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Cichlid
09-24-2007, 17:40
Will a back inflate BC still push you forward if you are properly weighted and inflated at the surface? My wife had a lot of trouble at the surface with the back inflate BC during our second day of pool work for our OW cert. The first day she had zero problems with a jacket style. Are there any other factors to consider? She liked the back inflate better under water, but it was hard for her to overlook the surface experience.

Illini_Fan
09-24-2007, 17:45
If you are perfectly vertical and do not use trim weights, then IME, my back inflate will push me forward. That being said, the percentage of time I'm on the surface is so small compared to the time underwater. Also, I use trim weights and keep 40-50% of my weight in the rear trim pouches. Finally, I just lean backwards as if doing a surface swim on my back, and find that I'm perfectly comfortable on the surface even for extended periods of time.

Chad
09-24-2007, 17:55
If I am on the surface either my bc is only inflated enough to get my head up or I have it full and am floating on my back. A fully inflated bc does push me slightly forward if I am trying to sit vertical on the surface but I rarely want to be in that position. Most of the time if I am on the surface I am floating comfortably on my back.

dallasdivergirl
09-24-2007, 17:57
I don't notice that my back inflate does that, but I don't put very much air in mine when at the surface.

ertechsg
09-24-2007, 18:01
First learn to relax and lay back don't inflate the BC so much it will push you foward if it is over inflated.

Vercingetorix
09-24-2007, 18:03
On the surface, there is no need to over inflate the back-inflate.I use a BP/W and have little trouble on the surface. If you over-inflate, then you must lie back (very rlaxing by the way).

CrzyJay456
09-24-2007, 18:46
On the surface, there is no need to over inflate the back-inflate.I use a BP/W and have little trouble on the surface. If you over-inflate, then you must lie back (very rlaxing by the way).

i see alot of back inflate divers that tend to just overfill and have a hard time staying back. i noticed that i put just a little bit of air in my BC and i just keep my head above water, and if feels just fine to me. no push forward.

Vercingetorix
09-24-2007, 18:51
On the surface, there is no need to over inflate the back-inflate.I use a BP/W and have little trouble on the surface. If you over-inflate, then you must lie back (very rlaxing by the way).

i see alot of back inflate divers that tend to just overfill and have a hard time staying back. i noticed that i put just a little bit of air in my BC and i just keep my head above water, and if feels just fine to me. no push forward.OK. That's what I said. I have no trouble on the surface because I don't put much air in the wing, so I never have a problem of being pushed forward.

Damselfish
09-24-2007, 20:15
Depending on how your weight is distributed a BI can push you forward on the surface even with very little air in there. It's going to depend on the person, the BC, the actual positioning and amount of the weights, it's just simple physics. I had this problem when I first got a BI and had to mess with trim weights a bit to get it right. Lots of people say just lean back, but I personally find that uncomfortable.

jwdizney
09-24-2007, 20:28
When I was researching this very topic, I found this practical explanation of BC design on the Zeagle site which explains the physics of BC buoyance fairly well:

http://www.zeagle.com/index.php?submenu=buoyancysystems&src=gendocs&link=BCDesign

this helped me gain a better understanding and make a LOT of sense! Hope it helps!

crpntr133
09-24-2007, 20:56
This depends upon the suit and your weight distribution. I know this from experience.
I had never had the issue of my BC putting me on my face even when fully inflated. I went to FL for a dive with a different suit and less weight, but distributed the same percentage. My first dive I came up from I inflated like I normally did and..yep face plant. Not really bad though. So I remembered the "don't fully inflate", deflated just a bit and TADA!! Tried moving all my weight to my waist and it really didn't help. Just screw my trim really bad.

I also like to get to the surface, lay back and hit the inflater. Kinda like an air mattress. Kinda neat to see how much that little bladder of air can lift you.

cummings66
09-24-2007, 22:11
I myself don't find it hard to avoid the face plant, as others have said it's because theres too much air in the BC. In fact, if you watch divers all over the place they ALL have too much air in the bc. It seems the instinct is to have your shoulders out of the water if you can, that's too high.

For what it's worth, I don't like floating on my back like on an air cushion, it works and is stable but I just don't like it much.

quasimoto
09-24-2007, 22:13
Yep, don't over inflate and all will be fine.
Another thing that a lot of newbs to a back inflate don't remember is that sometimes you might have to roll just a bit to your right to get that last little bit of bubble to the valve.

plot
09-24-2007, 23:21
My wing never does that to me, I keep trim weights on the top tank band though so maybe that pulls it back a bit when I'm surfaced.

Flatliner
09-24-2007, 23:46
I want to join the choir...I had real problems until I figured out the 'just a little air' thing.

Theepdinker
09-25-2007, 00:56
You want your chin out of the water, not your collar bone.

Theep

paintsnow
09-26-2007, 02:43
i just kinda lean back on it like a recliner. works great. even more comfortable then being straight up with a jacket bc pulling you up by your armpits....

reefugee
09-27-2007, 07:40
When I first started, my back inflated would push me forward because I had too much air. Now I only partial fill, and it no longer happens. Over time, as you become more confortable, you will be much less likely to overfill your BC.

DougNR
09-27-2007, 08:50
Will a back inflate BC still push you forward if you are properly weighted and inflated at the surface? My wife had a lot of trouble at the surface with the back inflate BC during our second day of pool work for our OW cert. The first day she had zero problems with a jacket style. Are there any other factors to consider? She liked the back inflate better under water, but it was hard for her to overlook the surface experience.

Reading through the advice so far, it pretty unanimous on the 'don't over-inflate' issue!

I'd like to add that it is also important with a back inflate system to keep it positioned low enough that the bc's center of buoyance matches your center of gravity. It makes your trim during the dive easier to manage and helps on the surface as well. I noted a couple of folks mention they weren't comfortable floating on their back. While personal preference is obviously a big part of that, there is also the issue that if your wing is positioned too high on your torso you can't easily push back and get 'on top' of it.

I'd suggest to any back inflate users, if you have some difficulty floating on your back, try loosening your shoulder straps a bit and snugging the waist band at the hips.

Tableleg
09-27-2007, 17:54
Yea, I do the trim weight thing, though I'll have to try the 'not so much air' thing the next time I go diving.

Splitlip
09-27-2007, 23:05
Good observations and recommendations by all.

Many inexperienced divers in back inflates find themselves going over when they over inflate. Their natural reaction then at that point is to, you guessed it, press down on the inflater and exacerbate the their situations.

danielh03
09-27-2007, 23:21
I just practiced not inflating my BC to much, and adding some trim weights. Works great for me!

FastPirate
09-27-2007, 23:38
i just lay on my back and chill out...its quite relaxing actually...especially when your tired....it really is a comfortable

CaribbeanDiver
09-28-2007, 19:17
ok, here is a twist, I do not find myself being pushed forward when wearing a BP/W but I do find myself being pushed forward (sometimes) when wearing my jacket.
now I know that seems backwards but I figured it out this way. I put very little air in my Wing, only enough to keep me above the water and since the BP is in the back, it balances it out -- therefore no forward push. Also, most of the time using my BP/W, I use steel tanks.
On the other hand, with a jacket BCD, I also put very little air in the bladder to just keep me above the surface and since the bladder is on the sides and front and the weights are integrated in the front, the front has a tendency to be pushed downward because of the weights and a tank (AL80) that is positive at the end of a dive. This downward push coupled with the floating upward of the positive AL80 tank equals a forward push.

scubasamurai
09-28-2007, 20:01
i will try the less air thing, but i just added some trim weights to the back hooks. seemed to level out nicely.

tonka97
09-28-2007, 20:30
Depending on how your weight is distributed a BI can push you forward on the surface even with very little air in there. It's going to depend on the person, the BC, the actual positioning and amount of the weights, it's just simple physics.

This is true for me.

I must lean and float on my back....I don't like this position as well as most divers report. (hard to see where you are going!)

jimmysdevoted
10-06-2007, 21:25
this was a great thread. I use my BC( US divers Elan) FOR A SNORKEL BC.
so if i use a little weight at the back i wont tip foward,,,,,,,,,,,,, how cool

BobArnold8265
10-06-2007, 22:12
My BCD does push me forward when on the surface but based on the previous replies, it is very apparent to m that I'm over-inflating. Will have to try less air next time I'm diving.