Enough lift?

[alfie227]

Hi

Both my girlfriend and I are looking at buying our first BCD's, we dive in cold water in a 7mm farmer john with a 7mm shorty over the top. Aside from that, standard equipment. I checked the BCD lift calculator at the top of this page but I'd like some confirmation just in case I messed up the numbers.

I'm 5,10 and about 170 lbs, she's 5,6 and about 143. We both wear about 22 lbs of weight which to be fair is probably excessive.

How much lift do we realistically need from a BC?

Thanks in advance
Alfie

 

[decompression]

When you add up all your negative weight (regs, lead weights, tanks etc), your BCD should have enough lift to ensure you are neutrally buoyant in order to reach the surface. You don't mention the thickness of the wetsuits but in general no more than 30 lbs of lift and preferably smaller in your case.

 

[racerx_]

Kinda wondering the same thing. Going cold water diving end of this month so ill probably be in a 7mm. Usually dive a rash guard with 2-3 lbs of weight and my bc has an 18lb lift. Assuming I Get my cold water weighting correct the 18lb lift should still be ok right since the weight is to offset the buoyancy of the wetsuit?

 

[boat sju]

Alfie,

22# sounds reasonable for the wetsuit you're wearing. I wear about the same at 5'9" 165. I wear a bit more weight with my drysuit. Seeing how you may end up with a drysuit someday too, I'd stick with the 30-35# wing. A 100 cft high pressure tank is 10# negative. Add some trim weight to your bc, your regulator, light, whatever, and your gear will easily be over 20#.

Since I'm an engineer I like to allow for a factor of safety. Also, I've taken my gear off prior to climbing a pontoon boat ladder and realized I didn't put quite enough air in the bc. Oops.

boat

 

[Instructor_Tom]

Dive Rite makes the transpack, which can be matted with different wings to allow you to use every thing from a 25LB lift wing to a 60lB lift for doubles.

the amount of lift you need complete depends on the configuration you are diving and the amount of secondary lift you have from your wet suit. at 6' 1" and 220lb my weight will vary between 6lb and 16lb depending on wether I'm diving steel 108s or AL80s it will also depend on the lights, reels and other gear I'm carrying.

the key to a good BCD is fit, beyond that is function, one that will serve your needs today as an OpenWater diver and possibly tomorrow as you move into more advanced technical diving. The transpack can even dive side mount with the right configuration.

otherwise I would recommend a backplate and wing if you want dive the DIR way and simply change out the wing for the kind of dive you will be doing.

hope this helps.


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[spectrum]

30 pounds will do you nicely for just abut any single cylinder diving scenario.. Be sure to do good periodic weight checks. Other than that 30 will deal with your 7mm gear as well as the potential future drysuit.

Pete

 

[GillScales]

Racerx, the extra weight helps sink the thicker suit; however,the thicker suit will compress and lose greater buoyancy at depth,which means you may need a larger wing to compensate.

 

[racerx_]

Racerx, the extra weight helps sink the thicker suit; however,the thicker suit will compress and lose greater buoyancy at depth,which means you may need a larger wing to compensate.

Good point.. Which means I may have to rent huh?

 

[ams511]

Alfie,

22# sounds reasonable for the wetsuit you're wearing. I wear about the same at 5'9" 165. I wear a bit more weight with my drysuit. Seeing how you may end up with a drysuit someday too, I'd stick with the 30-35# wing. A 100 cft high pressure tank is 10# negative. Add some trim weight to you're bc, you're regulator, light, whatever, and you're gear will easily be over 20#.

Since I'm an engineer I like to allow for a factor of safety. Also, I've taken my gear off prior to climbing a pontoon boat ladder and realized I didn't put quite enough air in the bc. Oops.

boat

Are you factoring in if one or the other has a wing failure and one of them needs to get the other off the bottom in a controlled manner? I recommend 35 lb to 40. lb.

---------- Post added June 2nd, 2013 at 10:04 PM ----------

Good point.. Which means I may have to rent huh?

How deep is the dive? If shallow, you may be ok. How cold is the water?

 

[Max Speed]

I dive exactly the same gear (7mm FJ and 22 lbs.) With a fully inflated small Dive Rite wing I was negative below 120' with an AL 80. Switched to a 35# Dive Rite EXP and can keep it neutral in fresh water.

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