Cold-water weighting vs. warm water

[Grey Goose]

If one is properly weighted for summer/pool diving in a dry suit, any suggestions on how much weight to add for cold water diving (just above zero) to compensate for more air in suit to stay warm. I realize buoyancy is same in warm and cold water. Reality is that to stay warm in really cold water, I like to add more air to my suit over that used in summer/pool diving. Put another way, how much extra weight does one need for a well-lofted drysuit vs. one run at a minimum loft (1, 2, 3 or more lbs). I assume factors are weight of air but also ability to evacuate air when ascending--that is, air expands when ascending and dump valve is only so good (recognizing that one should dump air before one starts to ascend).

Thanks in advance for sharing your expereince!

 

[tbone1004]

100% impossible to answer, sorry. No idea how big you are, no idea how thick your undergarments are, no idea if you're going to choose to dive in minimum suit volume vs add some extra air to stay warm, etc etc. Only way to figure that out is to do it. Wish I had a better answer, but it's truly impossible to even ballpark.

 

[BoltSnap]

Probably it is better to use a more appropriate thermals for the temps you are diving in the winter than trying to make the air cell inside the suit compensate for not using the appropriate thermals.

 

[Grey Goose]

I see you point tbone. Assume thermals are same just loft of thermals different. Given were are likely only talking about a pound or three, perhaps a real-life test is most appropriate.

 

[Steve_C]

perhaps a real-life test is most appropriate.

Yes.

Think about how much you can lift with a small lift bag. Now imagine the volume of air formed by say 1-2 inches covering your body. May be more than you think.

 

[Grey Goose]

Steve_c, good analogy with the lift bag vs. suit. Gives me something to frame the issue in a tangible way. Will add more weight above my baseline next time I'm out experimenting with loft.

 

[BRT]

Yes.

Think about how much you can lift with a small lift bag. Now imagine the volume of air formed by say 1-2 inches covering your body. May be more than you think.

I don't think anybody can carry enough lead to sink 2" of air around their body. I used an online body surface area calculator for me, 5' 11" and 212lb and I believe each 1/10" came to 12 lb of flotation.

 

[Steve_C]

I don't think anybody can carry enough lead to sink 2" of air around their body. I used an online body surface area calculator for me, 5' 11" and 212lb and I believe each 1/10" came to 12 lb of flotation.

Good information. My point was just that there is much more lift in the suit then OP may have realized. Your calculation shows it is even more than I would have guessed.

 

[olphart]

For me, the difference between drysuit diving with a track suit in wamish water, say 65F and cold, ~40 with my thermalfusion is a good 16lb

 

[REVAN]

It will be worth looking into slim undergarments to keep the weight requirements down. If you are just picking warm sweaters to wear with your DS, sweaters that fit tight without folding and creasing will still keep you warm without adding unnecessary bulk. But, don't use cotton stuff. It doesn't work when it gets wet or damp.