Need advice re: switching from Jacket BCD to Back Inlation type BCD

[sytech]

I had been diving with a Cressi-Aqualight-R jacket type BCD for several years. It's light and great for traveling and performed flawlessly.

I used to fill the weight pockets with 6 lbs. in each weight pocket (Cressi says not to exceed 6.6 lbs) and a 3 lb. weight in each of my "zippered pockets" for a total of 18 lbs. That amount worked fine in the warm Caribbean where I usually dive and sometimes with a 3mm shorty or a diveskin.

I recently purchased a Zeagle Escape BCD which seems to be a completely different "animal" as it is a back inflation BCD.

Was wondering what you would "guesstimate" my weight needs would be for the EZ-Lock pullout weight holders on the front right and left of the BCD as well as the 2 ballast pockets in the rear? Or what type of approach would you use to get to the right amount and to avoid rolling forward on the surface as I hear this is a characteristic of many back inflation BCDs?

I want to experiment with this weighting but until I am able to get to the Caribbean, I will have to do my experimenting at Dutch Springs Quarry in Pennsylvania. This is in fresh water and I will be wearing a 7mm wetsuit so I assume I'd have to make weight adjustments for the fresh water as well as the extra neoprene.

I am probably going to be doing this by myself inasmuch as I have Solo Certification. Any suggestions as to the best way to go about this will be appreciated. Would also like to hear what other "general" performance differences I can expect from this new BCD compared my prior jacket-type BCD?


Thanks,

Sy

 

[Jim Lapenta]

15% of your body weight would be a good ballpark place to start. Other than that there is really no way to give any kind of accurate figure since we don't know how buoyant the suit you're wearing is, the inherent buoyancy of the bc, what type of tank you are using, your body type, etc. Just one question I also have to ask is how did you get a solo cert without knowing how to figure your correct weighting since this is critical to successfully planning a solo dive? You have no one to save your ass and all aspects including weighting fall solely on your shoulders. If you should get into trouble what will you ditch and how much? When will you ditch and how will you do it? How is the weight distributed and accessed by you since no one will do it for you? And if you've never dove solo in cold water (Dutch) in a 7mil why are you going into that environment for the first time with new gear that way. Sounds like your solo course was lacking a few things as well as your ow course. Weighting yourself out is basic stuff. Or at least it should be.

 

[Warmwater Wank]

Well I guess JimLap asked the serious questions--and they should be heeded. If you overweight in a back-inflate, count on getting pushed face first on the surface, simple mechanics. (You end up over-inflating to counter that "sinking feeling" and yup, you get pushed face first.) Correctly weighted, there is no problem with a back-inflate. If you like riding high out of the water you can always lean back but w/ correct weight AND trim (some counter weighting in rear pockets, which the Z. has) you stay vertical on the surface w/ no real effort.

The quarry may help you get used to your new bcd somewhat but you would be well served (and safer) to do your testing under actual conditions in saltwater with a buddy to help out. 18 lb in a shorty seems heavy. Any idea what the relative inherent bouyancy difference is between your Cressi and the Zeagle? Could be that the Cressi is a floater compared to the Zeagle, so don't let your experience w/ it sway your judgement on correctly weighting the Z. "Let's be careful out there..." // ww

 

[Geezer]

Recommend that you do essentially what you have been doing - 1/3 of your total weight in each front weight pocket, and split the final 1/3 between the two back pockets. That's what I do with my Ranger, and it balances well - no feeling of being face-forward, either.

I'd suggest practicing in a pool - where you can more closely approximate the effects of the Caribbean, with a thinner wetsuit, however.

 

[Nismo]

Fresh water is a totally different animal than salt. I use about 10% of my body weight at Dutch with an 8/6 suit. 20 pounds would be a good start. If you go there on a weekend, try to get in with a group thats there so you can have a hand working it out. Having some weight in the rear trim and not inflating the BC fully on the surface will keep you from getting pushed on your face. Even doing our OW class we used back inflate and no one had the problem apparently everyone has if they switch to a back inflate BC.

 

[sytech]

To answer your question as well as to address your assumptions:

I recently sold my old jacket style BCD which was perfectly weighted using general "formulas" but mainly by trial and error, like most people do.

In case you aren't aware there is no way to "figure correct weighting" without a heap of trial and error after using a general formula, unless you have access to a Cray Supercomputer which even then would inaccurately calculate the weighting because of the multiplicity and interactivity of all the variables involved.

My questions were directed to the simple notion of different performance characteristics between jacket and back inflation BCs and were addressed competently and maturely by others.


Sy

15% of your body weight would be a good ballpark place to start. Other than that there is really no way to give any kind of accurate figure since we don't know how buoyant the suit you're wearing is, the inherent buoyancy of the bc, what type of tank you are using, your body type, etc. Just one question I also have to ask is how did you get a solo cert without knowing how to figure your correct weighting since this is critical to successfully planning a solo dive? You have no one to save your ass and all aspects including weighting fall solely on your shoulders. If you should get into trouble what will you ditch and how much? When will you ditch and how will you do it? How is the weight distributed and accessed by you since no one will do it for you? And if you've never dove solo in cold water (Dutch) in a 7mil why are you going into that environment for the first time with new gear that way. Sounds like your solo course was lacking a few things as well as your ow course. Weighting yourself out is basic stuff. Or at least it should be.

 

[boulderjohn]

Have you done a real weight check?

The reason I ask is that your current weighting and both of the suggestions you received seem high to me for your setup and the kind of diving you do. I weigh about 200 pounds, and when I dove a Zeagle Ranger in the Caribbean with roughly the kind of thermal protection you have, I used 6-8 pounds. Now, I tend to use less than most people because I have something of a dense body mass, but I have nto seen many people in those conditions who really need 18 pounds. If I use 10% or 15% of my weight, I would have been well overweighted.

We are all different, though.

Start with a basic weight check. See how much weight it takes to float you at eye level while holding a normal breath. Ideally, you should do it with a spent tank, but a full tank will give you a pretty good idea.

 

[Geezer]

There's a 5 to 8 pound weight differential between a full tank, and one that's mostly empty. If you're using a full tank to check your weight, you'll be five pounds underweighted (with an AL80, for example) compared to doing the same check when the tank contains only 300-500 psi. If you use a full tank, remember to adjust your calculations to compensate for the weight of the air in your tank.

 

[Divenanny]

I have about 150 dives logged. Just last summer I switched from a vest to a back inflate. Because I wear a steel tank I was able to evenly weight all four "pockets". I kept the same amount of weight that I usually wear (12 lbs wearing a 7mm wetsuit). The steel tank gave me additional weight in the back. When I went to the Carribean I was given an aluminum tank. I needed an additional 4 lbs total and they were placed with 2 lbs in each of the back "pockets". this seemed to work perfectly and I did not tip forward with either tank. Also, Dutch Springs is fresh water so you may need less weight than when you go into the ocean. Hope that this helps.