Buoyancy Changes

[headonkey]

I usually dive a 5/4 mm wet suit in the quarries around here. On Wed, I'm going to dive the Hyde and Stone of the coast of NC. Seeing that the water temps are low 80s, I'm going to have to rent a 3 mm wet suit. Taking the decrease in neoprene into account, should I just use my normal weight in the saltwater?

* I usually dive 6 lbs on my weightbelt and 6 in my SS bp in the quarries with the 5 mm wet suit.

 

[SharkDiver36]

Keep the weight the same for the first dive, see how you like it, how it feels.

I wouldn't make multiple changes that affect your bouyancy, figuring out which is what would be a real challenge. You're already dealing with 2 differences, salt.vs. fresh, thick vs. thin suit....that's enough for now. Do a couple of dives then make changes and the best advice will come from the people there, who dive it, not from someone on this board who has never done it or maybe done it a couple times, or may have done it somewhere else.

Enjoy the diving tho!

 

[bolantej]

it might be fine, but these things are usually trail and error, at least for me. If you have a float, bring some extra weight just in case.

 

[markfm]

A full suit, in the M - L zone, is about 2lb per mm. Switching from a 5/4 to a 3, IF both are in reasonably good condition, would be around a 3 lb swing (3 lb less lead).

The bigger swing is freshwater, quarry, to salt. If the tank size/type is the same (diving an AL80 in both cases, for example), you need more lead for that change, about 1/40 of your total surface weight (you plus all gear). If you're in the 160 - 200 lb weight range, this would be on the order of +6 lb total more lead.

These things are additive -- you lose a couple lb for the wetsuit change, you add some for the fresh-to-salt change. End of the day, if you're dialed in clean in fresh water, and you're around the weight I mentioned, and you're diving the same tank size/type, you'll likely need about +3 lb. I'd add a pair of 2s. (+4 total change) -- having 1 or 2 lb too much is not some terrible sin, while not having enough lead at the end is not a good thing.

Safe diving!