and I carry 22lbs of lead (which will go down with my new BP/W set up). So, I need at least 32lbs of lift?

 

[cerich]

How positive is you exposure protection (Dry or wet?)

 

[cool_hardware52]

Just so I understand what size wing I need, I should get a bag that will offset the negative boyancy weight of my tank and the carried weight of my lead?

If so, my Faber 104 is roughly 10lbs negative at the start of a dive, and I carry 22lbs of lead (which will go down with my new BP/W set up). So, I need at least 32lbs of lift?

Ob,

Any BC, including a wing needs to do two things:

1 Float your rig at the surface without you in it

&

2 Compensate for the loss or potential loss of buoyancy of your exposure suit.

First consider proper weighting. For single tank diving in the local fairly cold waters of SoCal I'll assume you are using a 5-7 mil wetsuit or a Drysuit.

I like to set my total weighting for single tank diving in a 5 mil or greater wetsuit so I'm eyelevel at the surface with no gas in my wing, and a full cylinder. I can easily hold my 15 ft or even 10 ft stop with a near empty cylinder becasue my wetsuit has compressed and lost significant buoyancy from the surface to 15 ft.

The weight of your rig is easy to estimate. Plate + Full Tank(s) + regs + can light + any additional ballast (weight plates or weight pouches) attached to the rig. Just add it up.

Tank (HP100) ~-8 lbs
Plate -5
Reg -2
Can Light -3
Weight Plates -8
Total -26

If you are using a wetsuit you can determine the initial buoyancy by rolling it up, throwing it in the pool and adding weight until it just sinks. This amount of weight represents the max your suit can loose, and you need to go to ~ 165 to zero out neoprene. Average 5 mil full suit 18-22 lbs, 7 mil 20-26. Suits vary quite a bit, different Neoprene, age etc.

Dry suit are a bit different. I like to put the diver in his under garment and DS in the pool with minimum air in the suit in the pool, add lead until the diver is neutral. This represents the max buoyancy the diver can loose in a total suit flood. Total floods are rare, but possible, and some undergarments compress less than others, but this process sets a max possible loss of buoyancy.


Which ever weight is greater determines the minimum lift required, i.e. the weight of the rig, or the initial buoyancy of the exposure suit.

In cold water it is very seldom the weight of the rig, almost always the exposure governs the minimum lift.

In warm water, and thin exposure suits it can be more often the weight of the rig.

Tobin

 

[cerich]

Much be nice to obviously know how to type correctly Tobin, here I was going to lead him into it and there you go and teach a course!

 

[Humuhumunukunukuapua'a]

LOL...I saw that you had posted a reply to this one, Tobin, and I knew what it would say. You have this reply memorized yet?

Tobin's advice is great, and you can find it in many other threads discussing this topic. See "Similar Threads" at the bottom of this page for more discussion of wing size.

If, perchance, you're looking at the DSS 30 or 40 LCD wing, as many on this board are on any given day, I'd say just get the 40. It isn't appreciably larger, and it'll give you an increased margin when at the surface, which is always more comfortable. The 40 is a tiny wing for its lift.

Cheers

 

[Ob1Stogie]

Thanks for the course guys, where do I send the check?

 

[kidspot]

I had forgotten about recalculating the rig weight recently when I got rid of my weight belt and put all the weigh on my rig (along with switching to a thicker suit in the process) I went diving on Monday and figured I'd gear up inwater for the second dive - I inflated the wing 27# Pioneer) and tossed it overboard... then watched it slowly begin to sink ... oops... that used to work before I added the extra weight LOL. fortunately it was only about 20ft deep there, but boy was it hard getting down 20 ft in a 5mil with no weight belt In other words... being able to support your rig can be rather important after all!

 

[Doc Harry]

Thanks cool_hardware52

Nice explanation. I was going to ask the same question that Ob1Stogi0e asked. I'm adding more gear and changing tanks and wondering how to calculate if my current bladder was of sufficient size. I got my answer!

Thanks again.