DSS wing - not a donut - discuss

[Splitlip]

Anyway, I too have wondered if the "empty" bottom area of the horseshoe wing had any benefits over doughnut styles and would like to hear more if there is more...it seems like having the bouyancy of the top area and the lack of it on the bottom might actually make it easier to get/stay vertical or to purposely go face down for snorkeling back to shore/boat?

Splain it please. How can this benefit both vertical and horizontal (snorkeling)swimming. It would seem to me as soon as you went vertical gas would go to the top of what ever buoyancy devise you have.
If you want vertical, wouldn't you want a vest?
Am I missing something?
I swim on my back for the most part on the surface so maybe I don't get it.

 

[jim T.]

Hi Splitlip,
Sorry, I wasn't as clear as I meant to be.
I realize that the gas will rise to the top of the bladder/wing and that I would most often surface swim on my back but I wondered if Physically/hydrodynamically, it would be easier to adjust my attitude to vertical or "flip forward" for snorkeling without as much effort/water resistance against the bottom of a doughnut vs an open/"empty" area just under the surface on a standard horseshore wing? Would either design make the physical act of leaning back or leaning forward at the surface any easier for a tired diver in choppy surface conditions?

Hope I'm making this clearer... I'm just getting back into diving after a 20 yr. absence and having been used to the old backplate systems of the past, I want to go to bp system. I hate jacket b.c.d.s.

Thanks for your response! Jim

 

[cool_hardware52]

Tobin, exactly what was the design constraint that a zipper imposed on your single wings?

A zipper installed in the top arc of a wing, is straight "in the flat", and each side is of equal lenght.

This makes installation straight forward and easily repeatable.

Other choices were considered, such as sewing the wing shut, or using velcro. Velcro would have made the wing stiffer than I wanted in this location, and sewing the wing shut would allow no access to inspect or repair the bladder, so a zipper was installed.

Regards,


Tobin

 

[cool_hardware52]

I think that's a pretty good start.

IMHO, a bladder-less wing can be more streamlined and can be easier to vent than a typical inner bladder/outer shell type wing.

Hi Stephen,

This has not been my experience at all. First let me say single layer wings are a vaild manufacturing techinque, and good quality well performing wings can be made using a single layer. There are current examples of nicely streamlined single bladder wings, but I credit good design, more than materials.

The materials used for single bladder wings is typically nylon with a thin laminated layer of urethane on one surface. These materials do not stretch, or yeild on the bias.
These laminated fabrics behave more like "crinkly cellophane", than "compliant stretch wrap" Cellophane vs Stretch Wrap are somewhat extreme examples, but useful none the less.

Single bladder wings are RF welded. This welds the inner urethane layer together. RF welding is, in almost all cases a "Two dimensional" process, meaning the welding takes place in a flat plane.

Now consider what would happen if you cut two circles of cellophane, glued the edges together and then inflated the resulting "pillow"

You'd get a "Puckered" edge. The more you inflate, the deeper the puckers. Consider the typical lift bag, it's a 2D shape, welded around the perimeter, using a urethane coated nylon fabric, pucker city. Puckered edges don't seem streamlined to me.

It is of course possible to make "3D" shapes using this technique. To give the "pillow" volume and reduce the "puckers" an edge band can be installed between the two circles. The gussets, or expanding panels, seen in the edges of many BC's and some wings, are for this exact purpose.

There are limits however to the use of gussets. Each requires additional welding, and welding dies, and each end of the gusset results in a small point with more than two layers, these points can be problematic.

Sewn shapes using compliant fabrics offer greater freedom than welded shapes. Think about the fit of a wetsuit, vs a welded shell drysuit. The wetsuit is a perfect example of a sewn, compliant material.

It has been my experience that wings using sewn outer shells, and pure urethane inner bladders can achieve smoother final shapes than welded single layer wings. A soft, properly sized slightly stretchable inner urethane bladder, will vent easily.

Granted, they might be more prone to puncture

I really don't know, I just don't have enough data to say with conviction whether or not the single layer wings are more prone to puncture. Some of the laminated materials are very tough, but so are the "ballistic" nylons used for outer shells.

and once punctured repairing them might be... hmm... controversial?.. but... if you take reasonable care, they should hold up well.

In my opinion the single layer wings are more difficult to repair, the urethane layer one might apply glue to is on the inside, the single layer has to provide both structure and gas tight layer. In addition damage that cannot be repaired requires replacement of most of the wing, unlike a wing with an inner bladder.

Another advantage to this type of wing is that they pack much smaller than their inner bladder/outer shell cousins. If packing small is a concern, then these are really hard to beat.

I would agree here, single bladder wings can be lighter and pack smaller. Other advantages include no water trapped between the layers, and quicker drying.

Regards,



Tobin

 

[GreenDiverDown]

Hey Tobin,

My remarks were made as personal opinion only. I certainly have no experience with designing wings, nor have I done any comparison studies. It just seems to me, based on my experience with both bladder-less and inner bladder/outer shell wings, that my simple bladders are more streamlined. Perhaps, because the bladder-less wings are less bulky, they only seem that way.

I understand what you are saying about puckering and so forth, but my single layer wings don't appear to do that much... especially when they are only partially filled. I rarely have need to inflate them a whole lot. But you're right... the edges aren't perfect... well, not until after the sweet spot in a dive when the wing requires little to no inflation. At that point, it would appear that these wings become very slick. In fact, they become so flat that they almost disappear. My double layer wings won't do that.

Just sitting here, with both type of wings partially inflated, I can see that the profile of the inner bladder/outer shell is smoother than the single layer wing. But, the single layer wing is significantly less bulky overall. How that translates to being more or less streamlined is difficult to say. I can only go by how they feel to me when I dive.




As far as venting is concerned, again my comments were made from personal observation.... nothing scientific... just the way it seems to me.

 

[cool_hardware52]

Perhaps, because the bladder-less wings are less bulky, they only seem that way.

I think your right here, and I would add that both dedicated narrow single tank wings, and single bladder construction are fairly recent developments. Most earlier wings were double bladder construction. So if you are comparing an older double bladder design, to a more recent single bladder design you see the effects of both the materials used and the newer shapes.

I understand what you are saying about puckering and so forth, but my single layer wings don't appear to do that much... especially when they are only partially filled. I rarely have need to inflate them a whole lot. But you're right... the edges aren't perfect... well, not until after the sweet spot in a dive when the wing requires little to no inflation. At that point, it would appear that these wings become very slick. In fact, they become so flat that they almost disappear. My double layer wings won't do that.

Just sitting here, with both type of wings partially inflated, I can see that the profile of the inner bladder/outer shell is smoother than the single layer wing. But, the single layer wing is significantly less bulky overall. How that translates to being more or less streamlined is difficult to say. I can only go by how they feel to me when I dive.

I'm not sure what you mean by bulkly? Do you mean less frontal area? Less apparent volume? The volumes should be pretty close, that's all based on the displacement.

As far as venting is concerned, again my comments were made from personal observation.... nothing scientific... just the way it seems to me.

Closely matching the inner bladder to the outer shell helps wings vent better. Often the same bladder is used in a range of wing sizes, say 40-70 lbs. Welding dies cost money, and having more sizes increases the required inventory of bladders, so this practice is not uncommon. A 40lb shell with a 70 bladder can result in less than ideal venting.


Tobin

 

[GreenDiverDown]

Here are some shots of the two side by side. The one on the left is an inner bladder/outer shell. The one on the right is a single layer.

Sorry... the pictures might be a little misleading... but, hey, I tried! They also don't reflect what these wings would look like under water where they would be compressed. But what the heck.

Still, they sorta demonstrate what I described above. One definitely 'appears' more bulky and 'potentially' less streamlined.

In the first pic, the bladders are empty. In the second one, there is about two breaths of air in each. In the last photo, each wing is completely inflated. You can get a rough idea about the "puckering" of the single layer wing.

This is simply offered for discussion. I don't suggest that this proves anything!

 

[Humuhumunukunukuapua'a]

Closely matching the inner bladder to the outer shell helps wings vent better. Often the same bladder is used in a range of wing sizes, say 40-70 lbs.

Interesting. I hadn't thought about that.

Tobin, (and Patrick and any other wing manufacturers who want to chime in) do you use a different internal bladder for your 20/30/40 lb lift wing?

Thanks again for all the info.

Gregg

 

[cool_hardware52]

Interesting. I hadn't thought about that.

Tobin, (and Patrick and any other wing manufacturers who want to chime in) do you use a different internal bladder for your 20/30/40 lb lift wing?

Thanks again for all the info.

Gregg

Gregg,

We use the same bladder in our 30 and 40 lbs wing, 10lbs of lift is less 1/6 of a cuft or about volume contained in a cube about 6" on a side, not very much spread out over a wing.

We make specific inner bladders for all other sizes.

Tobin

 

[cool_hardware52]

Here are some shots of the two side by side. The one on the left is an inner bladder/outer shell. The one on the right is a single layer.

Sorry... the pictures might be a little misleading... but, hey, I tried! They also don't reflect what these wings would look like under water where they would be compressed. But what the heck.

Still, they sorta demonstrate what I described above. One definitely 'appears' more bulky and 'potentially' less streamlined.

In the first pic, the bladders are empty. In the second one, there is about two breaths of air in each. In the last photo, each wing is completely inflated. You can get a rough idea about the "puckering" of the single layer wing.

This is simply offered for discussion. I don't suggest that this proves anything!

Stephen,

I'd guess that what you are seeing is the outer shell of the sewn wing holding form, while the inner bladder would be much smaller. As you point out in the water the outer shell would take on the shape or volume of the inner bladder.


Tobin