Back inflate questions

The GF and myself just completed out OW class last week. In the class we were using Scuba pro (only brand the shop sold) jacket style BC's.

This weekend we rented gear from a LDS in the town I work in which sold different brands. When I first stopped in to talk to the shop owner about stuff we were talking about styles of BC's. He really likes the back inflate set up and had one in my size to try so I rented that for myself. The BC is the Oceanic Excursion.

I did lots of reading about this style and one of my 2 problems is very common. I know diving is meant to be done underwater but trying to float at the surface sucks compared to a jacket style. I did notice some tipping forward but not bad. My problem is I cant really seem to get buoyant where I am not bobbing a mouth level sucking water. If I basically get into a back floating position I have no trouble but it is kinda hard to chat with your buddy or set you compass in that position. Any suggestions?

My other problem was getting air to dump. This vest only has the inflator hose coming off the left shoulder. When ascending/descending in the vertical position I felt like I had decent control. When I as hovering and needed to dump a little air I could not do it from the horizontal. I felt like I had to get almost vertical to get air to dump which is a pain. Am I doing something wrong?

It might just be I need more time/practice with this gear. As I said these were our first dives after our OW class. We were diving in 51* F water without outside air about 40* F. Both in 7mm wetsuits with 7mm outers. Max depth was 40' with most being under 25'. We spent about 1.5 hrs in the water on Sat and then again on Sun. This place is a 10 min drive from my house and there is nothing that is going to be any better in our area. Our goal was just to play with gear and work on our skills so when we travel somewhere fun we will be enjoying the scenery not messing with our gear.

Face Planting. It takes a bit more finesse to dive a back-inflate, particularly with surface floating. Think about where the air is being held. If you over-fill the bladder, then it will push you forwards. Just fill the BCD 'enough' so that you can comfortably float. Helps if you have your weighting sorted also. If it really causes problems, then fitting an after-market crotch strap will sort it out. If the BCD has (and you use) integrated weights, that's gonna pull you forward also.

Dumping. If you're horizontal, then it you might need to do a bit of wiggling if you want to dump air via the LPI exhaust. Air is held in your bladder, it will always rise to the highest point. Alternatively, just use the hip dump - most, if not all, BCDs of any design have hip dumps. If that is too much task-loading at this stage, just stick with vertical ascents and descents.

Set the reciprocal bearing before you leave
so you are using the correct bearing on the way home

If you can't float at the surface with minimal air in the bladder you may be overweighted and/or too much weight in front of you. Do a proper weight check and consider moving a bit of weight to the rear trim pouches (on the assumption the Excursion has them)

For dumping horizontal, I find I rolling my right side down a tad is sometimes needed to get the last bits of air out of my wing

Are you considering buying BCs, or were you just looking for back-inflate BC tips to help you with the ones that you are renting now? I didn't want to start THAT thread again if you weren't looking to buy!

Looking at the Excursion 2 (the current model) on the Oceanic website at Excursion 2 it has both a rear hip dump valve, and tank band weight pouches with capacity up to 10 lbs non-dumpable. I'd really be surprised if the Excursion original (if that's what you're actually looking at) doesn't also. I have an older original Oceanic Islander, a lighter-weight rear inflate BC, and it has both these features.

The rear dump is what I use under water. I usually rock side to side while venting to get the bladder really empty during ascent. I only use the shoulder dump for initial descent from the surface.

I put anywhere from <50 - 67% of my ballast weight in the trim pouches, depending on exposure suit and availability - Where do you put 6 lbs when the resort only has 2-pounders? That helps both at the surface, and with trim underwater.

I really don't have much trouble leaning back and lying on the bladder at the surface. Just takes a little getting used to, like a lot of things to do with scuba. Well worth the superior configuration for actual diving. Follow the advice above about using the trim pouches, and not maximally inflating the bladder. And just get used to waves splashing over your face, and timing your breathing. With the mask on, it's not hard, just takes getting used to.

If you can't get your head out of the water, one of two things is true. Either you do not have enough lift (for example, diving a BC designed for tropical water in very cold water with big steel tanks), or the lift is not where you need it. If you think about it, only the air bladder portion which is UNDER the water is doing any lifting. If the BC isn't snug around you, the air bladder can float up behind you -- this will tend to push you forward some, but it will also allow your body to sag down into the water. This is one of the things a crotch strap on a harness does for you -- it makes sure the wing can't float up your back.

When it comes to dumping, you can only dump air from someplace that is the highest point. Inability to dump from the inflator can be due to not getting the inflator orifice up above you (I see this with students all the time) or it can be due to having the air in the bladder somewhere away from the attachment of the inflator hose. This will be true if you are horizontal and properly weighted, with a relatively small tank and thin exposure protection. You won't need much air to compensate for your buoyancy, so it will end up in the side pontoons of the air bladder. To get it to the inflator, you WILL have to break trim, either forward or backward (remember, you have more than one dump in almost all BCs, and the one on the BOTTOM of the bladder can be used to vent, too). Remember, too, that it takes time for air to move around. If you go a little head up but still can't get the air out, wait a second before pitching even MORE up, because the air may get there.

All of these problems can occur with any BC. The one thing about jackets on the surface is that, as you inflate them, they "grab" you around the middle, so they're less likely to float up unless they're really too loose. With back inflates, you have to be a bit more careful about making sure they are snug (or use a crotch strap).

Lots of good points, thanks.

As for the gear it seems the back inflate is better for diving (I have been doing too much reading ). Everyone recommends renting gear and trying before buying. Really hard when there are only 2 dive shops with limited gear to rent. So at some point (probably sooner then later) we are looking at buying gear but want to try to make the most informed choices before dropping the $$$.

As far as the face planting goes I did not really have much of a problem with that. My problem seemed to be I wanted to float about lip level (I am sure I am a bit over weight, will comment on that in a min). I did not feel like the BC was riding up on the surface but I did not really pay attention to that. We are going to do one more dive this weekend so I will pay attention to that.

For weight it does have the back pockets. I had 5lb in each of the 2 rear pockets and 10lb in each front for a total of 30lb (how I was weighted in class). In class we had been using steel tanks. With this rental gear we had AL80's. On the first day I had no problem sinking when we started but as the tanks got lower it was harder. I am assuming that is cause of the buoyancy change with AL but dont know, so I added 4lb before diving on day 2.

On this BC it ONLY has the left shoulder dump. It appears to have a place where a bottom left dump could be installed. To me that seems kind odd cause all the other BC's I have seen have had bottom right dumps. I know I was not getting the inflator high enough when horizontal since it will only go so high with it strapped into the harness. Good points about how the air moves in the bladder. I will have to try the wiggle move.

Thanks for all the good information and help. That is why we are practicing all this stuff now close to home where the cost is minimal. Navigation is the next big thing we are going to work on. I do understand reciprocal bearing and know how to use them along with a compass. Now is it just how to apply it underwater where you can not see land marks. That is a whole different topic though.

Right... the reason that I was asking - and this seems to be the theme of every third thread here on scubaboard - is that you might want to look into a backplate and wing before buying a jacket BC (back inflate or otherwise). The reason that I mention it is that the vast majority of new divers are not even offered this for consideration, yet people who dive them seem to love them. They are not just for tech divers, my son's first BC was a BP/W.

I have no problem being on the surface with mine at all. Perhaps that's because unlike a back inflate BC, the device itself has a good counterweight in the form of the plate. I don't need to go into all of the reasons why they are great here in this post if you really aren't in a position to try or buy one, or if you aren't interested, but it's just something else to consider.

Mike

Nwcid:

a total of 30lb (how I was weighted in class). In class we had been using steel tanks. With this rental gear we had AL80's.

Click to expand...

That's.... ahem&#8203;....'quite a lot' of weight....

http://scubatechphilippines.com/scuba_blog/scuba-buoyancy-masterclass-4of9-assessing-your-weight-requirements/

(not that I'm saying your instructor may have over-weighted you for his own convenience)