Wetsuit buoyancy - 30 lbs????

[Bossman]

I took the time today to do a buoyancy check on my Neosport Farmer John, 7mm XL John with 7mm XXL Jacket. I folded the suit nicely with my weight belt wrapped around it. It took about 30-32 lbs to sink. I did my best to get all of the air out of it, but maybe I didn't. Does anyone think it's possible that the suit is 30 lbs. buoyant?

The reason I ask is that I recently bought a 30 lb wing and I'm thinking I should return it for the 40 lb wing. The wetsuit buoyancy is my biggest issue as my rig is only about 22 lbs negative with a steel HP100.

 

[fjpatrum]

According to the sticky at the top of the BC equipment forum ("The Ultimate wing lift calculator"), a 7mm full suit has approximately 18# of buoyancy, so it's reasonable to believe an XL/XXL 2 piece 7mm suit would be about 30.

I'd recommend checking out that thread and looking at the calculator if you have access to MS excel or similar spreadsheet program. It's enlightening.

 

[knowone]

I've got six and a half feet of that type of suit set up and use a 44 for Faber 100 twins.

 

[JohnB47]

Your measured buoyancy sounds reasonable.

 

[BioLogic]

Perhaps I'm missing something, but since the suit's not coming off in the water, won't it offset the weight needed to sink it, making the wing need to lift pretty much just the rig and you (supposing your lungs are empty)? Or are you planning on using that much weight integrated into the rig and are concerned about the rig being able to hold itself up in the water for in-water doff and don? The latter makes sense to me, but I don't see a concern if some of the weight's not integrated on the rig.

 

[knowone]

Neoprene compresses greatly at depth and progressively on the way there. From spongy to a slab of rubber. Not necessarily noticeable early because of the air glass water sight syndrome that we experience but if you measure suit wrist you will see. As you feel compressed so is your neoprene being resulting in bouyancy loss that returns with ascent.
Take a piece of neoprene and a tennis ball down with you one day.
It is very good that a greater percentage of the body is made of incompressibles.

 

[spectrum]

I agree it's reasonable. I never did my suit but I did do my vests. The 7mm Bare hooded step-in vest in XL alone is 11.

Regarding the wing get most of the weight back on your person. Load the BC only with the weight that needs to be carried high for trim. Once you do that the rig and yourself should be capable of positive buoyancy. The BC essentially needs to compensate for the loss of buoyancy in the suit (probably no more than 2/3 of #30 = 20) and the weight of consumable air in your cylinder (~#7). #30 is probably fine. That's what I use and it's ample for wet or dry.

Pete

 

[a22shady]

I was told when i bought my system to go with the 40lb wing. My LDS as well as others i know recomded it. Also said to go with the 60 for doubles. I am sure there is a lot of debate of which one might be better but thats what I use when i dive.

 

[String]

The reason I ask is that I recently bought a 30 lb wing and I'm thinking I should return it for the 40 lb wing. The wetsuit buoyancy is my biggest issue as my rig is only about 22 lbs negative with a steel HP100.

Why would your wing size have anything to do with the suit buoyancy? You aren't buying the wing to lift the suit, the wing is to lift the weight of the gas consumed on the dive. No other function.

If you're on a single thats about 3kg / 7lb of lift. Double that for surface buoyancy and suit compression at depth and you're up to about 15lb. Its plenty.

 

[GrumpyOldGuy]

I came close to that number when I originally tester my 7MM FJ+J. Regardless, at recreation depths your w/s does not loose all of its buoyancy. When properly weighted you should only need ~24lbs of lift max given your size, suite and a single tank. The 30lb wing work fine for this. If you want to dive over-weighted for some odd reason or have plans for some unusual configuration, then the 40 gives you a ton of tolerance with a slightly larger footprint.