A drag issue : to bungee wings or not to bungee

[Dr Wu]

The bungee's are there to make the profile of the wing smaller

You misspelled the words "profit" and "larger".

 

[Tortuga68]

Over weighted? No

No, you are not overweighted

So we agree I'm not overweighted, great

Again, though, what problem do I have in my non-bungee wings that you are solving with your bungees?

No-one is telling you to switch. In fact quite the opposite, if you have factual reasons not to use a bungee wing in non-OH, let's hear them

yeah, it isn't going to kill you or anything

At least two other people have implied it will in this thread

 

[Garth]

+1

i have real work to do.

not sure why i poked my head into this thread to begin with... been having this discussion for longer than i've been diving...

how have you been having this conversation longer than you have been diving. I don't think that helps your argument lending information that you were against bungee'd wings before you could even understand (or not understand) why they wouldn't work.

If what all of you are saying is true about the bungees forcing air out... then why do I have to put my inflator above my wing while pushing my exhaust to get air out? If the air would be pushed out like everyone has suggested then I would just have to push the exhaust... see what I mean or do I have to reword this.

 

[Blackwood]

Sigh.

Sooooo .. If I went for a dive with that equipment and had a great time and posted about on here, something would "happen" ?

Nothing is likely to happen in the water - that's statistics. Something akin to this thread may "go down" on scubaboard, but only if you post about it.

insecure divers tend to demean others and their gear selection, citing fallacious arguments, non-existent data and mythical studies. They have a hard time seeing that their criteria for selecting gear may not be the same criteria used by others. Go figure.

I think this statement by netdoc applies to you Blackwood

I think you're intentionally misinterpreting my statement because you're riled up. I really can't bring myself to believe that you honestly think that I was suggesting posting something on scubaboard will lead to an ex-post-facto dive injury.

 

[Rainer]

Sigh.

Further evidence of your obvious insecurities.

 

[Blackwood]

Looooooooooooooooooooooooooooove meeeeeeeeeeeeeeee

 

[PfcAJ]

I don't see where the mystery is here. The bungees constrict the wing (otherwise, why would they be there). Bungees force air out (as stated on OMS's website).

All that is just fine UNTIL some other part of your wing breaks. OPV is always a good one. They do stick open from time to time, unscrew, or otherwise come apart. Same with the corrugated hose. If it can break, it will break at some point. If none of these items ever failed, we wouldn't need redundant buoyancy to begin with.

So if the opv sticks open...and your bungees force air out of your wing... where are you going to go? The answer is to the BOTTOM. This is especially bad if you're on deco (tox/drown), in deep water (drown) or diving heavy tanks (drown). It might be funny in the pool, but its a real problem if you're in the ocean (thats the OW example you need) and its a real issue in a cave, too.

So, in conclusion, if the bungees create a bad situation that wouldn't exist without them...why take them?

 

[Tortuga68]

I remember back in around 1998, when we strarted seeing alot of "techdivers" using huge massive wings...

...One of the big things Halcyon began in the late 90's, was talking about how you DID NOT want all this monstrously excessive lift..that it was really dangerous if you had a runaway inflator problem...

...we would use a technique known as "Blow and Go". With everyone there, we all signalled ready, and we all FULLY INFLATED ...You would ROCKET to 100 feet...

...The deal for this thread, is that a big honking BC that has way more lift than you need, can rocket you to the surface so fast you won't even know you are on the way to the surface , until you get there !!!...

...We wanted "enough lift"....not alot more than enough....and with the end of blow and go, which fell out of favor soon after this incident, we were always "swimming" ourselves up from depth, never taking an elevator ride from the bc or wing

Interesting story - albeit unrelated to bungees - thanks for sharing it

Although I would have thought the moral was 'don't blow and go' rather than 'don't use a massive wing'

If you were trimmed out at the time rather than "FULLY INFLATED", wouldn't you just disconnect the inflator hose?

 

[Tortuga68]

Bungees force air out (as stated on OMS's website)

There's a difference between forcing air out and rapidly forcing all the air out. Bungees also trap air, remember?

All that is just fine UNTIL some other part of your wing breaks...If none of these items ever failed, we wouldn't need redundant buoyancy to begin with

So, use your redundant bouyancy?

So if the opv sticks open...and your bungees force air out of your wing... where are you going to go? The answer is to the BOTTOM. This is especially bad if you're on deco (tox/drown), in deep water (drown) or diving heavy tanks (drown)

Don't you wear fins?

 

[AndyNZ]

..... why are they both called fluid dynamics?

Because both water and air are fluids - but they have wildly different fluid properties in terms of say, viscosity.

Compare the relative ease with with supersonic flight is achieveable, witht the relative difficulty of a boat doing the same....which in essence is a boat having to overtake it's own bow wave.

The velocity of the fluid movement is also a major issue - essentially we are worrying about the transition from laminar to turbulent flow. At the speeds a diver can propel themselves through the water, it's unlikely that the flow over a bungied wing will in fact be turbulent. In which case, the "uneven" surface of the wing may in fact assist in reducing drag.due the relative "blunt" shape of a diver. The reason a golf ball has an uneven surface is to push the point where boundary layer separation occurs to further behind the ball and hence reduce drag.

Don't get me wrong, I think bungied wings are a POS. But there is no "science" in putting a wing into a wind tunnel. You're better off putting it into a water tunnel.

The reason I think that bungied wings are POS doesn't really have anything to do with drag, it's all their ther faults. The "lumpy" feeling of air moving around inside, the ability to trap air unintentionally, the difficulty in orally inflating them at depth and so on.

Though I would be curious to see the change in drag - a real experiement would include the diver and tanks as well. I suspect the overall difference between bungied and non-bungied wings would actually be quite small.