Too much lift?

[tdallen]

I've seen several references to large wings recently, in the context of back inflate BC's (though I believe this question applies to a BP/W setup as well). Most of my diving is vacation/tropical, though I live in chilly New England so local ocean diving is a possibility. I'm a new diver, but I think I understand the differing lift requirements for cold vs. warm water diving. 20lbs of lift would be more than adequate for my warm water diving but I'd need more for local diving.

A one size fits all solution would be ideal. Bungied wing setups like the Zeagle Stilleto or ScubaPro Hydros Pro would fit the bill for a warm water travelable BC with adequate lift for most cold water diving as well. But, I've seen the criticisms of setups like this - too large a bladder/wing, too much lift, etc. Even BP/W owners refer to having multiple wings...

Is it unrealistic to think that one setup could work well for recreational single tank diving in both warm and cold water?

 

[arew+4]

Get a dry suit for local, and ditch your warm water wing when using it.

 

[ronscuba]

A 30 lb wing is a good compromise for single tank warm and cold water. However, you might want rent a BCD and do some local dives to decide whether or not you enjoy cold water local diving enough to let it affect your buying decisions.

I live in NYC and mainly did warm water tropical. Did several local dives with friends and found local diving uninteresting. I ended up selling my 30 lb wing and buying a 17 lb wing which is perfect for warm water tropical.

 

[2airishuman]

I have two single-tank wings, a 17# and a 30#.

In reality, when properly weighted, either one will work OK for warm water dives or cold water single-tank dives.

With 7mm it's important to be weighted for neutral buoyancy at 15' at the end of the dive, which depending on how much air you bring may leave you somewhat buoyant at the surface at the beginning of the dive. So you have to do a "duck dive" to descend. There is risk that if you make a mistake and are overweighted you won't be able to become positively buoyant without ditching weights.

But then again I don't find that there is a noticeable difference in streamlining/drag between the 17 and the 30.

My advice would be to just buy a 30 and dive that.

I dive a BP/W so it's easy and relatively inexpensive to change the amount of lift.

 

[REVAN]

Few divers seem to really pay much attention to equipment drag. The default position will then fall toward getting the big wing. That doesn't mean that there is no difference though.

I haven't done any measurements for a 17 pound wing, but the difference in drag between a 40 pound wing and a harness without a wing is about 40% for the equipment alone, and about a 20% difference for the diver with equipment as a total. As a WAG, you might be looking at about an 8 to 10 percent overall difference for a 30 over a 17. It's not huge, until you hit that current that makes your performance a big deal. Then there is the rest of the time where you just get an extra 3 or 4 minutes of bottom time for working a little less hard to swim throughout your dive. Again, not a big deal unless you find yourself in a situation where you'd really like to have a few extra minutes.

It's all a trade. You can be a little more efficient at the expense of paying a little more attention to weighting details when diving in cold water, or just use a big BC to let yourself be inattentive to weighting details, or possibly use it to start diving multiple tanks in cold water environments (if the harness supports it).

 

[ronscuba]

In addition to drag, smaller wings pack smaller for travel and vent easier.

Towards the end of the dive you will have less air in your BCD. Let's say you have 5-10 lbs of air in the bladder. That is going to vent a lot easier in a 17 lb wing than in a 30. With my Oxy 30 and Dive Rite 25 wing, I had frequently had to position myself vertical and tilt my left shoulder up.

There is some debate that a few wing manufacturers are using larger bladders from their medium size wings and just inserting them in a smaller shell for their smaller wings.

 

[decompression]

With a big wing, drag is an issue but more important is something called Dynamic instability. This is affected by both small and large amounts in the wing. With a small amount of air in a large bladder the wing tends to "taco" and makes trim/buoyancy and deflating difficult. A larger amount of air (often from overweighting) compounds this issue of air movement and results in a very unstable platform.

 

[tdallen]

With a big wing, drag is an issue but more important is something called Dynamic instability...

I've experienced that. How much does a bungied setup on the bladder help?

 

[REVAN]

Get a dry suit for local, and ditch your warm water wing when using it.

Actually, you can ditch the wing for warm water diving also. I used to dive dry like you described. Now I dive warm water without a BC and love that even more. IMO, it makes for the best warm water diving when you get the details worked out and traveling is super lightweight, compact and easy (not to mention saving a couple hundred dollars on your gear). The biggest problem is that almost no one knows how to dive this way anymore, and most will say that it can't be done, is too dangerous or just plain stupid... none of which is true from my perspective. What is true is that you will have a near impossible time finding someone to train you for the techniques, which may leave it up to the individual to figure it out on their own. For sure, it will help if you are starting out as a good swimmer and have some basic freediving skills.

Bottom line, going with a harness and a DS is a viable option. Then just ditch the DS for warm water. Given the expense of a DS, I may be just as inclined to dive a 7mm freedive suit in cold water and use a 17 pound lift BC on the dives where it will benefit. Then for warm water I would still have the option of going with or without the BC. I'd go without the BC in 95% or more warm water situations and only pull it out when there was something unusual about the planned dive that would make it necessary for me to have it.

 

[stuartv]

In reality, when properly weighted, either one will work OK for warm water dives or cold water single-tank dives.

I'm not so sure a 17# wing is a good idea for cold water diving.

If you are properly weighted and diving a 100, you'll start the dive around 8# negative. If you're wearing a 7mm wetsuit and dive past 100' (just for example), I think suit compression could easily lose you 10 # of buoyancy. At which point, a 17# wing would not even be able to hold you up off the bottom.

Diving an AL80 is only 2# better. If your suit loses 12 # of buoyancy, you're in exactly the same situation.