BP/W - what's the go with air movement in the wing?

[ae3753]

Perhaps being so close to the surface also accentuated the issue.

Yes. Buoyancy changes in less than 30' are more abrupt than deeper. As the result, you have to manage your BC/lungs more actively.

I can't help but think that air would have a tendency to become trapped in one side, or the other, of a U shaped wing.

Trapped air is the result of wing width. A wide donut wing will trap air as much as a wide horseshoe wing.

There is one additional thought that I am having about weighting the rig. Many BCs and harnesses seem to have weights integrated into the side straps. While this seems the best for emergency dumping, I can't help but think that it is not an ideal location for trim. Certainly, having the weights forward of your back mounted wing would create a counter-lever effect and tend to pull you onto your face when vertical at the surface. A behaviour which has been experienced by many.

It would make more sense to me to have the weights actually strapped to the back of the tank or the backplate itself, situated right next to the wing.

What you're describing is "trim" weights. Some BCs (ex. Zeagle Ranger) have trim pockets in the location you describe.

For the BP/W set, the plate provides this effect. However, if you need more, there's additional weight plate (ala DSS) or many use weight pockets on the tank cam bands.

 

[drbill]

Certainly there are differences in the effect of the two wing types for divers who dive with nice horizontal trim and don't make many changes in depth. However, the only time I have nice horizontal trim is when I'm lying on the bottom filming (with little slope). Because I often go from horizontal to vertical (head-up or head-down depending) to film my subjects, there is no question that I can feel the difference between the two. For divers who are not filming critters like I do, it may make little to no difference. I haven't used either of my horseshoe wings in years.

 

[cool_hardware52]

Certainly there are differences in the effect of the two wing types for divers who dive with nice horizontal trim and don't make many changes in depth.

Changing depth in trim creates no special challenges for either a properly designed horseshoe, or properly designed donut wing.

However, the only time I have nice horizontal trim is when I'm lying on the bottom filming (with little slope). Because I often go from horizontal to vertical (head-up or head-down depending) to film my subjects, there is no question that I can feel the difference between the two. For divers who are not filming critters like I do, it may make little to no difference. I haven't used either of my horseshoe wings in years.

If you need to be heads down there could be an advantage to a donut, but again I'll point out that few choose to make butt first ascents.

Tobin

 

[gxtoast]

That is pretty much what I have found in both styles of wings.

Donut

Hi Saspotato, it is good to take a look at the wings in action. What brand is the Donut single wing in the image?

Certainly there are differences in the effect of the two wing types for divers who dive with nice horizontal trim and don't make many changes in depth. However, the only time I have nice horizontal trim is when I'm lying on the bottom filming (with little slope). Because I often go from horizontal to vertical (head-up or head-down depending) to film my subjects, there is no question that I can feel the difference between the two. For divers who are not filming critters like I do, it may make little to no difference. I haven't used either of my horseshoe wings in years.

Hi drbill, to me it makes sense for someone that is often changing position, especially with their head-down, to benefit more from a wing that has a lower arc that allows air to transfer from one side to another and find balance at the sides more easily.

Cheers,
Nick

 

[Sas]

Gxtoast, it is a Deep Sea Supply wing.

 

[drbill]

If you need to be heads down there could be an advantage to a donut, but again I'll point out that few choose to make butt first ascents.

Tobin

Tobin, I'm head down frequently when filming over tropical coral reefs where I can't plant on the reef without damaging the critters. Here on our rocky reefs, I'm often kneeling on the bottom with my head down to get the shot in some crevice. When I'm in those positions, it is much easier to more uniformly evacuate a donut wing using the lower dump.. doesn't work with a horse shoe wing unless I really contort myself before filming. I've tried several different wings of both kinds and I really notice the difference. I'm I'm not filming and I'm diving with primarily horizontal trim, it makes little difference.

Obviously you haven't been watching the OW classes at Casino Point much... LOTS of butt first descents (and a few ascents!).

 

[cool_hardware52]

Tobin, I'm head down frequently when filming over tropical coral reefs where I can't plant on the reef without damaging the critters. Here on our rocky reefs, I'm often kneeling on the bottom with my head down to get the shot in some crevice. When I'm in those positions, it is easy to more uniformly evacuate the wing using the lower dump.. doesn't work with a horse shoe wing unless I really contorts myself. I've tried several different wings of both kinds and I really notice the difference.

The specific needs of a "working diver" may be different from most. Hopefully most recreational divers won't be kneeling anywhere.

I'm I'm not filming and I'm diving with primarily horizontal trim, it makes little difference

This is the preferred attitude for most recreational BP&W users and the preferred attitude for ascents, where close control of venting is most important.

Tobin

 

[gxtoast]

Gxtoast, it is a Deep Sea Supply wing.

Ah, looks pretty slim. I've heard nothing but good things about the DSS gear. Same with the OxyCheq gear.

I am 70kg (154 lb), 170.5cm (5'7") and less than 5% fat. I will be diving with a one-piece 7mm dry-suit with hood and some kind of BP/w (probably a lightweight back-plate for travel) and either an Apeks XTX200/100/50 or the Apeks Flight. So, with this I would assume the 30 lb donut would be more than ample. Oh yeah, and some kind of steel tank. I would prefer a high pressure fatboy.

 

[cool_hardware52]

Ah, looks pretty slim. I've heard nothing but good things about the DSS gear. Same with the OxyCheq gear.

I am 70kg (154 lb), 170.5cm (5'7") and less than 5% fat. I will be diving with a one-piece 7mm dry-suit with hood and some kind of BP/w (probably a lightweight back-plate for travel) and either an Apeks XTX200/100/50 or the Apeks Flight. So, with this I would assume the 30 lb donut would be more than ample. Oh yeah, and some kind of steel tank. I would prefer a high pressure fatboy.

If you are using a buoyant 7mm suit I would recommend a Stainless plate. The dry travel weight of a SS plate vs a aluminum or Kydex plate is onkly about 3 lbs more.

The advantage is the ballast it provides up over your buoyant lungs.

Wing selection is a bit trickier without knowing the actual buoyancy of your suit.

Having said that very few 7mm suits for somebody your size will be more than 200 lbs buoyant. That makes a ~26 lbs wing a reasonable choice.

With most Steel tanks your rig will be about 18-20 lbs negative with a full tank, and will provide about 10-12 lbs of ballast with a empty cylinder.

If your rig is a max or -20 lbs a 26 lbs wing will float it at the surface.

If your suit is +20 at the surface it can only loose 20 lbs max at depth. That also makes a 26 lbs wing OK.

Tobin

 

[Bubbletrubble]

Having said that very few 7mm suits for somebody your size will be more than 200 lbs buoyant. That makes a ~26 lbs wing a reasonable choice.

@cool_hardware52: Is the typical buoyancy of a 7mm wetsuit about the same as a 7mm drysuit (without undergarments)? It might be pretty close...but I'm guessing that the drysuit could have some additional positive buoyancy due to the existence of some air on the inside of the suit. Just curious. I have zero personal experience with 7mm drysuits.