Do you hate BP/ wing arguments?

[MSilvia]

Most people have to learn what horizontal is before nit picking.

Yeah... most do, and they have bigger obstacles to overcome than equipment induced drag. For the rest of us though, it makes a difference.

In my case, first hand experience was enough to convince me. If that isn't verifiable enough for you, I'm okay with that.

 

[Keysdrifter454]

It's not gross speculation, it's simple math.

Then show us this simple math.

I think the advantages due to streamlining are shared with most other back-inflate systems.

Then we agree.

There isn't any automatic drag decrease to assume with a backplate.

Whatever decrease there may be, has never been quantified.

What was your point?

BTW, what discipline makes all the decreased drag claims?

 

[Keysdrifter454]

Yeah... most do, and they have bigger obstacles to overcome than equipment induced drag. For the rest of us though, it makes a difference.

In my case, first hand experience was enough to convince me. If that isn't verifiable enough for you, I'm okay with that.

My first hand experience apparently didn't have the same effect.

Or maybe my previous gear choices were better.

But a little open minded speculation raises questions about the party line speculation.

 

[David K]

It should be pointed out that slight changes in drag via weight, accessories, air in wing or drysuit, etc., etc., etc. will not produce a measureable change in air consumption.
--Matt

Slight is relative, from personal experience I can tell you that carrying an extra 5lbs of weight when its not needed will cause a measurable increase in your SAC rate.

David K

 

[MSilvia]

Then show us this simple math.

Again, I'm no physicist, but I believe drag force in water is equal to the cross-sectional area of the object, multiplied by 1/2 the product of the density of water and the squared velocity of the object, multiplied by the drag coefficient of the object.

I don't have access to a wind tunnel for calculating drag coefficients, but assuming a sphere with a radius of 10cm and a drag coefficient of 0.44 moving at 1 meter/second through water at 4 degrees centigrade, it would look something like this:

Drag force=314cm^2*(1/2*1000kg/m^3*1m/s)*0.44

 

[matt_unique]

I'm an advocate for streamlining. The physics makes sense to me, seems very straight forward. It just seems silly to me when people make such a big deal about tiny differences in drag. Especially if we're talking about a slight difference in air volume in a wing, drysuit, etc. If I do dive 1 with X pounds of lead for 30 minutes lets say I burn through 1300psi of air. If I do dive 2 with X + 5 pounds of lead I still use 1300 psi of air. It does not make one bit of difference on the big picture, in my example air consumption, because the difference in resistance/work load/etc. is so tiny.

Do dive 1 with your regular weight and no reel. Then add 5lbs and a reel for dive 2 for example. You will not see a change in your air consumption.

As another example....do you adjust your SAC rate for deco dive planning based on the size of your stage bottle? Reels? Lights? Of course not....

--Matt

 

[DeWDiver]

Although I usually don't respond to most post, check my history, this one intrigues me.

First, I dive a Ranger and have never tried a BP/W set up. My thoughts are if someones on this board asking about a BC they probably know about BP/W. So quit beating the dead horse and answer the question that were asked about the BC. If they wanted to know about BP/W they would ask. Seems simple enough to me.

Now for the drag topic. Being an engineer, it seems very silly for people to assume a BP/W is less of a drag. Drag is not mearly to Cd times area formula previously stated. There is this and other types of drag involve including that cause be wetted area. So lets say a stab jack adds some to a persons diameter. True but it adds very little to wetted area. A wing on the other hand adds quite a bit more to the wetted area. Also, in less tech terms, the stab jacket is more or less in the slip stream produced by the rest of the body, a Wing is not. Let's not forget those massive drag inducers, fins and kinking legs. So even a wind tunnel/ tow tank might not answer the question unless there is motion of the legs and fins. Finally as already stated early, those tech divers, who I do admire for there skills and experience, are toting around more drag inducing items, (ie stage bottles, how about those camera rigs some have) than any BC or BP/w could possibly generate.

Just a thought.

 

[Keysdrifter454]

Although I usually don't respond to most post, check my history, this one intrigues me.

First, I dive a Ranger and have never tried a BP/W set up. My thoughts are if someones on this board asking about a BC they probably know about BP/W. So quit beating the dead horse and answer the question that were asked about the BC. If they wanted to know about BP/W they would ask. Seems simple enough to me.

Now for the drag topic. Being an engineer, it seems very silly for people to assume a BP/W is less of a drag. Drag is not mearly to Cd times area formula previously stated. There is this and other types of drag involve including that cause be wetted area. So lets say a stab jack adds some to a persons diameter. True but it adds very little to wetted area. A wing on the other hand adds quite a bit more to the wetted area. Also, in less tech terms, the stab jacket is more or less in the slip stream produced by the rest of the body, a Wing is not. Let's not forget those massive drag inducers, fins and kinking legs. So even a wind tunnel/ tow tank might not answer the question unless there is motion of the legs and fins. Finally as already stated early, those tech divers, who I do admire for there skills and experience, are toting around more drag inducing items, (ie stage bottles, how about those camera rigs some have) than any BC or BP/w could possibly generate.

Just a thought.

Kudos.

 

[gfisher4792]

Yeah, I do hate the BP/W arguments. I have a BP/W and I like it just fine. If someone is comfortable and happy with their stab or back inflate or what have you, that's fine with me too. Won't stop me from diving with them.

In other words, the arguments (as opposed to the honest fact/opinion gathering discussions) and vehement opinions (from both sides) are pointless and a waste of time. Just dive.

 

[Rick Inman]

When I first took the blue pill and fell into this board, I remember seeing thread titles that looked interesting,like, "Pony Bottle or Not?", and thinking, yeah good question. Then, when I went to the thread, all there would be is page after page of arguing and name calling about the question being asked in the first place. So, maybe I would post, "What about the pony bottle?", and the replies would be something like, "do a search, moron!"
If you're sick of these questions, find another one - there are plenty. Or (heaven forbid) think of a better one and start your own thread. In the mean time, the question was geared to those who have tried both BC Jackets and PB/wings and prefer the Jacket. And "why". Could be an interesting topic for those interested.
Personally, I like my BP/wing because it is such a vintage idea, and reminds me of when I dived as a kid in the mid 70's. I loved my AtPac.