Coldwater BP/W lift question

[movementality]

Do I need a 30# or 40# wing?

Disclaimer: I'm a noob, don't have ready access to a pool, don't know how much weight I'll need to keep neutrally buoyant yet, and all other similar posts (that I saw) referred to warm water wetsuits. Sorry to waste everyone's time rehashing an old issue, but any help would be greatly appreciated.

Wetsuit: 7mm Full + 7mm Hooded Vest
Rig: Assume large single steel tank, SS Plate (~5lb for the plate)
Noob: 5'9", 145lb.

I know the rig itself (SS BP, single Steel tank) plus all my equip. probably won't surpass 30lb, so I'm good there, but I'm not sure about my wetsuit buoyancy.
I will be diving a 7mm full + 7mm hooded vest. Not sure how much weight I'll need to get neutrally buoyant since this will be my first equipment purchase and I didn't wear a wetsuit during the pool sessions (OW next month). I'm assuming 6-8 lbs extra weight to get neutral, but that's a number I pulled out of thin air.

I'm deciding between a 30# and 40# wing. I'm thinking 30, but thoughts of becoming a dirt dart flit through the empty space between my ears. I'm calculating for worst case scenario (no buoyancy from wetsuit, 30lb rig plus 6-8 pound ditchable weight that gets stuck) but I know if I'm even approaching that depth, I'll be diving a completely different rig with completely different training (and a better grasp on how to do this calculation properly).

Any help would be greatly appreciated. Thanks!

 

[cool_hardware52]

MM,


Without actually testing the initial buoyancy of an actual wetsuit, it's all an educated guess. My "guess" is that a 7 mil wetsuit on a guy your size will be less than 30 lbs positive at the surface. Wetsuits vary, in material, in actual thickness, how any times have they been compressed etc.

Very few people diving a single tank need more than 30 lbs of lift. Who does? Big people wearing lots of neoprene.

Remember you need to take your wetsuit down to ~165 fsw to fully compress it, no place to be with a single tank, so in typical use your wetsuit will remain at least somewhat buoyant.


Tobin

 

[Mr.X]

I second what Tobin is saying. Very variable. I once had a guy wearing a full 5mm suit with hood and vest, no weightbelt sink fast in salt water. I couldn't believe it. His body density was amazing!

That being said, when I use a 7mm with a hood I need about 22 lbs of dead weight to get me down. I use a 40 lb wing (with a bailout bottle - 30/40 cu.) and a 22lb wing in warmer waters with a 3-5mm. The 40 lb is a tad overkill, but the wing itself is very compact and has the same dimensions as a 30 lb wing (as far as I remember). X

 

[Green_Manelishi]

I second what Tobin is saying. Very variable. I once had a guy wearing a full 5mm suit with hood and vest, no weightbelt sink fast in salt water. I couldn't believe it. His body density was amazing!

That being said, when I use a 7mm with a hood I need about 22 lbs of dead weight to get me down. I use a 40 lb wing (with a bailout bottle - 30/40 cu.) and a 22lb wing in warmer waters with a 3-5mm. The 40 lb is a tad overkill, but the wing itself is very compact and has the same dimensions as a 30 lb wing (as far as I remember). X

And I third it.

With a 5mm or 7mm one-piece suit, hooded vest, steel tank and SS backplate I do not need a weight belt. As a matter of fact I am overweighted. So I use an AL backplate.

 

[limeyx]

And I third it.

With a 5mm or 7mm one-piece suit, hooded vest, steel tank and SS backplate I do not need a weight belt. As a matter of fact I am overweighted. So I use an AL backplate.

jeez, what are you eating for breakfast? I need about 8 pounds with an LP 80 in a 7MM with SS BP. I guess I need to get my backside to the gym.

 

[dumpsterDiver]

If I was as thin as you are, I would at least try an aluminum plate rather than a SS one before I made a purchase. If you add a pony bottle to that rig with a SS plate, you might end up having no ditchable weight, which would not be desirable in my opinion. I think a 30 lb wing should be enough lift, but barely. Again I would see if I could try out the 30 and 40 lb wings before making a purchase.

 

[cool_hardware52]

If I was as thin as you are, I would at least try an aluminum plate rather than a SS one before I made a purchase. If you add a pony bottle to that rig with a SS plate, you might end up having no ditchable weight, which would not be desirable in my opinion. I think a 30 lb wing should be enough lift, but barely. Again I would see if I could try out the 30 and 40 lb wings before making a purchase.

It's pretty unlikely in my experience that even a skinny diver wearing a 7mil + 7mil hooded vest will be overweighted using a SS backplate. Maybe with an extremely negative tank , HP80 for example, but not with typical steel tanks, and not with AL80's


Tobin

 

[Green_Manelishi]

jeez, what are you eating for breakfast? I need about 8 pounds with an LP 80 in a 7MM with SS BP. I guess I need to get my backside to the gym.

I have never been a "floater". At the surface, just my body, I float only if I am on my stomach with a lung full of air. As soon as I exhale any of the air, I sink. If I am on my back, forget it, the only part of me that stays out of the water is my nose ... until I exhale. So, I "get away" with less weight than many.

Another other "key" is, like Tobin mentioned, the tank that is being used; it's a HP80 which is very negatively bouyant even when empty. They are absolutely sweet when using a drysuit With a wet suit and SS backplate I am overweighted so I use an AL BP.

 

[limeyx]

I have never been a "floater". At the surface, just my body, I float only if I am on my stomach with a lung full of air. As soon as I exhale any of the air, I sink. If I am on my back, forget it, the only part of me that stays out of the water is my nose ... until I exhale. So, I "get away" with less weight than many.

Another other "key" is, like Tobin mentioned, the tank that is being used; it's a HP80 which is very negatively bouyant even when empty. They are absolutely sweet when using a drysuit With a wet suit and SS backplate I am overweighted so I use an AL BP.

Well, with the way fills go around here, the HP80 is a no go for most diving (below 30 feet). I'd be lucky to get anything over 3000 psi hot in it.

Usually I dive an HP100 or LP80 which are essentially neutral at 500 psi. maybe a touch negative.

 

[dumpsterDiver]

well he said that he wanted a large steel tank... a 121 is what around what 9 lbs negative full with reg?, a pony and reg can be another what 2-3? and then a steel plate is another 6 lbs.

That's close to 18 lbs negative, I use about 25 lbs of lead with that suit and aluminum tank and unfortunately I'm a lot fatter than this guy. I think 18 lbs of unditchable weight MIGHT be a little too much

I would think that an Aluminum plate and having 6, 8 or 10 lbs on the belt to ditch for a wetsuit diver would be safer than having nothing to ditch, maybe I'm old fashioned?