7mm 20lb buoyant?

[amajamar]

I don't know if anyone can say for sure what your additional weight requirements would be. For me, (I wear a medium-large) the difference between 3mm and 7mm wetsuits is about 16-18 lbs.

 

[Mike Veitch]

wow.. i have a brand spanking new (worn it 6 times) 7mm semi dry (one piece) and i need only 10 pounds with an al 80, planning on dropping that to 8 pounds on the next outing.

guess i am just weird..

 

[ScubaSpicher]

I dive the bare artic suit, size 2x, and would agree amajamar, i think my added 20lbs, but again that was most like a result of the suit size. Somewhere from 16-20 is not a bad bet though...

 

[GrumpyOldGuy]

Deleted by me, grouchy due to lack of coffee and more *******ing snow.

 

[Don Wray]

I just got back from San Carlos it was my first Saltwater dive in my 7-6-5 Tilos Hyperstretch. Using a AL80 I dive with 24 lbs in freshwater. I'm 200 lbs and wear an XL. My first attempt to submerge was with my BCD weight and trim pockets maxed out with 30 lbs and that wasn't quite enough. So I wouldn't need to keep my buddy waiting to long I grabbed another pair of 2 lbs and slipped them into my accessory pockets. At 34 lbs I was a bit heavier than needed but it was easily manageable. Next time I may start with 32 lbs and see if I can submerge again at the end of my dive with 500 psi left in the tank.

Sorry to semi-hijack; RA, consider not maxing out your bc but split your weighting by adding a weight belt. That way if you do have to drop your weights, you can do it partially and not jet to the surface like a rocket. Just make sure you let your buddy know during your predive check. That's what I do when I'm in a 7mm with lots of weight.

 

[miketsp]

wow.. i have a brand spanking new (worn it 6 times) 7mm semi dry (one piece) and i need only 10 pounds with an al 80, planning on dropping that to 8 pounds on the next outing.

guess i am just weird..

If that is with a jacket BC there is something very wrong. I'm average height at 5' 10" and my body area using various of the formula on the market is just under 2 m2 and multiplied by the suit thickness of 7mm means 14 liters of water displaced or around 14kg of water, say 31lb which is exactly the weight I need.

Now if you're wearing a steel backplate with an STA and some additional hidden weight then maybe you're not so weird.

 

[Mike Veitch]

If that is with a jacket BC there is something very wrong. I'm average height at 5' 10" and my body area using various of the formula on the market is just under 2 m2 and multiplied by the suit thickness of 7mm means 14 liters of water displaced or around 14kg of water, say 31lb which is exactly the weight I need.

Now if you're wearing a steel backplate with an STA and some additional hidden weight then maybe you're not so weird.

nope, just a regular scubapro jacket...

as i said, i must be weird..

i would say i have 4% body fat but then i would be lying

 

[MagicChicken]

Hi!

Am I wrong to think that all these calculations are to some extent irrelevant since weight requirements will change depending on where and when you dive? IMO, empirical beat theoretical results.

I wear a full 7/5mm + 7/5mm jumpsuit. I have used 18 to 36lbs when diving with a 80cft aluminium tank in saltwater. My average would be 24lbs, but to our own amazement, we really did need a monstruous lest of 36lbs to dive that one site. In Canada! :O

 

[spectrum]

Hi!

Am I wrong to think that all these calculations are to some extent irrelevant since weight requirements will change depending on where and when you dive? IMO, empirical beat theoretical results.

I wear a full 7/5mm + 7/5mm jumpsuit. I have used 18 to 36lbs when diving with a 80cft aluminium tank in saltwater. My average would be 24lbs, but to our own amazement, we really did need a monstruous lest of 36lbs to dive that one site. In Canada! :O

Sort of and Maybe....

True, all of attempts to guide the OP (mine included) are nothing more than estimates based on personal experiences and some data regarding certain items With enough data points and a solid baseline the OP can arrive at a decent starting point and an understanding of the drivers.

What seawater or even fresh to salt water will have an effect but generally nowhere near an 18 pound swing if all of the other gear is a constant.

For a diver who dresses out at 280 pounds with all gear 7 more pounds (1/40) will be needed compared to a perfect freshwater weight. If the plan in to lay low in surge or river current then 2-4 extra might be added intentionally. That's 11 pounds going from placid fresh to a surggy ocean site. A 280 pound heavier diver could get to 18. This is in common ocean water.

Setting aside surge the whole weight for water issue depends on the specific gravity of the water. Fresh will be 1, the ocean around 1.026. This will vary slightly, often without notice. Some places such as the Dead Sea are very salty/dense with a high SG (1.166) That specific gravity difference suggests needing an extra pound of weight for every 6-7 pounds (1/6.5) of dry diver weight! That has our 280 pound fresh water diver adding something like 43 pounds of weight. Somebody check me on this because I find this amazing!

If your Canadian site is a salt concentrator then that would explain it.

Pete

 

[MagicChicken]

If your Canadian site is a salt concentrator then that would explain it

Hey Pete.

Most of the time I need around 24lbs. But at that one site, Les Islets (Les Méchins, QC), we just couldn't go down.

Neptune: diving in Quebec, Les Méchins

It's a shore dive, very shallow (6-10ft) until you reach the small island, saltwater and A LOT of current in the shallow canal. I went back to the shore 3 times to add more weight.

Your calculations make sense, though.

I don't think the salinity was a problem as much as the current.

Anyway, I only wanted to remind the OP that there is no universal weight rule.



*** in case you want to know : the shallow diving was breathtaking... a biologist's dream come true! One of my favorite Quebec sites