Nice and simple question about wings

[OneBrightGator]

I'm sorry Bob, but I just don't understand that. My line of thinking is identical to Spectre's, so a trilam drysuit would actually require less lift then a wetsuit, and unless you're using wickedly huge cylinders I don't see how a 30lb. wing would not be adequate.

 

[MXGratefulDiver]

I'm sorry Bob, but I just don't understand that. My line of thinking is identical to Spectre's, so a trilam drysuit would actually require less lift then a wetsuit, and unless you're using wickedly huge cylinders I don't see how a 30lb. wing would not be adequate.

On my singles rig I usually dive either an E8 119 or a Faber LP95. The trilam suit doesn't add buoyancy ... but the air required to keep the undergarment warm does. Even though I use minimal air in the suit, what I do use cannot be considered any less buoyant at depth than on the surface, since you have to add air to the suit as you descend in order to maintain adequate loft for warmth. I weigh roughly 250 lbs (without my scuba gear), and wear 18 lbs on a weight belt.

In theory, Spectre's thinking makes sense. I'm a big believer in experimentation and empirical data, however. In my case, the 30# Venture wing simply wasn't adequate to keep my head above water (when fully inflated) on those long surface swims. The 45# Oxycheq is.

... Bob (Grateful Diver)

 

[Spectre]

*shrug* I don't buy it. I mean, you know what works for you, but I'd be surprised if you didn't find out that you are actually a little overweighted.

 

[lamont]

the other thing that you need a wing to do is float your gear at the surface, that means you need enough lift to offset the negative buoyancy of tank, plate, can light and any trim weights or ACB system.

and if you've got a wetsuit you need to be able to get yourself slightly positive with a full tank of gas and your wetsuit totally compressed at depth.

those are probably the two major considerations for how big a wing *must* be.

but i think i'm with bob -- i like it when my 40# wing is fully inflated at the surface -- less would be annoying, and in severely rough circumstances might be more dangerous... (and i might be overweighted by a pound or two, but i've only got 10# on my weightbelt, so it isn't much).

 

[MSilvia]

the other thing that you need a wing to do is float your gear at the surface, that means you need enough lift to offset the negative buoyancy of tank, plate, can light and any trim weights or ACB system.

Uhh... not the way I understand it. If you have to offset all that negative bouyancy with a wing, you have too much negative bouyancy for the exposure protection you're using. Your tank, plate, can light, and trim weights should be offsetting the positive bouyancy of your other gear, not overweighting you. If you're negative with that stuff, you might consider switching to an aluminium backplate and finding other ways to adjust your trim.

I've got to go along with Spectre and OBG on this one... if you aren't over or under weighted, you should be neutral at the surface (or 15 fsw, in which case you'd be slightly bouyant at the surface) with 500 psi in your tanks, right?

Really, you shouldn't need to have much gas at all in a BC of any size to be bouyant at the surface... only enough to offset the weight of your breathing gas. Unless your single tank is 30 lbs more negative when it's full than when it's nearly empty, an extra 30 pounds of bouyancy added to your presumably neutrally bouyant rig should be way more than enough to float you like a cork.

If it doesn't, the only two conclusions I can come to are either that you aren't neutrally bouyant, or you somehow have a magical exemption from the laws of physics.

Either way, if you're 30 lbs negative at the surface, I'd hate to think what would happen if you had a bc/wing failure at depth. (Good thing you dive dry!)

 

[lamont]

Uhh... not the way I understand it. If you have to offset all that negative bouyancy with a wing, you have too much negative bouyancy for the exposure protection you're using. Your tank, plate, can light, and trim weights should be offsetting the positive bouyancy of your other gear, not overweighting you. If you're negative with that stuff, you might consider switching to an aluminium backplate and finding other ways to adjust your trim.

No, I'm talking about throwing your gear into the water without you (and the positive buoyancy of your exposure protection) and that you should still be able to float it with the wing.

 

[MXGratefulDiver]

Uhh... not the way I understand it. If you have to offset all that negative bouyancy with a wing, you have too much negative bouyancy for the exposure protection you're using. Your tank, plate, can light, and trim weights should be offsetting the positive bouyancy of your other gear, not overweighting you. If you're negative with that stuff, you might consider switching to an aluminium backplate and finding other ways to adjust your trim.

I've got to go along with Spectre and OBG on this one... if you aren't over or under weighted, you should be neutral at the surface (or 15 fsw, in which case you'd be slightly bouyant at the surface) with 500 psi in your tanks, right?

Really, you shouldn't need to have much gas at all in a BC of any size to be bouyant at the surface... only enough to offset the weight of your breathing gas. Unless your single tank is 30 lbs more negative when it's full than when it's nearly empty, an extra 30 pounds of bouyancy added to your presumably neutrally bouyant rig should be way more than enough to float you like a cork.

If it doesn't, the only two conclusions I can come to are either that you aren't neutrally bouyant, or you somehow have a magical exemption from the laws of physics.

Either way, if you're 30 lbs negative at the surface, I'd hate to think what would happen if you had a bc/wing failure at depth. (Good thing you dive dry!)

Yeah, I'm sure you're right ... despite over 1,000 dives worth of experience and experimentation, I MUST be overweighted.

Funny, even my GUE instructor didn't pick up on that ... when we did the weight check, I checked out about right ...

... Bob (Grateful Diver)

 

[MSilvia]

when we did the weight check, I checked out about right ...

No offence intended Bob, and I don't mean to call your skills or experience into question. I'm sure you know what you're doing, and I'd be VERY suprised to find out you (or any other experienced diver) were 25+ lbs. overweighted. That said, I'm having a lot of trouble understanding how it's possible for you to simultaneously be properly weighted and unable to be supported by 25+ lbs of positive bouyancy. In my experience, it's awfully difficult for me to sink or even swim down with that much flotation at the surface.

Is it a matter of positioning in the water (head more elevated, etc) that makes the larger wings more comfortable, or do you really sink (as opposed to flip over or something like that) if you don't kick? If it's the latter, there's definately something about the situation that I'm completely failing to wrap my head around, which is probably the case since you have many times more dives logged than I do. I'd just like to understand what it is that I'm missing.

It sounds to me like you're saying that you sink when you add bouyancy to a neutral rig, and I hope you can see why I have trouble with that.

 

[PatH]

Well, the way if figure it, if you had a BC of 30# lift and you inflated it completely, hung a 35# weight on it and put it in the water, it'd sink. Or if you put a 30# weight on it, it would be neutrally buoyant at the surface.

Close, but you're ignoring the displaced volume of the weight (admittedly small for high density objects like weights! ;-) )

 

[MXGratefulDiver]

No offence intended Bob,

None taken ... don't mind my sarcasm, I'm having a bad hair day (those who know me will find humor in the concept) ...

Is it a matter of positioning in the water (head more elevated, etc) that makes the larger wings more comfortable, or do you really sink (as opposed to flip over or something like that) if you don't kick? If it's the latter, there's definately something about the situation that I'm completely failing to wrap my head around, which is probably the case since you have many times more dives logged than I do. I'd just like to understand what it is that I'm missing.

It sounds to me like you're saying that you sink when you add bouyancy to a neutral rig, and I hope you can see why I have trouble with that.

Yep, it's something I've given a lot of thought to, and haven't quite been able to explain ... as I said earlier, in theory I agree with what y'all are saying. There's a big discrepency between theory and practice in this case.

Yes, with the 30-lb wing I would literally sink too far into the water to effectively surface swim (keeping in mind that, out here at least, the preferred method is to swim on your back) ... my head would be submerged up to my ears, and my face barely out of the water. With even the slightest waves, breathing became an issue.

With the larger wing, I'm able to keep my body positioned properly and surface swim comfortably.

When diving I have almost no gas in either my wing or my suit ... and to hold my 10-foot stop I have to squeeze it all out (literally). So I don't think overweighting is the issue.

That said ... I just made arrangements to try Tobin's 30-lb wing. He's shipping it tomorrow. So one more data point ... we'll see what effect a different configuration wing will have on the subject.

... Bob (Grateful Diver)