Few questions regarding fitting of a BPW

[TT_Vert]

Bubbletrouble, the problem is more than likely in freshwater I'm going to be quite negatively buoyant even w/o any lead because of the SS backplate. So I'll really have no way to know the lead equivalent to the amount of air i'd have to put in my bcd to be able to surface. I'm going to play around tomorrow and see how everything goes.

 

[TT_Vert]

Did a freshwater pool dive today. I had to tighten the shoulder straps a tad and the crotch strap to keep the tank from moving much. I'm probably going to loosen my shoulder staps a tad unless I can confirm the issue I've described below is the culprit I'm not 100% sure what kind of tank side to side movement is acceptable but I can move the bottom of the tank a good 4" or so side to side. I did notice that on occasion I felt as if I was pitching and rolling a bit. I checked to ensure shoulder straps were even and the plate was square on my back. This behavior isn't uncommon for me but I usually have a weight belt I can rotate on my waist slightly to offset this and keep my chest level with the bottom. The odd thing is is that the rotation seemed to be inconsistent and from what I recall it was on occasion rolling me right and sometimes left. I didn't inflate or deflate my bcd at all after I got my initial buoyancy where I wanted it. I am still a tad leg heavy but not nearly as much. At the bottom of the pool I can hover my chest at about 1' above the bottom but my feet are always on the bottom and I'm pretty much doing a fin pivot when I inhale/exhale (moving up/down about 1 foot with my upper body). It definately takes less fin movement to keep my legs up though.

Dave

 

[Bubbletrubble]

Dave, how much dive experience do you have? It sounds like you're pretty new to the sport. I'm sure all this stuff could easily be sorted out in person with an experienced diver/mentor or a good instructor. It's pretty difficult for us to help you over the Internet.

The horizontal trim issue gets solved with experience, proper body positioning, attention to detail, and the appropriate distribution of weight.
If you are still a tad leg heavy, then you can always shift weight toward your head a smidge. One way of doing this is sliding the tank up a little. Arm/leg/foot/head positioning can also make a big difference.

I've encountered some beginners who have had an issue with rolling left or right underwater. After making sure that the BC is properly adjusted and the tank anchored securely to their back, it really just came down to an issue of balance. With experience and no further equipment changes, the rolling instability magically disappeared.

Hope this info helps...

 

[TT_Vert]

I am a new diver. 2 years and 40 dives now. I had the instructor who did my OW cert a few years ago in the pool with me today and he said everything looked fine but truth be told I'm unsure how much he knows about backplates. I asked him his opinions on adjusting the straps and I didn't get much input. I did play w/ my tank and moved it up to the point it was really hitting my head and then moved it down until the straps were just about at the curvature of the top of the tank and I still had the feet down issue at any tank position. I was only able to get down 7' in this pool unfortunately so I wonder if perhaps these issues are being amplified? I have lots to learn and I'd be more than happy to pay a knowledgeable instructor whatever to take a look at me in the water and offer their input. I have a feeling I'm just nitpicking a tad here. At this point I'm going to do my dives in the bahamas w/ the new rig and see how it does. I do know w/ just the rig and my 3mil shorty at 500 psi I dropped to the bottom of the pool like a 10 ton weight. I did some skills like removing and redoning the BP/W at the bottom of the pool and w/o a weight belt it is a challenge to do any type of under water adjustment due to my buoyancy w/o the belt but definately possible in an emergency.

Dave

 

[Bubbletrubble]

What doesn't make sense to me is that you transitioned from a conventional BCD + weightbelt to a BP/W setup (no weightbelt). Effectively, this moved weight towards your head. If anything, with your BP/W rig, you should be less head-up/feet-down than you were with the old BCD + weightbelt.

As you gain experience, you'll realize that body positioning can significantly affect your trim. I suspect that your leg/arm/head positioning is suboptimal, but I can't say for sure since I've never seen you in the water.

Any decent tech diving instructor should be able to get you squared away. In my experience, instructors affiliated with the more mainstream agencies are hit-or-miss when it comes to fine-tuning horizontal trim.

 

[DevonDiver]

BP&W Fitting

1. Shoulder straps loose, as other have mentioned. You should be able to fit a clenched fist (horizontally) between the straps and your chest. My straps are so loose than I can easily chicken-wing my arms out of the harness, whilst the waist strap is still fastened.

2. Crotch strap as tight as possible, without causing actual discomfort.

3. Waist strap tight.

4. You should be able to reach back and touch the top of the backplate. Note: there is a technique for this - many divers have difficulties with reaching back for valve drills and it is normally because they are reaching back wrong. Your arm needs to come up vertically, not out to the side. The hand, wrist and then inner-forearm should 'brush' against your ear as your reach back. Most bring their arm back at an angle, with the elbow sticking outwards. That seriously decreases the range of motion in the shoulder.

Buoyancy/Trim/Hover

Read: Scuba Techniques - 10 Tips To Attain A Better Horizontal Hover -Scuba Tech Philippines

Read:Scuba Buoyancy Masterclass 5of9 - Trim and Position -Scuba Tech Philippines

 

[Splitlip]

Step away from the key board. Get in the water. The internet ain't all that.

 

[TT_Vert]

Thanks guys I do realize I have tons to learn. One thing that sparks my memory is something the above poster posted in the 10 ways to improve horizontal hovering. I do not have my knees bent and my legs pointing up. I did play w/ that position today in the pool and noticed it helped a bit. Perhaps that is my issue all along, keeping my legs mostly extended during my hovering.

Bubbletruble, I know what you're saying and that horizonal hovering issue was part of the reason I went to the BP/W among others of course. It is better now w/ the BP/W than it was with the BCD and waist lead no doubt and perhaps now it is just a matter of fine tuning. Moving weight from my waist to my back I also assumed I'd be face down until I trimmed out a bit w/ weigh distribution. I wonder if the fact I was only at 6' and in fresh water changed any of the outcomes today.

Dave

 

[Bubbletrubble]

Thanks guys I do realize I have tons to learn. One thing that sparks my memory is something the above poster posted in the 10 ways to improve horizontal hovering. I do not have my knees bent and my legs pointing up. I did play w/ that position today in the pool and noticed it helped a bit. Perhaps that is my issue all along, keeping my legs mostly extended during my hovering.

Yes, head/arm/leg positioning can make a big difference when it comes to trim. Think about your weight distribution with knees bent/legs pointing up vs. weight distribution with legs straightened out. You probably kept your legs straight because subconsciously you were reverting to a "fin pivot" position. If you try to assume a skydiver horizontal position (with bent knees/legs), you'll probably find it easier to get trimmed out properly.

Good luck and have fun practicing...

 

[TT_Vert]

Thanks for all of the input guys, the BPW performed great while diving in the bahamas. No pitching or rotating to speak of like I experienced in the pool. I was also able to hold my safety stop w/o a weight belt but I did have 1400 psi of air still unfortunately. I didn't have the presence of mind to purge air to 500ish psi while holding my stop. I was mostly able to keep my feet slightly above my head but I wasn't able to keep my knees bent and legs up comfortably. I did play w/ my arm position and kept them forward a bit and that helped some. Is there a technique I can try to perfect that knee bent "skydiver" type position?

Thanks much

Dave