A drag issue : to bungee wings or not to bungee

[Randy43068]

I guess I look stupid when Im diving a single tank then, which is pretty much never because a snug bungee expels the air out much better than if it wasent on it. But as stated, were all individuals and have different methods for gettin er done.

I'd agree with you on how it looks. Nonsense on the elastic cord expelling air.. water pressure will do a better job of that.

Hey, it's your stuff, do what you want to with it.

 

[Randy43068]

Again, I don't see the need to wrap the wing in a bungee cord. I just don't.

 

[Lenaxia]

I like my BC to deflate faster. I don't add air willy nilly to my wing and when I dump, I dump most of the air because I'm ascending. I'm weighted well enough that if I have air in my BC at all, its a small amount and my lungs provide enough lift capacity in and of themselves for more then adequate attitude control.

I really don't get why any divers are crying about hydrodynamics or any of that other stuff. Frog kick is extremely inefficient from a hydrodynamic point of view. If you ever paid attention to how it's done, you slow down as you move your feet forward because guess what? There's more drag! Then your quick acceleration as you snap your feet back? Well guess what? Drag is squared proportionally to acceleration. That's even more drag that you are generating.

Slow mod-flutter? No acceleration drag, no excess drag from your feet spreading out and fins kicking out to the side. Does it take more energy? No, it doesn't, if you're moving at the same average speed as you were doing with your frog kick, you're using less energy, thus less air.



If your lung capacity isn't enough to overcome the bungees on your BC, I question whether you're fit enough to be diving. My Zeagle Brigade (Escape wing) has bungees but they aren't all that strong or tight; I have no problem inflating my BC orally after a hard workout (yes I have tried). Not only that, the bungees are only on the underside, thus don't trap air when I'm emptying it.

Both problems solved in my case, and the bungees provide the added benefit of emptying my BC faster. They also don't provide more turbulence because they are UNDER the wing and thus the upper surface of my wing is still smooth and the under surface is already turbulent from the water passing over and around my head and shoulders.

So what's the problem?

 

[stairman]

It comes bungeed from Dive-rite. It has tabs to run the bungee through and pull as snug as you want it. If your diving doubles then you take it off. I dive sidemount 99% of the time and to some it may look stupid as well as my truck and dog. Big deal! My wife thinks Im handsome so thats all that matters to me.

 

[LiteHedded]

I like my BC to deflate faster. I don't add air willy nilly to my wing and when I dump, I dump most of the air because I'm ascending. I'm weighted well enough that if I have air in my BC at all, its a small amount and my lungs provide enough lift capacity in and of themselves for more then adequate attitude control.

I really don't get why any divers are crying about hydrodynamics or any of that other stuff. Frog kick is extremely inefficient from a hydrodynamic point of view. If you ever paid attention to how it's done, you slow down as you move your feet forward because guess what? There's more drag! Then your quick acceleration as you snap your feet back? Well guess what? Drag is squared proportionally to acceleration. That's even more drag that you are generating.

Slow mod-flutter? No acceleration drag, no excess drag from your feet spreading out and fins kicking out to the side. Does it take more energy? No, it doesn't, if you're moving at the same average speed as you were doing with your frog kick, you're using less energy, thus less air.



If your lung capacity isn't enough to overcome the bungees on your BC, I question whether you're fit enough to be diving. My Zeagle Brigade (Escape wing) has bungees but they aren't all that strong or tight; I have no problem inflating my BC orally after a hard workout (yes I have tried). Not only that, the bungees are only on the underside, thus don't trap air when I'm emptying it.

Both problems solved in my case, and the bungees provide the added benefit of emptying my BC faster. They also don't provide more turbulence because they are UNDER the wing and thus the upper surface of my wing is still smooth and the under surface is already turbulent from the water passing over and around my head and shoulders.

So what's the problem?

there is no problem. your brigade and the dives you're doing with it aren't what we're talking about here

 

[Blackwood]

Drag is squared proportionally to acceleration.

Wait, so if I'm not accelerating there's no drag? Awesome, my life just got a whole lot easier.

In actuality, fluid dynamic drag is proportional to the square of velocity.

The power to overcome drag (i.e. accelerate) is proportional to the cube of velocity. That holds for whatever kick type you use.

What does that have to do with bungeed wings?

 

[Lenaxia]

Wait, so if I'm not accelerating there's no drag? Awesome, my life just got a whole lot easier.

In actuality, fluid dynamic drag is proportional to the square of velocity.

The power to overcome drag (i.e. accelerate) is proportional to the cube of velocity. That holds for whatever kick type you use.

What does that have to do with bungeed wings?

Good job. Way to nit pick. And I'm refering to parasitic drag, not profile drag.

This has to do with bungeed wings because people also argue that bungees over the top of the wing create turbulence and eddys in the water that cause more drag.

In the big picture though, you're already pretty crappy hydrodynamically and already moving so slowly that drag really doesn't matter.

I've never felt that a trilam drysuit provides significantly more drag over a form fitting wetsuit. If I were swimming at full speed, yes, but otherwise no. A bungeed wing isn't going to making things much worse. Just like that 7' hose around your neck doesn't add much either.

 

[Blackwood]

Good job. Way to nit pick. And I'm refering to parasitic drag, not profile drag.

This has to do with bungeed wings because people also argue that bungees over the top of the wing create turbulence and eddys in the water that cause more drag.

In the big picture though, you're already pretty crappy hydrodynamically and already moving so slowly that drag really doesn't matter.

I've never felt that a trilam drysuit provides significantly more drag over a form fitting wetsuit. If I were swimming at full speed, yes, but otherwise no. A bungeed wing isn't going to making things much worse. Just like that 7' hose around your neck doesn't add much either.

It's not nitpicky in the slightest. It's fundamentally different. Constant speed (which seems to be what you are describing with your flutter kick discussion) = zero accereration, so if drag were proportional to the square of acceleration, that would mean that there's no drag once you reach your constant speed (0^2 = 0). That's obviously wrong. Once you're cruising at a constant speed, drag = kick force.

In any case, my question was intended as: what does kick type have to do with this discussion?

Your post seemed to suggest that bungeed wings don't make sense for frog kick but they do for flutter kick, or something like that. It just seemed like an odd addition to the thread.

FWIW, I agree. Whether they create more or less has yet to be answered, but more than likely bungees will have an insignificant effect on drag.

 

[Lenaxia]

there is no problem. your brigade and the dives you're doing with it aren't what we're talking about here

While I'm aware a great deal of the discussion centers around significantly more technical diving than what I do, the two main reasons that are cited for not using bungeed wings are universal to all types of diving.

The two can be summarised as (or in more detail below in a quote from BAUE's site):
*Increased resistance to oral inflation
*trapped air in the BC

Both of these apply not only to tech divers but also to rec divers.

The use of bungied/bondage wings is strongly discouraged. To start with, one of the primary reasons stated for their use is that they streamline your rig. Ironically, they generally do the exact opposite. Hydrodynamics dictates that rough surfaces create increased turbulence which consequently increases drag. The bungies create a very rough surface and thus are adding to drag. Furthermore the bungies have a tendency to trap air which cause both static and dynamic instability issues. However these issues are not the most important reasons to avoid these wings. There are two large reasons that bungied wings are normally avoided. Probably the largest problem with bungied wings is the increased resistance to oral inflation. The bungies will make it significantly more difficult to orally inflate the wing, which can be a serious safety issue. A related issue is that the bungies create a stronger positive-pressure deflate than normally exists. So deflating the wing tends to dump air much faster than a non-bungied wing. This makes proper buoyancy control more difficult. And finally, due to this positive-pressure deflate, it is nearly impossible to use your BC as a "third regulator". This is somewhat of an advanced topic, however your BC can be used as an alternate regulator in very serious conditions. The deflate and inflate buttons are depressed simultaneously to provide air and then the diver breaths out their nose, or removes the BC inflator from their mouth when exhaling. It is important to note that you are not rebreathing the air in the BC, you are effectively breathing it straight from the BC inflator mechanism. Obviously you will want to practice this skill in a pool before trying it "for real"!

 

[The Chairman]

In addition to my TASAR I also carry a Sig .40 cal. I have never been shot with it,

Shenanigans. That's one of the biggest red herrings I have seen. You should contact IGFA and see if you set the record. You don't need to have been shot by it to understand it's lethality in terms of recoil, consistency, speed and other parameters, No, you would fire that weapon at a target in order to determine it's effectiveness. Would you feel competent (or compelled) to discuss it's merits if you had not discharged that firearm at least once?