FW wetsuit buoyancy

[MGW1979]

I normally dive salt water with a 2mm 2piece. With that rig I wear 4 kg of weight. This weekend I'm going to be diving freshwater and will wear a 7mm 2 piece. Anyone have a clue how much weight I should try? I'll going to do a buoyancy test but I want to at least be in the ballpark!
Thanks

 

[crlavoie]

I normally dive salt water with a 2mm 2piece. With that rig I wear 4 kg of weight. This weekend I'm going to be diving freshwater and will wear a 7mm 2 piece. Anyone have a clue how much weight I should try? I'll going to do a buoyancy test but I want to at least be in the ballpark!
Thanks

You can probably get pretty darn close before you even get in the water. You will be less bouyant in fresh water and I belive the rough math is approximately -4.5 lbs for every 140 lbs of TOTAL diver weight including gear. Someone else will need to keep me honest on that number as it's been a while but it's close.

After that, you just need to add what ever is necessary to off set your suit which you can do in a pool or a really big tub.

Your gross ballast requirement should be easy. Your trim may require a little more fine tuning depending on your config. My thought - and I'm totally guessing - is that with a typical warm water rig, you will end up with floaty feet because of all the additional neoprene.

 

[TeddyDiver]

I normally dive salt water with a 2mm 2piece. With that rig I wear 4 kg of weight. This weekend I'm going to be diving freshwater and will wear a 7mm 2 piece. Anyone have a clue how much weight I should try? I'll going to do a buoyancy test but I want to at least be in the ballpark!
Thanks

10kg is close if you use the same config except the WS. For the thicker suit about 10kg more and 3,5kg less in fresh water.

 

[*Floater*]

I normally dive salt water with a 2mm 2piece. With that rig I wear 4 kg of weight. This weekend I'm going to be diving freshwater and will wear a 7mm 2 piece. Anyone have a clue how much weight I should try? I'll going to do a buoyancy test but I want to at least be in the ballpark!
Thanks

Here's a graph from Peter Steinhoff's site (dir-diver) for a 7mm XL neoprene full suit:

It's just an example, and your suit will be different of course because the neoprene quality may differ, salinity of fresh water is lower, your size is probably different and yours is thicker where the two layers overlap, however, you can extrapolate, and also note that the suit lost about 20% of it's total buoyancy at 3 meters and about 40% at 6m, so depending where you do you last safety stop you can take that much weight off the total weight needed to sink the suit. (With a full tank you'll still be able to get down at the beginning of the dive).

 

[TeddyDiver]

It's just an example, and your suit will be different of course because the neoprene quality may differ, salinity of fresh water is lower, your size is probably different and yours is thicker where the two layers overlap, however, you can extrapolate,

2 piece suit is more or less 60% more boyant than same thickness longies (2 piece 7mm has about the same boyancy as 7mm longies+5mm shorty)

note that the suit lost about 20% of it's total buoyancy at 3 meters and about 40% at 6m, so depending where you do you last safety stop you can take that much weight off the total weight needed to sink the suit. (With a full tank you'll still be able to get down at the beginning of the dive).

Second that!!