Looking for a BC??

[Tanked Monkey]

Uh oh. Here we go again.

My advice to rovendiver: try out the BC's you're leaning toward and try out a BP/W to see for yourself. Give them all a fair chance. I'm glad I did when I bought my first rig.

Mike

 

[-hh]

Uh oh. Here we go again.

Sorry 'bout that.

Matt's in Washington Twp, which is ~45 minutes south of me in NJ. Its probably going to be hard for me to find the free time this summer, but if he's going to be up this way, I'm game to finding the time to toss him into my diveshop's pool with my gear + Nikonos and see how he floats in it and what he suggests to get the system's surface float balanced out better. Naturally, it will be done with no fins on and with fingertips breaking the water's surface, so as to limit the energy exertion. If we do get a time, someone please also remind me to bring along one of my doublehose regulators...they're an experience too.

My advice to rovendiver: try out the BC's you're leaning toward and try out a BP/W to see for yourself. Give them all a fair chance. I'm glad I did when I bought my first rig.

Agreed. Its always a good idea to try out various products before committing to buy.

The trick is to recognize hype for what it is, and to strive to really understand what exactly is being traded off between the different products' designs and the implications thereof. All products have comprimises in them somewhere, since there's no such thing as a free lunch. For example, the best BCD for a face-up surface float orientation is an old horsecollar (been there, done that).


-hh

 

[jonnythan]

-hh, I will disagree with you and agree with mx.

Back-inflate BC's have, in my experience, no real tendency to push you forward on your face. It's a lot of BS and new divers would be better off not listening to such rubbish.

 

[halocline]

Rovendiver, you might try to rig a crotch strap on your current BC; that'll keep it from riding up when you're at the surface (or any other time). Regarding what to buy, the most likely scenario is that you'll eventually want to try a few different things out as you get more diving experience. As someone posted, it usually takes several dives in open water to really get to know a given BC set up. With that in mind, if you can try the zeagle zena in a pool and it seems comfortable to you, it's a good "risk" to buy it because unless you're really an odd size, it will retain excellent resale value. You could dive it for a season or two; if you still like it, terrific, if you don't you won't be stuck with it. This is a nice thing about zeagle BCs. I also wouldn't worry about the "face forward when floating" worries; most people who have a back inflate BC or BP/wing set up adjust well to floating with it, and they really are more comfortable under water.

 

[-hh]

Back-inflate BC's have, in my experience...

Our experiences differ.

Please do note that not all Back-inflate BC's come with 6lb SS backplates or keel weights...my rig has neither, and its surface orientation gets accentuated by my negatively buoyant Nikonos V with dual SS-200's that's held in front of me.

Yes, I could go to SS and/or a keel weight, but as I alluded to, it won't exactly be a lightweight rig suitable for dive travel.

Everything's going to have a trade-off in it somewhere, and the general conclusion that I'm coming to is that a warmwater UW photographer doubly needs a lightweight travel BC because of transporting his camera gear, and that BC probably shouldn't be of the back-inflate style.

If you wish to differ, come on down to NJ and I'll toss you in a pool with my gear & camera rig. My old college roommate used to teach at RPI, so I know that its not too long of a drive.


-hh

 

[jonnythan]

Our experiences differ.

Please do note that not all Back-inflate BC's come with 6lb SS backplates or keel weights...my rig has neither, and its surface orientation gets accentuated by my negatively buoyant Nikonos V with dual SS-200's that's held in front of me.

Yes, I could go to SS and/or a keel weight, but as I alluded to, it won't exactly be a lightweight rig suitable for dive travel.

Everything's going to have a trade-off in it somewhere, and the general conclusion that I'm coming to is that a warmwater UW photographer doubly needs a lightweight travel BC because of transporting his camera gear, and that BC probably shouldn't be of the back-inflate style.

If you wish to differ, come on down to NJ and I'll toss you in a pool with my gear & camera rig. My old college roommate used to teach at RPI, so I know that its not too long of a drive.


-hh

I dove with a regular back inflate BC before my bp/wing. I'm OK with our experiences differing.

 

[Rovendiver]

Hey hh

You have supplied some serious eye opening :11: information. I am a little confused but it does help me understand what people are talking about when they tell me back inflate tend tip you forward.

In engineering terms, this is because of a Moment force (think "torque"), and the only way to reduce it is to either get rid of the BC & weights (not possible), or to decrease the distance ("Moment Arm") between the two by moving the two forces closer together.

The common techniques to minimize this Moment Arm with a Wing include:
- use the heavier SS backplate
- add a lead keel weight
- use steel tanks
- & with a STA (since this displaces your St tank rearward another inch or so)
- add a lead weight onto your BC's tank strap
- locate your weightbelt weights along the small of your back instead of in front.

What you'll notice is that all of these remedies involve moving weight backwards. This is because you can't move the BC bladder forwards without the BC...by literal definition...ceasing to be a Wing and becoming a Jacket BCD. Yup, that's the other way to skin this cat

Now what do you do when can't rent these BC's for trial dives? :06:

There's a difference between 'trying' something and really diving with it for awhile.

-hh

Rovie ~ on her qwest for a great BC

 

[Mishelle]

just my 3 cents, but your LDS can probably get you a rental one for pretty cheap. They are generally in great condition and you get it at a fraction of the cost. Just an idea if you want to save the $$. Good Luck!

 

[Rovendiver]

Oceanic Ocean Pro FX BC is on Scuba toys for a great price. I am still leaning toward the Zena but missed the last year's model special and spousal unit KTRJC and I are both shopping for BC's.

One more question, please I need feed back on this one. We are diving next weekend and looking to rent.

Hey Larry or Joe if you guys still have last year's Zena model medium hiding in the backroom let me know!!

Rovie

 

[-hh]

Hey hh

You have supplied some serious eye opening :11: information. I am a little confused but it does help me understand what people are talking about when they tell me back inflate tend tip you forward.

Glad to be of help. And for what its worth, you can try these illustrations to see if it helps you visualize what I've been talking about:

Horizontal Orientation (trim during the dive):
http://www.huntzinger.com/dive/sb/BC_physics1.jpg

Vertical Orientation (trim at surface):
http://www.huntzinger.com/dive/sb/BC_physics2a.jpg

I've set up both of the latter's examples so that they'll both provide a "face down" counter-clockwise torque, although of different magnitudes (because the Moment Arm ... think "leverage" ... of the one is longer).

You'll hopefully notice that I deleted a red weight off the weightbelt on the righthand diver, to indicate that he moved some of his weighting rearwards, onto a SS backplate...that's why his little orange dot that indicates his center of mass is shifted slightly towards his back (to the right).

The green dots on both are hopefully reasonable representations of the virtual point of bouyancy (BC lift) is, due to introducing air into the bladder.

FWIW, do note that this is a very 'homogenized' simplification that I've not really spent a whole lot of time on. Afterall, to do this accurately, we would model the diver, his weightbelt, his wetsuit, his tank, BC, etc, etc, etc, each as an individual piece and then mathmatically combine all of the weights/bouyancies and their relative locations.

FWIW, you can also think of this trim exercise as being like a giant see-saw onto which you're tying lead weights and helium balloons...the only problem with this analogy is that it needs to be done twice: once for horizontal trim, and once for vertical trim. As such, we would need to add another dimension to our see-saw: think of it as a clock face that's balanced on a pin, and not only do you need to balance out left-and-right, but also top-to-bottom...if you put 2lbs at 10 o'clock, putting 2lbs at 2 o'clock does balances it left/right, but not top/bottom.

Now what do you do when can't rent these BC's for trial dives? :06:

Unfortunately, generally, you don't...you borrow it from a friend to try out. The problem is that not only does this tend to limit options, but you also can fall into the "new car test drive" phychology trap, where things you've experienced almost always are preferred to those things that you've not experienced...this is generally why the first car you test-drive is also your last...its not because we always get lucky and picked the perfect car purely by accident, time and time again.


-hh